q_id
stringlengths 6
6
| title
stringlengths 3
299
| selftext
stringlengths 0
4.44k
| category
stringclasses 12
values | subreddit
stringclasses 1
value | answers
dict | title_urls
listlengths 1
1
| selftext_urls
listlengths 1
1
|
|---|---|---|---|---|---|---|---|
7iltma | Why do airlines make you put your phone in airplane mode/turned off despite it being repeatedly proven to have no interference to the aircraft? | Other | explainlikeimfive | {
"a_id": [
"dqzoug3"
],
"text": [
"Lack of impetus to change, basically. [The logic behind banning phone calls during flights is, essentially, that it'd annoy other passengers, who can't escape your chatter.]( URL_0 ) Nothing about technical issues. So the law doesn't change because no one really cares enough to change it. And airlines don't really enforce airplane mode rigorously anymore, because, well, it doesn't matter."
],
"score": [
5
],
"text_urls": [
[
"http://thehill.com/policy/transportation/198090-house-committee-passes-in-flight-phone-call-ban"
]
]
} | [
"url"
] | [
"url"
] |
|
7im628 | Why is it illegal to feed polar bears? | Other | explainlikeimfive | {
"a_id": [
"dqzux1z",
"dr079s3",
"dqzsf92"
],
"text": [
"They can eat humans with minimal effort. You don't feed them because you don't want them associating humans with food. This is why you won't see them at your local petting zoo.",
"Because if polar bears start associating humans with food, and loses its fear of them, it's very, very likely that they'll be a danger to the humans that feed them (\"mmm, this food sure is tasty...you seem tasty too and I know where to find you and that you're pretty slow\") and to humans who do not feed them (\"hey! You're supposed to have food for me!\"). Not to mention, if a polar bear is habituated to getting food from humans, it's not going to really bother hunting for its own food. So now you have a thousand-pound aggressive apex predator that doesn't want/know how to feed itself anymore, and no longer tries to stay away from humans. No choice but to kill it, which is bad since they're already endangered.",
"They're dangerous and the species is vulnerable. You don't want them getting comfortable with humans, much less growing reliant on our aid"
],
"score": [
17,
5,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7im9dr | Why are the rules for elections for federal offices allowed to vary between different US states? | Different states have different voting hours, eligibility rules, ballot access requirements... why is this not standard for Congress and the Presidency nationwide? | Other | explainlikeimfive | {
"a_id": [
"dqzrcib",
"dqzrf27"
],
"text": [
"The country was formed from 13 States (hence the name of the country), and the Constitution preserves a lot of autonomy on their part. For most purposes, the federal government is very loose. States establish and conduct the elections that send representatives to the federal House and Senate, and also that apportion electors to Presidential races. This was a huge problem in the century after the Civil War because the Southern states rigged their systems so that black people had no possibility of voting, and under the laws at the time, they were allowed to do so. That changed in a big way only with the Voting Rights Act of 1965 that allowed the federal government to stop race-based state discrimination in election procedures. But the same forces are at it again, it seems, finding ways around those federal laws.",
"The Constitution doesn't specify much about *how* voting should be done. This means that the specific rules fall under the 10th Amendment: > The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people."
],
"score": [
7,
5
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
7im9j5 | Terminal burrowing | I saw Everest when it came out and one of the deaths in the movie sort of deals with this. I saw a post that rekindled my curiousity. Why does our brain tell us we are hot? Then proceed to say, "Hey, you know what's a good idea, u/andturner1, taking off your clothes when its -20 degrees. | Biology | explainlikeimfive | {
"a_id": [
"dqzvo58"
],
"text": [
"One theory is that a part of the brain called the hypothalamus, which regulates temperature, starts to fail. Another is that through exhaustion, your constructed blood vessels in the skin suddenly relax, leading to a hot flash. URL_2 URL_1 URL_0"
],
"score": [
4
],
"text_urls": [
[
"https://www.livescience.com/41730-hypothermia-terminal-burrowing-paradoxical-undressing.html",
"https://io9.gizmodo.com/why-freezing-to-death-makes-you-want-to-get-naked-1688151366",
"https://www.reddit.com/r/explainlikeimfive/comments/3o8s07/eli5_why_does_one_feel_hot_during_long_term/"
]
]
} | [
"url"
] | [
"url"
] |
7imi87 | Why do military paratroopers use round umbrella-like parachutes, and not the rectangular ones, like sport/recreational skydivers? | Physics | explainlikeimfive | {
"a_id": [
"dqzstrx",
"dr001xs",
"dqzswif"
],
"text": [
"Has been asnwered before here : URL_0 Even though I don't think it is a satisfactory answer. If they could steer, they could steer themselves to a central landing spot. Having additional control does is not worse than having no control. But, they claim to be a paratrooper, so I am going to take their answer for what it is.",
"Because the limited maneuverability of a round parachute makes sure that troops land in one general area, remember a lot of combat parachute drops happen at night, for example: * [In Afghanistan]( URL_2 ) * [In Panama]( URL_1 ) * [In Iraq]( URL_0 ) Being in one area makes it easier to regroup and pursue your unit's objective. In the US Military jumping into combat gets you a gold star to add to your jump wings, troops call it a \"Mustard Stain\".",
"The rectangular chutes are designed to be steered by the operator. Paratroopers don’t need that capability"
],
"score": [
5,
5,
3
],
"text_urls": [
[
"https://www.reddit.com/r/AskReddit/comments/1szu7k/why_do_paratroopers_use_a_round_parachute/ce2x04d/"
],
[
"http://www.socnet.com/showthread.php?t=35752",
"https://en.wikipedia.org/wiki/United_States_invasion_of_Panama",
"http://www.blackfive.net/main/2004/05/recently_declas.html"
],
[]
]
} | [
"url"
] | [
"url"
] |
|
7imjo8 | Why does alcohol damage a filter so much more than water and how? | Chemistry | explainlikeimfive | {
"a_id": [
"dqzxngv"
],
"text": [
"Water belongs to a group of chemicals called inorganic while alcohol belongs to the organic group because it contains carbon. It is likely that whatever filter you're using is also made up of organic carbon containing molecules. In chemistry there is a general rule that \"like dissolves like\" or molecules belonging to the same group are usually good at dissolving each other. Since the alcohol and filter are organic, that means the alcohol can dissolve the filter, whereas water is inorganic so it doesn't. There are other things that can contribute to how quickly things can dissolve each other but this is a quick and dirty explanation of what's likely going on."
],
"score": [
13
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7imu06 | If influenza is always mutating, why does getting a flu shot help? Doesn't the shot only prevent attacks from a certain strain? | Biology | explainlikeimfive | {
"a_id": [
"dqzv8p4",
"dqzxux9",
"dr06d1n",
"dqzuw1i",
"dqzvdcx",
"dr03d7l",
"dr0d6c9"
],
"text": [
"Every year the world health organization researches which variation of the flu is going to be most common. After they come to a decision, the flu shot is made specifically for that virus. The flu shot contains a dead part of the virus that your body can identify and recognize when you actually come in contact with the virus later on.",
"Yes, only for certain strains. But last year, on one of my trips to the ER for my death flu, and resulting pneumonia, and 103 degree fever for 10 days, I got to see all the nurses and doctors treating me and saying \"we got the flu shot, it's for this flu, and we've been treating dozens of people for it this last month, and none of got sick. Why didn't you get the flu shot? It's free, you know.\" Decided I'll get the flu shot for now on.",
"They try to guess which strains are going to be most common in the upcoming year and immunise you against these.",
"Yeah, but those strains are somewhat yearly. The flu shot immunizes you against the strains that they're seeing that year. Next year they'll be different; that's why you have to get one every year.",
"Yes, the flu shot is only good for certain strains based on the past year research. They are often better than 50% but sometimes are lower. I believe two years ago it was only a 36% efficacy.",
"Yep! Sometimes multiple strains (i.e., the shot contains the material to make you immune to multiple strains). Think of different strains like different breeds of dog - all flu, but all different. Basically, what happens is that a bunch of people look at distributions of where different strains are common, and decide which they think will be the primary strains the following year. Once they figure this out, it's a race against time to figure out how to make the proper vaccine. This is why the flu shot comes out at different times each year. This is also why people talk about it being less effective some years - that means they 'missed' in their guess of which strains would be more common. Briefly, in case anyone was wondering - the reason that each vaccine only works against a single strain. Every cell basically has a label on it - your cells have labels that tell your other cells not to attack, etc. Your immune system then comes and reads these labels, and checks to see if each cell belongs there or if it should be killed. If the cell should be killed, your immune system then takes a bunch of time to prepare itself to attack. This time is a problem - it gives the chance for your flu to spread, which makes the fight much more painful and drawn out. The way vaccines work is they come in with some labels and tell your immune system 'watch out for things with this label', and your immune system gets ready in advance to fight that thing. That's why you sometimes feel a bit sick after a vaccine- your immune system is busy.",
"The flu is not exactly mutating constantly. Rather, it mutates frequently enough that we can expect a different selection of strains every year, but once those strains show up they tend to stick around for a while. It's not like I get sick, it mutates in me, and then you get a different version when I pass it to you. Rather, one strain will pass through our community this year a slightly different strain will pass through. In any given year there are a handful of strains that outbreak across the world. Researchers try to track the various strains as they move from country to country and try to predict which strains will be most common. Sometimes they pick the wrong strains, and sometimes one of the strains will have a mid-season mutation that causes a fork in the virus strains, both of which reduce the effectiveness of the virus. The standard flu shot contains the 4 most important predicted strains, though there are version of the flu shot with only 3 strains. In most years, the accuracy of the flu shot is about 60%, though sometimes it can vary. For instance, this year in Australia the accuracy was only about 10%, and researchers are watching carefully to see if this means the flu shot will be less effective in the Americas this year too. That being said, even if the flu shot is not accurate, you do get some cross-protection, and the flu shot is thought to make the flu milder if you do manage to catch it from another strain."
],
"score": [
111,
42,
16,
13,
6,
5,
3
],
"text_urls": [
[],
[],
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7imujp | Why does hot water make dish soap so intense and cold water make it all disappear? | Chemistry | explainlikeimfive | {
"a_id": [
"dr0gz17"
],
"text": [
"Hot air that is rising from hot water expands making more and bigger bubbles, this is aided by soap mixing with hot water more easily providing more soap to the waters surface. water colder than surrounding air makes little bubbles due to a greater pressure being pressed against water surface in addition to water having a low density of soap on the surface due to soap not mixing as well in unexcited cold water molecules. Honestly I'm just guessing tho."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7imyil | What does a "double mickey mouse" in the artery mean? | I went to the hospital for an injection and they did an ultrasound on my arm. They were checking my veins and arteries then the doctor pointed out I have a double mickey mouse in my artery which she said she hasn't seen in a very long time. What does this actually mean? | Biology | explainlikeimfive | {
"a_id": [
"dqzw74j",
"dr00716"
],
"text": [
"It's nothing scary or anything like that. When doing ultrasounds, a Mickey Mouse is a collection of veins and arteries that form the characteristic shape of Mickey's head and ears. A double Mickey is just two groups smooshed together, which doesn't happen often, and you have to get just the right angle to see it. The best example of the Mickey comes from the portal triad ( URL_1 , URL_0 )",
"Means the blood vessels look like Mickey Mouse. One makes up the face, one for one ear, and one for the other. Double Mickey Mouse means there are two Mickey Mouse patterns near each other."
],
"score": [
14,
3
],
"text_urls": [
[
"http://vetpacs.com/files/images/cs_MickeyMouse.jpg?width=500&height=434&iframe=true",
"https://i.pinimg.com/736x/55/42/4a/55424a53d0e3c82fc79c7901525dc06e--curved-arrow-the-portal.jpg"
],
[]
]
} | [
"url"
] | [
"url"
] |
7in2kr | How come units of area are squared? | Mathematics | explainlikeimfive | {
"a_id": [
"dqzwult",
"dqzwupc"
],
"text": [
"We create units by combing the units of the values used to calculate the value (e.g. speed is distance over time, so measured as metres per - divided by - seconds or miles per hour). Area is calculated by multiplying length and width (or any 2 dimensions). Length and width are measured in the same way, as distance, for example in meters. So to get the unit for area we multiply the unit of distance we want (metres, feet etc) by itself, so represent it as a square (m*m =m^2)",
"Because an area is the length multiplied by the width. For example, let's say you have a square that's 1 meter long and 1 meter wide. The area is 1 meter times 1 meter, 1*1 = 1, meter * meter = meter^2 so the area is 1 meter^2"
],
"score": [
7,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7in8kb | Why is it easier for snow to stay some places than others? | I live in Alabama and the rare times when it snows, it only really accumulates on grass and on top of cars. Driveways and roads are wet, but the snow never stays long. why is that? | Physics | explainlikeimfive | {
"a_id": [
"dqzy5e7",
"dqzy5xz"
],
"text": [
"They retain heat. It takes longer for them to cool to freezing. It only takes very little heat to melt a snowflake",
"The ground is too warm for the snow to stay as snow due to thermal mass. It will take a long time of sustained cold weather to make the ground cold enough for the snow to stick. A car is mainly just air inside so it will become close to the temperature of the air outside and the grass just elevates the snow off the ground keeping it colder than the ground."
],
"score": [
12,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
7inlmq | When something stressful happens, people are initially calm. Once the situation is passed, then stress sets in | Biology | explainlikeimfive | {
"a_id": [
"dr00qr5",
"dr00pmo"
],
"text": [
"Stress actually focuses you initially. Afterwards adrenaline is still in your body, which triggers other physiological reactions we normally associate with panic. Some people just react differently to the situation mentally.",
"As a survival mechanism, people are surprisingly good at staying focused during a serious emergency. Their emotions are temporarily suppressed so that they can act."
],
"score": [
12,
4
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7innhg | What makes full-motion video "full"? | I've seen the term "full-motion video" for a while. Why do we call it "full-motion"? Isn't it just "video"? | Technology | explainlikeimfive | {
"a_id": [
"dr010j1"
],
"text": [
"The term started in 1983, when most video game graphics were a fixed image (\"background\") with a little bit of moving stuff (\"sprites\") put in front of it. They really weren't full motion, so this was a contrast."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
7intl6 | How are fetal genetic abnormalities determined through the testing of the mother’s blood? | Doctors can test for chromosomal abnormalities and genetic disorders of a fetus. Yet it’s done by testing the mother’s blood, not the baby’s. How are they able to test the baby without getting a direct DNA sample from it? | Biology | explainlikeimfive | {
"a_id": [
"dr02c72",
"dr02c9r"
],
"text": [
"You're most likely referring to the quad test, a blood test done for pregnant mothers to screen for possible chromosomal abnormalities in the fetus. This is done by looking at the concentration of 4 different proteins in the mother's blood. Unusually high or low levels of these proteins have been shown to have a significantly high correlation with the baby being born with a chromosomal abnormality. One thing to be clear on is that there are two different types of tests in medicine: screening and diagnostic. This is a screening test, which means it is really good at being positive if there's a higher than normal chance of having a disease or problem. It in no way means that the condition is for sure present. In order to be more sure of the chances, a diagnostic test then needs to be done.",
"The mother's blood contains some dead placental cells, which are genetically connected with the fetus. URL_0"
],
"score": [
6,
3
],
"text_urls": [
[],
[
"https://www.reddit.com/r/explainlikeimfive/comments/74mcch/eli5_how_do_doctors_detect_down_syndrome_in/"
]
]
} | [
"url"
] | [
"url"
] |
7io1ic | What happens in the brain during different states of consciousness (sleep, coma, passed out, "unconscious" etc)? | I know that sleeping is basically a way for your body to repair itself, consolidate memories and all that fun stuff..... But what happens during those other periods of unconscious-ness (even though sleeping isn't technically being unconscious). What functions still remain during those states, and what parts of the brain are still active? What differentiates these states from each other? | Biology | explainlikeimfive | {
"a_id": [
"dr04vbw"
],
"text": [
"The brain never really shuts down any of its parts, no matter what. The only time parts stop working is if they're forced to stop working because they've been damaged. When you sleep or pass out, it's like a laptop where the screen saver got turned on after you didn't move the mouse or hit any keys for a few minutes. The whole computer is still on, but it hasn't gotten any input from the outside for a bit so it stopped showing anything on the screen other than the screensaver. Same with the body during sleep. You could say any dreams you have are like whatever you see on your screensaver. A coma is a different matter altogether. Comas are almost always caused by damage of some type. Here, the higher functions of the brain, like moving around, can be no longer possible. The lower level functions, or more basic things for survival like breathing, tend not to be lost as easily. They are controlled and kept going by the more ancient/primitive/basic parts of the brain, closer to the bottom of the skull and nearer to the spinal cord."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
7io2el | Why is email free to use? How do they make up the costs to running servers, staffing etc... | Technology | explainlikeimfive | {
"a_id": [
"dr04z0z",
"dr06a5y",
"dr046ud"
],
"text": [
"Modern webmail services aren't really free, they're ad-supported. It turns out that email isn't that expensive to run, and most of the companies giving you \"free\" email have other sources of income that they use to make most of their money, so they run the email to keep you tied in to the rest of their ecosystem and making them more money from serving you ads and you using their other products.",
"Email wasn't really free. In the past, your email was usually provided by your internet service provider so it was basically a part of your internet package. Webmail sites such as Hotmail only gave a small free mailbox (something like 10mb), but if you wanted something bigger you had to pay them. Google really revolutionized Webmail by giving you a whopping 1gb of storage for free. As in other Google services, Google made money from premium services and ads.",
"Once a person has email, they are then able to email all those e-businesses, and can order products over the internet, collectively generating countless billions of dollars in annual commerce. It pays to get people started on this for free. The fact that they can also email their friends and relatives to engage in inconsequential chatter does not really matter. Even then, their inconsequential chatter could include recommendations about commercial web-sites as well. Yes, I shopped at Amazon and I got exactly what I wanted! It was wonderful! Aside from that, your free email is not entirely free. You do have to subscribe to an internet service provider of some kind. Someone connects you to the internet, that is not free. That is where the money comes from, to pay for servers, staffing, etc."
],
"score": [
6,
4,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7io523 | How are beakers and graduated cylinders not affected by chemical reactions? | It seems like all chemical reactions can be contained in those Pyrex containers just fine without them melting/ dissolving. | Chemistry | explainlikeimfive | {
"a_id": [
"dr04tmo",
"dr0dxpr",
"dr0g8i3"
],
"text": [
"They are, if the reaction does stuff with the material it's made of. For example, hydroflouric acid will eat apart anything it's in if it's made of glass Meanwhile, flouroantimonic acid will straight up eat through more or less anything that isn't teflon, since teflon is held together with the strongest bonds in organic chemistry (Carbon-Flourine bonds) Edit: [Here's]( URL_0 ) an example of hydroflouric acid reacting with a regular glass container. Do not attempt this, the guy is doing this shit very, very unsafely. Edit: Flour to Fluor, flour acid isn't very dangerous",
"When you make an experiment, you usually plan ahead to make sure that the chemicals you are using don't react with your equipment. Beakers and graduated cylinders are made of material that is very strongly bonded to itself, making it hard to react with- you want to make sure it's much easier for the chemicals inside to react with each other than it is for the chemicals to dissolve your container. You have to use the right tool for the job- same reason why you don't store water in paper bags, or why your hammer doesn't break when you use it to hammer nails. Some examples of reactions/chemicals you don't put in beakers: -Hydrofluoric acid (so highly reactive it can dissolve glass, melt protective gloves, and will eat away at flesh so fast you don't even notice before losing a finger) -Thermite (so hot the glass breaks) -Pure alkali metals and water (it explodes)",
"Glass is pretty close to completely chemically inert. In other words, the molecular Bond is pretty stable, so you’d have to have a fair bit of energy involved to get anything to react with it. As many have said, there are some specific exceptions, but MOST things don’t react with glass, even when they’re reacting with each other, so it’s a pretty solid go-to material for chemistry, etc. Its also a pretty tight molecular structure, so it is not gas-permeable, unlike many plastics."
],
"score": [
46,
9,
4
],
"text_urls": [
[
"https://www.youtube.com/watch?v=Lf4vq2UU9hk"
],
[],
[]
]
} | [
"url"
] | [
"url"
] |
7io9ld | What prevents pain from coming back after pain killers wear off? | So when you take something like ibuprofen for a headache. It lasts for 8-12 hours (depending on the dosage). It blocks the pain receptors and you don’t feel the pain. But what prevents the pain from coming back? Does your body fix what ever was wrong? | Biology | explainlikeimfive | {
"a_id": [
"dr05vds",
"dr0627e"
],
"text": [
"If the pain doesn’t come back after the medicine wears off, it is because your body has healed itself. If the pain is still there, you notice when the medicine wears off and either take another dose or ride it out. Generally pain decreases over time, so by the time your medicine wears off, the pain may be lessened enough that you don’t need another dose. Source: Have had many painful injuries. Some long-term pain, some recovered quickly.",
"Over the counter painkillers just help you get through the period without pain until the body fixes itself. For a typical headache it works just fine because the body will most likely heal itself in 8-12 hours. But in chronic pain situations, the pain comes back after the painkillers wear off. Ankle sprains are a good example, the pain comes back after a few hours because the body cant fix sprains that quickly."
],
"score": [
9,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
7iocf6 | In the chess games between Google's AlphaZero and Stockfish 8, why is each game different? Why isn't each game just the same every time | Technology | explainlikeimfive | {
"a_id": [
"dr07d8s",
"dr079nk"
],
"text": [
"Ahoy, matey! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why a chess computer doesn't respond the same way every time to the same attack pattern. ]( URL_2 ) ^(_5 comments_) 1. [ELI5: Why does a computer use different openings when playing chess? ]( URL_0 ) ^(_7 comments_) 1. [ELI5: If I let two chess engines play each other 100 times, how do they play 100 different games if there must be one optimal game? ]( URL_1 ) ^(_10 comments_)",
"In the evolution of AlphaZero's and other AIs brains, they add a little bit of randomness into it, analogous to how humans and other species have adapted over the years, because some random mutation might facilitate reproduction and survival much better, so that feature becomes more pronounced over time. In the same way, until the game is completely solved, they continually add a little bit of randomness so that for example the program doesn't get caught in the same trap over and over again, whats called a local minimum."
],
"score": [
13,
12
],
"text_urls": [
[
"https://www.reddit.com/r/explainlikeimfive/comments/21qt18/eli5_why_does_a_computer_use_different_openings/",
"https://www.reddit.com/r/explainlikeimfive/comments/1ts924/eli5_if_i_let_two_chess_engines_play_each_other/",
"https://www.reddit.com/r/explainlikeimfive/comments/2v719l/eli5_why_a_chess_computer_doesnt_respond_the_same/"
],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iody6 | how pulse detection apps work | I have a heart rate monitor app on my phone which works pretty gosh darn well. I place my finger over my phone's camera and LED flash and it accurately measures my heart rate in real time. My nurse girlfriend has taken my actual pulse at the same time and it's always very close. So how does it work? | Technology | explainlikeimfive | {
"a_id": [
"dr0d6ys",
"dr0b0h8",
"dr11whq"
],
"text": [
"Try this: open the camera app on your phone and start recording video while turning the flashlight (LED lamp) on, and then press your finger on the camera lens. You will see a blurred image of your finger and if you look closer you'll see a slight pulse in the color. Thats your heart beating. It works because the flashlight will penetrate your skin and scatter all the way around in your finger including your artery, and some of the light getting back to the camera gets slightly dimmer when your heart pumps.",
"Basically, they shine a light through your skin, and then using the camera they measure changes in reflected light that can tell them how fast your heart is beating.",
"BTW heart rate monitors on smartwatches use the same principle. In this case, tiny green light emitters, and tiny light detectors. Why green light? Better contrast with the red blood pulses."
],
"score": [
25,
15,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
7iohto | When people say "there is more genetic variety within Africa than outside it" | Biology | explainlikeimfive | {
"a_id": [
"dr07sqi",
"dr0943b",
"dr0e2d7"
],
"text": [
"Modern humans evolved in Africa. A relatively small group of those humans left Africa and all non-African people are descended from that small group. So, the rest of us only got a small slice of that initial human gene pool. Look up the “founder effect” in genetics for more information",
"It depends on which two black African men, but yes. For every pair of non-African individuals in the world you can find a pair of Africans that are more genetically distant. Two Shona dudes you pull off the street in Harare will be more similar to each other than you and a Japanese man are, but the genetic distance between one of them and an Ashanti guy from Ghana or an Ethiopian or a San bushman may well be greater.",
"In addition to when different people groups split up, there is another level of diversity. Old populations have had more time for different recombinations of genes to come together, and the oldest populations of humans are all in Africa. There bas been more time for mutations to occur and for those mutations to be paired with other random genes."
],
"score": [
293,
112,
6
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ionfx | why do soccer fields look bigger when watching games in Europe then watching games in the US, even though (I think) they’re the same size? | Other | explainlikeimfive | {
"a_id": [
"dr0937d"
],
"text": [
"Europe’s stadiums are generally a lot bigger as well. For example, the Orlando Pride’s stadium seats 25,500. In Anfield, Liverpool the stadium seats 54,000. Wembley, London the stadium hold 86,000 to 87,000 for futbol matches."
],
"score": [
10
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7ionrz | How did early humans survive in cold weather before the invention of clothes? | Technology | explainlikeimfive | {
"a_id": [
"dr08t7m",
"dr08xrb",
"dr08vtc",
"dr0clut",
"dr0916t",
"dr0dh6p",
"dr0eygw",
"dr0frz2",
"dr0e1t5",
"dr0eoc4"
],
"text": [
"Humans originated in warm locations, and when it was cold, that was usually night when they were in their shelters anyway. Evidence supports the hypothesis that humans didn't move to icy-cold locations until *after* the invention of clothes.",
"According to the most widely-accepted theory, for most of the existence of our species we didn't live in areas that were cold. Homo sapiens evolved in central eastern Africa about 500,000 years ago, and remained only in Africa until about 150,000 years ago. There's also no particular reason to believe that early humans were unclothed. By definition all members of homo sapiens in the last half a million years have had the same capacity for intelligent thought and reasoning that we do, so it's entirely within possibility that when humans did start to migrate to colder parts of the planet they used animal skins and furs to keep themselves warm.",
"Before the invention of clothes (even in their most primitive form, which was basically just the scraped hide taken off an animal) people did not survive in cold weather; they evolved as tropical animals living in tropical climates.",
"Although the oldest fibers known are about 34,000 years old, the oldest jewelry is [74,000 years old]( URL_0 ) to [100,000 years ago]( URL_2 ). If humans were wearing jewelry, you can bet they were wearing clothes. [Humans didn't leave Africa]( URL_1 ) until 200,000~150,000 years ago and there weren't many really massive migrations until 60,000~50,000 years ago. We stayed put where is was warm for a very long time. So, by the time humans start to get into cooler areas, it's pretty clear we have clothing of some sort.",
"Humans evolved in warm/hot regions of Africa. They did not move into cold regions until after they invented clothing and harnessed the use of fire.",
"What people are saying about when humans left is true, modern humans started wear clothes about 170,000 years ago well before leaving Africa. However, other hominids were living outside of Africa and tools to take hide from animals show up about 780,000 years ago.",
"The first hominin species to move out of Africa was Homo erectus, around 1.6 million years ago. Fast forward a few hundred thousand years, Neanderthals came about in Europe. Their bodies were specially designed for cold weather, with short, stout stature, thick muscles, and large noses. There is evidence that they created clothing, but their bodies were very well adapted to cold climates as well which allowed them to survive the cold.",
"The first explorers to the tip of South America recorded that the natives there could make fire very quickly, only made crude shelters, and wore almost no clothing. I do not know how they did it but I trust the observations. A fire, sometimes two fires, can warm a person. People can stand a lot of cold without dying. I would definitely try to fashion clothing myself. [Despite the extremely cold climate in which they lived, early Yaghan wore little to no clothing until after their extended contact with Europeans.]( URL_0 ) They were able to survive the harsh climate because: They kept warm by huddling around small fires when they could, including in their boats to stay warm. The name of \"Tierra del Fuego\" (land of fire) was based on the many fires seen by passing European explorers. They made use of rock formations to shelter from the elements. They covered themselves in animal grease.[6] Over time, they had evolved significantly higher metabolisms than average humans, allowing them to generate more internal body heat.[7] Their natural resting position was a deep squatting position, which reduced their surface area and helped to conserve heat.[6]",
"Humans were not living in places that got that cold until well after they started wearing furs to protect themselves. At first pelts were likely worn to protect our skin from bushes and plants that we would brush against while running after prey.. or perhaps to help us \"blend in\" while hunting. They most certainly were not worn to help protect us from cold weather until we started living in colder places.",
"By avoiding that degree of cold. We weren't able to survive in those climates until some wise ancient humans started covering themselves with animal pelts"
],
"score": [
333,
77,
30,
23,
16,
14,
5,
5,
4,
3
],
"text_urls": [
[],
[],
[],
[
"http://news.bbc.co.uk/2/hi/science/nature/3629559.stm",
"https://www.sciencedaily.com/releases/2007/05/070509161829.htm",
"http://www.dailymail.co.uk/sciencetech/article-2990149/Did-Neanderthals-invent-BLING-World-s-oldest-jewellery-eagle-claws-worn-human-relatives-130-000-years-ago.html"
],
[],
[],
[],
[
"https://en.wikipedia.org/wiki/Yaghan_people"
],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ioo56 | How is it possible that when talking on the phone, person A can suddenly lose signal and not hear person B, but Person B can hear person A perfectly well? | Technology | explainlikeimfive | {
"a_id": [
"dr09cx9",
"dr09j2m",
"dr0dglo"
],
"text": [
"Modern communication systems use digital streams of data to connect calls. In most systems the signalling (setting up a call, putting it on hold, ending a call) is sent using SIP while the voice itself is sent in RTP (real time protocol) streams. The RTP streams are one way. So you have a dream from you to your destination and they have one back. It is possible that one of these streams gets disrupted, leading to one side hearing the call but the other not. Edit: I'm staying dreaming!",
"Transmitting and receiving are on different frequencies negotiated by the cell tower. Sometimes there will just be interference on the receiving channel, sometimes just the the transmitting, and sometimes both. If you are in a densely populated area, your signals may be even going to different towers. There are a lot of things that can go wrong.",
"Compare it to regular wifi: Have you ever noticed that you sometimes can detect wifi-networks with low signal strength but that you can never connect to? The wifi router usually has a much better antenna and transmitter, while your phone has a built-in much smaller one. So the wifi router is able to scream, but your phone can only whisper in response. In the cellphone case, the cell tower is the router. So person B can hear person A because the tower is able to transmit (scream) through the interference, but person A cannot hear person B, because B's phone cannot transmit back through the same interference. I.e. these kind of problems are usually only on one side of the call, between A and the tower, or between B and the tower (in this case between B and the tower). So if you are talking on the phone, and you can hear the other person well but he can't hear you, the problem is most probably on your side of the call."
],
"score": [
100,
23,
11
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ios8c | What is the exact purpose of a hunger strike? | Of course, it's passive resistance and protest but what is the sense behind it? For example with the ex-president of Georgia, Saakaschwili. If he dies, he dies. Why should the government he's protesting against stop him from killing himself if they have one enemy less after his death? Same applies to everyone who does hunger strikes: If they die, as hard as it sounds: So what? What does their strike achieve except that the party letting them die is indirectly guilty? And only indirectly, because they decide to possibly die? | Other | explainlikeimfive | {
"a_id": [
"dr0b6k3",
"dr0hrm5"
],
"text": [
"For example, let's say that you have captured a prisoner of war (POW) from an enemy you're at war with. The POW is your leverage, your way of getting something in return from the other country (could be prisoners of war that they have). You could potentially trade. The POW's have some value as long as they are high ranking enough. If that person dies, you lose the value. You can no longer use the POW in a trade. In other cases where the person is no prisoner of war, it is usually down to guilt and spoiling of public image. It reflects badly on a country if somebody is resorting to self starvation as a protest. They must really have a reason to do it. Also, each and every person does not want to have this guilt following them for the rest of their lives. They would rather not let the person kill themselves.",
"In civilised society, it is inhumane to let people die and the public will hate the state for allowing someone to die. This means that the state often has to cave into this persons demands or they will lose popularity. And in the example of POWs, they are valuable alive as negotiating tools."
],
"score": [
6,
5
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
7ip40t | If graphene is so great, why isn't it be used in anything? | Chemistry | explainlikeimfive | {
"a_id": [
"dr0cbxx",
"dr0dxz8",
"dr0ddlk",
"dr0dd9h",
"dr0e14u",
"dr0e5ct",
"dr0dvxp",
"dr0dhmb"
],
"text": [
"Graphene is a very new technology. Right now the benefits don't outweigh the costs of mass production, although iirc mass production of hybrid Li+/graphene supercapacitor batteries was announced this year (by Samsung I think, could be wrong). It usually takes 10-15 years for new materials and designs to go from academic labs to mass production. Even the transistor didn't enter consumer technology until about a decade after its invention.",
"I just did a term paper on this! To keep it simple: 1. At this point there does not exist a cost effective method to produce high quality graphene on a large scale. You can use Hummers method to make graphene oxide flakes, which is like a mid-level quality graphene. But flakes are too small of a \"sheet\" for some applications like solar cells. For bigger sheets you need to use chemical deposition, which is really expensive but can produce higher quality graphene. But this method doesn't scale up well. 2. Carbon nanotubes were discovered years ago. And they're just graphene sheet rolled up into cylindrical tubes so they have very similar properties as graphene and is already a more established technology. Edit: I noticed my response was kind of generic and similar to alot of other answers.",
"It took carbon fiber decades to hit the market. Now, you can't swing a dead cat without hitting something made out of it. It used to be that wonderful super material of the future.",
"Graphene is like most new super technologies It is absolutely amazing at everything *except making it out of a lab* Graphene is really good at a lot of things, but really expensive to manufacture. Until someone can come up with a good way to make tons of graphene cheaply it'll stay in the lab and other specialized(read high budget) applications",
"It's great, just not cost-effective right now. That's why you see all sorts of cool things in laboratories, but nothing has actually reached the store shelves yet. Kind of like solar panels; they are really nice in theory, but still very expensive and kinda hard to set up for the average consumer.",
"I hate these answers of 'cant make it out of the lab' If you don't know why its so expensive to produce then let someone else answer.",
"No one has found a way to mass produce high quality, usable graphene. It's great properties pretty much rest on being a perfect layer of carbon where all the atoms are oriented correctly and bonded to other carbons in a sp2 configuration, and there are no voids and everything is in a perfect surface.",
"In addition to being hard to manufacture, it and its close relative carbon nanotubes are sort of hot research topics now. Non-scientists think they sound cool but get very watered down explanations about them that can make it seem like they are a perfected technology. These topics get tons of research funding because of that though, because the people granting funding are not scientists, they are regular people who think things sound cool based on a little blurb summary about it. It's sort of like the average person doesn't see the whole picture."
],
"score": [
336,
47,
36,
15,
9,
6,
5,
3
],
"text_urls": [
[],
[],
[],
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ip59k | Why is there no measuring unit for darkness? | Physics | explainlikeimfive | {
"a_id": [
"dr0ce6y",
"dr0cdq7",
"dr0chxh",
"dr0cigs",
"dr0cntw"
],
"text": [
"Light is measured in lumens. The reason there is no measure of darkness is the same reason that there is no measure for shortness, or coldness...because there is already a measure for length and heat.",
"How do you measure cold? It's the same thing as heat, just less of it. Same with darkness. It's just a measurement of how *not* bright it is.",
"Because darkness is the absence of light. Total darkness is zero light. So instead of measuring darkness we would simply measure the light which is there and get a low to zero reading.",
"Same reason there's no measuring unit for cold: because darkness isn't its own thing. Darkness is, in physical terms, low levels of light. So to measure darkness, you'd use one of the units we have for light, most likely lux, and remember that lower numbers mean it's darker.",
"Measuring brightness and measuring darkness are both the same methods but happen in opposite directions, like the measuring of acidness or baseness happens in liquids with the pH scale which ranges between -1 and 14 (or so) where -1 is a high acidness and 14 is a high baseness. Measuring brightness gets done by measuring the amount of photons reflected. A white surface will reflect all photons, a dark surface will reflect nearly none. From Quora: > In terms of physics, an object is said to be dark when it absorbs photons, causing it to appear dim compared to other objects. For example, matte black paint does not reflect much visible light and appears dark, whereas white paint reflects lots of light and appears bright See also: URL_0"
],
"score": [
261,
90,
20,
9,
3
],
"text_urls": [
[],
[],
[],
[],
[
"https://en.wikipedia.org/wiki/Bortle_scale"
]
]
} | [
"url"
] | [
"url"
] |
|
7ip7sm | How is an ultra-sound tech able to calculate the weight of an unborn baby? | Technology | explainlikeimfive | {
"a_id": [
"dr0eojo",
"dr0d4q1"
],
"text": [
"Cardiac Sonographer here, with my little bit of experience in OB sonography I can tell you it's a calculation based on four measurements. Femur length (FL), head circumference (HC), abdominal circumference (AC), and the biparetal diameter (BPD) which all give you an estimated fetal weight (EFW). I don't remember the actual formula but there are calculators online to punch your info into to get your result. As with most measurements with height and weight (especially with children) there are standard deviations and percentiles Sonographer come up with based on an average bell curve.",
"They measure certain things and compare that to an average. Aka they take an educated guess."
],
"score": [
20,
15
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ip82l | How do we actually find out how old something is? Lets say the dinosaur skeleton or just a human body that we find in a glacier? | Biology | explainlikeimfive | {
"a_id": [
"dr0e7rx",
"dr0dib9"
],
"text": [
"Lots and lots of differing ways. The more of them that agree with each other, the more confidence we have. One of the more important general techniques is stratigraphy. Basically the ground is in layers (strata) and we can find unique things about them. So if we're digging a hole in spot A and we find a layer of soil that has a unique identifier, then we dig a hole in spot B and find the same identifier, it lets us know some relative dates for different soil layers at the different spots. Another general technique is radiometric dating. Whenever there are radioactive compounds in something, they slowly transform from one element into another. If we know (or have a really good guess) how much of the original element we started with, we can measure how much we have left to figure out how long that thing has been isolated. On shorter time frames, you can even use things like how fast gas diffuses through a solid material like volcanic glass, or what direction magnetic north was pointing the last time a rock was heated up. There are also loads of other techniques that are used, and all have various degrees of accuracy and confidence, which is why it's important to get dates from multiple different sources and compare them to see how reliable the information you're getting is. For archaeology, radiocarbon dating is pretty commonly used. For geology Uranium decomposing into Lead or Potassium to Argon are used a lot. The big difference being the time scale involved. Carbon dating isn't useful past about 60k years, but 60k years is a drop in the bucket when you're talking about geological processes.",
"Carbon dating. Using radioactive materials. What this means is eli5: Everything has some sort of substance that gives off an amount of carbon, and it only has so much, by figuring out how much is left in a skeleton or material, we can figure out how long it's been there as substances in the skeletons have \"half lives\" this is an amount of time it talk half of the substance to \"disappear\". From website: Formation of carbon-14 Carbon-14 (C14) or radiocarbon as it is often called, is a substance manufactured in the upper atmosphere by the action of cosmic rays. Ordinary nitrogen (N14) is converted into C14 as shown to the right. Ordinary carbon is carbon-12 (C12). We find it in carbon dioxide in the air we breathe (CO2), which of course is cycled by plants and animals throughout nature, so that your body, or the leaf of a tree, or even a piece of wooden furniture, contains carbon. When C14 has been formed, it behaves just like ordinary carbon (C12), combining with oxygen to give carbon dioxide (C14-O2), and also gets freely cycled through the cells of all plants and animals. The difference is this: once C14 has been formed, it begins to decay radioactively back to N14, at a rate of change which can be measured. If we take a sample of air, and measure how many C12 atoms there are for every C14 atom, this is called the C14/C12 ratio. Because C14 is so well ‘mixed up’ with the C12, we find that this ration is the same if we sample a leaf from a tree, or a part of your body. Think of it like a teaspoon of cocoa mixed into a cake dough—after a while, the ‘ratio’ of cocoa to flour particles would be roughly the same no matter which part of the cake you sampled. The fact that the C14 atoms are changing back to N14 doesn’t matter in a living thing—because it is constantly exchanging carbon with its surroundings, the ‘mixture’ will be the same as in the atmosphere and in all living things. As soon as it dies, however, the C14 atoms which decay are no longer replaced by new ones from outside, so the amount of C14 in that living thing gets smaller and smaller as time goes on. Another way of saying it is that the C14/C12 ration gets smaller. In other words, we have a ‘clock’ which starts ticking at the moment something dies. URL_0"
],
"score": [
6,
3
],
"text_urls": [
[],
[
"http://creation.mobi/carbon-14-dating-explained-in-everyday-terms"
]
]
} | [
"url"
] | [
"url"
] |
|
7ipb0w | Best angle of shots to minimize the splash damage when peeing into a toilet? | Physics | explainlikeimfive | {
"a_id": [
"dr0e81v",
"dr0esvo"
],
"text": [
"If you're worried about splashing/missing, just sit down. Seriously. Zero mess every time, even when drunk/just waking up. Aside from that, any of the walls of the bowl will angle your stream into the water.",
"As close to tangent as possible to the surface onto which you're urinating. Splash is normal force on the urine stream and this geometry minimizes it."
],
"score": [
5,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ipx06 | Why do older people have such problems with technology? | Technology | explainlikeimfive | {
"a_id": [
"dr0iu4l"
],
"text": [
"When you have spent decades becoming familiar with certain kinds of technology, and then it all changes, it can be hard to adapt. When I first learned how to use a telephone, I could use any telephone anywhere, since they all worked exactly the same way. Now every brand of telephone has its own particular operating procedures. I find that this makes the world very complicated. That is aside from the fact that some old people do become senile, and consequently have difficulty understanding anything. As you age, all organs of the body tend to wear out, and that definitely includes the brain."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7ipxvt | How do gorillas/chimps etc get so strong when the vast majority of the mass in their diet is fruit and vegetables? | Biology | explainlikeimfive | {
"a_id": [
"dr0iw3k",
"dr0iqzw",
"dr12tda",
"dr0iipf"
],
"text": [
"Genetics. Chimps have muscle that works differently to ours. It is complicated, but the simple version is that during our evolution, we sacrificed 'strong' muscle for very fine control over our muscles - it's what lets us be able to use tools so well. Chimps have great strength, but bad penmanship. Edit: Here's a [news article]( URL_0 ) about very strong children that touches on the genetics of muscle building.",
"Meat == Protein is a sort of myth; there's lots of protein in many types of vegetables. It's just not as easily accessible so you need to eat more of it. But the big thing is that apes spend a lot of their day actively foraging for food. You build up a lot of muscle doing that.",
"Chimps are stronger than humans for a few reasons but that wasn't your question. Your question is, how can they build muscle if they are herbivores, and this question would also apply to cows, hippos, rhinos, deer, sheep, giant pandas, and all other animals that eat primarily or exclusively plants. The answer is, proteins are made out of amino acids, and the metabolisms of these animals can synthesize amino acids, and thus proteins from the plant material they consume. Humans can also synthesize amino acids and proteins from plant material, but we can also take this in in it's presynthesized condensed form, meat, dairy, and eggs, and seem to do best with a little bit of animal protein in our diet. On the opposite end of the spectrum is the domestic house cat...in fact most feline species, who are \"obligate carnivores\". They are unable to synthesize certain essential amino acids from plants...for example, taurine, and must eat a diet containing animal protein with the proper amino acids. That being said, anyone who ever tells you they are feeding their cat a vegan diet should be reported to authorities or the cat will become very ill.",
"Yer not alone in askin', and kind strangers have explained: 1. [ELI5: How do vegetarian animals get the protein necessary to build and maintain muscle? ]( URL_1 ) ^(_5 comments_) 1. [ELI5: How do huge herbivores such as Elephants and Rhino's build muscle and mass without meat? What makes a human's body unable to grow similarly from just grass/leaves? ]( URL_3 ) ^(_32 comments_) 1. [ELI5: Why are gorillas so strong when all they eat are fruits and vegetables? ]( URL_7 ) ^(_38 comments_) 1. [ELI5:How can gorillas get so strong? ]( URL_6 ) ^(_4 comments_) 1. [ELI5: Why can horses and cows eat grass alone yet still pack on muscles while humans need more than just vegetables to bulk up? ]( URL_5 ) ^(_100 comments_) 1. [ELI5: how are cows and rabbits able to eat grass and turn it into muscle mass, but humans have to eat cows and rabbits to do the same thing? ]( URL_4 ) ^(_8 comments_) 1. [ELI5:How horses are vegetarian and can convert that into muscle but I need to eat meat to build muscle? ]( URL_0 ) ^(_8 comments_) 1. [ELI5: how can animals that subsist on food with virtually no protein -- such as cows, which eat grass -- build big strong muscles, yet humans must consume protein as an essential part of their diet. ]( URL_2 ) ^(_11 comments_)"
],
"score": [
29,
8,
4,
4
],
"text_urls": [
[
"http://abcnews.go.com/Health/MedicineCuttingEdge/story?id=7231487&page=1"
],
[],
[],
[
"https://www.reddit.com/r/explainlikeimfive/comments/2c8ynz/eli5how_horses_are_vegetarian_and_can_convert/",
"https://www.reddit.com/r/explainlikeimfive/comments/35lg09/eli5_how_do_vegetarian_animals_get_the_protein/",
"https://www.reddit.com/r/explainlikeimfive/comments/3zxos7/eli5_how_can_animals_that_subsist_on_food_with/",
"https://www.reddit.com/r/explainlikeimfive/comments/34w95e/eli5_how_do_huge_herbivores_such_as_elephants_and/",
"https://www.reddit.com/r/explainlikeimfive/comments/617zbk/eli5_how_are_cows_and_rabbits_able_to_eat_grass/",
"https://www.reddit.com/r/explainlikeimfive/comments/27ep7m/eli5_why_can_horses_and_cows_eat_grass_alone_yet/",
"https://www.reddit.com/r/explainlikeimfive/comments/3s9aec/eli5how_can_gorillas_get_so_strong/",
"https://www.reddit.com/r/explainlikeimfive/comments/1jp7hj/eli5_why_are_gorillas_so_strong_when_all_they_eat/"
]
]
} | [
"url"
] | [
"url"
] |
|
7iq337 | how come putting water on your face makes it dryer? | Or licking your lips makes them dryer | Biology | explainlikeimfive | {
"a_id": [
"dr0jr2z",
"dr0jvp2"
],
"text": [
"Your skin stays plastic due to oils in the outer layers; water can help strip those oils out of the skin, and then it all wipes off/evaporates. Same thing for licking your lips. Skin doesn't need water, it needs oil.",
"Yer not alone in askin', and kind strangers have explained: 1. [ELI5: why does water dry out skin instead of moisturizing it? ]( URL_5 ) ^(_5 comments_) 1. [ELI5: Why does consuming water hydrate your skin, but putting water frequently on your skin dry it out? ]( URL_3 ) ^(_9 comments_) 1. [ELI5: Why doesn't water help with dry skin? ]( URL_4 ) ^(_ > 100 comments_) 1. [Why does water cause skin to become drier as oppose to hydrating it? ]( URL_2 ) ^(_1 comment_) 1. [ELI5: Why doesn't water cure dry hands? ]( URL_0 ) ^(_23 comments_) 1. [ELI5: Why do I end up feeling dryer after having a shower than before? ]( URL_1 ) ^(_2 comments_)"
],
"score": [
11,
3
],
"text_urls": [
[],
[
"https://www.reddit.com/r/explainlikeimfive/comments/1xafd3/eli5_why_doesnt_water_cure_dry_hands/",
"https://www.reddit.com/r/explainlikeimfive/comments/39a74k/eli5_why_do_i_end_up_feeling_dryer_after_having_a/",
"https://www.reddit.com/r/explainlikeimfive/comments/1re6ui/why_does_water_cause_skin_to_become_drier_as/",
"https://www.reddit.com/r/explainlikeimfive/comments/3a60kk/eli5_why_does_consuming_water_hydrate_your_skin/",
"https://www.reddit.com/r/explainlikeimfive/comments/1tt92d/eli5_why_doesnt_water_help_with_dry_skin/",
"https://www.reddit.com/r/explainlikeimfive/comments/67zza4/eli5_why_does_water_dry_out_skin_instead_of/"
]
]
} | [
"url"
] | [
"url"
] |
7iq66u | How do cords get tangled? | Technology | explainlikeimfive | {
"a_id": [
"dr1440t"
],
"text": [
"This is actually something that physicists have studied. Long story short, wires, strings, and cords tend to fall into rest in loops and those loops, and the ends, tend to fall in to other loops easily when disturbed. But this is just the set up. When you come along and pick it up, if you pick it up in the wrong place, it's like pulling your shoe laces tight when you are tying your shoes. You have picked it up in a place such that you have pulled one loop through the other or one end through a loop. Unaware of what you have done, you start grasping other areas as you try to figure out this seemingly messy puzzle, ultimately making the situation worse. I've seen what I've known to be neatly coiled wires go from slightly tangled looking to actually tangled because the person picked them up in the wrong place and became \"disoriented\". The best away to avoid things coming tangled is to wrap them the right way to begin with and use ties to keep everything in place. URL_0 For the alternating coil wrap, pay attention and make sure you actually alternate or you will end up knotting it (yes, you can knot a cable without touching the ends). For christmas lights I recommend multiple ties because the lights will catch on other loops and can pull them through and catch on the other lights, causing a tangle, when you are handling them. When you go to uncoil things, make sure you are starting from the right end in the right orientation."
],
"score": [
3
],
"text_urls": [
[
"https://lifehacker.com/six-ways-to-wrap-your-cables-like-a-pro-1443520196"
]
]
} | [
"url"
] | [
"url"
] |
|
7iqdn2 | How come having the sun visible in your peripheral vision doesn’t permanently damage your vision? | Biology | explainlikeimfive | {
"a_id": [
"dr0p3z7",
"dr133ib"
],
"text": [
"The pupil of the eye is on the front, so you only get the most intense, direct light when you are looking directly at something. The further a source of light is from the center of your field of vision, the less of the light will get into your pupil and onto your retina. This will make it both appear less bright (so the sun doesn't dazzle as much when it is in your peripheral versus direct vision) and do less damage. That said, if you stood staring at one exact spot for long enough it very well could do damage. But we rarely do that, since our eyes are constantly darting around, especially when outside because there are usually a good number of visual stimuli.",
"Take a magnifying glass out into the sunlight and hold it so the sun strikes the lens at an angle. Nothing happens. The light isn't focused into a death ray, it just kind of passes through like normal because it's not coming in at an angle that the lens of the glass can focus to a point. Now turn the glass lens to face the sun and it's shape concentrates all of that light into a single little point of ant burning fury. The lens in your eye works similarly and the focal point on the back of your eye is small with the area around it going further and further out of focus the farther you get. This is one of the reasons why peripheral vision isn't very sharp and you have to stare at something and move your eyes over it, scanning, to pick up detail. If you stare directly at the sun though, your eyes lens is the magnifying glass, and your retina is the ant."
],
"score": [
15,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iqez2 | In a zero gravity environment, would a 10kg, solid metal sphere be more difficult to throw than, say, a baseball? And would it accelerate less given the same force behind the throw? | For the purposes of this, let’s also assume I’m somehow anchored in place and so none of the force of my throws would in any way push me backward. I know F=MA, so it seems like the math says yes, but I had a hard time wrapping my head around how two weightless objects could give more resistance in a throw. If acceleration is affected, would momentum and inertia be affected in the same way? | Physics | explainlikeimfive | {
"a_id": [
"dr0mald",
"dr0mf69",
"dr0mf51"
],
"text": [
"Although it *weighs* nothing, it still has just as much mass and inertia. Given the same amount of push, it will go more slowly. You can see this effect on Earth. Put two toy trains on a track. One weighs 300g. The other weights 300g plus a 5kg weight you've placed on it. Shove both equally. The heavy one doesn't move away as fast.",
"> I know F=MA, so it seems like the math says yes, but I had a hard time wrapping my head around how two weightless objects could give more resistance in a throw. Because the \"M\" refers to mass, not weight. They are weightless but they sure as heck aren't massless. If they were, they'd be zinging away at the speed of light.",
"They are weightless but not massless, they still have resistance to motion Think of it like something floating in water. The weight is now effectively cancelled out and there is basically no static friction. Consider pushing a small plastic boat, you can push it easily and a light force can accelerate it quickly. Consider pushing a battleship, it would take a much larger force to result in any motion at all because you need to accelerate 100 million pounds of steel Inertia is what causes acceleration to be effected, inertia is a property of mass. This increased mass/inertia causes the increase in force/momentum to achieve the same speed."
],
"score": [
17,
5,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
7iqipj | Why do bladeless fans have a large open space in the middle? | I looked how they work up and it seems to me like it's wasted space and a small one with equal circumference would work just as well, of any shape. | Technology | explainlikeimfive | {
"a_id": [
"dr0n6va"
],
"text": [
"These fans work by directing high pressure air into a ring. The high pressure air drags the air that's in the ring forward with it. Conservation of momentum gives a larger amount of air moving more slowly (and thereby quietly). A smaller one wouldn't accelerate as much air, so it would be a small amount of air moving faster. This would cause more noise."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
7iqo71 | Why does yawning limit our hearing so much? | Biology | explainlikeimfive | {
"a_id": [
"dr0q5gz",
"dr0zl12"
],
"text": [
"it opens a tiny valve in the inner ear. the flap's primary purpose is to allow ambient pressure to equalize with the outside world. when it's open (yawning tends to open it), the vibrations in that pocket get messed up.",
"Yer not alone in askin', and kind strangers have explained: 1. [Why does our hearing get suppressed during a yawn? ]( URL_1 ) ^(_5 comments_) 1. [ELI5: Why does yawning temporarily block or alter your hearing? ]( URL_2 ) ^(_22 comments_) 1. [ELI5: Why is hearing reduced when you yawn? ]( URL_3 ) ^(_ > 100 comments_) 1. [ELI5: How/Why does yawning affect our ears? ]( URL_0 ) ^(_11 comments_)"
],
"score": [
10,
6
],
"text_urls": [
[],
[
"https://www.reddit.com/r/explainlikeimfive/comments/74jw3i/eli5_howwhy_does_yawning_affect_our_ears/",
"https://www.reddit.com/r/NoStupidQuestions/comments/7f8vf2/why_does_our_hearing_get_suppressed_during_a_yawn/",
"https://www.reddit.com/r/explainlikeimfive/comments/5fvet6/eli5_why_does_yawning_temporarily_block_or_alter/",
"https://www.reddit.com/r/explainlikeimfive/comments/3uckp8/eli5_why_is_hearing_reduced_when_you_yawn/"
]
]
} | [
"url"
] | [
"url"
] |
|
7iqpf1 | Why do we care about the national debt? | Economics | explainlikeimfive | {
"a_id": [
"dr0os0c",
"dr0ooez"
],
"text": [
"The thing is that there's absolutely no reason to not be in debt. We constantly pay it back and get more. When people talk about raising the debt ceiling, that means paying back what we borrowed. So that's not an issue, we do it every year just fine. But another reason is because except for about a year in the 1800s, the US has continuously held a debt since its founding. (We had to pay back countries that helped finance the revolution.) So everything in this country's history has been done while in debt. Clearly, it's not an issue, or that would not be the case.",
"Well, it's complicated. For one, you must understand the debt is less like the shackles that grip, say, a struggling neighbor, but more of a tool, manipulated in order to meet economic goals. The amount of debt, for instance, is linked to the supply of US dollars. When the Fed decides it wants more money in the economy, it buys debt from people (well, private banks) for dollars (which it poofs from nowhere; that's the fed's responsibility). When the fed decides the economy is growing too quickly and it needs to slow it down, we need less money in the economy, it sells debt. Since the fed can create any amount of money, when you pay the fed it effectively disappears."
],
"score": [
3,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iqqi7 | Freshman here- why wouldn’t everybody apply to as many colleges as possible? | Other | explainlikeimfive | {
"a_id": [
"dr0opzh",
"dr0pah3",
"dr0opim",
"dr0osgc",
"dr0p3j2",
"dr0p2d2"
],
"text": [
"> Freshman here- why wouldn’t everybody apply to as many colleges as possible? Time and effort. Also, application fees upwards of $100 of dollars for higher valued colleges.",
"It would cost money, and what would you get for it? If 20 places admit you out of the 50 applications you send in, are you seriously interested in all of them equally? Once you have a couple where you have very good chances, the only reason to apply to more than 1-2 of your favorites is to make your parents happy that you applied to their alma maters.",
"Some colleges and most universities have an application fee. It just seems more feasible to apply to a community college, get the basics done, then transfer out. source: college student",
"Cost. Applications range from $60 to $90, with most being 70-80ish. So there's a practical limit. Back in my day, which wasn't that long ago, most people I know (me included) applied to 10-15 colleges (hurrah for the common app). 15 colleges, with an average of $75, is $1,125 spent on applications. Ouch! Of course, I came from a higher income area. Some families definitely couldn't justify spending a thousand dollars. How many colleges would you have wanted us to apply to, ha?",
"why would you do that? why not just find a college that you want to go to and apply there. maybe apply to a backup too if your application isn't very strong of the school is very selective.",
"Colleges know that they'd be spammed with shitty application if they didn't charge application fees so the application fees are enough to discourage this. When you take the SATs, you only get to send scores to 3 schools for free. Each additional school costs $10. It also takes time to fill out an application. Many schools require you to write an essay on a particular topic. Beyond that, what benefit do you get to applying to as many schools as possible? Most students know about where they stand in terms of getting into a school or not. They'll apply to a good state school, a \"safety\" state school and one or two \"dream\" schools to see if they get lucky with financial aid."
],
"score": [
22,
5,
4,
4,
3,
3
],
"text_urls": [
[],
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iqtew | How does glass shatter when run under super hot water or in a dishwasher? | Chemistry | explainlikeimfive | {
"a_id": [
"dr0phzr"
],
"text": [
"When things heat up, they expand. This is true for most types of glass†. When you heat something up unevenly, the heat can bend/warp it. Glass no likey bending. The resulting stress can cause the glass to break. † Yes, they make special borosilicate glass with very low coefficient of thermal expansion, but I presume the OP is talking about ordinary glass."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iqvgz | Why is plant protein less bioavalible than animal protein? | People keep saying that animal protein is more "bioavalible," but isn't an amino acid an amino acid? | Biology | explainlikeimfive | {
"a_id": [
"dr0rhgv",
"dr0t85u"
],
"text": [
"Plant cells contain more soluble fiber, which has been shown to reduce how much protein and other macromolecules we can digest for reasons not completely understood.",
"> isn't an amino acid an amino acid? Yes. But most amino acids in meat or vegetables are not present as individual amino acids. They are assembled into proteins. Your body has special things called proteases that break down proteins into amino acids. Different proteins are different shapes. Proteases like to break down some protein shapes more than others. They are good at breaking down protein shapes found in meat, and not as good at breaking down protein shapes found in plants. So the protein in meat is easier to break down into amino acids. It is more available for your cells to make use of. It is more 'bioavailable'."
],
"score": [
7,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
7iqxs5 | What's the deal with the clothing brand Supreme? | Other | explainlikeimfive | {
"a_id": [
"dr0r844"
],
"text": [
"The brand sells its shirts in limited amounts, which causes people to feel like that product is \"special\" because of the small amount. This coupled with celebrities often wearing the brand has created a huge subculture around spending insane amounts of money on lazy streetwear. Tldr they restrict the market to create a false sense of uniquity"
],
"score": [
7
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7ir2up | How long does it take from the slaughtering a cow, to me being able to pick up the meat at my supermarket? Also, what exactly goes on during that time? | Economics | explainlikeimfive | {
"a_id": [
"dr0twjh"
],
"text": [
"the cow is humanely transported to the slaughterhouse from the farm, stunned so that it does not feel any pain when it is bled out, and then eviscerated. It takes about 36 hours for a bovine carcass to reach 4 degrees celcius or below (this is considered to be a safe temp). After that it is further processed into different products. Side note: a cow is a female bovine which has given birth. A heifer is a female bovine which has not given birth. A bull is a male bovine which has not been castrated and a steer is a male bull which has been castrated. The 36 hr cool down time is the rule of thumb for all genders of bovine."
],
"score": [
14
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7ir3lb | How does your body produce blood? | Biology | explainlikeimfive | {
"a_id": [
"dr0s81u",
"dr0sxrf"
],
"text": [
"Blood is composed of several components, each produced in/arising from various places. The bone marrow is responsible for the production of most blood cells including platelets and red & white blood cells (although some white blood cells, such as T cells, will mature in the thymus). Plasma (the liquid) is simply made up of the water and salts absorbed from the digestive tract. Hundreds of soluble proteins are also found within the blood which can be produced from almost any organ or tissue! The process of blood cell production is called haematopoiesis, where progenitor (stem cells) specialise into the various types of red and white cells.",
"You have special cells inside your bones that divide into new red and white blood cells. The liquid comes from water you drink/eat. The colour comes from iron inside your red blood cells."
],
"score": [
15,
5
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7irbol | How does half-life work in radioactive decay? Why does how much is left effect how fast the rest disappears? | Physics | explainlikeimfive | {
"a_id": [
"dr0u67d"
],
"text": [
"The amount doesn't affect the rate of decay, the rate of decay is constant. To illustrate, imagine you have 1024 quarters. Every hour you flip them all. Any that are tails you remove from your pile of quarters. On average, after the first hour you'll remove half, or 512. Then the next hour you'll remove half again, or 256. And so on, removing 128, 64, 32, 16, 8, 4, 2, 1, leaving you with 1 that has a 50% chance of being removed any given hour. This is analgous to a substance with a half life of 1 hour. But these are just averages. In reality radioactive atoms have a fixed chance of decaying at any moment."
],
"score": [
9
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7irlsn | Why is Eggnog not sold year round? | Other | explainlikeimfive | {
"a_id": [
"dr0w5w8"
],
"text": [
"Because sales drop outside of Christmas time. If more people wanted it, it would be sold all the time. If you like it a lot, [try making it yourself]( URL_0 )."
],
"score": [
3
],
"text_urls": [
[
"http://www.taste.com.au/recipes/eggnog/73e4cf93-dd1b-43d4-b86b-7bb6196a4d55"
]
]
} | [
"url"
] | [
"url"
] |
|
7iro4t | Why does massages relieve body ache when it adds pressure to the already sore muscle or joint? | Biology | explainlikeimfive | {
"a_id": [
"dr0xzvb",
"dr12z7v"
],
"text": [
"My wife is a massage therapist. Massage helps improve blood flow to the muscles. The improved blood flow helps the muscles recover faster. Not all massage pressure is the same either. When a muscle is tight or sore she has to apply very little pressure or it causes a lot of pain. On that same note if the muscle feels fine she can do some pretty aggressive deep tissue work with little to no pain.",
"One theory is that lactic acid builds up in muscles making them sore; squeezing these muscles is like squeezing the lactic acid out of spongy muscle and letting it be absorbed and processed naturally by the body, this is why you are sore after a massage but then feel better in 1-2 days"
],
"score": [
7,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iruye | How do creams that you put on your skin help muscles? | Don’t know the right flair to use | Biology | explainlikeimfive | {
"a_id": [
"dr0yh5c",
"dr1014s"
],
"text": [
"Chemicals in the cream react with chemicals in your skin. This reaction generates heat. The heat helps your muscles to relax, and it makes you feel good.",
"If you're talking about muscle rubs, they usually contain analgesics (aka pain relievers) that can be absorbed through the skin and therefore only act in that area rather than spread all over the body. These typically are menthol or capsaicin. IcyHot, for instance, is menthol."
],
"score": [
11,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
7irvgz | How can the FCC force a vote? | Other | explainlikeimfive | {
"a_id": [
"dr0yfdy"
],
"text": [
"Not sure I follow the question. The FCC is an independent agency created by Congress. There are five commissioners and one of the commissioners is selected by the president to be the chairman. The chairman controls the agenda and decides what the commission votes on. He can \"force\" an FCC vote on just about anything he wants. The current FCC chairman, Ajit Pai, opposes net neutrality. So he's going to hold a vote in a few days to repeal regulations that were put in place by the previous FCC chairman during the Obama administration. Does that answer the question?"
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7is00v | Why do some people have sparkling eyes (in contrast to "blank" inexpressive eyes)? | Other | explainlikeimfive | {
"a_id": [
"dr100rr",
"dr191x9"
],
"text": [
"I'm pretty sure this is just the lighting / angle at the time. Also, some people are active in their facial expressions, and so their eyes are more open over someone who is passive / perpetually laid back, so they may not be opening their eyes as much as someone who is outgoing or excited. Finally some other factors could be glasses reflections, contacts, touched photos, camera filters, etc. etc. I think generally it's what I said about being passive/active, which determines more exposure to 'opportunities' that could result in an eye sparkle or glint.",
"Aside from some rare medical conditions it's just you reading their body language. If you subconsciously notice someone looks tired, indifferent etc but you can't quite grasp what it is you are likely to think their stare is \"blank\"."
],
"score": [
8,
4
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7is5h3 | Why are humans the only species that communicate using words? Are there other animals that have the capability to create/form words? | Biology | explainlikeimfive | {
"a_id": [
"dr114hr",
"dr16ex3"
],
"text": [
"Our vocal cords are pretty good at creating complex sounds (not to say that other animals don't). Other animals communicate using sounds that act as words and if you think about it there really are no \"words\" because we created the concepts of words, we are also just making random sounds that mean something. Besides that point as far as I know it could easily be attributed to the fact that animals making understood sounds come down to basic calls, for example mating calls and S.O.S. calls to name a few. As humans evolved our brains developed past the point of basically every surrounding animal, and with that we created new sounds to communicate more complex things. It could also be attributed to early humans explaining knowledge to the youth by trying to tell them what they mean when they say certain things, basically they were just passing down information that eventually could have morphed into full language.",
"Other animals have the ability to communicate, and there are some that have \"words\", in the sense that they have very specific calls that convey very specific messages. The usual go-to example is the vervet monkey, which has different alarm calls for different types of predator. That way, when a monkey gives an alarm call, the rest of the group know whether to climb a tree, duck and cover, stand on their hind legs and scan the ground for snakes, or whatever. There are even cases of vervet monkeys telling \"lies\" (and eventually the rest of the group learns to ignore them). That's still a long way off human language, though. There are certain things that characterize human language and which are probably unique to us: 1. Animals can only really talk about things that are *here* and *now*: \"There is danger,\" \"I am hungry,\" \"It is safe to sleep,\" \"Are there any females out there looking for a good time because right now I'm horny,\" that kind of thing. We have the ability to talk about things that are removed from us in space and in time: \"Yesterday, about fifty miles in that direction...\" Bees appear to be able to tell their fellow bees exactly where to find good sources of nectar, but AFAIK that's the only non-human example we've found. 2. Animals have only a very small range of sounds and gestures (which also belong to language) for a very small range of possible messages, and they can't combine those sounds and gestures to invent new messages. Human language also has a small range of symbols, but these can be combined as desired to communicate messages that have never been communicated before, and those messages will be understood. You can be nearly 100% certain that no human being has ever spoken or written this paragraph, and yet you have no trouble understanding it. It has been claimed that some primates may be able to do these things. The most famous is Koko the gorilla, who has been taught American Sign Language. The researchers who are studying her claim that she can talk about things in the past (in one case blaming her pet kitten for smashing up the sink in her compound) and that she can invent new phrases (e.g. signing \"dirty bad toilet\" as an insult). However, other scientists are very skeptical of these claims, saying that her signs are so badly executed that they could mean almost anything -- that is, they're suggesting that Koko's researchers are reading things into her gestures that aren't actually there. Also, Koko only ever reacts when somebody communicates with her: she never initiates a conversation or asks a question. This makes some researchers think this is little more than a highly sophisticated party trick. Aside from Koko and a few other similar cases, which are similarly controversial, it really does seem as if our linguistic ability is unique. We are the only animals to have evolved the ability to learn this kind of communication system. Why? Well, I don't think anyone really knows. But it is true that we are not the strongest or fastest species on the planet. What gives us a huge advantage is our ability to share large amounts of information and plan ahead, and to form new and innovative plans and communicate them unmistakably. Wolves cannot say to each other, \"Look, I think we've been doing this all wrong -- we need to think of a better way to hunt. Does anyone have any ideas?\" We, however, do it all the time."
],
"score": [
7,
6
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7isfdu | How did we come up with the asteroid theory for dinosaur extinction? | ELI5 | Other | explainlikeimfive | {
"a_id": [
"dr12pcs",
"dr145hi"
],
"text": [
"It's not the only theory but it's the one best explained by all the evidence. First, there's the 150km wide impact crater off the Yucatan peninsula. It was created by a roughly 10km wide asteroid impacting at 30+km/s and it's been date to 65 million years ago which is exactly when the dinosaurs became extinct. We know how catastrophic an impact like that would be so it already makes sense as the cause of the extinction. There's also evidence of a large impact besides the crater such as ejecta layers in the rock, shock formations in the rock, melted rock from the molten impact site, and the high presence of certain rare elements that are only found in asteroids or deep within the Earth. This is all exactly what you'd expect to find in rock layers from the same time period, and there's a lack of evidence for other explanations. The fossil record also indicates a sudden, catastrophic die-off rather than a slow decline in the number of fossils, which is what you'd expect from a sudden mass-extinction event.",
"Say that you find a dead body and you try to figure out what killed them. You examine the person and find a wound. You can look at the shape of the wound, and you can poke around inside the wound looking for any foreign material. You find small shards of glass, leading to the conclusion that glass was the murder weapon. You have a mystery, you gather evidence, and you form a conclusion that can explain all the facts. When scientists began finding fossil relics, they found that the age of the rock that the fossils were embedded in could tell you when those animals walked the Earth. It's a misconception that the oldest rocks are the deepest, because rock formations are displaced all of the time, and weathering and uplift, and many other geologic processes can sometimes bring old rock to the surface. But even before radio carbon dating, scientists could look at other things in the rock, seeds, plants, even pollen and insects, and get a general idea of how old the rock was. Well they found that dinosaur fossils tended to be located in rock layers that were millions of years old, however [at a certain point]( URL_0 ), those fossils just stopped. In newer rock they found only smaller animal fossils like rodents and such, and in older rock they had megafauna like dinosaurs. So they could pretty much look at a layer of rock, and pinpoint the layer of rock between living dinosaurs, and dead dinosaurs. And much like finding those glass shards in the murder victim, they looked at what was inside these rock layers. They found some odd things. There were beads of glass there and glass usually forms in volcanic events and meteor impacts. They also found layers of rock that seemed to be made of ash. The final nail in the coffin of \"What killed the dinosaurs\" was a chemical analysis of the rock found large amounts of an element that is relatively rare on Earth, but common in asteroids; [Iridium.]( URL_1 ) This iridium dust was present in rocks all over the planet that were from that time period. So some how a rare element, mostly found in asteroids, managed to cover the entire earth in ash, all at the same time. Before this event you had dinosaurs and after the event you didn't. The only thing they couldn't figure out was where was the crater? Surely something that big, that catastrophic left a crater behind right? And it turned out there [was a crater]( URL_2 ), but that it was so large, we didn't even know we were looking at it. The crater was partially under water, and it was so large that you can't see it all at once because of the horizon; we didn't see it for a very long time."
],
"score": [
8,
5
],
"text_urls": [
[],
[
"https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_boundary",
"http://www.pbs.org/wgbh/evolution/extinction/dinosaurs/asteroid.html",
"https://en.wikipedia.org/wiki/Chicxulub_crater"
]
]
} | [
"url"
] | [
"url"
] |
7ish8t | why do eyes roll back when people die? Or is that made up? | Biology | explainlikeimfive | {
"a_id": [
"dr12x80",
"dr12xrl"
],
"text": [
"It's fiction. When a person dies, their eyes stay fixed where they were at the moment of death.",
"They may or may not roll back when a person dies. I think it might depend on whether or not the person attempts to close their eyes. When we close our eyes, they roll back. It's called Bell's Phenomena."
],
"score": [
6,
5
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iso0a | How come you have that break in your voice that separates falsetto and normal voice? | Biology | explainlikeimfive | {
"a_id": [
"dr1lp83",
"dr1olhv",
"dr1wzm9"
],
"text": [
"I think I have the answer. When you are singing out of your falsetto, you are not using your diaphram as much as normal. This is also the reason why non vocally trained peoples voices crack when switching from falsetto to normal. There is a term that some singers use called chest and head voice. Your head voice is your falsetto, and your chest is your normal voice. tl;dr its because your using different parts of your body",
"Falsetto just vibrates the edges of your vocal cords, regular sound production vibrates the whole thing. When you really stretch out those vocal cords, they can still vibrate the edges even though there’s too much tension to vibrate the whole thing, producing higher frequencies, but with less volume. The “break” is whether the vocal cord body is vibrating or not.",
"That break is very much like hearing your vocal chords hammer onto a new fret, or hearing an engine rev while it switches gears. On a guitar, there are two ways to change the pitch of a string. The normal way to change pitch during music production is to change fret. This changes the effective *length* of the string. Shorter effective length produces a higher pitch. The unusual way to change pitch, which usually happens between periods of music production, is to turn the tuning keys. This smoothly changes the effective *tightness* of the string. You could re-tune a guitar to play in a slightly lower key, or just match whatever tuning standard is useful at the moment. Vocally, we have similar methods for changing pitch, but we use them in the opposite way. The normal way to change pitch during vocal production is to smoothly adjust muscle tension, which changes the effective tightness of the chords. The unusual way to change pitch, which doesn't produce a smooth sound, is similar to changing fret. Actually, it's changing harmonic. Think of that guitar again and, instead of pressing down between frets, just lightly touch the very center of a string. This also changes the effective length of the string -- you effectively have two half-length strings. The pitch pops up a full octave. When you pop up to falsetto, you're shifting between harmonics while dialing way down on tension. This is similar to shifting gears on a car. The tension-to-pitch ratio changes are similar to a car's power-to-speed ratio. All of a sudden, the same input produces a significantly different output. So, your voice must either fall silent or crack. There's your break. The transition between two sets of harmonics are significant. Vroom vroom."
],
"score": [
19,
8,
4
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7isoym | Why did the 1892 Populist Party in the United States demand inflation through free and unlimited coinage of silver (what was its benefits)? | Economics | explainlikeimfive | {
"a_id": [
"dr14nt4",
"dr14osi"
],
"text": [
"It wasn't inflation. You had uncoined silver that turned into coined silver. The uncoined silver already had purchasing power before it was coined. It is like the government purchased the silver, reducing the money supply and then increase the money supply by the same amount.",
"Because they were in debt. Inflation would lower the value of what they owe in real terms so it would be easier for them to pay off the debt (they'd still owe $100, but if $100 is worth baking 10 hours of labor, it's easier to pay off than if $100 was worth 100 hours of labor)"
],
"score": [
3,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7isy5r | And non-american by the way,how did New York City get so populated compared to other US cities and why does it stay so populated ? | Economics | explainlikeimfive | {
"a_id": [
"dr1660t"
],
"text": [
"It was the main trans-Atlantic shipping destination between Britain and its New World colonies, so it built up wealth and population more quickly than the other colonial cities in the 18th century. Even after the Revolutionary War, it remained the dominant entrypoint to European commerce and immigration and just continued to grow. Things just snowballed from that. Because it already had so much money and people, it was an attractive place for even more money and people. The surrounding region became a major industrial hub and accelerated the process. It was also the financial hub for funding business ventures further into the interior of the country. As to why it's so much more densely-populated than other parts of the country, it's because (a)it's an island that was already filled up a long time ago, and (b)its core was designed and built at a time before powered transportation, so cities in general were usually denser. While most of the country's older cities spread out with the automobile, and only small urban cores remained dense, New York was already so dense and geographically confined that it was more practical to just keep building higher. As to why people stay there, it has a unique, rich, and widely diverse culture that changes from one neighborhood to the next, and never lacks for surprises if you can afford to live there."
],
"score": [
9
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7isyix | How can a film that grosses higher profits than the budget it took to make it still sometimes be considered a financial flop? | Economics | explainlikeimfive | {
"a_id": [
"dr1647r",
"dr16gv6"
],
"text": [
"In addition to the money to make the film, there are substantial costs to distribute and promote it. A film generally needs to gross double its production budget to be considered a great financial success. But often, as you suggest, high expectations can result in a near-or-moderately successful film being considered a flop.",
"> How can a film that grosses higher profits than the budget it took to make it still sometimes be considered a financial flop? There are a lot of other things you can do with money. If you have $20 million sitting around you can invest it in a variety of things, not just movies. If for example I could invest it in a fast food chain and get a better return on my investment than making a movie, even if it is profitable, then it was a financial failure. I lost money compared to if I did the fast food thing."
],
"score": [
4,
4
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7it1yq | Why can't some functions be integrated? | Why can't some functions be integrated? For example, my friend told me to evaluate Integral sin( x^2 ) without limits but it was impossible to do it... I've tried to use integration by substitution but to no avail. I've looked online and people said stuff about elementary functions(?) and that the integral can only found within limits(?) send help plis? danku < 3 | Mathematics | explainlikeimfive | {
"a_id": [
"dr17kxe",
"dr17w9b"
],
"text": [
"These functions can be integrated as well, but we can't write that integral down as a closed-form expression. For some functions (such as sin(x^(2))), we can only express the integral with the integral notation, but that integral exists nontheless.",
"The Riemann integral is defined like this: Take the domain of integration (which is a subset of the real line), and partition it into intervals. Pick a point x_i in each interval Then on each interval, draw a rectangle with height f(x_i), and compute the total area. This is called a Riemann sum, and when graphed it looks like [this]( URL_0 ). If you partition the domain into smaller and smaller integrals, the area of these rectangles should tend to the same value (which is the integral), and this value shouldn't depend on the specific choice of intervals or the points x_i. If this is the case, then the function is Riemann integrable. An example of a function which is not Riemann integrable is the function f(x) which is equal to 1 if x is rational and 0 otherwise. If you try to compute Riemann sums of this, you'll find that in *any* interval, no matter how small, you can find a point x_i such that f(x) is 1, and another point such that f(x) is 0. Therefore you can construct two sequences of Riemann sums, one that tends to 0 and one that tends to 1 - so this function is not Riemann integrable (it is however Lebesque integrable and the Lebesque integral is 0). It can be shown that all piecewise continous functions are Riemann integrable (including f(x)=sin(x^2 ))."
],
"score": [
9,
6
],
"text_urls": [
[],
[
"https://en.wikipedia.org/wiki/Riemann_integral#/media/File:Riemann_integral_irregular.gif"
]
]
} | [
"url"
] | [
"url"
] |
7it7bb | why do milk alternatives [soy almond etc] get called milk and not *name* water? | Other | explainlikeimfive | {
"a_id": [
"dr17jap",
"dr18d1q"
],
"text": [
"Because they are white in color, and often used as a milk alternative. If they were clear they would be called waters or juices.",
"[Almond milk]( URL_0 ) is pretty ancient. I've linked to a 14th C source but I think there are recipes for almond milk going back to the Romans. Milk does not refer to something that comes from a cow or a goat, it also refers to a consistency - such as a \"milky\" glass - or color - such as the \"milky\" way. It can also refer to an action; ie, \"S/he's milking him/her for all s/he's worth!\" Using the term milk for Almond milk - the oldest of the alternatives- could have come about for any of these three reasons. It could be because of the color, the consistency, or because to get almond milk, you need to put all the smashed up, ground up, blanched almonds in a mesh bag and slowly pour water through the bag, \"milking\" it. Almond milk itself is a 1 to 1 alternative for regular cow's milk. It has the same fat content which makes it excellent for baking and cooking."
],
"score": [
8,
6
],
"text_urls": [
[],
[
"http://medievalcookery.com/search/display.html?forme:86:ALMNT+MLK"
]
]
} | [
"url"
] | [
"url"
] |
|
7itcpl | Why do things creak when you moved/touched it after not touching/moving it for a long time? | i have not touched my computer monitor for more than a week and when i decide to adjust it, it creaked. I adjusted it 10mins later and the creaking sound was gone. This only happens if i never adjust my monitor screen for more than a week. | Other | explainlikeimfive | {
"a_id": [
"dr18xx6"
],
"text": [
"QUite certain its from a mixture of the weight slowly pushing down to a minimal resting position, along with the materials constantly changing volume based on temperature, similar to wooden houses in the winter."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
7itd15 | What does it mean to have something notarized? | Other | explainlikeimfive | {
"a_id": [
"dr19myq",
"dr1gqj6"
],
"text": [
"A document that's been notarized has been approved by an a neutral and trusted public official called a notary public. Basically it means the notary witnesses and confirms the identity of the person or persons signing the document and that they understand what the document does so there's no question later as to its validity. This is usually required for documents that you really don't want questioned, like property deeds, wills, and powers of attorney.",
"Contrary to popular belief, a signature isn't a magic thing that makes a contract binding. A contract is established simply by agreement, and a signature is evidence that agreement has been made. A claim that isn't your signature or that you were tricked or coerced into signing can invalidate the contract. Similarly, a contract can also be considered binding without a signature if there is other evidence it was agreed to. A notary is a neutral third party, registered with the government, who verifies your identity, logs when and what kind of document you are signing, and witnesses you actually signing it. Note this is still just evidence you have entered into an agreement, but it is much stronger evidence."
],
"score": [
7,
6
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7itdq6 | How does a pool table know to return the white ball when it's sunk, but keeps the coloured balls? | Physics | explainlikeimfive | {
"a_id": [
"dr18q3w"
],
"text": [
"Years ago it used to be that the cue ball was ever so slightly larger than the other balls. Nowadays, the cue ball on most coin-op tables has a magnetic core. The return chute inside the table has a magnet that pulls the cue ballaway from the colored ball depository into a separate return chute."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7itke9 | How does my penis know I’m looking at something sexual? | Biology | explainlikeimfive | {
"a_id": [
"dr19tjb"
],
"text": [
"Your brain finds whatever you’re looking at arousing and as a result releases endorphins and sends blood to the penis to make it erect"
],
"score": [
9
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7itkuy | How do deep space spacecraft such as Voyager orient themselves to point in a specific direction? | Physics | explainlikeimfive | {
"a_id": [
"dr1as82"
],
"text": [
"They have inertial guidance systems which have 3 axis-stabilized gyroscopes and accelerometers that track their attitude so the probe always knows which way it's oriented. Some probes like the Voyagers have their science instruments, including cameras, mounted on movable platforms, so they can rotate independently of the spacecraft. As long as the spacecraft knows which way it's pointed, it knows how many degrees in which axis it needs to pitch, roll, or yaw to point where it needs to point. If mission control wants to reorient the spacecraft for any reason, they send the command via radio and it used small thrusters to make the change."
],
"score": [
7
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7itnyd | How can we so distinctly remember things that never actually happened? | Biology | explainlikeimfive | {
"a_id": [
"dr1ac22"
],
"text": [
"It is possible to vividly imagine something and then simply re-categorize that mental image as a memory rather than something you imagined. The act of remembering it works just the same. You can see what it looks like, hear the sounds or voices, and so forth. You just have attached a wrong category to it."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7itps7 | why does even a little bit of heat aggravate a (fresh) burn wound? | Biology | explainlikeimfive | {
"a_id": [
"dr1j3bv"
],
"text": [
"Great question, but first you need to know how pain works in the first place... There are certain cells in your body that are designed to feel pain, they are called nociceptors. There are different nociceptors for different kinds of pain (pressure, heat, etc) and they all have a trigger mechanism. The mechanism is that when a certain tolerance is reached, such as a certain temperature, the nociceptor will activate and send a signal to the brain. How bad the pain feels is based on how many nociceptors are triggered, more triggered nociceptors = more pain. When you get a wound your body immediately activates it's defense mechanisms, and one of those defense mechanisms is to send out a chemical that lowers the activation threshold of the nociceptors, meaning it's easier to trigger them... this means that what would normally have been mild heat is now enough to trigger a bunch of nociceptors and cause more pain"
],
"score": [
7
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7itwv6 | If there was a pill that contained all the nutrients, vitamins, energy etc., would you still need to eat? | Biology | explainlikeimfive | {
"a_id": [
"dr1bxwi"
],
"text": [
"Yes. Because the calories you would need cannot be consumed in something as small as a pill."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iu7k0 | Heart rate increase and decrease | Increasing the heart rate means more available blood so the body can cool it self better, right? So that's why we have an increased heart rate during hot weather. But what happens when it's cold? Why for example animals thst live in cold. Environments have lower heart rates? Do we also have lower hear rates in cold weather then compared to normal? Sorry for any mistakes, I am not a native speaker | Biology | explainlikeimfive | {
"a_id": [
"dr1ez7j"
],
"text": [
"In warmer weather, the blood vessels in your skin open wider to allow more blood to flow near the surface, which helps you lose heat - that's why hot people look flushed even before they start sweating. In cold weather, the blood vessels contract so less blood flows near the surface, helping to retain heat, so people look paler (and, if extremely pale already, can even look slightly blue). Increase in heart rate is linked to an increase in energy usage - you want blood flowing faster around the body, bringing more oxygen to the muscles. It isn't really connected to the temperature. The exception is if it's cold enough to make you shiver violently, which is your body burning energy in the muscles to heat you up. It's not a good idea to stay out when you're in that state, as it's a sign you're struggling to maintain core temperature, which is not good for you."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
7iueza | Considering how inept the pinky finger is, why do humans actually need it? | Biology | explainlikeimfive | {
"a_id": [
"dr1fj78",
"dr1ghui"
],
"text": [
"You would be surprised how much use I get out of my pinkies. Right now, I am holding my phone supported on the back with my middle and ring fingers, and the weight of the phone on the bottom by my pinky. I use my pinkies to uncap pens, too. Granted, it's not as much use as I get out of my thumbs or my index or middle fingers, but I'd feel... Naked without my pinkies.",
"Individually it's not as strong as the other fingers or uniquely useful. But to grip things it's good to have several fingers. Not only do more fingers provide more strength (which could also be achieved by making the fingers larger or bulkier), it's also easier to wrap your hand around a wide array of shapes if you have multiple fingers to place around them (imagine if instead of separate fingers you had a hand that looked like a mitten, and how difficult it would be to grasp things). And apparently 4 fingers and a thumb is what evolution arrived at as the optimum."
],
"score": [
7,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iui3g | how does DNA trace ancestry? | Biology | explainlikeimfive | {
"a_id": [
"dr1geya",
"dr1pedb",
"dr1wfdg"
],
"text": [
"They have a list indicating where specific genes come from and compare your DNA against that list. If you have a gene that resulted from a mutation that happened only in Northern Europe then your ancestors came from that area.",
"When populations live in reproductive isolation (they're not having children with other populations), the makeup of their DNA diverges over time. This happens due to random factors, because the founding population did not have the same makeup as the group it originated from, and because natural selection pressures depend on the environment. The result is that certain alleles in the DNA are characteristic of ancestry in certain peoples. The problem is that humans aren't actually rigidly reproductively isolated. People move around a lot today, but unlikely mixing from people that grew up far away from each other has occurred forever. For example, ancient China already had populations of Jews and Christians from the Middle East. So a DNA test can't tell you where your ancestors lived, but it can give you a pretty decent guess. Between close members of the same family, the factors that cause genotypes to diverge haven't had a lot of time to operate--e.g. you don't see a lot of mutation in just one generation. That means that when you have reason to suspect someone is a close relative, comparing DNA samples should show a high level of similarity, much more than strangers whose ancestors are from the same general area. At this scale, it's a quite reliable way to confirm ancestry.",
"You actually cant trace genes that well in humans or most animals due to the amount of introns and exons (parts of a gene that isnt transcribed, and the parts that are, get snipped and spliced into something to be transcribed into something useful). Besides defects such as mutations of mutant alleles well defined, the human genome is mostly made of structural components to even keep the dna readible from its intense use of exons and transposons and t factors. It is INCREDIBLY DIFFICULT to trace actual genes of most eukaryotes. Our genes are just frikkin loaded with all kinds of things that its so complicated to even find them sometimes, and if they are polymorphic (vary among a population) it probably isnt even heritable. Eukaryotic genes arent used for sequencing because of this reason besides a few well studied ones such as diseases or easy to spot polymorphism (sickle cell is a VERY simple mutant compared to how complicated genes can be) What actually gets sequenced for heredity is whats called microsattelites. The term microsattelite is an inctedibly huge umbrella term, but what it means is defined sequences that are polymorphic in the population of genomes (between people, they are different). These sequences range from so much, sometimes a short tandem repeat in the dna (humans have a repeated sequence of CA in the genome almost every 5,000 base pairs, people have different amounts of these throughout their genome). Another thing can be changes in the dna sequence that let restriction enzymes cut parts of a dna. Restriction enzymes are specialized enzymes harvested from bacterium that cut a specific site in a genome, its selected to target certain sequences in the dna. People are polymorphic for these too, so some restriction enzymes will cut at different sites for other genomes. Therss all kinds of other microsattelites, such as single nucleotide polymorphism, where we are able to isolate one specific part of a sequence thats changed in one base pair. Microsattelites are all of those along with a ton of other things. They are simply easy to spot changes in a genome, and they are inhereted throughout the ancestry of an individual. It took us a looong time to find some of these microsattelites, years of research and cloning and blotting to identify these sequences. What happens is you can give your genome to a lab, and they can run all kinds of sequence tests for microsattelites, and they can do it easily using some standardized spray and pray method to isolate all these microsattelites in your genome. All they have to do is grab a couple sequence tests that can spot some very accurate microsattelites that show a high degree of variation in the population, and are inhereted well. They shove the primers they need into PCR batches and run them a couple of times, then pull them out and instead of blotting they just do small sequencing of the microsattelites they were looking for and sync the data from small sequencing processes into the database they havr to check ancestry. PCR is a process to multiply a crapload of specific sequences of a particular sequence of DNA. Using PCR in this way is super simple, because youre not targeting some unknown or are trying to do any blotting, you just put the subjects dna in, place primers that you know will only amplify the sequence youre looking for and since PCR has incredible fidelity at only amplifying the sequences you need, you will only get the sequences you are looking for anyways. Once they sequence the product from the pcr they just upload the different amounts of genetic markers that fit the criteria - microsats that vary a lot in the population and are inherited with high fidelity. You match the subjects sequence products to known clades of microsattelites. Aka most african populations have these sequences, australians have these sequencss whatever (way more complicated than that). The database uses sequences already given to them from people living now or relatively recently and they have some generic sense of where people came from using the history of individuals they first sequenced from. Its a huge web of data that uses sequences and noted actual ancestral history. There you have it. The process seems more complex than it really is. Thankfully theres markers in our genome that fit the perfect target to find this stuff."
],
"score": [
7,
4,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iujro | How do Snowflakes get that cool pattern? | If you are able to get a good picture, you can see the cool pattern. How do snowflakes get it? | Physics | explainlikeimfive | {
"a_id": [
"dr1hxip",
"dr1k8it",
"dr1kitb"
],
"text": [
"Great question. There are many different shapes of snowflakes, but all of them follow 1 basic rule, they want to maximize attractive forces between the molecules and minimize repulsive ones... and because the shape of a water molecule has a very specific structure, all snowflakes have a 6 way symmetry because that is the only way to balance those forces. There are different ways to do this of course, but they all have that basic hexagonal structure. And once the base crystal forms any new water molecule that freezes to it has to fall in line with the other ones to keep those forces balanced, so the crystal keeps growing in the same pattern over and over.",
"Hydrogen bonds make snowflakes adopt a six-sided shape always. The reason for the variety is due to several factors. A snowflake forms a crystal, but it is not a perfect crystal. Some molecules would be out of form and result in imperfections. Some molecules are made with the ^(2)H isotope of hydrogen, or ^(18)O isotope of oxygen. With the huge number of molecules in a single snowflake and the different places these isotopes can be in within the snowflake, a massive number of different snowflake designs can occur. So many in fact, that we say no two snowflakes can be identical. [This site]( URL_0 ) explains what I just said in more detail.",
"Yarr! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: What makes snowflakes different everytime? ]( URL_3 ) ^(_3 comments_) 1. [ELI5 how do snowflakes get patterns on them? ]( URL_4 ) ^(_1 comment_) 1. [ELI5: How do snowflakes always look like a beautiful piece of art? What makes them so intricate and symmetrical? ]( URL_0 ) ^(_2 comments_) 1. [ELI5: Why are snowflakes shapes so complex? ]( URL_2 ) ^(_2 comments_) 1. [ELI5: How do snowflakes get their unique shape? ]( URL_1 ) ^(_3 comments_)"
],
"score": [
13,
5,
3
],
"text_urls": [
[],
[
"https://www.its.caltech.edu/~atomic/snowcrystals/alike/alike.htm"
],
[
"https://www.reddit.com/r/explainlikeimfive/comments/3x9oet/eli5_how_do_snowflakes_always_look_like_a/",
"https://www.reddit.com/r/explainlikeimfive/comments/5ne46c/eli5_how_do_snowflakes_get_their_unique_shape/",
"https://www.reddit.com/r/explainlikeimfive/comments/3wf9mz/eli5_why_are_snowflakes_shapes_so_complex/",
"https://www.reddit.com/r/explainlikeimfive/comments/3v0irb/eli5_what_makes_snowflakes_different_everytime/",
"https://www.reddit.com/r/explainlikeimfive/comments/34in14/eli5_how_do_snowflakes_get_patterns_on_them/"
]
]
} | [
"url"
] | [
"url"
] |
7iuqu7 | Why can we HEAR our joints crack? How does sound escape the inside of our body? | Physics | explainlikeimfive | {
"a_id": [
"dr1i0t1",
"dr1i17z",
"dr1i7dy",
"dr1xz2r",
"dr20tkw"
],
"text": [
"The sound we hear is actually vibrating air that pushes against our eardrums, making them vibrate as well. But lots of things can vibrate (not just air), and when those things are in contact with air, they cause the air to vibrate as well. This is how materials can transmit or produce sound. For example, the sound of a violin is produced by the vibrations of its ~~snares~~ strings against the air. And the ~~snares~~ strings will also cause vibrations in the wood of the violin, which has a larger contact surface with the air, and thus amplifies the sound. Sound 'escapes' the body because it makes the tissues in the body vibrate, and then those vibrations reach the air. It's the same reason why inside a sealed (airtight) room you can still hear sounds produced outside: the sound is transmitted through the walls and (especially) the windows.",
"Sound is a compression wave. You body's structure is relatively good at transmitting waves of this type, that's how sound gets from the air in your ear into the part of your ear that senses it.",
"we don't know 100% for sure, but the leading hypothesis is cavitation. the motion causes the fluid in the joint to form tiny gas bubbles which then violently collapse, making a \"pop\" sound.",
"Your joints aren't cracking per se, it's the fluid around the joints being released. Think of it more like a glass of water that is suctioned upside down on a table that's been lifted up and the pressure being released. The reason you can hear it is the same as hearing any internal bodily function, like a tummy rumbling or a heart beat.",
"Sound actually travels faster through solids (and liquids) than air because the next molecule to be pushed by the wave is closer in these media than in a gas. So sound speed is gas < liquid < solid. That's all to say that it just goes from your meat space to the air space with a change in the medium, but no real problem for the wave propagation,but the sound exists inside you too. Think about hearing something with your head under water. The water is a different medium than we're used to listening in, but our eardrums are still vibrated by it and so we can still hear."
],
"score": [
393,
76,
38,
8,
5
],
"text_urls": [
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ius9g | why does ESPN keep writing articles on what shoes NBA players wear? | Other | explainlikeimfive | {
"a_id": [
"dr1ilt4"
],
"text": [
"The easy answer is money. Companies pay media for product endorsement. Nike, Adidas, UnderArmor, etc. pay for advertising on ESPN, the contract probably includes a clause that includes name drops in news segments."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iv3sz | Why are babies so flexible? | Biology | explainlikeimfive | {
"a_id": [
"dr1km5m"
],
"text": [
"Their bones are not as hard as big people bones. When we grow up we get harder and stronger. Babies have to be super flexible to be born. Edit: this post from two years ago has some good answers: URL_0"
],
"score": [
3
],
"text_urls": [
[
"https://www.reddit.com/r/explainlikeimfive/comments/37ehwj/eli5_why_are_babies_so_flexible/"
]
]
} | [
"url"
] | [
"url"
] |
|
7iv7ck | How do physicists generate a stream of neutrons to fire in their experiments? | Physics | explainlikeimfive | {
"a_id": [
"dr1mwqu",
"dr20vai",
"dr214mp",
"dr1yl6o"
],
"text": [
"A common way is to use a nuclear reactor. The chain reaction produces a lot of neutrons. By construction a neutron transparent \"window\" into the reactor, some of the neutrons will escape through the window, in a crude beam. You can then place the experiment in the beam. Some experiments, can simply be done in the reactor - and a small test tube containing the experiment can just be installed into the reactor core. While fission reactors are low tech and can produce very large numbers of neutrons, they are limited in the energy of neutrons that they can produce. Many designs of nuclear reactor use a \"moderator\" to reduce the neutron energy for the chain reaction, and this will reduce the energy of the neutrons available for experiments. Even \"fast\" reactors without a moderator are limited to the maximum energy of fission neutrons. Where faster neutrons are required, a fusion reactor can be used. However, while fusion reactors can be constructed extremely cheaply and compactly, this type of design has been limited to very low power and therefore very low neutron production rate. A new generation of advanced \"compact neutron source\" fusion reactors optimised for very high neutron production rates ( URL_0 ). Some of the latest technology versions are so powerful and efficient, that they are often easier, cheaper and safer to use than fission reactors. Due to the risk of fission reactors being subverted for production of nuclear weapons, many governments are pushing for research institutions to replace their fission reactors with fusion sources. You can always add a moderator to reduce the neutron energy if the fusion neutrons are too fast for your experiment. For experiments requiring neutrons which are faster than the maximum fusion neutron energy, then you need to use a particle accelerator and a \"spallation target\". A proton accelerator is produce a beam of high energy protons - which are directed at a target made from a heavy metal. The protons hit the nuclei in the target and smash off neutrons. These can have energies as high as the proton beam energy.",
"Follow-up if I may: How does one 'aim' a neutron beam since it will not react to magnetism or electric fields?",
"One of the projects I work on uses a dense plasma focus machine, also known as a z-pinch machine. Trying to keep it ELI5, it uses a huge electric current to create plasma in a tube filled with tritium and deuterium. The way it's designed, the extreme magnetic fields crush the deuterium and tritium together, which causes a fusion reaction, to provide a burst of high energy neutrons. We then place the target in the path of those neutrons next to the source. I don't think I can really get more technical without leaving ELI5 territory, but at least I don't have to worry about what is and isn't classified.",
"The second way of doing it is to take very fast moving protons (the middle of a hydrogen atom) and smash them into Tungsten. A process called spallation happens, but basically the protons are moving fast enough to 'knock' some neutrons out. This works well for scientists because essentially if you turn of the proton source you turn off the neutron source, unfortunately it requires building particle accelerators, which is quite an expensive thing to do."
],
"score": [
891,
51,
25,
12
],
"text_urls": [
[
"https://www.phoenixwi.com/product/high-yield-neutron-generator"
],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ivgg1 | Why is plastic such a good insulator on windows in the winter? | Chemistry | explainlikeimfive | {
"a_id": [
"dr1nh2u"
],
"text": [
"The plastic itself is a pretty weak insulator. It's actually the *trapped air gap* that acts as the insulator. Air's a good insulator if you don't let it move around. For example in a down jacket, it's actually the tiny bits of air *between* the down feathers that insulate so well."
],
"score": [
30
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7ivled | How does an athlete using smelling salts work? | Biology | explainlikeimfive | {
"a_id": [
"dr1rwvr"
],
"text": [
"Smelling salts release ammonia gas. If you breathe in this gas, it irritates the insides of your nose and lungs to such an extent that it stimulates your sympathetic (\"fight-or-flight\") nervous system. This is an autonomous part of your nervous system that, when activated, has all sorts of arousing effects on your body, releasing adrenaline, increasing your heart rate, opening up your lungs, increasing blood flow to your skeletal muscles (while decreasing it to your digestive system), and generally preparing your body for action. For athletes, these effects may be desirable and performance-enhancing, although perhaps especially so for athletic feats that require quick bursts of action. Smelling salts have also been used to revive athletes that have been rendered unconscious (e.g. boxers), because their arousing effects counteract the fainting response."
],
"score": [
40
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7ivr8d | Graphene, Graphite, and why one is an amazing super-material and the other is pencil lead and skateboard layers? | Technology | explainlikeimfive | {
"a_id": [
"dr1qgt6"
],
"text": [
"*Graphite* is many *graphene* sheets layered on top of eachother. Graphene is only a single atom thick, and this gives it some odd properties because so many electrons are exposed in identical configurations. You can't make a bulk material out of it though, stacking them up allows the electrons in each layer to interact and changes the properties."
],
"score": [
16
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7ivxe9 | How do words get mapped to concepts within the brain? | Biology | explainlikeimfive | {
"a_id": [
"dr1v7g5"
],
"text": [
"Hebbian learning is a concept in neuroscience that says neurons that fire together wire together. In terms of biology this means when two neurons fire at or about the same time, the synaptic connection between them strengthens and the likelihood of them firing together in the future increases. When you hear a word, you hear it in a context. That context is represented in your brain by the current set of firing neurons. The word you heard is also represented by a set of firing neurons. So according to Hebbian theory, the set of context neurons and the set of word neurons will “wire together” more strongly. Over time, this wiring will become more specific as your hear the word in different contexts."
],
"score": [
17
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iw5z5 | Why does the bathroom get steamy when the water is well below the boiling point? | Physics | explainlikeimfive | {
"a_id": [
"dr1ti1g"
],
"text": [
"water does not need to be boiling to evaporate, water evaporates all the time, heat just speeds up that proces."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iw7lg | why do plastic wrappers tear much easier after an initial cut? | Physics | explainlikeimfive | {
"a_id": [
"dr1twbv"
],
"text": [
"The tip of the cut becomes a point of ultra-high strain, because none of the adjacent plastic (alongside the cut) is taking up any of the load. Without a cut, the stretching force is spread across millions of different molecules, with no one particular weak point."
],
"score": [
15
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iwb4m | Why can't Canadians watch certain American programs (like Saturday Night Live) online? | Other | explainlikeimfive | {
"a_id": [
"dr1uksh",
"dr1x8sn"
],
"text": [
"Because every country has different people who own the broadcast rights of each show and the streaming service that you are trying to use does not have those rights in Canada.",
"In 1978 the Canadian and US governments signed a treaty in secret. You guys get free health care and we get all the sketch comedy. This was almost broken by the Kids in the Hall."
],
"score": [
5,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iwdqw | how does left-cardiac hypertrophy lead to cardiac arrhythmias? | Biology | explainlikeimfive | {
"a_id": [
"dr1v8u6"
],
"text": [
"With left-sided hypertrophic cardiomyopathy, the left ventricle is very muscular and that leaves little room for blood to fill up in it between beats. As a result, you can get blood backing up into the left atrium. This stretching can cause electrical signals to get \"messed up\" (simple way to put it), resulting in the heart doing weird stuff as it tries to keep up with the blood flowing into it. There's also the issue of that super muscular chamber contracting really hard, which can throw off the normal rhythm."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iwigh | Can mass abortion eradicate inherited genetic defects? | Biology | explainlikeimfive | {
"a_id": [
"dr1w6f3",
"dr1xfrx",
"dr1y967"
],
"text": [
"You are describing *eugenics.* To a significant degree it can work -- look at dog breeding programs for example, or even farm plant breeding programs. Of course the moral issues are terrible. And it won't *completely* prevent these problems, since random mutations do occur.",
"> Iceland has almost eradicated Down Syndrome Actually, Iceland has almost eradicated *people* with Down Syndrome, via abortion. It hasn't prevented DS from occurring in new conceptions.",
"Eugenics can and does work, but that's not how Iceland got rid of Down's Syndrome. Eugenics is when the government stipulates that people with X and Y conditions are not allowed to breed and enforces it somehow. There's even worse versions - Nazi Germany outright killed the people it wanted to not breed and forced the people it did want to breed to do so. Down's syndrome is a special case because it's not really necessary to employ eugenics to get rid of it - the vast majority of people with Down's Syndrome are unfit and can/will not reproduce on their own. However it does spontaneously happen at a not-insignificant rate. Iceland 'eradicated' Down's by pre-natal screening almost all women and encouraging them to have abortions. This would be eugenics only if the children who were aborted were reproductivly fit and could carry on their genetic mutations. They also have to keep it up forever - Down's won't be 'eliminated' from the gene pool like you would expect from real eugenics because most cases are not inherited. Real eugenics would work on something that is inherited at a significant rate because carriers are normal enough to reproduce. Like Tay-sachs or skin color."
],
"score": [
17,
9,
6
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iwx5n | How do bacteria develop resistance to drugs but not to the human immune system? | Biology | explainlikeimfive | {
"a_id": [
"dr21f1o"
],
"text": [
"They do. Our immune system is just amazingly adaptive. The adaptive immune system is what gives us antibodies. A baby isn't born with any, except some from its mother. Upon the first infection, cells of the immune system find some bacteria, bind to them, and start producing antibodies. They are called antigen presenting cells. (There's more than one class of them. The names don't matter that much.) Antibodies are markers for other immune cells to attack the bacteria. When your body has learned to produce antibodies against a specific pathogen it never loses that ability. The antibodies bind to specific parts of the bacterial cell wall - and when the bacteria change their cell walls because of mutation, i.e. adapt to the immune response, a new, different antigen presenting cell binds to that new cell wall structure. And so on. There are some bacteria which have means to trick the whole immune system, Borrelia for example. But that's much more complicated than just evolving a resistance against some antibiotics."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7ix5tr | How does every $1 Billion dollars spent in commercial construction add $3.4 Billion to the GDP? | URL_0 for reference | Economics | explainlikeimfive | {
"a_id": [
"dr222ik",
"dr22v4a",
"dr22ilf",
"dr255gj",
"dr2ahbc"
],
"text": [
"You track where the money goes. \"The economy\" or \"the GDP\" can be thought of as the sum of all transactions. You're referring to the concept of an \"economic multiplier,\" which can be thought of as \"how many other times will this dollar get spent after the first time?\" If you spend a billion dollars to build a building, some part of that is profit for the construction company, some of it gets paid in taxes, and the rest of it goes to suppliers and workers. The suppliers also pay their suppliers and their workers. Workers spend it on food and rent and gas. The tax money pays for programs that have employees who then spend their wages on other stuff, et cetera. Obviously there are a lot more transactions and other things than just what I've listed, these are just examples, not an exhaustive list. This is one of the reasons why many people consider shopping from big box stores or Amazon to be bad; companies like those have extremely low multipliers because their cost structure is so low and because a huge percentage of their revenue just goes to \"money bins\" never to be spent again.",
"Money doesn’t get spent once a year. A developer pays his workers, and they pay rent, buy new TVs, go on vacation, buy groceries, etc. The brick supplier pays his workers and they do the same. Also the brick maker buys a new kiln for his business. The kiln salesman buys a new car and sends his daughter to college. The car dealer sponsors a Little League team and the college professor buys tickets for the symphony. And so on, money keeps moving through the economy...",
"First of all, anyone citing figures like these is describing a study someone did - the assumptions for which may or may not be valid. Chances are that the study was paid for by some institution that had an expectation of a certain outcome of the study. However, the basic notion is easier to understand if you understand the concept of an atomic 'trade'. Let's say I have a waffle. You want a waffle. So you beat me over the head with a baseball bat and take my waffle. In this case, you've destroyed aggregate value. I no longer have a waffle (and have the added liability of a sore head). You do have a waffle, but you're out the time and effort you spent in batmanship. Alternatively, you can offer to *trade* me the baseball bat for the waffle. This creates an increase in aggregate value. I have a baseball bat (which, since I agreed on the trade, I value more highly than a waffle). You have a waffle (which, by the same principle, you value more highly than a baseball bat). We've both increased our value, less the time/effort it took for the trade. In this purely abstract sense, every time people are able to engage in a low-overhead consensual trade, aggregate value is increased. The more such transactions occur, the more aggregate value is created. However, the rate at which such transactions can occur - the 'velocity of money' - is sharply limited by available capital. Infusing capital into the system thus not only provides the value of the capital, but also the value from the additional transactions it facilitates. Another way to look at this is to think about what you're buying with that money. Let's say we live in two towns separated by a wide and fast river. If we spend $1 billion dollars on a bridge, we get the benefit of $1 billion dollars in terms of worker pay, sales from construction material firms, etc. But we also get a bridge - and that bridge reduces the overhead on every transaction that takes place between the two towns. Indeed, it probably enables a large number of transactions that would have otherwise never taken place by its existence.",
"A yogurt store owner will have a hard time selling yogurt without the physical store. So if a real estate developer builds a mall, the yogurt store owner can put his store in that mall, allowing him to access the thousands of potential customers he can sale to who will be in that mall. No mall, no yogurt store, thus none of the economic activity the yogurt store produces. And over time that yogurt store will sale yogurt in total value far in excess of what it cost the developer to build that part of the mall. Thus, the developer spending some money now to build the mall allowed the yogurt store owner to make much more money over time with his store.",
"Classical economists refer to this phenomenon as the \"velocity\" of money, or the amount of times it is spent in a single year. The velocity of money is determined by the population's marginal propensity to consume and marginal propensity to save. By dividing 1 by the MPS, we find the amount of time per dollar that a transaction occurs. In other words, money is spent multiple times in a year. If I pay you $1 for a soda, then you will most likely spent that dollar somewhere else, and that person will spend it again and so forth. By the end, the one dollar has been spent 4 times, producing $4 in revenue. Thus, we can just make the numbers bigger and you've got the situation you've described. Hope I helped."
],
"score": [
14,
5,
5,
3,
3
],
"text_urls": [
[],
[],
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
7ixdfx | What are the side effects of having a currency with a real, fixed value? Is such a thing even possible? | I seem to remember Ron Paul arguing during one primary debate or another that a dollar subject to inflation and to manipulation by the Federal Reserve isn't real money. I'm sure some cryptocurrency boosters would say the same thing. So, what's the harm in having a stable dollar? Why does the Fed have a nonzero inflation target? And, is it even possible for the dollar to have a single, stable value? Wasn't there inflation and deflation when it was backed by gold? | Economics | explainlikeimfive | {
"a_id": [
"dr23h33",
"dr23a5e"
],
"text": [
"> So, what's the harm in having a stable dollar? Pegging the value of a dollar to the price of some commodity (i.e. gold) makes it much harder to manipulate the wider economy. Had the Fed not been able to as effectively increase the quantity of dollars available following the 2008 crash, the subsequent recession would have been *much* worse. > Why does the Fed have a nonzero inflation target? Principally because deflation is both sticky (as in, deflation tends to feed on itself) and terrible for the economy. Also, inflation is a spur to both spend and invest that cash rather than hold it and see it's value decrease. > And, is it even possible for the dollar to have a single, stable value? Wasn't there inflation and deflation when it was backed by gold? Yeah, the buying power of a dollar is determined by more than just the quantity of some commodity that it can be traded for. It would be effectively impossible to have 0 inflation just by mandating what a dollar can buy.",
"> So, what's the harm in having a stable dollar? That isn't possible even with backing the currency with something of real value. If you used gold for example then your currency changes in value as more gold is found. Also if you want more units of currency you need to get more gold which can be problematic. > I seem to remember Ron Paul arguing during one primary debate or another that a dollar subject to inflation and to manipulation by the Federal Reserve isn't real money. If he did he doesn't understand money and should be ignored."
],
"score": [
7,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
7ixgmx | Why athletes in the same Olympic event don't use the exact same equipmrnt? | Other | explainlikeimfive | {
"a_id": [
"dr24aka"
],
"text": [
"Whats most important to an athlete is being comfortable with their equipment that compliments their physique. A good example would be gloves in boxing. A knock out artist will usually wear harder gloves so they hit harder, Meanwhile a more defensive fighter will usually box with softer gloves to reduce the wear and tear on their body."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7ixnsj | Why do some people develop a mental illness during childhood instead of when they are older? Are there different factors involved? | Biology | explainlikeimfive | {
"a_id": [
"dr2iu0c",
"dr26ua4"
],
"text": [
"The brain is a tricky thing to grow but once grown it is usually stable in whatever state it ends up in. A child's brain is very simple on a network level and hasen't had a lot of patterns written down into it yet. If a child has a mental disorder it's typically also simple as well as severe - their brain didn't wire itself right in infancy and only the most basic things are done during that time. As a child grows patterns are written into his brain by both nature and nurture. Abusing a child will quickly give them a mental condition (even if most moral ninnies greatly exaggerate what is considered 'abuse'). Stress during schooling can also lay down unhealthy patterns. As can hormones during puberty. Injuries/fights/accidents. But once you're an adult you've been exposed to most of the things that you will be - you've been abused a little, you've been heartbroken, you've been in a fight, you're past puberty, you don't take huge risks by jumping out of trees. You've also developed coping strategies (good or bad) to deal with these things. Life settles into a routine and only the scenery changes.",
"Childhood mental illness is a strange thing, and it usually shows itself in a number of ways. One is simply having a genetic history that makes them more predisposed to it. Another one, which is the most common, is trauma - usually some form of child abuse. Another that I do hear a bit of now and then is from some form of an accident or illness; like onset trauma from strep causing severe OCD like symptoms for example."
],
"score": [
9,
5
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ixq4r | For fires as extreme as those occurring in California currently, how are these fires put out? | Technology | explainlikeimfive | {
"a_id": [
"dr2myj3",
"dr26tqm",
"dr28ind"
],
"text": [
"Actual California firefighter here. We begin by cooling the fire where we can access from an anchor point like a road. Once the fire line is cooled by air drop or hose line we put in control line by hand. It doesn’t have to be much, usually only a few feet wide. The area behind the control line is cooled further and mopped up. Hotshot crews burn out areas of unburned fuels from pre established control lines either hand made or existing roads, rivers, etc. thereby bringing the fire to more advantageous ground when we choose. Weather plays a big part in where and when we can really attack a fire. As a guiding principle we usually attack large fires from the flanks or sides. Making a frontal assault under the wrong circumstances is suicide so we are careful when we use that tactic. We don’t “draw a line in the sand” so to speak, but we can have a real measurable influence on the fire’s growth and where it stops.",
"In general they arn't. When they can they will try and keep them away from houses, by clearing brush, and dumping water/anti-fire chemicals, but most of the time they just let them burn out.",
"The most important step in fighting wildfires isn’t putting out the fire, it is containing it. The thing is that we generally don’t have nearly enough and fast enough access to water to put out these fires. So instead what we do is we try to do is surround the fire. Fire needs fuel to spread and if we can surround the fire with a small 20 or so meter thick area of no fuel (which I will call a wall) where there is no fuel, it effectively becomes contained. Wildfires tend to be kind of like a ring, the center is all burned, it consists of basically all hot coals and embers, while the surrounding part is actually what is burning. So the strategy here is twofold, have people surround the fire, generally by cutting down trees and even using small scale fires to burn out the fuel there. This is what percent containment means, it is the percent that this wall has been created. Beside that, we also have other crew actively battling the ring of fire where there is a risk that the fire will reach the wall before it is actually built, buying time for this wall. This is particularly true near residential areas, where if there isn’t enough space between the fire and the buildings to construct this wall, efforts are concentrated there to slow the fire enough that a wall can be constructed there. It is a losing battle, the sheer scale of the fire is too large to completely stop, but it buys time. After that, the fire runs out of fuel and it effectively becomes cleanup, we need to wait for the hot coals to die down and make sure that there isn’t any place that the embers may penetrate and start a fire in a new area."
],
"score": [
15,
3,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ixtuv | what's the difference between a $4 bottle of honey and a $15 jar of honey? What am I missing out on by buying the cheaper honey? | Other | explainlikeimfive | {
"a_id": [
"dr27zq7",
"dr273ow",
"dr286qy",
"dr2iue4"
],
"text": [
"Honey is a lot like wine in that, when unprocessed, it contains subtle and nuanced flavors, textures and colors that vary based on region and season. Cheap honey in a plastic bear is commercially homogenized. So it’s tasty, but exactly the same every time. The better stuff is from small beekeepers that have to raise the price to turn a profit.",
"There was an episode on BBC’s the one show on this. I think it’s more pure honey from like one set of bees. So like different bees from different countries make different honey. They taste different depending on the region of the bee. With more expensive honeys you might be paying for a specific region. With cheap honey it’s a mix of all different kinds from everywhere. Could also be things like how fresh/processed it is.",
"There was a study in 2011 that showed most ['honey' sold in grocery stores isn't really honey]( URL_0 ) - manufacturers filter out the pollen and water down the product. Some of this 'honey' comes from China or India and has been found to contain illegal antibiotics and heavy metals. Removing the pollen really decreases the flavor and makes it so you can't trace where the honey came from. Also, please don't buy star thistle honey as star thistles are an invasive species that produces it's own herbicide to kill other nearby plants.",
"Honey can be made from different kinds of flower, there are hundreds of varieties, each with a different flavor. Honey is also processed in different ways, it can be removed from the comb, processed with the comb, dried, frozen, and sometimes ever sold along with part of the comb. Honey can also be pasteurized or sold raw. Different kinds and processing of the honey will result in different products with different prices. Also, a lot of people ascribe dubious health benefits to different kinds of honey, which can increase the demand for certain types depending on which fad is currently in vogue."
],
"score": [
6,
6,
5,
3
],
"text_urls": [
[],
[],
[
"http://www.foodsafetynews.com/2011/11/tests-show-most-store-honey-isnt-honey/"
],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ixu3z | Why does salt and ice make it colder, but at the same time when you put salt down on snow, it melts it faster? | Chemistry | explainlikeimfive | {
"a_id": [
"dr29eip",
"dr28acg",
"dr2lb9l"
],
"text": [
"Putting salt on ice doesn't make it colder or change the temperature of things at all. It only lowers the temperature required to make water a solid, which is why ice begins to turn back into water (it's not cold enough anymore). If you're wondering why you mix ice and salt when using things like an ice cream churn, it's because having 32 degree Fahrenheit (or less) water helps by creating more contact area with the ice cream tub. So by having literally ice cold water, it helps freeze the ice cream faster than having ice cubes stacked around it with minimal contact.",
"If you have a block of ice in equilibrium in a glass of water, it will be 0 degrees celsius (32 degrees fahrenheit) until the ice is all melted, or the water freezes. If you add salt to this glass of water the melting point will decrease, making it \"colder\" and have an equilibrium at less of a temperature. While the snow melts faster when salt is added to it, this is because the melting (freezing) point is decreased. The temp of the water will be actually be colder, but it will be a liquid. This is also why salt doesn't work when the temp reaches a certain point. Tl;dr adding something (anything really, salt included) to water lowers the melting point of the water, and raises the boiling point of the water.",
"Salt water freezes at a lower temperature than fresh water. Fresh water freezes/melts at 32 F (0 C). Salt water freezes/melts depending on how much salt is present. A 20% salt solution freezes/melts around 2 F (-16 C) and salt on the road generally freezes/melts around 15 F (-9 C). **Scenario 1** - You place an ice cube on the back of your right hand. Your freezer is set to 0 F (-18 C), so you now have a 0 F ice cube on your hand. Your hand gradually warms the surface of the ice cube to 32 F (0 C), where it melts and makes 32 F water. This continues until the ice cube is gone, at which point the water starts warming up again. Your right hand feels 32 F cold during this process. - You dump some salt on your left hand and then place an ice cube on top of it. You again have a 0 F ice cube on your hand. Your hand gradually warms the surface of the ice cube to 15 F (-9 C), where it gradually mixes with the salt and starts to melt into salt water. This continues until the ice cube is gone, at which point the water starts warming up again. Your left hand feels 15 F cold during this process. **Scenario 2** - It is 25 F (-4 C) outside. There is ice on the road. You dump some salt on it. The salt mixes with the ice to make salt water. Since the melting point of this salt water is lower than 25 F, the ice melts. You now have salt water on the road."
],
"score": [
16,
4,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7ixvzl | Why is there a wait period between when we eat and when we feel full? | Why don’t we feel full right when we eat something? It usually takes about 10 minutes or so? | Other | explainlikeimfive | {
"a_id": [
"dr2iwmc"
],
"text": [
"A stretching stomach is one way we feel full, but there are also chemicals released in the body that cause you to either feel full or cause you to be hungry. These chemicals are passed along to the brain to regulate our appetite. Ghrelin (the hunger hormone) is made in the stomach and makes you hungry. As food enters the stomach, ghrelin production decreases and your appetite slows. As your food digests, ghrelin production goes back up when the stomach empties and we get hungry again. Another hormone, cholecystokinin (CCK), is produced when food reaches the upper small bowel. CCK tells the brain that you are getting full, and the more CCK that is present, the fuller we feel. Another strong appetite suppressant is Leptin, found in fat cells. Leptin is the opposite of ghrelin as it inhibits hunger. The reason we don’t immediately feel full is because the production of these chemicals isn’t instantaneous. Food has to make it to the stomach or bowel before the chemicals like CCK get passed along to the brain to make us feel full. There are plenty of other food chemicals in the body like insulin, glucagon, and amylin, but CCK probably does the most to make you feel “full”."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
7iyhj3 | Remember when point and shoot cameras had a flash that made a high pitched tone when you turned it on? What made that sound? What was the purpose of that sound? | Technology | explainlikeimfive | {
"a_id": [
"dr2crdl",
"dr2c6td"
],
"text": [
"The whining you hear is the mechanical vibration of circuit elements from the very fast voltage stepping. Modern camera flashes have changed electronics and often don't do this anymore.",
"That was probably the sound of a capacitor charging up. Then the camera has enough power for one flash. Then it charges up again. Capacitors are a way for an electronic device to get steady energy and at high bursts. It acts like a battery being quickly charged and discharged."
],
"score": [
8,
8
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
7iyhnl | how do we make different notes when we whistle? | Biology | explainlikeimfive | {
"a_id": [
"dr2carh"
],
"text": [
"By changing the shape of the hole between your lips, you make the air passing through it move past your lips at different pressure and speeds, which changes the way it vibrates, which is what sound is."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iykdt | How Blue Whales eat/swallow and what would happen if a human was diving nearby? | Biology | explainlikeimfive | {
"a_id": [
"dr2f3ze"
],
"text": [
"Blue Whales are baleen whales. What this means is they are filter feeders. Instead of teeth, they have large, bristle-y plates in their mouths (called baleens). Essentially, the way a Blue Whale feeds is to open its mouth wide (and its mouth is huge) and take a huge gulp of krill-rich water. It then uses its tongue to force the water out of its mouth through the baleens. The krill, which is bigger, is left behind against the baleens (filtered out) and then swallowed. Because the Blue Whale feeds on only such tiny animals, its throat passage is actually also pretty small for an animal its size. No more than a foot wide. Now, what would happen if a Blue Whale accidentally took a gulp of water with a human in it? We don't really know. It has never happened. What we do know is that a human will not be swallowed. It cannot pass through the throat passage. It is possible that the pressure of the whale forcing the water out of its mouth will hurt (or maybe even kill) the human as it is pushed up against the baleens. Most likely the whale will end up pushing the human out of its mouh with its tongue."
],
"score": [
9
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iypxp | Is time is relative to your reference frame, how can the universe be described as 13 billions years old? | Physics | explainlikeimfive | {
"a_id": [
"dr2ef1h"
],
"text": [
"It is framed from the point of us compared to the farthest thing (red shifted light) that we can detect. So the furthest back we know things existed was 13 billion years because that is the longest light that has reached us. Could the universe be older? Absolutely, but we think we are getting pretty close to being correct from what I understand"
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iyvic | Which countries don't rely on the US for their internet? | Technology | explainlikeimfive | {
"a_id": [
"dr2g3m6"
],
"text": [
"Net neutrality won't really affect other countries. Comcast, Verizon don't control the backbone and messing with the backbone would quickly get America as a whole thrown off the internet. As a general rule most big/wealthy countries control their own internet. China for instance blocks most foreign web sites for political reasons. If America did something stupid they could have their own internet up and running in a few days. tl,dr - America is not in a position to charge other countries for specific content. If we tried we'd quickly find out how impotent we are in the modern era."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
7iz8mo | why do trees have different colored leaves in the fall | Biology | explainlikeimfive | {
"a_id": [
"dr2hxkp"
],
"text": [
"The lower temperatures and reduced sunlight make it undesirable for trees to spend energy maintaining leaves. They recall fluids and resources from the leaves into the trunk and allow the leaves to die and fall off. As the chlorophyll in the leaves gave them their green color was removed they instead turn a variety of other shades as they are discarded."
],
"score": [
12
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.