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bvpj1e
What happened in the Tiananmen Square and what is the backstory/context and the consensus on what happened?
Intellectuals and students were protesting the Chinese communist government and it's policies. Protests against communist regimes were commonplace in the late 80's near the fall of the Soviet Union. The Chinese government responded with a violent crack-down by rolling tanks into the square and putting town the protests with prejudice. A unknown number of people were killed or arrested. The most notable image from the incident is the widely publicized "tank man" a lone man standing in the road in front of the tanks in non-violent protest. Which has become a lasting symbol of anti-communist propaganda. The events of Tiananmen square have been effectively erased from Chinese history by the ruling Communist party. While it is widely discussed in the Western world the Chinese population as a whole have no idea it happened because discussion about the subject is forbidden and the evidence is actively suppressed by the ruling party.
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bvq888
Is trade/tariff/deficit good or bad? | How Trade War Happens and Destroys Countries
Lets take this step by step. Is trade good? Yes. One party ends up with some liquid cash the other ends up with products they need. All is good. Are tariffs good? Usually not. Tariffs are a tax put on the importers of certain goods. They drive price up for people who want to buy those goods and drive demand down for foreign trade. The country implementing the tariff will lose a trading partner. The country getting the tariffs implemented on them will lose business. Of course there will be winners, and tariffs aren't automatically bad. If you run a business that doesn't rely on foreign imports it will be much easier for you to compete. It essentially gives a handicap for domestic businesses. Are trade deficits good? The answer is complicated. A trade deficit just means that a country buys more from another country then it sells to them. Large trade deficits can result in a devaluing of currency relative to another, but even that impact is usually pretty unimportant. Its a statistic that can be indicative of a bigger problem, but the existence itself is not a problem. How do trade wars happen? Remember early when i said tariffs can hurt the economy on the country they are target against? Sometimes the retaliation against a tariff is to implement one of your own. This goes back and forth until someones economy hurts enough that they have to back off. With global supply chains being incredibly common nowadays these can have far reaching implications.
fc358034-6b7e-4163-a25e-d16d2186ab68
bvq8hj
Why are some animals more likely to be pets than others?
They've been bred for it over centuries, and often have symbiotic relationships with humans. Also, imho, predators make better pets than prey animals. They don't have prey response, and live longer.
315c7dd8-bdab-457e-aaa1-51652aab64e1
bvqehp
Before electrics, how did pipe organs work?
A *lot* of adjoined levers and pulley systems. Before the advent of electronic and digital systems everything was based on mechanical principles. Edit: [here is a YouTube video giving a rough explanation of a mechanical organs innards](_URL_0_)
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bvqggq
What is the Fibonacci sequence?
Start with 1 and 1. Add them together. You get 2. Put that on the end: 1, 1, 2 Now add the last two together again. That's 1+2=3. 1, 1, 2, 3 Now add the last two together again. 1, 1, 2, 3, 5. Now just keep going forever. That's the Fibonacci sequence. 1, 1, 2, 3, 5, 8, 13, 21, ..... It pops up in some things when you look closely (things like the number of petals on a flower, or buds in the centre of a big spiral sunflower, and that stuff like that). Not because there's some inherent magic, it just happens to be that some things work out that way. If you do certain things with the numbers, like treat them like a distance from a point, it can draw the golden spiral, which also occurs in nature (in snail-shells, etc.). It's a mathematical toy that sometimes pops up and is useful when it does, but otherwise is just "interesting". To be honest, Fibonacci being remembered only for that is actually quite an insult to the man. "The most talented Western mathematician of the Middle Ages", who brought the numbers we use (Arabic numerals) to Europe.
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bvqobk
If the sun never sets during arctic summers how come it's still cold?
Because near the poles, the sun’s rays hit the earth at extreme angles. Although the sun is “up” all day long, it doesn’t travel across the sky from one horizon to the other, peaking high above. It travels along the horizon as if it is always close to sunrise or sunset.
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bvr2bi
the C computer language compiler was written in C. How did it get compiled if there was no C compiler until it was written?
The first C compiler was written in B. That sounds like a joke, I know, but it's true. C was originally called "NB" for "New B." Dennis Ritchie wrote up the history of C for his website at Bell Labs, which you can read here: _URL_0_
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bvr70m
Why does temperature affect how much water vapor the air can “hold”.
Think of it instead as affecting the water instead of the air. Higher temperatures make the water molecules jiggle harder, so that of two water molecules happen to stick together, they'll soon jiggle apart. At lower temperatures, the molecules jiggle less, so they stick together more, and droplets can form.
84432d9d-2761-4bb5-add7-52d579a13cc4
bvr827
do planes have to keep tilting down for long flights to make up for the earth's curvature?
No. Gravity is pulling them down while the lift from the wings is pushing them up. They stay at a constant height above the surface of the planet.
e8efd76b-2e70-4a4e-83c7-9bb1610f9315
bvru2p
How does your stomach know the difference between food/liquid - bowels/bladder?
Simply, it doesn't. Solid food is broken down in your intestines and eventually expelled from your bowel. On the way, blood vessels extract moisture from your bowel contents by osmosis. Your kidneys filter your blood, and extract excess minerals and water, which are excreted from your bladder in the form of urine.
42307942-d2e3-498f-b0f2-4ae179fdf1ee
bvrw7i
what is the difference between a single-celled organism and just a regular cell?
A single cell organism can reproduce on its own. A cell inside a multicellular organism might undergo a mitosis for the purpose of organ building and cell replacement, but will not be able to achieve reproduction.
76cdc223-383a-4fe3-9b18-1c2968a65864
bvrz27
Why, after so many years, printers are still poorly designed and constantly run into problems?
Printer tech here. The reason for most printers jamming is due to crappy paper and/or dirty rollers and improper humidity. The pickup and feed rollers become dirty due to paper dust and more commonly regular dust. This causes the rollers/tires to slip on the paper causing paper to not feed straight anymore. Too dry of paper causes static which causes paper to stick to each other and too humid causes paper to stick to each other as well. There's also engineering involved to have fewer motors, in turn having more clutches and solenoids. Printers are always being built to be faster and faster and smaller and smaller allowing for less discrepancies in paper feed. I hope that answers it enough for you.
ed3cbfcb-fa17-4894-bfd3-30467e289eb5
bvs5av
how does Uber work payment wise for drivers- like pool vs. solo rides, time, etc? How much does a diver make for a $25.00 ride?
You might want to check out _URL_0_. There might be information there already, but it would definitely get you an answer.
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bvsay2
How do we know that we humans perceive multiple colors as purple if we can't see them?
There aren't shades of purple that are other colours some how. It's just purple or shades of purple in that part of the spectrum. The only thing I can think of is that there are '2' separate purples in the rainbow, indigo and violet. This is only the case because Isaac Newton discovered how rainbows work and he was sometimes a bit dippy about these things. He decided there should be 7 colours instead of the 6 we really see so it would line up with the number of days in a week.
7adeebb0-0240-4c1f-94e5-b064772b0e40
bvsfqo
What causes clouds to appear large and bulbous?
Many clouds (i.e. thunderstorm supercells and ice clouds) aren't fluffy at all. But we'll ignore them for a moment and talk about those weird white ones. Those are made of water droplets ([sort of](_URL_0_)), and heat from the ground causes them to stay aloft. They have to meet a sort of balance between the up force of ground heat and the down force of gravity. This will happen in different places for different sizes of drop. Plus, they won't all form in the same place--they'll be separated side to side too. So the cloud now looks sort of blobby. It doesn't help that wind directions high up the atmosphere can change direction either, which pushes and pulls the cloud into different shapes. One other big factor in cloud shape is how hot and cold air are moving through a region. This actually brings us back to supercells; they form when hot air gets trapped under cold air, they mix, and start to rotate. Water condenses where they're mixing as well, so the whole storm starts rotating. And that's where baby tornados come from. src: I'm a physicist, so I'm pretty sure about most of this stuff (plus I grew up in a heavy-tornado area), but if any meteorologists weigh in, I'd trust them more.
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bvsg7o
Why do sensations such as heartbreak/sadness/anxiety feel like physical pain?
To grossly oversimplify, negative emotions like heartbreak, rejection, and embarrassment, trigger some of the same regions in the brain as physical pain. Specifically, the secondary somatosensory cortex and dorsal posterior insula. Processing these emotions as if they were physical pain helps your brain teach itself to avoid the feelings in the future.
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bvsi0l
how do cameras in movies get a shot of someone looking into a mirror from behind without the camera being in the shot?
Usually, it's just angle trickery, the mirror is angled to not have the camera in it. Other times, it's removed via CGI. Other times it's very complex with multiple mirrors and identical sets through windows giving the illusion of a reflection.
9c8949e4-c7fb-4ed6-8dd1-cb2012b13ee7
bvsp1l
I need help with anti VAX.
Anti vaxxers have heard it all before and decided not to listen to it. There is no way to use rational argument against an irrational opponent. This is the sort of game where refusing to play makes you the real winner.
1ff31688-55d7-419f-a710-c06faa1ff4b1
bvswu2
How is the velocity of a spaceship measured?
The velocity of a spacecraft is measured by taking advantage of something called the *Doppler effect.* If you've ever watched an ambulance go past you, you've heard the pitch of the siren change as it approaches and goes past you, right? That frequency shift is directly related to the object's velocity relative to the measurer's frame of reference, so if a satellite (edit: or spaceship!) is constantly broadcasting a signal on a known frequency, ground-based computers can calculate the velocity from the perceived redshift of the signal.
01301d2b-7e6e-41f4-ac6d-74d533cb8556
bvtcyc
How does carved ice last so long without instantly melting?
Most people imagine ice at 32f/0c degrees, because 32 is the freezing/melting point of ice, but the ice itself gets as cold as the freezer it is stored. A typical freezer is 0° F (-18° C). So when removed from the freezer, the ice must first warm up enough, even to allow the outside to begin to melt. Air is also a poor thermal conductor. Throw the same sculpture in the pool and it would melt much faster, even if the water is cooler than the air.
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bvtjyx
How does splitting an atom create so much energy using the law of conservation of energy?
Normal energy in chemical reactions comes from the bonds between electrons and the positively charged nucleus. Energy in nuclear reactions come from the bonds between nucleons (protons and neutrons). It's not that splitting an atom inherently liberates energy, but that some atomic nuclei are in high-energy states, and letting them fall into a lower energy state liberates energy. This is akin to the fact that splitting molecules in general doesn't liberate energy, but splitting hydrocarbons does, because they have so much energy stored in their bonds. You can't burn ash, and similarly you can't get more energy from the byproducts of nuclear decay (this isn't entirely true - usually the results are sometimes still unstable, but less so, and they can fall apart a handful more times before getting to fully stable products).
2174c89d-8214-425f-9d93-4a80bf9a883a
bvtriq
When light passes through a colored translucent object, how does the light take on that color. (How does the light “pick up” the color of the thing it passes through?)
White light contains all colors in it. The colored translucent object absorbs all the colors except the color it lets through. For example, red stained glass absorbs all the light except for the red which passes through.
ddcaf693-0729-4d1a-a778-5eb0ca304a16
bvtw8c
How non-radioactive objects become radioactive after the contact with the source of radiation?
Non-radioactive objects can become radioactive themselves *or* they can simply be contaminated with radioactive particles. In the context of your question, I think you mean the latter, so I'll answer that first. Something being contaminated isn't the same as being radioactive itself. If you have a chunk of radioactive material that explodes, there's going to be a ton of debris and dust that settles on everything, and this dust is radioactive, since it's still made of same radioisotope. Once you wash the dust off of whatever was contaminated, it's clean. The atoms of the contaminated object did not become radioactive. & #x200B; Sometimes stable atoms can actually *become* radioactive themselves. When a bunch of neutrons are emitted, sometimes atoms can capture one or more of these neutrons. The atom then has too many neutrons and has turned into a radioactive isotope until it decays. This is called neutron activation. Not all atoms are good at capturing neutrons, so some materials don't readily become radioactive via neutron activation. Neutron activation also doesn't tend to last long, as the atoms usually quickly eject the extra neutrons they captured. edit: spelling
a0c014ac-401f-4710-a6f7-6a39d105cc6f
bvtxvz
What fractionating columns are and why they are useful
Fractionation is a process which takes a mixture and spreads that mixture out over a space in an attempt to purify it. If done properly one "fraction" - maybe the portion that moves the least from the starting point - will be one pure substance and another "fraction" - maybe the portion that moves the farthest from the starting point - will be another pure substance. There may be any number of these fractions in between the extremes and that's really why fractionation is useful: you can separate all the components of a mixture in a single process. As a hypothetical example let's say you had a mixture of propane, ethane, and methane gasses. You could pump this mixture at a carefully chosen speed down a pipe that was room temperature at one end but got colder and colder and colder as it went along, falling to 100 K. If you collected liquid condensation near the front of the pipe it would be almost all propane. Liquid condensing in the middle of the pipe would be almost all ethane and liquid condensing at the far end of the pipe would be almost all methane. This is an example of fractional distillation and it's basically how raw mixtures of petroleum products are refined. Oil refineries have such tall towers because fractions are being separated all the way up. Fractionating with a chromatography column is similar in practice but, well, it's chromatography: it relies on the differences in solubility between mixture components rather than differences in boiling point. You run your mixture, dissolved in a solvent, through a column of silica gel and mixture components which are more soluble in the gel move slowly and stay at the top which components which are less soluble in the gel race to the bottom. On a small scale, this is cheaper, safer, and more efficient than working with large temperature differences.
330c8714-e3f9-496a-9ff2-bbcbcc80bf60
bvtyz1
How does the new heart start beating again after a heart transplant?
The default position for a healthy heart is to always be contracting. For example, here is a video of [heart cells contracting in a lab dish.](_URL_0_) Heart cells have special connections between them that allow them to beat in a coordinated rhythm. So imagine 10 heart cells in a line. One beats first and is called the pacemaker. It squeezes and sends a signal to the next cell to also squeeze, and so on until all 10 have contracted. It's like how a cox tells rowers to pull, and they all do it in a coordinated fashion. In a sudden cardiac arrest or other electrical problem, the heart cells are all squeezing, but they aren't doing it in a coordinated manner. So the electric shock resets so that all cells beat in a proper order. It's like if the rowers are all just randomly putting their oars in the water so that one person is pulling while another one is creating drag. The key thing here is that the cells are all still beating and fine, but they are just not coordinated properly. The only way for heart cells to actually stop beating is if they run out of fuel to beat. In a heart attack, there is often a block in a heart artery that prevents part of the heart from getting oxygen and fuel. It's like how a car stops working when it runs out of gas. There's nothing wrong with the car, it just needs oil. The problem with a heart attack is that if cells go too long without fuel, they die. So to answer your question, think about a heart donor. Say some guy is riding his motorcycle along on the highway. He's perfectly healthy, but gets cut off in traffic, falls off his bike and dies. He loses a ton of blood. The heart keeps pumping just fine, but there isn't enough blood to carry the oxygen and nutrition to feed itself. So it stops beating. Now they remove the heart, put it in someone else. The heart now has an supply of adequate energy and oxygen. This means it will just start beating again on it's own. You can add a shock if it's beating irregularly, but that's rarely necessary. **Tl;dr: A car that runs out of gas automatically starts working again when you add fuel. A heart that runs out of oxygen and fuel automatically starts beating again when you reintroduce oxygen and fuel. The default status of a living heart cell is to always be squeezing.**
0197e042-5737-4455-9694-9a981085aa8e
bvuaj5
How does a crystal oscillator work?
Oscillators are amplifiers with positive feedback. Some of the output is fed back to the input. That is what causes squeal in a PA system if the microphone is too close to the speaker. If you use a crystal in the feedback path of an oscillator, the crystal will pass signals which match its resonant frequency and block other frequencies.
2ef4ddba-19ba-484a-a146-655401abee4d
bvuhp2
What is it exactly that determines the frequency of a piezoelectric material?
piezoelectric crystals physically resonate much like a tuning fork, a large tuning fork can fit a longer wavelength, and hence will have a lower frequency than a small one.
d7f65980-5bde-4ea8-af81-b62adbea7835
bvuqj5
What makes things go stale?
Evaporation of any liquid inside the food - Why bread gets hard and stiff. & #x200B; Bacteria breaking down components in food (fat, protein, sugars etc.) and their waste product contaminating the food itself - Why the food will decolour, smell bad, taste goes bad and begin to rot (You are basically eating bacteria waste product smeared all over the food).
c59b699d-199a-41b5-b483-029d5990bd61
bvv0pu
How are the numbers within pi determined?
**Please read this entire message** --- Your submission has been removed for the following reason(s): * ELI5 requires that you search the sub for your topic before posting. There are absolutely no exceptions to this rule. Users will either find a thread that meets their needs or find that their question might qualify for an exception to rule 7. Please see this [wiki entry](_URL_1_) for more details (Rule 7). --- If you would like this removal reviewed, please read the [detailed rules](_URL_0_) first. If you still feel the removal should be reviewed, please [message the moderators.](_URL_2_?)
32a316a2-dc3e-4a6c-a304-9d7a8123b4f8
bvv0tf
How can the official motto of USA be "In God We Trust", while 1st Amendment states "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof"?
Its not the official motto. It was written on to the money in the 50's in order to differentiate from the godless Soviet communist, not making that up at all, please fact check me.
f31ce721-3c81-4b29-9b4a-9ccddbda5f0d
bvv4no
How can humans share so much DNA with Lettuce, Banannas and Mushroom's? Do we share the same ancestors?
Because there's a lot of DNA that codes for stuff common to all multicellular life. How to build a cell membrane, how to build a nucleus, how to make the proteins that hold everything together, how to make and use ATP, how to transport ions, there is so much stuff that is just like "here are the basic mechanics and parts to run a cell" that are mostly the same.
48337a20-9d46-4730-8f57-2cdb216a9aa3
bvvo6c
[Psychological] Why do children love screaming when they play?
Not being mature enough yet to deal with the overstimulation?
89c30444-3ab3-482c-ac26-60c5d7c4dae0
bvvq33
How does the UN work?
All the countries that are members of the United Nations send representatives to the council, and they have meetings, discussions, and hopefully agreements over all the subjects that are important to people all over the planet. "The United Nations is an intergovernmental organization tasked with maintaining international peace and security, developing friendly relations among nations, achieving international co-operation, and being a centre for harmonizing the actions of nation."
ee96c964-f74e-434a-a991-165daa4c9a6b
bvvwo1
What is this weird feeling that causes to feel like your sorroundings are getting bigger or smaller when going to sleep and closing your eyes?
I've had this too. I look at my chest of drawers at the far end of my bed and it's like they're not 10feet or so away, they seem like they're 40foot away. I always thought it was called derealization. Detachment of yourself from your surroundings.
255a8ed9-070b-4a4a-8d34-e3eb73f54ff7
bvw4x9
How do ears help in keeping balance?
There are little canals in your ears with hair and fluid. When you move the fluid moves, the hair recognizes that movement and sends the signal to the brain. It detects both angular and linear movements, and therefore the ears can literally detect in which position your head is. But in the end it's your brain that analyzes all the data it receives. If the data between eyes and ears mismatch, you start feeling sick, or even start having trouble keeping balance. It's a complex mechanism that even allows us to move on two legs.
54a2de0a-48d5-4bed-b9e0-10399f78c9e8
bvweym
Why do coffee drinkers feel more clear headed after consuming caffeine? Why do some get a headache without it? Does caffeine cause any permanent brain changes and can the brain go back to 'normal' after years of caffeine use?
Your brain knows when it needs to sleep by measuring a chemical which builds up during the day. When you sleep, this chemical, adenosine, gets cleared out - and then once you're awake, it builds up again, slowly. The more of it you have in your brain, the tireder you become. Then eventually you fall asleep, and your brain clears the adenosine out and resets it to zero for the next day. Caffeine basically blocks your brain's ability to measure this chemical. There isn't an easy way to ELI5 this part, but your brain has these things called "receptors" which this chemical connects with, and that's how the brain knows how much of it there is - caffeine gets in between the chemical and the receptors, preventing them from connecting together. So even though you have a bunch of this chemical in your brain because you've been awake for a long time (or you didn't get enough sleep last night), caffeine falsely tricks your brain into thinking "wow, there's basically no adenosine here at all, I must be properly well rested and not have any need for sleep right now!" This leads to a clear-headed and alert state of mind, as your brain isn't trying to get you to wind down for sleep because it thinks you don't need any. Think of the receptors like smoke detectors - caffeine stops them from detecting the smoke. The reason you get a headache from withdrawal is because unfortunately, eventually your brain cottons on to the trick caffeine is playing, and it creates new receptors to measure the levels of adenosine. So it's like "Ah, you're blocking my receptors to stop me measuring it! No problem, I'll make new ones, and there won't be enough caffeine to block *all* of them". This is why, over time, you need more caffeine in order to feel the same effects. The brain simply adjusts to the caffeine and tries to return your sleep cycle to normal. The headache arises because when you *don't* drink caffeine, your brain falsely believes you're a lot *more* tired than you are, because these receptors are measuring all of the adenosine in your brain - but your brain had become used to not measuring much of it at all, because the caffeine was blocking it. So now, it thinks you're suddenly absolutely *wrecked*, because out of nowhere, it's detecting a whole bunch of adenosine that it wasn't detecting before. As regards permanent changes, we don't really know. Abstaining from caffeine for several weeks causes a "reset" of sorts - after a few weeks, your brain realises that most of the extra receptors it created are surplus to the amount of adenosine you actually have, and it starts getting rid of them again. In theory, there's no reason why this would change over time, but it's not fully understood or known right now, so nobody can say for sure. **EDIT**: Holy *shit*, I did NOT expect this level of interest when I posted this! Thanks for all the precious metals, kind caffeinators! A lot of people have written some incredibly interesting questions and replies in response to this, I'll hopefully be able to answer a lot of them tomorrow! Two things: 1: You're absolutely correct, caffeine also has a vasoconstrictive (narrowing blood vessels) effect, but this effect itself isn't what causes the headache - it's actually caused by the blood vessels rapidly *dilating* when the caffeine wears off. This is an important aspect of the caffeine-related headache which I forgot to mention, as I was thinking purely of the effects on brain chemistry - which also play a role in adding to and triggering headaches. Thanks to everyone who pointed this out! 2: "Tireder" may indeed not be a word in most English speaking countries, but I can assure ye that it is used extensively in Ireland 😂 The Irish dialect of English has a lot of leftover quirks, because a lot of our grammar is derived from the original Irish language and then transposed on top of English, which we started speaking because our lovely ancestral neighbours obnoxiously objected to us speaking Irish whilst they were pillaging the place and generally getting up to all kinds of mischief. I blame whatever primordial substitute we had for Guinness all those hundreds of years ago. And this comment is of course meant in jest, I adore our present-day English neighbours and can be immediately and helplessly hypnotised by a woman speaking in an English accent 😂 Finally, the rambling nature of the above comment most likely came about because while caffeine can keep us physically awake, it cannot stem the inevitable descent into madness and moronity which accompanies staying up all night partying two nights in a row. Ergo, I will continue answering everyone's questions tomorrow morning 😉
41226a9c-7a11-4438-aac9-f6c5dbb84c28
bvwqa5
Why do people have different skin colours?
Different skin colours help in different climates, darker skin tones nearer the equator, lighter towards the North and south poles etc
267d608f-4338-4239-9c7f-27c427a40f77
bvwt2w
What are endocrine and exocrine in hormone system?
The best example of this is the pancreas, since it has both endocrine and exocrine parts. Endocrine means the things are secreted directly into your blood. The endocrine part of the pancreas makes insulin. It secretes insulin into your blood system. Exocrine means secreted through an epithelium (or endothelium), typically out of your body. The exocrine part of the pancreas secretes digestive enzymes. The digestive enzymes go into your gut and you poop them out.
e7b253af-f01f-4f59-bc4c-661b70165c59
bvwto6
Why aren't iPhone viruses more common? What does Apple do that makes iPhones so secure virus-wise?
They don't allow iPhone owners to modify and screw around with their products as much as Google does with Android. The devices are locked down more. Also, they have much stricter quality control requirements for their App Store. The Google Play store deletes harmful apps if they are detected but that doesn't mean someone can't upload something that does something bad in the first place. And you can download programs from multiple places, so you're not even restricted to the Google app store.
e7526214-ba48-4d2a-af83-74fdd2b58ac3
bvx60p
Why do scars sometimes hurt after they heal?
The skin has healed but the nerve endings don’t necessarily heal at the same rate as skin. Nerves can take up to years to heal.
5aae3c36-da98-49cd-a3ca-96d1e13f850b
bvx7xt
On hills or even mountains why doesn’t trees not grow according to the slope? Why do they turn up?
Trees can feel where the light is with their leaves. Most trees grow in a particular direction to get as much light as they can. This is called 'phototaxis'. If you replant a tree at an angle, or something like an earthquake moves the tree into an angle, then any new growth will bend upwards. Softer parts of trees, like leaves, will actually move and rotate over the course of the day to constantly face the sun. Many softer plants will do this with the whole plant - sunflowers are a famous example. If you plant a tree in a dark room with one window, though, it will grow towards the window. This doesn't always mean growing upwards, though - different trees have different strategies based on where they are. Tall trees are trying to get above other plants in a crowded environment. Short but broad trees are trying to cover as much space as they can - usually because they're under taller trees. Rounder trees are trying to use as little growth as possible - usually because they don't have to compete for light as much. Roots and seeds/very young sprouts also know which way is up, but they seem to use gravity instead of light, since they're underground. We don't really know how they do this as far as I'm aware. It may be down to the liquid inside a cell pushing more on the bottom of a cell than the top, thanks to gravity.
27ee2034-65b4-40dd-97f8-d6e5a3e37657
bvx8ay
How light can bounce off objects but it has no mass.
Light does not "bounce." A photon of light is absorbed by an atom, which excites an electron in that atom. The electron then relaxes, which causes the atom to give off (or emit) a photon of light. Think of it more like a person catching and then throwing a ball, as compared to a ball bouncing off of a wall.
4ceaa658-6d07-4846-a38e-e81f79b6d055
bvxzob
What is 'healthy food'?
There is no universal healthy food. The trick to healthy life is to eat all kinds of food in reasonable amounts.
f3e92068-0ee3-4b30-8fd2-e333a9960f49
bvyd9d
Why do toilets bowls most notably in America fill up during a flush before the water has appeared, and then almost empty before rising to the normal level?
Some toilets in the US flush like this but usually I see them in commercial buildings. Those usually dont have a basin and are connected to a direct water feed. There is piping, in the ceramic bowl, that feeds a portion of the high pressure water directly into the trap under the toilet bowl to help pull stuff down the drain. Most residential toilets have a basin that release the water into the bowl until the weight of the water overcomes the pressure created by the air in the trap under the bowl, allowing it to finally flow through. There are some residential toilets that function in manor like the commercials ones but do so in conjunction with a basin.
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bvygoj
The amounts of elements formed during supernovaes
You are many order of magnitude off with the amounts of element formed in a supernovae. 20 tonnes of uranium is nothing. Just the crust of earth have 40 trillion tonnes of uranium and the crust of earth is 1% of the mass of earth. Humans mine around 60 000 tonnes of uranium per year. & #x200B; In a type II supernovae the star had a initial mass of between 8 and 50 times the mass of the sun and the white dwarf that is left behind have a max mass of 1.4 solar masses. So the mass ejected is 5-48 solar masses. The sun have a mass of 2\*10\^27 tonnes that is 2 octillion tonnes or 2 billion billion billion tonne. & #x200B; If you look at [_URL_0_](_URL_1_) wit abundance of elements in the solar system most is hydrogen with 10\^10 compared to 10\^-2 of uranium. So the the solar system is approximate 1/10\^12 uranium If what is ejected from a super nova is similar to the composition of the solar system you would have 2\*10\^27\* 1/10\^12=2\*10\^15 tonnes ejected per solar mass of eject matter. That is 2 quadrillion tonnes or 2 million billion tonnes. So a Type II supernova eject somewhere around 10 million billion of tonnes of uranium. So the numbers in the original post is 15 orders of magnitude off. The answer might be a couple of magnitudes because I do not know if the abundance table is by number of atoms or by mass. If it is buy mass the amount is 200x more.
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bvzg0x
Why does your stomach hurt after running for a long time?
Simply put the blood that your internal organs need to break down the food inside your belly gets rediverted to the muscles that are used when running. The feeling of pain is the stomachs cry for blood. That also explains why it is alot easier to run on an empty stomach.
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bvzj35
How do musicians that actively talk about their illegal drug consumption not immediately get arrested, if their music acts as a confession?
Simple: Their music doesn't act as a confession. Music is a performance, you wouldn't arrest an actor for being a murderer just because they play one in a movie would you? Similarly you wouldn't arrest Eric Clapton for admitting he shot the sheriff, and you can't arrest a rapper for saying they are "ridin' dirty". All they would need to do is claim their statements were a performance (which they really shouldn't need to do) and no judge would accept their performances as probable cause for a search.
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bvzl9q
Why do you still feel the motion of waves after a long day at the beach?
It is a form of vertigo. Your brain adjusts to the feeling and it becomes normal. When you are back on land, your brain continues to go through the same process, trying to keep you up right, even though it's not needed anymore.
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bvzljs
why do comets take a sharp turn near the sun instead of continuing past it a longer distance that's more equal to their voyage toward the sun?
The main issue is how much angular momentum they have with respect to the sun (or other body being orbiter). Starting from a great distance away they have time to accelerate a lot toward the sun from its gravity, but they don't have the momentum to the side to form a roughly circular orbit like the planets do. As they get in close to the sun the angle of the sun's gravity starts to change and the relatively greater force of gravity pulls their path around, pointing their momentum from falling toward the sun into pointing away from it. Then it coasts outward being slowed by gravity until it falls back in.
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bvzxra
"Zero Tolerance Machining"
Zero tolerance machining is a bit of a misnomer, it really is just any form of machining with incredibly low tolerances. Parts manufactured by Electronic Discharge Machining (EDM), usually the ones you are describing, can have dimensions accurate to the millionth of an inch scale. EDM involves a wire or electrode brought close to a part underneath a bath of dielectric fluid. At very high voltages a spark can travel a precise distance to the nearest location on the metal part and vaporize a small piece that the fluid carries away. Repeat this process a lot and you can remove enough metal to produce the part you want accurate to a millionth of an inch. Do it twice to make parts that fit together and you get what you have described.
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bw0959
Why are the front of commuter trains flat?
There are 2 main kinds of air resistance or drag at low speeds: form drag and skin drag. Form drag refers to drag resulting from a objects geometry on the front/leading or end/trailing edges while skin drag is caused by friction with the air along the objects length as air moves over its surfaces. It turns out that for aspect ratios greater than 100:1 (an object 100 times longer than it is wide) that the skin drag will always be more significant that the form drag, so no matter what the front or end of the train looks like, the shape along the sides matters more. Thus if you are going to sink time and effort into reducing one, skin drag is the best bang for your buck and the flat front really isn't that bad. This doesn't mean a pointed end isn't helpful though, especially as the average speed of the train increases.
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bw0ktw
Why is it so much harder to stay awake when someone next to you is sleeping?
This is definitely just my own thoughts, as I’m not sure there is a medical reason, but likely the person sleeping next to you is a friend or someone very close to you, emotionally. People have a nature tendency to mimic those they feel close to (we see this in apes too). So if they cross their legs, you do the same. The same likely happens for sleeping. Your body is used to mimicking their actions, so you feel like you too should be laying flat with your eyes closed. Therefore, it’s time to sleep!
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bw0kzc
How did early humans know how to make fire?
We didn't for quite awhile. People took the Olympic Torch method with it and just kept one burning constantly. Our relationship with fire was probably fairly quick to understand that if you can find a fire you can bring one back with you. Us actually understanding how to supply the ignition source was probably an accident. The fuel is easy to see. Oxygen we had an abundance of, but the ignition source would've been a mystery outside of lightning or lava, etc. Us understanding how to create an ignition probably happened when someone dropped a flint stone and saw the sparks. Maybe even luckier the flint dropped against a sharp rock and the sparks hit dry grass. Someone familiar with fire characteristics of smoke would've seen this and immediately thought of a fire more than likely. Wouldn't take long to start experimenting with that flint rock until they made it work. Pretty much what we do now.
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bw0ngc
How do we measure how many calories are in food and drinks?
Using a device called 'calorimeter'. A calorie is equal to the amount of energy needed to raise the temperature of 1g of water by 1°C. You use the calorimeter to burn a piece of food and the released energy is used to heat a known quantity of water. From this information, you calculate the number of calories.
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bw0pcm
Why do video games need high budgets?
Indeed, paying the staff is the main reason why games cost so much. Play a game and count how many names appear in the credits for it. Then realize that they have to pay the salary of every single person who worked on the game, most of whom are highly skilled professionals with training in that field. That adds up very quickly.
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bw1zyf
If basically every plastic product is made with molds, how are molds made?
The mould isn't made of plastic. It can be carved from wood or formed with fibreglass. or even metal, and then fitted together so the melted plastic can be injected in
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bw209j
How can people take clear pictures of celestial bodies? Given both earth and that celestial body are constantly moving. And on top of it, earth's rotating.
Because they are really big and far away. Think of it like looking out at a mountain in a fast car/train, or a cloud thats moving at wind speed. Though we are moving and rotating really fast celestial bodies are really big and really far away so we can get a good photo.
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bw266y
What is a luxury tax as it refers to sports teams? How does signing potential free agents possibly impose the tax on a team?
It is a sort of soft cap. A hard cap like football is you can’t spend more than x amount of money on player salary . A luxury tax is a soft because you can spend more than the cap but at a penalty. If you spend more than x amount of money you will have to pay a penalty of a certain percentage for every dollar you go over the amount ultimately making signing players over the cap even more expensive. This money in some sports is given to teams with lower payroll. It is meant to make up for some teams being in smaller markets.
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bw2h1r
How do we know such specific things about extinct animals?
Everything we know about extinct animals comes from either fossil records or preserved animal specimens. If it’s an animal that has recently gone extinct, there may be observation records from scientists. There’d be a fair amount that is an educated guess, too.
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bw2ib9
What makes a song more prone to be stuck in someone’s head? What about it makes it catchy in that way?
Repeating the chorus. I have counted some songs and they will repeat the same line 24 times or more
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bw2qtj
What is MOA (Minute of Angle)? Its used alot in target shooting and hunting.
There's 60 minutes in a degree; they're used when a degree isn't precise enough. I know very little about shooting (guns), but I know a lot about math, so that's my best guess.
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bw2r0w
what causes hypoglycemia and how can it be prevented? Does a hypoglycemic reaction cause damage on the body?
Lots of things cause hypoglycemia. Having low blood sugar is fundamentally a problem of more sugar being removed from your blood than is being put back. Some things that can cause increased removal would be things that make your demand for energy go up, like intense exercise, or sepsis. Some drugs like insulin can take sugar out of the blood and shift inside all the cells, making your blood sugar go down. On the other side, there are also many things that impair your replacement of blood sugar. Fasting can cause low blood sugar. Your body has mechanisms to prevent this. For example, we store glycogen in our heart and muscles, and we can break this down into sugar when we need to, particularly if we haven't eaten in a while. Newborn babies don't have much glycogen storage, and have difficulty eating enough to keep blood sugar up, which why they are particularly at risk for low blood sugar. The best way to prevent it is by eating. If people are unable to eat, or otherwise can't keep up with eating alone, we can give IV glucose. Yes, hypoglycemia is dangerous. If a diabetic has blood sugar that is too high, that's usually more of a long term problem. Too low blood sugar can quickly kill you. When we have people come to the hospital with diabetic ketoacidosis (the blood sugar is very, very high), we take great care to bring it down slowly and in a controlled manner, because we could easily kill them if we go too fast and overshoot it. There is also increasing evidence that babies with even a single episode of hypoglycemia in the first day of life are at increased of having lower IQs and developmental problems.
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bw2sdv
How do MREs not expire? There are channels on youtube that review some of them that are from 1980s or older?
It's all about how well they are stored and what they are designed for. If you look at what goes into an MRE today, or what went into ration containers over the last century you'll see some common things. Anything that spoils on its own is removed. Anything that can spoil is packed in a way that minimizes the risk of spoilage, or has its recipe altered to make it more resistant to spoilage (for example, shelf stable bread and milk). The exterior container is designed to keep air and water out of the package, ensuring that no outside influences attack the food either. If the container is properly stored these things can last for years without trouble. When you watch someone like Steve1989MRE eat old rations one of the first points of commentary he will make (other than looking for a hiss) is how damaged the container is. He can usually tell just by looking at the exterior how viable the food inside will be.
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bw2uhf
How and why does the body/brain become "alcohol dependent" after continuous drinking? And what makes it possible for an alcoholic to experience seizures, hallucinations, heart failure, etc. (the "DTs") when they stop drinking?
Physiological dependence occurs because alcohol (ethanol, which is the principal form of alcohol in booze) binds to receptors that normally take a molecule called GABA (gamma aminobutyric acid), which primarily works as a depressant for the central nervous system. GABA is usually produced in a way that balances out a different molecule called glutamate, which primarily works as to excite the central nervous system. When ethanol increases the activity at GABA receptors continuously, the brain becomes accustomed to that artificial influence and decreases its natural production - the balance of GABA and glutamate receptor activity, on average, "appears" balanced to the brain's normal mechanisms. Ceasing to consume ethanol leaves the brain with a lower-than-normal amount of GABA receptor activity, and either a normal or increased amount of glutamate production and receptor activity, resulting in over-excitement of the CNS. This can have effects ranging from unpleasant (shakes, confusion, mild anxiety) to very distressing or even life-threatening (alcoholic hallucinosis, delirium tremens, seizures) because the excess glutamate causes the nervous system to be active in ways that it should not normally be. EDIT: It is also worth mentioning that something very similar happens with other GABAergic drugs such as benzo- and thienodiazepines (e.g. alprazolam, diazepam, etc.). This is why benzo withdrawal can be similarly dangerous.
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bw30nj
why do scabs disintegrate after prolonged exposure to water?
Scabs are principally clumps of clotted platelets (one type of cell in blood) the air-exposed part of which dries out and hardens. Rehydration can restore the "wet" version of scab in part and make it less structurally stable. Add movement (such as the flow of water in a shower) and the sloughing away of the clot is relatively easy under wet conditions.
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bw3lwe
Why do all the planets orbit the sun horizontally instead of vertically, or at random angles?
Most of these answers are flat out wrong or answer the wrong question. When the solar system was being formed, the was a cloud of dust, gas, and maybe rocks/ice in space much much larger than the current orbital radius of Pluto. If you calculated the center of mass of this cloud of material, every particle had some amount of angular momentum or angular motion around this point. If you did a vector sum (so things orbiting in opposite directions cancel out proportional to mass) of the angular momentum of every particle, you would find that there was some arbitrary "net" axis of rotation for the entire cloud. Normal (at 90 degrees) to this axis is the net orbital plane for the majority of objects in the solar system. Since according to physics, angular momentum like linear momentum or energy, must be conserved in the absence of an outside force, the cloud will maintain this "net" axis of rotation as things crash into each other and stick together forming planets and larger bodies. You can think about this, as if two objects, one moving downward across the orbital plane hits another moving upward across it, the resulting new body formed from the collision will have the "up" and "down" components canceled out, leaving only the motion in the direction around the axis along the net orbital plane. Visual Explanation: [MinutePhysics](_URL_0_)
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bw3wh8
If neutering or spaying an animal is necessary to prevent unwanted babies, why not just give them a hysterectomy or vasectomy instead? Do the remaining hormones still have other negative effects?
Spaying a female animal IS a hysterectomy - the uterus is removed. Yes, the hormones are a reason for neutering male animals. Testosterone can cause aggressive, territorial behaviour such as fighting and spray-marking, or wandering in search of females.
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bw406y
When suspects are being interviewed, why are they advised by their lawyer to say “no comment”?
Literally anything you say can be used against you. You wont help yourself by speaking to the police in any way.
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bw42u6
WHat causes split ends?
With my hair, it's the result of a hair snapping partway along. Kinda like bending a twig back and forth until it breaks - it doesn't break cleanly. Then if it gets the chance, the rough broken end opens up along the hair and *voila*, split end.
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bw46f8
When you cut something in half, what happens to the stuff in the middle? Does it fall off or is it destroyed? Or has it just been pushed to either side?
short answer: it depends. things are made of atoms. atoms are extremely small. atoms bond together in different ways to make up hard objects. some of the ways they bond are strong, and some are weaker. when you cut something it breaks some of these weaker bonds and separates the atoms. & #x200B; so the stuff in the middle usually ends up on either side, like when you cut with a knife, or winds up as sawdust or powder when you cut with a saw.
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bw480b
Why does drinking juice hurt when you have a sore throat?
Juice is acidic and causes a stinging on abbrased or inflamed tissue such as when your throat is sore Example: poor lemon juice on a cut, same effect
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bw4edy
How can space bend, expand, and ripple if it’s just an empty void?
General relativity posits the existence of something called a metric - a structure in spacetime that determines the distances between objects. This isn't wholly dissimilar to how quantum field theory posits the existence of quantum fields, or classical electromagnetism posits the electric and magnetic fields, except that we generally think of distances as a fixed background property, so it's a bit odd to think of this as a variable property. When physicists say that 'space' bends or expands, they really mean that the metric takes on different values, and so distances and anything related to them (velocities, time intervals) become properties contingent on where in space you are. Like for quantum fields, we don't have any underlying physical model for what this metric is (which I think is what zdepthcharge was trying to get at). It's just an assumption of the theory that, whatever the physical object 'actually' is, corresponds to this mathematical structure. String theory explains it one more layer, by radically changing the entire structure of spacetime, and having this metric be an emergent property of graviton field within this structure and its interaction with the other fields. The issue is that it's not an experimentally tested theory, or even a theory that describes a single universe - it's a family of particular models which can describe many kinds of universe, and as such can make a variety of predictions. There are some universal ones (classes of new particles, or higher-order effects in currently known interactions) which could be used as tests, but none have yielded anything so far.
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bw4hfo
Why aren’t commercial aircraft using electric engines? Aviation is a huge carbon emission source after all.
Batteries are heavy. An electric airliner isn't really an option. They also need to fly frequently, landing to deliver passengers then turning around to take off with more, and recharging an aircraft for ages also won't work.
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bw5c7h
Why and what makes clouds opaque?
So there's a fun feature in physics called Mie Scattering, and it only works in spherical drops. If the drops and the wavelength of light are about the same size, then all colors (wavelengths) of light scatter about equally. In even simpler terms, the length of the waves of light in a cloud are about the same size as the water droplets, so all the colors bounce out into other directions about the same amount. when all these colors reach your eyes, you register that the cloud is white. The actual process is so complicated that my grad school course in electrodynamics didn't bother cover it in depth, but hopefully that was clear enough.
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bw5f1y
Sedation and Psychiatric Drugs
First: SSRIs(Citalopram/Celexa, Prozac, Lexapro) are not sedatives. They work on a mechanism that we don't exactly understand. SSRIs work, in a general sense, by blocking certain neurons from re-uptaking serotonin. This makes more serotonin available in the brain, which can treat a number of mental disorders, among those dealing with unstable emotions and eating disorders, as serotonin is a key emotional and appetite regulator. Over time, an excess of serotonin has actually been shown to grow areas of the brain related to depressive states. The only sedation is related to the new amount of serotonin in the brain, which if the depression is actually caused by a lack of serotonin, should not cause any sedation, but a return to normalcy. SNRIs(Cymbalta/Dulexotine, Effexor) work in much the same way, but they also inhibit norepinephrine(I'm calling it N from now on because spelling that takes forever) reuptake. SNRIs are more blunt, in that they inhibit more of each uptake. N is responsible for energy and motivation. Again, if it's working correctly, it should not cause sedation at all, but a normal feeling. This is mainly for things like anxiety disorders, while combining the serotonin reuptake inhibition, as depressive states and social dysfunction disorders usually go hand in hand. If these are not working as intended, they are more likely to cause a manic state than sedation. & #x200B; SSNRIs(Savella) are different entirely. They are not intended to treat depression, but fibromyalgia. It is a pain regulator medicine. & #x200B; As someone with both low dopamine, N, and serotonin, with pretty severe depression, social anxiety, and ADHD, dopamine is much less understood, and there is no good treatment for this combination aside from a drug cocktail, I currently take bupropion(Wellbutrin), an NDRI(N-dopamine reuptake inhibitor) for social anxiety disorder and ADHD, as well as an add-on for depression and Celexa, an aforementioned SSRI for major depressive disorder. NDRIs work much the same way as for the two above, but inhibit N and dopamine reuptake. & #x200B; We know a lack of dopamine leads to emotional ennui, an inability to feel anything, a disturbed sleep schedule, and inability to focus/hyperattention and difficulty in remembering, AKA ADHD. An excess of it can lead to delusions and hallucinations, like with schizophrenia and psychosis. I am far less versed on antipsychotics though.
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bw5sgg
Why do wine “spoil” so quickly after being opened as opposed to hard liquor?
Others pointed out the wine oxidizes, but they missed the main thing: There are air-breathing bacteria that can survive a moderate alcohol content, turning the stuff into acetic acid (aka vinegar). The way they used to make vinegar was to just take wine, cider, beer or any other alcoholic beverage, and let it sit in an open vessel, so that bacteria from the environment would infect it and turn acohol into acid. So when you open a bottle of wine, the exact same thing is going to happen. Oxygen and bacteria get into the bottle, and start producing acetic acid. Hard liquor doesn't do that because it has a too high alcohol content for bacteria to live in, although some can survive in a dormant form - alcohol for disinfection has a much higher alcohol content than the usual 40%.
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bw624c
Why do sharks have to continuously move to breathe but fish can breathe just fine while sitting still?
It depends on the fish. & #x200B; Some fish(and sharks by proxy) have to keep moving to keep water over their gills. & #x200B; Some have the ability to use their mouths to push water over their gills to be able to breathe, and thus can be immobile.
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bw63fv
Why does cutting onions open hurt our eyes?
When you cut an onion, the onion releases a gas which combines with the water in your eyes to form a mild acid. This acid is the burning feeling you get.
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bw64rw
Why do you hear helicopter sounds when you have your windows down while driving on a highway?
Resonant frequency of the cabin. You can relieve this by opening another window a small amount, preferably on the other side of the car. The resonant frequency thing is the same reason why a whistle, or a flute works, too. It's just that a car cabin is so much larger that it's resonant frequency is much lower. So low, it's subsonic. (lower than 20hz).
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bw68aw
How do restaurants charge your card for tips after having already run them?
When they run your card, they are preauthorizing a charge to your card for the minimum amount of your bill with zero tip. They get approval from the card issuer for the minimum amount, but the transaction is left open until they know what tip you left. When they see the tip, they add that to the preauthorized charge and then the transaction is officially closed.
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bw6drw
Cooling Sheets/Pillows Magic?
To understand that, you need to know that there is more than temperature of an item that determines how hot/cold it feels. It is mostly about how quickly heat enters or leaves your body, which is dependent on a property called thermal conduction. Something very conductive, like metal or stone, will feel much colder on a cool morning than something that is more of an insulator, like carpet, even though they are exactly the same temperature when you walk across them in the morning. So, to answer your question, the way to make something feel cooler would be to make it out of more thermally conductive materials, spread your heat over a bigger area, which will more efficiently transfer your body heat out f your body to the room making you feel cooler.
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bw7335
What does this hand symbol mean that is frequently used by Jesus?
It is a symbol for benediction. It is the first part of the Benediction prayer(where you cross yourself), fingers up is "in the the name of the Father(God)", pointed down, "The Son", the then sweeping from left to right" in the name of the Holy Spirit". & #x200B; When the fingers are pointed up, as in this, it is referring to God, and is also a blessing onto the viewer to "speak well", or live in the words of God. It is a simplified version of a more complicated hand sign, which references Phil 2:10.
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bw7724
how can employment rate be 70% instead of 93% if unemployment rate is 7%?
Because "employment rate" takes into account people who do not wish to work, or are not actively seeking work, while "unemployment rate" excludes these people.
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bw7j0c
Why are busses significantly safer than cars when they have far fewer safety features (eg airbags, seatbelt etc)?
1. They are very large and heavy so a collision with a small car doesn't crush them, or even completely stop them. 2. They are professionally driven.
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bw7sqg
Considering that, developmentally, the ureter grows from the bladder and joins the kidneys later on in development. How does the body manage to get the ureter to join when the two organs are so distant?
The kindey forms from a structure called the mesonephric duct. This duct ends in a blind end just near the cloaca which at the early stages is just the front part of the very basic gut tube at the bottom. The cloaca will develop into the bladder as the embryo grows. The early kidney or mesonephric duct at this stage starts out very low in the embryo so the distance between the duct and the cloaca is very small. The top parts of the duct degenerate during development until the very bottom part is all that remains. The kidney then moves up to its adult position, nestling under the adrenal glands. The adrenal glands dont grow out of the kidney, but are often pictured as if they are one object. Think of it more like a hat the kidney moves up into wearing. The ureter elongates as the kidneys move up. This makes the ureter long despite the fact that in development the distance between the "mesonephric duct" and the "cloaca" is very small. This explains it in greater detail. _URL_0_
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bw89oj
why does the water pressure drop a little bit once the water heats up?
Do you mean water flow? Usually rubber in taps expands when it heats so the flow decreases.
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bw8hqb
How come you can go for days without eating and not feel hungy when you're sick?
Your body usualy has "reserves" that can sustain you for a while. When you're sick, it can prioritize healing, not "waste energy" digesting and to avoid chances of ingesting more contaminants (more things to fight off). So it doesn't send you hunger signals. (Ofc that can go wrong, especialy if you don't have much reserves to start with, and you can require an IV, but generaly a few days shouldn't be a problem)
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bw8qnv
How you can isolate the vocals on a song using the instrumental
It depends on how the song is mixed, and it generally works better with tracks that are in mono rather than stereo. It’s to do with a thing called phase cancellation - exactly the same way noise cancelling headphones work. You play a sound, and at the same time you play the same sound but with the waveform flipped upside down. The peaks and troughs in the waveform cancel each other out and you’re left with silence. So - if you use this technique with an identical instrumental track, the sound of the instruments will cancel each other out, and you’ll be left with nothing but the vocals. Some recording studios use this technique for playback, so a musician or singer can record without requiring headphones and still end up with a clean, isolated track. Here’s an example of guitarist Tommy Emmanuel doing just that: _URL_1_ And here’s some further reading if you’re interested in learning how to do it yourself: _URL_0_
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bw8v78
Why can faking confidence develop into real confidence but faking happiness doesn’t develop into real happiness?
Is it a fact that faking confidence can be real and that faking happiness can’t be? Does anyone have data on that?
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bw8vj1
How come wood or paint becomes reflective the finer the sanding process go?
The smoother a surface is the less diffrence there is in reflection of light. Its the same thing when you take a standard sheet of steel and grind/buff it down to be extremely smooth. Youll have almost a mirror because most of the light is now reflected in a uniform manner.
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bw8wsg
Planes use flaps to land and to take off. So why do they retract them while they are on the ground, ie why not just leave them deployed?
People keep mentioning the possibility of damage to extended flaps (which I'm sure is a secondary reason), but the main reason is to keep the plane on the ground. Flaps are designed to create significantly more lift at low speeds at the expense of increasing drag. They deploy them on takeoff and landing so the plane can transition to and from flight at lower ground speeds, which reduces stress on the airframe and landing gear and is just easier for the pilot to manage. If you leave flaps deployed on the ground you risk gusts of wind lifting one or both wings while the aircraft is parked. That's bad. Since they also increase drag (especially in landing configuration) in windy/gusty situations they also increase the forces on the brakes and chocks while parked. The risk of the aircraft moving uncontrollably, tipping, flipping, etc is all significantly increased with the flaps down on the ground. So they retract them when they don't need them.
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bw99hh
What is the reasoning behind us getting excited when meeting celebrities, asking them for photos, signatures, and such?
For the same reason that a person may get excited if they see a super rare car, or rare animal, or an astronomical phenomena that only occurs every 100 years. It is an unusual occurrence that may only happen a couple of times within your life time. & #x200B; As for interacting with the celebrity, the same applies, but anxiety will amplify the feeling.
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bw9cuc
How does a store know I'm stealing something?
I’m not sure if I can write enough words for ELI5: Sensors by the door don’t work for everything, it’s only certain high value items, such an item will have a little strip on them that the cashier passes over something several times to deactivate when you buy it. I guess the strip is probably an RF chip, but I’m not sure. If you try to pilfer something that doesn’t have this tag, the alarm will not go off, but the store may or may not have other loss prevention measures such as people monitoring cameras that would watch you try to steal the other thing.
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bw9gwf
How do speakers work?
I can totally see how this is confusing, it might help to think about a speaker as a reverse ear - they both have surfaces that move with the changing air pressure. Your ear has no problem hearing two different tones at once. The reason this works is the idea of superposition - when you have two tones playing together they add up to make a complicated shape. These tones can be split up by clever maths (fourier transform) or by your clever brain. I guess it's a bit like a pixel on the screen you're looking at right now. There are three 'tones' red, blue and green. When you have multiple of these 'tones' on in the same pixel they mix together to make another colour, but still contain all the information from the base colours, which can be separated from each other. When you see a waveform in a program like Audacity you're seeing the result of adding all these tones together. The speaker follows the waveform shown, but it is built from lots of different tones which can still be extracted. If you do an image search for superposition you'll get a better understanding of how all these different frequency components add together.
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bw9hfl
Why does exposure to air make food go stale?
Moisture evaporates out of the food when it's exposed to air for to long. Moisture is what makes the food squishy and easily chewable. If you put the food in the microwave and put a damper paper towel near it, this helps a lot
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bw9ie2
why is is still hard to fall asleep when you’re sleep deprived?
When you are sleep deprived, your body produces more cortisol (stress hormone), which among many things, keeps you awake. It is one of our evolutionary adaptations in which when danger is present (or in modern day, stressors), our body is able to somehow keep going despite decreased sleep.
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bw9jj4
what exactly is Tinnitus and is there a way to get rid of it?
I found this remedy on Reddit somewhere. It sounds silly, but it seems to work for me. Place your hands behind your head with the tips of your middle fingers touching with your hands over your ears. Your index fingers should be resting at the base of your skull. Place your index fingers on top of your middle fingers and snap them down on the base of your skull and alternately drum several times. Somehow this disrupts the nerves and it has always worked for me.
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bw9tpj
why do comets look like barren deserts in close-up pics when they're described as dirty snowballs?
Nearly all of the water, ice and other volatiles on a comet are BENEATH the surface. So ya, that's basically it! That's the main straight forward answer to your question, as to why you don't see water-ice in most upclose photos of comets. --------------------------------- However, just to go into a bit more deeply So... as the comet comes soaring into the inner solar system (where Earth is), is does the following: - At a certain point it crosses over the "frost-line" of our solar system. - The frost-line is the point that is close enough to the sun to begin heating and warming the surface, along with a few layers directly beneath the surface, to the point where ice melts, and water begins to evaporate/vaporize. - So at that point, that's when the water and other volatiles start to vaporize, and begin escaping from beneath the surface. - Sometimes they can't escape right away from below the surface and get trapped or blocked, and form pockets of gas. - The pockets of gas then build up more and more pressure, then burst upwards, causing a small eruption on the surface, and a jet of gas. - These jets of gas/volatiles can even act like mini rocket engines and change the speed, course of the comet! - Anyways as the comet gets closer and closer to the sun, all these vaporizing volatiles begin to leave a hazy cloudy trail behind. That's why you get these beautiful hazy tails with comets. - NEXT, the comet swings around the sun, and then begins moving further and further away from the sun. - It then goes back across the frost-line, freezing in a deep cold state, so that no more water and volatiles are escaping very much anymore. - And so, if you visit the comet in the cold part of the frost-line border, then all you will see is a rocky surface, because on it's last approach to the sun, the sun vaporized all the surface ice, and the stuff directly below. - IN THE END, that means gradually with each crossing of the frost line and approach to the sun, the comet will loose more and more of its water/ice/volatiles. - So it's hazy comet tail will become less and less spectacular and impressive with each future orbital pass.
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bw9wkv
when a helicopter's blades are spinning incredibly fast, why do they sometimes look distinguished as if they're actually barely moving at all?
Are you referring to videos of helicopters? Because this shouldn't happen in real life. As for the videos, the rate of the spin of the blades simply matches the "shutter" speed of the camera, so that every time an image is generated the blades happen to be in the same or nearly the same position
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bwa8ez
Why does it "feel good" to look at someone that cute?
When looking at something or in your case someone attractive, your body releases some happy hormones which make you feel good. This is because of the fact that our bodies are biologically always in search for a mating partner and the 50 year man is most likely not a prefferable mating partner for you.
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