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Talk of particle physicists testing theoretical physicists' predicted particles by colliding particles in accelerators suggests that quantum particles are tiny Newtonian particles that experimentalists "crack" open to reveal their structure. Instead, when two particles, each of a certain mass—measured in terms of "energy" as electronvolts—are collided, they can combine into a particle of that combined mass/energy, and the generated particle is "observed" for correspondence with the prediction. |
It is not controversial among physicists that all particles are "energy". Loop theorists, sometimes in rivalry with string theory, claim that spacetime itself converts into the particles. Matter's being a special variant of energy was a consequence of Einstein's special theory of relativity, and thereupon Einstein formalized the mass-energy equivalence, E=mc. When sufficiently energetic photons collide, they can combine and generate matter—matter creation. All particles have antiparticles, and atoms of matter have antiatoms of antimatter, whose union annihilates the particles and matter while leaving energy. |
An inspiring development is discovery of mirror symmetry, whereby Calabi-Yau spaces tend to come in pairs such that solutions previously difficult within the extreme vibrational mode of one string can be solved by through the mirror Calabi-Yau space's geometry in its opposite range. |
String theory is usually solved through conformal field theory, a quantum field theory on 2D space. It is confirmed that molecules can collapse to 2D. And the electron, long presumed an elementary particle, apparently splits into three entities separately carrying the electron's three degrees of freedom when the molecules that contain the electrons are channeled through a 1D pathway. |
Scientist |
A scientist is a person who studies or has mastered the field in science. A scientist tries to understand how our world, or other things, work. Scientists make observations, ask questions and do extensive research work in finding the answers to many questions others may not know about. Scientists have researched many things. |
Scientists may work in laboratories for governments, companies, schools and research institutions. Some scientists teach at universities and other places and train people to become scientists. Scientists often do experiments to find out more about reality, and sometimes may repeat experiments or use control groups. Scientists who are doing applied science try to use scientific knowledge to improve the world. |
Scientists can work in different areas of science. |
Here are some examples: |
Soapbox |
A soapbox is a temporary platform used to give a speech. During the 19th century, soap was transported in wooden boxes. When a person had new or unusual ideas, and wanted to talk to a crowd about them, sometimes he or she would stand on an empty soapbox so that everyone could see and hear the talk well. |
People sometimes use the word "soapbox" to mean a place to say new or unusual things. |
Supernatural |
The word supernatural (from ) is used for things that some people believe are real, but that are not part of nature or inexplicable by the scientific laws of nature. Because we cannot prove whether these things are real, people often disagree about these things. |
Some say that we should talk about things without talking about the supernatural, because we cannot prove that supernatural things are real. Other people say that although we cannot prove supernatural things in a scientific way, they are real. Some examples of supernatural things or examples are: |
Spirit |
A spirit is considered to be the part of a being that is not the body. Other words with the same meanings are soul and ghost. When a body is alive, it has a spirit in it. Death is when the spirit separates from the body. |
Christians believe that spirits exist in Heaven or Hell. (See 1 Timothy 3:16, 4:1) |
Spiritualists believe that spirits can talk with people, or change things in the world. Many religions forbid communicating with such spirits in any way, (see Leviticus 19:31) but a few include this as part of their practice. |
Another use of "spirit" means the main purpose or meaning of a sentence or document. For example, the "spirit of a law" is the true meaning of the law which the creator wanted. This phrase is often used when the words and sentences of a law could mean more than one thing, but a judge must decide what meaning is correct. |
Seed |
A seed is the part of a seed plant which can grow into a new plant. It is a reproductive structure which disperses, and can survive for some time. A typical seed includes three basic parts: (1) an embryo, (2) a supply of nutrients for the embryo, and (3) a seed coat. |
There are many different kinds of seeds. Some plants make a lot of seeds, some make only a few. Seeds are often hard and very small, but some are larger. The coconut is as big as a child's head, but it contains more than just a seed. At the start, seeds are "dormant" (resting inside their coat) for a while. When the seed is ready to develop, it needs water, air and warmth "but not sunlight" to become a seedling. |
Seeds carry the food that helps the new plant begin to grow. This food store is in the endosperm, and/or in the cotyledons. Many kinds of seeds are good food for animals and people. The many kinds of grain that people grow, such as rice, wheat, and maize, are all seeds. Seeds are often inside fruits. |
A seed, though not active, is a tiny living thing. It contains the embryo of the future plant, which is not changing or developing: it is "dormant". The common idea is that the seed "sleeps" until it gets what it needs to wake up. That is not correct. Different seeds have different habits, no doubt adapted to their habitat. There are different kinds of resting stages in seeds: |
When a seed germinates ("wakes up"), it begins to grow into a little plant called a "seedling". It uses the soft fleshy material inside the seed for nutrients (food) until it is ready to make food on its own using sunlight, water and air. |
Most seeds germinate underground where there is no sunlight. The plant does not need the nutrients in soil for a few days or weeks, because the seed has all the things it needs to grow. Later, though, it will begin to need sunlight. If there is sunlight, the plant will use it to grow healthy. If there is no light, the plant will still grow for a while, but its plastids will not mature: the chlorophyll does not turn green. If the plant does not get enough light, it will eventually die. It needs light to make food for itself when the reserve in the seed runs out. |
Seeds have been an important development in the reproduction and spread of conifers and flowering plants. Plants such as mosses, liverworts and ferns do not have seeds, and use unprotected spores and other methods to propagate themselves. Before the upper Devonian period, land plants, like modern ferns, reproduced by sending spores into the air. The spores would land and become new plants only in favourable conditions. Spores have little food stored, and may be just single cells rather than embryos. |
The evolution of seeds changed the plant life cycle by freeing plants from the need for external water for sexual reproduction, and by providing protection and nutrients for the developing embryo. These functions allowed plants to expand beyond the immediate neighbourhood of water sources. They were able to exploit environments which were drier and more upland. This can be seen by the success of seed plants in important biological niches on land, from forests to grasslands both in hot and cold climates. The present-day seed plants are the Gymnosperms, with naked seeds, and the Angiosperms with covered seeds, usually fruits. |
The first true seeds are from the upper Devonian 370–354 million years ago, which is probably the theatre of their first evolutionary radiation. The earliest seed-producing trees were in the forests of the Carboniferous period. The seed plants steadily became one of the most important elements of nearly all ecosystems. |
Sail |
A sail is a large piece of cloth on the top of some boats. The wind goes around the sail and makes the boat move through the water. The piece that the sail is attached to is called a mast. Some boats have many sails, and some have only one. Usually, small boats have only one sail, and bigger boats have more. Boats with sails are called "sailing boats". There are many different names for different kinds of sailing boats with different kinds of sails. |
Before people made boats with engines that used coal or oil, sailing boats were an important way to travel across oceans. Now they are not so important for transport, but they are still used for recreation and competition. |
Modern sails can be classified into three main categories: |
High-performance yachts, in particular some catamarans such as the International C-Class Catamaran, have used or use rigid wing sails, which are said to perform better than traditional soft sails. In particular, a rigid wing sail was used by Stars and Stripes, the defender which won the 1988 America's Cup, and by USA-17, the challenger which won the 2010 America's Cup. |
Most modern yachts, including bermuda rig, ketch and yawl boats, have a sail "inventory" which usually includes more than one of these types of sails. Although the mainsail is “permanently” hoisted while sailing, headsails and spinnakers can be changed depending on the particular weather conditions to allow better handling and speed. |
Spanish |
The word Spanish means: |
Skin |
Skin is the outside covering of animals. The skin of different kinds of animals is very different. Many kinds of animals have hair or fur on their skin. Birds have feathers on their skin. Most fish, and reptiles, like snakes and lizards, have scales on their skin. |
The skin of human beings usually has very small hairs on it that are hard to see. Some people have more hair, or hair that is easier to see, and some have less. People have hair that is longer and easier to see on some parts of their bodies, such as the tops of their heads and men's beards. The skin is actually the largest organ of the human body. Without our skin we would easily get infected with diseases. Keeping it clean is important to health, and skin care is a big industry. |
The skin of cows can be made into leather. Leather is sometimes used to make shoes, bags, and balls. |
Other things can be said to have "skins". People often say that fruits, such as apples, bananas, grapes, kiwis, and strawberrys, and vegetables, such as potatoes, have "skins". |
Search engine |
A search engine is a website that allows users to look up information on the World Wide Web (WWW), known as the Internet. The search engine will achieve this by looking at many web pages to find matches to the user's search inputs. It will return results ranked by relevancy and popularity by the search engine. Some popular search-engines are Google, Yahoo!, Ask.com, Forestle and Bing. Older services include Webcrawler, Lycos, and Alta Vista. |
To use a search engine you must enter at least one keyword in to the search box. Usually an on-screen button must be clicked on to submit the search. The search engine looks for matches between the keyword(s) entered and its database of websites and words. |
After the user inputs their search or query into the search bar, a list of results will appear on the screen known as search engine results page (SERP). This list of webpages contains matches related to the user's query in a particular order determined by a ranking system. Most search engine will remove "spam" pages from the list of results to provide a better list of results. The user can then click on any of the links to go to that webpage. |
Search engines are some of the most advanced websites on the web. They use special computer code to sort the web pages on SERPs. The most popular or highest quality web pages will be near the top of the list. |
When a user types words into the search engine, it looks for web pages with those words. There could be thousands, or even millions, of web pages with those words. So, the search engine helps users by putting the web pages it thinks the user wants first. |
Search engines are very useful to find information about anything quickly and easily. Using more keywords or different keywords improves the results of searches. |
A search service may also include a portal with news, games, and more information besides a search engine. Yahoo! has a popular portal, and MSN Search is part of the MSN portal, while Google has a simple design on its front page. Search services usually work without charging money for finding sites, and are often supported with text or banner advertisements. |
Sabbath in Christianity |
Sabbath in Christianity is the day of rest and service to God. The idea of the Sabbath in Christianity comes directly from the idea |
of the Sabbath (or Shabbat) in Judaism. In fact, the word Sabbath itself comes from the Hebrew word "Shabbat." Like the Jewish Sabbath (Shabbat), the Sabbath in Christianity comes from the Genesis story of Creation. But unlike Jews, most Christians have Sabbath on Sunday, not Saturday. They also rest, but not the same way as Jews. The exact way depends on the church denomination. |
Most Christians honor the Sabbath on Sunday to remember the Resurrection of Jesus on the first day of the week on the Jewish calendar. They say that there is an analogy between the obligation of the Christian day of worship and the Sabbath-day ordinance. These two rules are not literally identical though. They say that this ordinance is no longer valid, because God has replaced his old creation by a new one. For this reason, the obligation to keep the Sabbath is not the same for Christians as for Jews. They say there are examples in the New Testament, and in other writings surviving from the first few centuries. |
Some conservative Christians are "Sabbatarians". Most of these follow the Reformed traditions. Sabbatarians think the first day of the week or "Lord's Day" is the new Sabbath. This is because the 4th commandment has never been revoked and Sabbath-keeping is in any case a creation ordinance. |
Still others believe that the Sabbath remains as a day of rest on the Saturday, reserving Sunday as a day of worship. In reference to Acts 20:7, the disciples came together on the first day of the week (Sunday) to break bread and to hear the preaching of the apostle Paul. This is not the first time Christians assembled together on a Sunday; Jesus appeared to the Christians on the "first day of the week" while they were in hiding. One can maintain this argument in that Jesus himself maintained the Sabbath, although not within the restrictions that were mandated by Jewish traditions; the Pharisees often tried Jesus by asking him if certain tasks were acceptable according to the Law. This would seem to show that while the Sabbath was still of importance to the Jews, Sunday was a separate day for worship and teaching from Scriptures. |
The Seventh-day Adventists and other churches disagree with some of these views. They argue that the custom of meeting for worship on Sunday originated in paganism, specifically Sol Invictus and Mithraism (in which sun god worship took place on Sunday). This is therefore an explicit rejection of the commandment to keep the "seventh" day holy. Instead, they keep Saturday as the Sabbath as a memorial to God's work of creation believing that none of the Ten Commandments can ever be destroyed. Seventh-day Sabbatarians claim that the seventh day Sabbath was kept by the majority of Christian groups until the 2nd and 3rd century, by most until the 4th and 5th century, and a few thereafter, but because of opposition to Judaism after the Jewish-Roman wars, the original custom was gradually replaced by Sunday as the day of worship. The history of these changes is certainly not altogether lost regardless of any belief in a suppression of the facts by a conspiracy of the pagans of the Roman Empire and the clergy of the Catholic Church. |
Jews had come to be hated in the Roman Empire after the Jewish-Roman wars. This led to the criminalization of the Jewish Sabbath. Hatred of Jews is apparent in the Council of Laodicea (4th Century AD) where Canon 37–38 states: "It is not lawful to receive portions sent from the feasts of Jews or heretics, nor to feast together with them." and "It is not lawful to receive unleavened bread from the Jews, nor to be partakers of their impiety." In keeping with this rejection of the Jews, this Roman council also criminalized the Jewish Sabbath as can be seen in Canon 29 of the Council Laodicea: "Christians must not Judaize by resting on the Sabbath, but must work on that day, rather honoring the Lord's Day; and, if they can, resting then as Christians. But if any shall be found to be judaizers, let them be excommunicated from Christ." |
In the Gospel of Mark 2:28 Jesus says 'the Son of Man is lord even of the sabbath'. |
Statistics |
Statistics is a branch of applied mathematics that deals with collecting, organising, analysing, reading and presenting data. Descriptive statistics make summaries of data. Inferential statistics makes predictions. Statistics helps in the study of many other fields, such as science, medicine, economics, psychology, politics and marketing. Someone who works in statistics is called a statistician. In addition to being the name of a field of study, the word "statistics" can also mean numbers that are used to describe data or relationships. |
The first known statistics are census data. The Babylonians did a census around 3500 BC, the Egyptians around 2500 BC, and the Ancient Chinese around 1000 BC. |
Starting in the 16th century mathematicians such as Gerolamo Cardano developed probability theory, which made statistics a science. Since then, people have collected and studied statistics on many things. Trees, starfish, stars, rocks, words, almost anything that can be counted has been a subject of statistics. |
Before we can describe the world with statistics, we must collect data. The data that we collect in statistics are called measurements. After we collect data, we use one or more numbers to describe each observation or measurement. For example, suppose that we want to find out how popular a certain TV show is. We can pick a group of people (called a "sample") out of the total population of viewers. Then we ask each viewer in the sample how often they watch the show. The sample is data that one can see, and the population is data that one cannot see (assuming that not every viewer in the population are asked). For another example, if we want to know whether a certain drug can help lower blood pressure, we could give the drug to people for some time and measure their blood pressure before and after. |
Numbers that describe the data one can see are called descriptive statistics. Numbers that make predictions about the data one cannot see are called inferential statistics. |
Descriptive statistics involves using numbers to describe features of data. For example, the average height of women in the United States is a descriptive statistic: it describes a feature (average height) of a population (women in the United States). |
Once the results have been summarized and described, they can be used for prediction. This is called inferential statistics. As an example, the size of an animal is dependent on many factors. Some of these factors are controlled by the environment, but others are by inheritance. A biologist might therefore make a model that says that there is a high probability that the offspring will be small in size—if the parents were small in size. This model probably allows to predict the size in better ways than by just guessing at random. Testing whether a certain drug can be used to cure a certain condition or disease is usually done by comparing the results of people who are given the drug against those who are given a placebo. |
Most often, we collect statistical data by doing surveys or experiments. For example, an opinion poll is one kind of survey. We pick a small number of people and ask them questions. Then, we use their answers as the data. |
The choice of which individuals to take for a survey or data collection is important, as it directly influences the statistics. When the statistics are done, it can no longer be determined which individuals are taken. Suppose we want to measure the water quality of a big lake. If we take samples next to the waste drain, we will get different results than if the samples are taken in a far-away and hard-to-reach spot of the lake. |
There are two kinds of problems which are commonly found when taking samples: |
We can reduce chance errors by taking a larger sample, and we can avoid some bias by choosing randomly. However, sometimes large random samples are hard to take. And bias can happen if different people are not asked, or refuse to answer our questions, or if they know they are getting a fake treatment. These problems can be hard to fix. See standard error for more. |
The middle of the data is called an average. The average tells us about a typical individual in the population. There are three kinds of average that are often used: the mean, the median and the mode. |
The examples below use this sample data: |
The formula for the mean is |
formula_1 |
Where formula_2 are the data and formula_3 is the population size (see also Sigma Notation). |
This means that one calculates the mean by adding up all the values, and then divide by the number of values. For the example above, the mean is: |
formula_4 |
The problem with the mean is that it does not tell anything about how the values are distributed. Values that are very large or very small change the mean a lot. In statistics, these extreme values might be errors of measurement, but sometimes the population really does contain these values. For example, if there are 10 people in a room who make $10 per day and 1 who makes $1,000,000 per day. The mean of the data is $90,918 per day. Even though it is the average amount, the mean in this case is not the amount any single person makes, and thus is not very useful for some purposes. |
The mean described above is the "arithmetic mean". Other kinds are useful for some purposes. |
The median is the middle item of the data. For a given data formula_5, this is sometimes written as formula_6. To find the median, we sort the data from the smallest number to the largest number, and then choose the number in the middle. If there is an even number of data, there will not be a number right in the middle, so we choose the two middle ones and calculate their mean. In our example above, there are 10 items of data, the two middle ones are "57" and "64", so the median is (57+64)/2 = 60.5. |
As another example, like the income example presented for the mean, consider a room with 10 people who have incomes of $10, $20, $20, $40, $50, $60, $90, $90, $100, and $1,000,000. Here, the median is $55, because $55 is the average of the two middle numbers, $50 and $60. If the extreme value of $1,000,000 is ignored, the mean is $53. In this case, the median is close to the value obtained when the extreme value is thrown out. The median solves the problem of extreme values as described in the definition of mean above. |
The mode is the most frequent item of data. For example, the most common letter in English is the letter "e". We would say that "e" is the mode of the distribution of the letters. |
As another example, if there are 10 people in a room with incomes of $10, $20, $20, $40, $50, $60, $90, $90, $90, $100, and $1,000,000, then the mode is $90, because $90 occurs three times and all other values occur fewer than three times. |
There can be more than one mode. For example, if there are 10 people in a room with incomes of $10, $20, $20, $20, $50, $60, $90, $90, $90, $100, and $1,000,000, the modes are $20 and $90. This is bi-modal, or has two modes. Bi-modality is very common, and it often indicates that the data is the combination of two different groups. For instance, the average height of all adults in the U.S. has a bi-modal distribution. This is because males and females have separate average heights of 1.763 m (5 ft 9 + 1⁄2 in) for men and 1.622 m (5 ft 4 in) for women. These peaks are apparent when both groups are combined. |
The mode is the only form of average that can be used for data that can not be put in order. |
Another thing we can say about a set of data is how spread out it is. A common way to describe the spread of a set of data is the standard deviation. If the standard deviation of a set of data is small, then most of the data is very close to the average. If the standard deviation is large, though, then a lot of the data is very different from the average. |
The standard deviation of a sample is generally different from the standard deviation of its originating population . Because of that, we write formula_7 for population standard deviation, and formula_8 for sample standard deviation. |
If the data follows the common pattern called the normal distribution, then it is very useful to know the standard deviation. If the data follows this pattern (we would say the data is "normally distributed"), about 68 of every 100 pieces of data will be off the average by less than the standard deviation. Not only that, but about 95 of every 100 measurements will be off the average by less than two times the standard deviation, and about 997 in 1000 will be closer to the average by less than three standard deviations. |
We also can use statistics to find out that some percent, percentile, number, or fraction of people or things in a group do something or fit in a certain category. |
For example, social scientists used statistics to find out that 49% of people in the world are males. |
In order to support statisticians, many statistical software have been developed: |
Speed |
Speed is the distance of a moving object in a given amount of time. Speed is a measure of how fast something is moving. The average speed of an object in a certain time is the distance the object travelled divided by the time. Speed is also the distance covered by an object per unit time. |
To find speed formula_1, |
formula_2formula_3 |
where formula_4 is the distance and formula_5 is the time that has gone by. |
There are many units of measurement for speed. For example, an object's speed can be measured in |
When an object changes speed, it gets faster or slower. If the speed of the object increases, it is called acceleration. If the object gets slower, and the speed decreases, it is called deceleration, or negative acceleration. |
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