Question: Why is the sky blue?

Explanation: If you stick your hand out of the car window when it's moving, you can feel the air pushing against your hand. But what if you're just standing in your room? Does that mean the air isn't there? No...it just means that you can't FEEL the air unless it bounces off something. Light works kinda the same. Most of the time we don't see light unless it's bouncing off something, like a sidewalk or a cat or something. When the light from the sun comes through the air bubble that surrounds the earth, it sometimes hits little bits of air (oxygen and nitrogen, mostly) and gets scattered. Some kinds of light bounce better off of oxygen and nitrogen than other kinds of light. Blue light (and colors that are close to blue, like indigo and violet) bounces really well off the air, and so blue light gets scattered best. So we mostly see blue because it's bouncing off the air particles. And remember, we usually see light only when it bounces off stuff. The other kinds of light (red, orange, green, and a bunch of other colors) go sailing right through the air and don't bounce off it, so we don't see those colors until they bounce off something on the ground, like grass or a stop sign.


Question: Why is the sky blue?

Explanation: When sunlight reaches Earth's atmosphere, it is scattered in all directions by all the gases and particles in the air. Blue is scattered by air molecules more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.


Question: Why is the sky blue?

Explanation: The blue colour of the sky is nowadays usually explained by Rayleigh scattering, an explanation that is, however, not entirely correct. In his 1953 publication entitled "Explanation of the Brightness and Color of the Sky, Particularly the Twilight Sky", Edward Olson Hulburt (1890–1982) demonstrated that for specific illumination and viewing conditions, Rayleigh scattering plays only a second-order role for the blue colour of the sky. Based on simplified radiative transfer simulations and single-scattering approximation, Hulburt (1953) concluded that for a solar zenith angle (SZA) of 90∘ only 1/3 of the blue colour of the sky of the zenith is caused by Rayleigh scattering and 2/3 by absorption of solar radiation in the Chappuis bands of O3.


Question: Why do music trends change over time?

Explanation: Innovation. If you sound nothing like anyone else, you're one of a kind, which in art equals popularity. Soon after, everyone tries to copy you, and that's how genres are created.


Question: Why do music trends change over time?

Explanation: Technological developments played a vital role in bringing popular music to people's homes. The invention of the phonograph and gramophone in the late 19th century enabled the reproduction and mass distribution of sound recordings for the first time. The invention of the reel-to-reel tape recorder and the development of vinyl records in the 1940s drastically improved this process. The postwar prevalence of radio hugely impacted popular music, with radio airplay of popular songs promoting record sales.


Question: Why do music trends change over time?

Explanation: It was found that fame of the artist, ties with other media and compilation albums featuring several artists prolonged the hit's chart period. A survival analysis was also used in a study, which measured the statistical correlations of the period that an album stayed in the weekly hit charts in the US music market. They found that the rank at which an album debuts in the hit charts, the artist's career, promotion via major or minor labels, and the artist's gender influenced the hit charts' longevity.


Question: Why do organisms require oxygen for survival?

Explanation: Most living things need oxygen to survive. Oxygen helps organisms grow, reproduce, and turn food into energy. Humans get the oxygen they need by breathing through their nose and mouth into their lungs. Oxygen gives our cells the ability to break down food in order to get the energy we need to survive. Although other animals may use different organs to breathe with, they all get oxygen into their bodies through respiration.


Question: Why do organisms require oxygen for survival?

Explanation: Aerobic respiration, which takes place in the presence of oxygen, evolved after oxygen was added to Earth’s atmosphere. A major advantage of aerobic respiration is the amount of energy it releases. Without oxygen, organisms can split glucose into just two molecules of pyruvate. This releases only enough energy to make two ATP molecules. With oxygen, organisms can break down glucose all the way to carbon dioxide. This releases enough energy to produce up to 38 ATP molecules. Thus, aerobic respiration releases much more energy than anaerobic respiration.


Question: Why do organisms require oxygen for survival?

Explanation: Gaseous oxygen is essential for all aerobic animals, without which mitochondrial respiration and oxidative phosphorylation cannot take place.


Question: Why do we dream?

Explanation: When we go to sleep at night, it can look like our bodies and our brains are turning off. But while the rest of your body is resting and recharging, your brain is actually working pretty hard -- and showing you dreams, like a movie going on inside your head! When you're dreaming, some parts of your brain are switched on and working hard -- like the ones that think about what you see, and some of the parts that focus on your feelings. Meanwhile, the part that does some of your more complicated thinking, like by asking great questions -- like why you're suddenly able to fly, for example -- is turned off. So if you're flying in your dream, you can just enjoy the ride!


Question: Why do we dream?

Explanation: Dreams provide a "psychic safety valve"—expressing otherwise unacceptable feelings; contain manifest (remembered) content and a deeper layer of latent content—a hidden meaning. stories our brain tells us while we are sleeping. A collection of clips, image, feelings, & memories that occur during our REM sleep.


Question: Why do we dream?

Explanation: J. Allan Hobson’s definition that dreaming is mental activity during sleep with most of the following features present – hallucinations, delusions, narrative structure, hyperemotionality, and bizarreness – emphasizes the qualitative features of dream content. Antti Revonsuo recently suggested that instead of strict definitions and categorizations, we should consider dream phenomena as a continuum. At the one end of the continuum resides full-blown dreaming, defined as complex, organized, temporally progressing, multimodal contents of consciousness during sleep that amount to a simulation of the perceptual world, and at the other end there is sleep mentation, that is, simple contents of consciousness during sleep that show a low degree of complexity and organization.


Question: Why do we use binary code in computer systems?

Explanation: Binary has two states: off and on. If computers were to use the decimal system, there would be 10 states instead and they would have to work a lot harder to process them all. Binary is easier for computers to process, and it also takes up less space.


Question: Why do we use binary code in computer systems?

Explanation: The binary number system is the base of all computing systems and operations. It enables devices to store, access and manipulate all types of information directed to and from the CPU or memory. The binary schema of digital 1s and 0s offers a simple and elegant way for computers to work. It also offers an efficient way to control logic circuits and to detect an electrical signal's true (1) and false (0) states.


Question: Why do we use binary code in computer systems?

Explanation: Binary encoding in digital systems is fundamentally aligned with the bistable nature of CMOS transistors, which serve as the primary switching elements in integrated circuits. The inherent two-state operation—where each transistor represents a logical high or low voltage corresponding to binary 1 or 0—facilitates highly efficient circuit topologies. A transition to MVL would exponentially increase the complexity of circuit design, as maintaining precise discrimination between multiple voltage thresholds would require sophisticated analog control mechanisms. Moreover, such systems would exacerbate issues related to signal degradation, noise immunity, and dynamic power dissipation due to narrower noise margins and heightened sensitivity to process, voltage, and temperature variations.


Question: Why is iodine added to salt?

Explanation:
Iodine is used by the thyroid gland in your throat to make thyroid hormones. These hormones control your metabolic rate (the rate at which your body uses energy when it is resting). They also help your brain and body grow and develop.

If there isn’t enough thyroid hormone circulating in your blood, your brain sends a chemical message to your thyroid gland to release more of these hormones.


Question: Why is iodine added to salt?

Explanation: Iodine is an element found mainly in seawater and in soil close to the sea. The human body needs iodine to make thyroid hormone. During fetal development, infancy, and childhood, thyroid hormone is essential for the brain and nervous system to develop normally. Too little iodine, and thus too little thyroid hormone, can lead to mental retardation, dwarfism, hearing loss, and other problems. Later in life, thyroid hormone controls metabolism. Adults who don't take in enough iodine can develop a goiter (a swelling of the butterfly-shaped thyroid gland in the neck), and the low output of thyroid hormone can lead to sluggish metabolism, poor thinking skills, infertility, thyroid cancer, and other conditions.


Question: Why is iodine added to salt?

Explanation: Adequate levels of iodine, a trace element variably distributed on the earth and found mostly in the soil and water of coastal areas, are required for the synthesis of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3), which play key roles in the metabolic processes of vertebrate life. The major concerns regarding the global burden of iodine deficiency are related to goiter, neurocognitive impairments, and in severe deficiency, hypothyroidism resulting in cretinism.


Question: Why is the Amazon rainforest important?

Explanation: The Amazon is of vital importance because people around the world, as well as locally, depend on the rainforest. Not just for food, water, wood and medicines, but to help stabilise the climate—150-200 billion tons of carbon is stored in the Amazon rainforest.


Question: Why is the Amazon rainforest important?

Explanation: The Amazon rainforest region functions as a carbon sink through the process of photosynthesis. During photosynthesis, trees and other vegetation absorb CO2 from the atmosphere and use it to produce energy, storing the carbon in their roots, branches, leaves, and trunks. This process not only removes CO2 from the atmosphere but also helps to stabilize the global climate by reducing the greenhouse effect.


Question: Why is the Amazon rainforest important?

Explanation: A large fraction of precipitation in the Amazon basin is recycled, and, therefore, simulations of Amazon deforestation typically generate ≈20–30% reductions in precipitation (78), lengthening of the dry season, and increases in summer temperatures (79) that would make it difficult for the forest to reestablish, and suggest the system may exhibit bistability.


Question: Why isn't Pluto considered a planet anymore?

Explanation: So, in the 19th century, we discovered a new planet between Mars and Jupiter called Ceres. However, over time, we started discovering a ton of other, similar objects, around the same orbit. We discovered so many that we realized it didn't make any sense to call them all planets so we classified them differently. Pluto is essentially the same story.


Question: Why isn't Pluto considered a planet anymore?

Explanation: Pluto is now classified as a dwarf planet because, while it is large enough to have become spherical, it is not big enough to exert its orbital dominance and clear the neighborhood surrounding its orbit.


Question: Why isn't Pluto considered a planet anymore?

Explanation: For a long time, no one searched for other TNOs as it was generally believed that Pluto, which up to August 2006 was classified as a planet, was the only major object beyond Neptune. Only after the 1992 discovery of a second TNO, 15760 Albion, did systematic searches for further such objects begin. A broad strip of the sky around the ecliptic was photographed and digitally evaluated for slowly moving objects. Hundreds of TNOs were found, with diameters in the range of 50 to 2,500 kilometers. Eris, the most massive TNO, was discovered in 2005, revisiting a long-running dispute within the scientific community over the classification of large TNOs, and whether objects like Pluto can be considered planets. Pluto and Eris were eventually classified as dwarf planets by the International Astronomical Union.


Question: Why can't we divide by zero in mathematics?

Explanation: Okay so say you have 10 apples. You can put those apples into 10, 5, 2, or 1 group/s quite easily. You could even put them into 4 groups by splitting 2 of the apples in half. How many apples would be in those 0 groups? How do you put 10 apples into 0 groups? The answer is that you cannot physically put those 10 apples into evenly into 0 groups. So the answer is undefined.


Question: Why can't we divide by zero in mathematics?

Explanation: It’s not that it’s “impossible” to divide by 0, it’s simply not defined. Intuitively, this means that if we were to take a number n and say that n÷0=q, then the quotient q, whatever it was, would not make sense based on the meaning and properties of division.


Question: Why can't we divide by zero in mathematics?

Explanation: Localization of every commutative ring at zero is the trivial ring, where 0=1. so nontrivial commutative rings do not have inverses at zero, and thus division by zero is undefined for nontrivial commutative rings.


Question: Why do geese fly in a 'V' formation?

Explanation: The bird breaking the air creates a mini updraft, which the bird behind it can ride. The bird in front does most of the heavy lifting, and the birds at the end of the V get the least amount of help, so the flock regularly rotates positions to ensure that each bird has equal time 'resting' and equal time 'working'.


Question: Why do geese fly in a 'V' formation?

Explanation: Geese fly in a V formation for several reasons. Firstly, this arrangement allows for improved energy conservation. As each goose flaps its wings, it creates an uplift for the one following it, thereby reducing the overall energy expenditure of the flock. Secondly, the V-shaped formation enhances communication and coordination between geese during flight. It enables them to maintain visual contact with one another, ensuring a synchronized movement that aids navigation and avoids collisions.


Question: Why do geese fly in a 'V' formation?

Explanation: An aerodynamic advantage resulting from formation flying has been discussed by several authors. Lissaman and Schollenbergcr (1970) proposed that in one type of line formation,the V, an aero-dynamic advantage is gained by an individual bird by maintaining a particular wing tip-to-wingtip distance, and by angular positioning relative to other birds in the formation to capture tip vortex energy from the wings of neighboring birds. Cone (1968) argued, on grounds of aerodynamic theory, that the tip vortex arising from a flapping wing should not resemble that flowing from the fixed wing typical of aircraft.


Question: Why are trans fats bad for health?

Explanation: Trans fat is considered the worst type of fat to eat. Unlike other dietary fats, trans fats — also called trans-fatty acids — raise "bad" cholesterol and also lowers "good" cholesterol. A diet laden with trans fats increases the risk of heart disease, the leading killer of adults.


Question: Why are trans fats bad for health?

Explanation: Trans fats raise your bad (LDL) cholesterol levels and lower your good (HDL) cholesterol levels. Eating trans fats increases your risk of developing heart disease and stroke. It’s also associated with a higher risk of developing type 2 diabetes.


Question: Why are trans fats bad for health?

Explanation: Trans fatty acids raise plasma low-density lipoprotein (LDL) cholesterol levels in volunteers when exchanged for cis unsaturated fatty acids in the diet. In addition, trans fatty acids may lower high-density lipoprotein (HDL) cholesterol levels and raise triglyceride and lipoprotein(a) levels in plasma. Trans and cis unsaturated fatty acids are thus not equivalent, and diets aimed at reducing the risk of coronary heart disease should be low in both trans and saturated fatty acids.


Question: Why do we adjust for degrees of freedom in variance and standard deviation?

Explanation:
Degrees of freedom are the number of independent variables that can be estimated in a statistical analysis and tell you how many items can be randomly selected before constraints must be put in place.

Within a data set, some initial numbers can be chosen at random. However, if the data set must add up to a specific sum or mean, for example, the number in the data set is constrained to evaluate the values of all other values in a data set, then meet the set requirement.

The formula to determine degrees of freedom is: D_f = N-1, where: D_f = degrees of freedom, and N = sample size.

For example, imagine a task of selecting ten baseball players whose batting average must average to .250. The total number of players that will make up our data set is the sample size, so N = 10. In this example, 9 (10 - 1) baseball players can be randomly picked, with the 10th baseball player having a specific batting average to adhere to the .250 batting average constraint.

Some calculations of degrees of freedom with multiple parameters or relationships use the formula D_f = N - P, where P is the number of different parameters or relationships. For example, in a 2-sample t-test, N - 2 is used because there are two parameters to estimate.


Question: Why do we adjust for degrees of freedom in variance and standard deviation?

Explanation:
Degrees of freedom are the number of independent values that a statistical analysis can estimate. You can also think of it as the number of values that are free to vary as you estimate parameters.

Degrees of freedom encompasses the notion that the amount of independent information you have limits the number of parameters that you can estimate. Typically, the degrees of freedom equal your sample size minus the number of parameters you need to calculate during an analysis. It is usually a positive whole number.


Question: Why do we adjust for degrees of freedom in variance and standard deviation?

Explanation: Degrees of freedom is a parameter that is dependent upon sample size, which is used to calculate the probability distributions for certain statistical models. Degrees of freedom may be considered a measure of parsimony, as it is a measure of the number of observations available to vary, to estimate additional parameters. In other words, as the precision increases in estimating model parameters, fewer degrees of freedom are available.


Question: Why do we enjoy horror movies or stories?

Explanation: All the same reasons people like sad songs, Halloween, war documentaries, apocalyptic fiction, etc. etc. It’s like any other film genre. Horror movies can be artistic; the performances can be entertaining; the movies can be well-constructed or conceived; they can be relatable or provide personal insight. Etc.


Question: Why do we enjoy horror movies or stories?

Explanation: According to these researchers, stimulation is one of the driving forces behind the consumption of horror. Exposure to terrifying acts like stories of demonic possession or alien infestation can be stimulating both mentally and physically. These experiences can give rise to both negative feelings, such as fear or anxiety, and positive feelings, such as excitement or joy. And we tend to feel the most positive emotions when something makes us feel the most negative ones.


Question: Why do we enjoy horror movies or stories?

Explanation: “The horror film occupies in popular culture roughly comparable to that of horror literature. That is to say, it is generally ignored, sometimes acknowledged with bemused tolerance, and viewed with alarm when it irritates authority - rather like a child too spirited to follow the rules that rendition has deemed acceptable” (p. ix), a view that is echoed elsewhere. For example, Tudor (1997) noted that “a taste of horror is a taste for something seemingly abnormal and is therefore deemed to require special attention” (p. 446). Part of the reason for the disdain, apart from the broad and base nature of the content, may be the relative cheapness of horror film: these are often much less expensive to create than are other genre films such as westerns, comedies, or science fiction.


Question: Why do cultures evolve over time?

Explanation: This may happen when the environment changes. It also happens when different groups come into contact with one another. Each group brings new ideas that can cause changes in the other group’s culture. Sometimes conflict happens when different cultures come into contact. Other times the contact is peaceful, and the groups share their cultures in positive ways.


Question: Why do cultures evolve over time?

Explanation: And just like in genetic evolution, not all cultural change is due to selection. Culture can change due to random chance or population structures such as bottlenecks. This is called cultural drift, analogous to genetic drift. Or migration and mutation can bring new cultural traits into a population, just as it brings in new genes.


Question: Why do cultures evolve over time?

Explanation: What makes this program evolutionary resists any brief answer, but some relevant factors include the following: researchers in this tradition often examine how cultural inheritance interacts with the forms of inheritance (especially genetic inheritance) studied by mainstream evolutionary theorists; they seek to understand culture using explanatory models and investigative tools adapted from those used in evolutionary and ecological theory; they reach back into human pre-history when determining the origins of the capacity for culture; and they ask comparative questions concerning differences between species in terms of their abilities to create and maintain storehouses of valuable socially transmitted information.


Question: Why is voting an important responsibility in democratic nations?

Explanation: If you decide to opt out of the political system by not voting, others will. That means that their preferences and not yours will determine which politicians pass the laws that have power over you. Those laws determine who will gain and lose money and property (taxation, fines, eminent domain, grants, government contracts) and even their lives (penal laws, draft). They will set the boundaries of your rights - how you can live, love, and even speak.


Question: Why is voting an important responsibility in democratic nations?

Explanation: Voting is morally special in its own right regardless of the fact that citizens may also be bound to discharge other duties of aid. Because governments are powerful entities that distribute and shape access to basic social goods as no other organization does, the mechanism to install them is unique and deserves moral attention separately. Other political, non-electoral ways of influencing government matter, but they lose all relevance if elections are absent.


Question: Why is voting an important responsibility in democratic nations?

Explanation: Although voting certainly encompasses the notions of self-governance and democratic expression, today's clashes over elections and participation are really about equality. By focusing so much on equality, we gives too short shrift to the power of the foundational importance of voting and democratic participation to resolve our election administration disputes.


Question: Why is Beethoven's Fifth Symphony popular?

Explanation: The same reason the Mona Lisa is the "best" painting and The Barber of Seville is the "best" opera. Most people are fairly ignorant of the fine arts, and tend to latch on to one token example that has drifted into popular culture to the point it becomes a cliche.


Question: Why is Beethoven's Fifth Symphony popular?

Explanation: There is a reason for all this exposure and inclusion in mainstream culture well beyond the 1808 Vienna premiere: the music itself, all stemming from that iconic four-note opening. Syncopated, catchy, impactful; it’s just so distinctive.


Question: Why is Beethoven's Fifth Symphony popular?

Explanation: One of the aspects that makes the Fifth Symphony remarkable is that the “fate motif” is not treated as simply a first theme. Instead, Beethoven put it throughout the entire piece—an obsessive repetition of the motif at different pitch levels, combined with interruptive stops that fight its restless momentum.


Question: Why do we feel guilt?

Explanation: It's just a type of social pain. You feel guilt when you think you've caused harm to others: this is useful because it generally teaches you to stop hurting others in the same way that pain teaches you to stop hurting yourself.


Question: Why do we feel guilt?

Explanation: In a psychological context, guilt is considered the more proactive emotional response to an occurrence or action taken, as opposed to shame. Guilt is tied to empathy, pushing a person to look beyond themselves and consider how their behavior may impact others. Shame centers on the individual and how they feel about behaving; anger is the more likely emotional companion to shame.


Question: Why do we feel guilt?

Explanation: Guilt has a cognitive component, in that the negative emotion presupposes one’s responsibility for the problematic action or inaction. The attribution of responsibility to one’s own behavior (something that can be changed) is important, insofar as it suggests and motivates different behaviors that can make amends for the previous transgression.


Question: Why is racism still prevalent?

Explanation: It's normal to want to spend time with people that have the same interests, background, culture and language. It creates a sense of belonging that is really important. The downside is that it can also set up differences between other groups and, over time, this might lead to us to thinking that our group is better than others.


Question: Why is racism still prevalent?

Explanation: Essentially- it is human nature to defend the group you align yourself with (can be a sports team, a gender, a race, a career type, etc etc) vs the group you perceive to be a competition (the other team, race, gender, etc). So if someone has a higher degree of emotional insecurity, chemical imbalance, lesser education, less life experiences, or stronger indoctrination- this in group out group will play out much stronger.


Question: Why is racism still prevalent?

Explanation: Although there have been some remarkable gains in the labor force status of racial minorities, significant disparities remain. African Americans are twice as likely to be unemployed as whites (Hispanics are only marginally so), and the wages of both blacks and Hispanics continue to lag well behind those of whites (author’s analysis of Current Population Survey, 2006). A long line of research has examined the degree to which discrimination plays a role in shaping contemporary labor market disparities.


Question: Why is love a universal concept?

Explanation: Some researchers suggest that love is a basic human emotion just like happiness or anger, while others believe that it is a cultural phenomenon that arises partly due to social pressures and expectations.


Question: Why is love a universal concept?

Explanation:
It’s suggested that areas of the brain, particularly the ventral tegmental area (located in the middle of the brain), responsible for motivation and emotional regulation are associated with maternal and romantic love.
Feelings of love help us form social bonds with others. As social creatures, these natural chemicals developed to help us survive by encouraging: nurturance, cooperation, reproduction, and mutual support.


Question: Why is love a universal concept?

Explanation: Defining romantic love has been a challenge for theorists. Researchers have found that people’s conception of romantic love varies across cultures. The fact that romantic love is documented in cross-cultural samples stands in direct contradiction to the popular ideas that romantic love is limited to or the product of Western culture. Overall, suggesting that romantic love constitutes a universal experience. For example, studies have found that Bosnians reported higher importance of intimacy and passion than Turkish participants. Love for Brazilians has been defined through characteristics of honesty, for Russians through suffering, and for Central Americans through tenderness. Several other studies have found that Asians report lower scores on eros (love that starts suddenly with a strong physical attraction of an intense and emotionally disturbing nature) and higher scores on pragma (love based on companionship, trust, and security between two people with similar values) compared to African Americans and European Americans.


Question: Why do athletes make more money than other professionals?

Explanation: It's mainly the economics surrounding sports. Sports bring in billions of dollars through ticket sales, broadcasting deals, jersey sales, endorsements, etc. If getting a better player helps the team and leads to more money coming in, teams will pay more to improve the team.


Question: Why do athletes make more money than other professionals?

Explanation: Sports is only such a massive and profitable industry because of the enormous global fan bases that love it. If there was not such a high demand for these athletes and their performances, the industry would not be turning over so many figures a year.


Question: Why do athletes make more money than other professionals?

Explanation: The explanation for the salary differences lies in a 'personal scale of operations' effect in sports compared to teaching and most other jobs.


Question: Why are there different seasons?

Explanation: The Earth is tilted, and the axis of that tilt moves around during the year. When the north part is pointing towards the sun, the northern hemisphere has summer and the southern hemisphere has winter. When the north part is pointing away from the sun, it's the opposite. When it's pointing off to the side, we have spring or autumn. It all has to do with how directly the sunlight hits the part of the planet you're on.


Question: Why are there different seasons?

Explanation: As the earth spins on its axis, producing night and day, it also moves about the sun in an elliptical (elongated circle) orbit that requires about 365 1/4 days to complete. The earth's spin axis is tilted with respect to its orbital plane. This is what causes the seasons. When the earth's axis points towards the sun, it is summer for that hemisphere. When the earth's axis points away, winter can be expected. Since the tilt of the axis is 23 1/2 degrees, the North Pole never points directly at the Sun, but on the summer solstice it points as close as it can, and on the winter solstice as far as it can. Midway between these two times, in spring and autumn, the spin axis of the earth points 90 degrees away from the sun. This means that on this date, day and night have about the same length: 12 hours each, more or less.


Question: Why are there different seasons?

Explanation:
When the Earth is in position A (June 21), the tilt of the axis is exactly towards the sun, causing the sun to appear 23.5 degrees higher than it would be if the axis had no tilt. The "little man" at the North Pole sees the sun at an altitude of 23.5 degrees above the horizon. Since he is turning with the Earth, the sun appears to him to be running around the sky at a fixed altitude of 23.5 degrees. If he were in any other position in the Northern Hemisphere, the sun, due to the tilt, would appear elevated by this amount at midday. This elevation causes the Northern Hemisphere to receive the maximum amount of heat and experience its summer season.
As the Earth moves toward position B, the direction of the sun gradually departs from the direction of the tilt. When it reaches position B, the two directions are at right angles to each other, meaning the tilt has no effect on the sun's altitudes. Thus, the two hemispheres receive equal amounts of heat; it is the equinox.
As the Earth moves toward position C, the sun's direction and the Earth's tilt become more and more opposed, until they are opposite when the Earth reaches position C. At this time, the sun's altitude is lowered by 23.5 degrees, marking midwinter. As the Earth moves past position C, the changes described above occur in reverse order, returning to the initial conditions when the Earth reaches position A.
The cycle of changes, as seen from the Southern Hemisphere, is the same as in the Northern Hemisphere but occurs six months later. These changes in the relative directions of the sun and the Earth's axis explain the apparent shift of the sun back and forth across the equator over a belt that is 47 degrees wide.
[Note: Corresponding figures have been redacted.]


Question: Why does DNA have a double helix structure?

Explanation:
DNA is made up of small components called nucleotides. A nucleotide is made up of 3 parts: a phosphate group, a sugar, and a base. The base can be 1 of 4 varieties: A, T, C, or G. Simply put, because of their structures, A and T bond nicely with one another and C and G bond nicely as well. As a result, a single strand of DNA will bond to a strand with another strand with a "complimentary" sequence of bases. In other words, there will be two strands with opposite, for lack of a better word, sequences of bases. The production of strands that complement one another is a result of how DNA copies itself (known as DNA replication). The second strand's base sequence is ordered based on the first strand's sequence.

So that answers the question of why DNA is a double helix instead of a single helix. But why is it a helix at all? Why not a shaped like a ladder? In a cell, most of the material present is water. Water is shaped in such a way where positive and negative charges aren't spread evenly throughout the water's molecules. This is known as being a polar molecule. Polar molecules "like" being around other polar molecules. Non-polar molecules don't "like" being around polar molecules like water. In DNA, the bases are non-polar, but the phosphate groups are polar. As a result, the preferred shape puts the phosphates in contact with the water and the bases are covered by being on the inside. The twisting shape of DNA reduces the extent to which the bases are exposed to the water in the outside environment.

TL;DR: DNA is made of 3 components: bases, sugars, and phosphates. The sugars bond with one another explaining the double-configuration of DNA. To be stable, the bases need to stay in the inside of the molecule and phosphates need to make up the molecule's exterior, and a helical shape allows this to happen.


Question: Why does DNA have a double helix structure?

Explanation: The three-dimensional structure of DNA—the double helix—arises from the chemical and structural features of its two polynucleotide chains. Because these two chains are held together by hydrogen bonding between the bases on the different strands, all the bases are on the inside of the double helix, and the sugar-phosphate backbones are on the outside. To maximize the efficiency of base-pair packing, the two sugar-phosphate backbones wind around each other to form a double helix, with one complete turn every ten base pairs.


Question: Why does DNA have a double helix structure?

Explanation: The stability of double-stranded DNA (dsDNA) at physiological temperature is due to the hydrogen bonding between complementary bases and the stacking between neighboring bases. However, these base-stacking interactions are of the order of magnitude of a few k_B T thermal energy and the thermal fluctuations can lead (even at physiological temperature) to local and transient unzipping of the double helix.


Question: Why does oil not mix with water?

Explanation:
You can group substances into 2 types - polar and non-polar. A polar substance has different electric charges on different parts - water, for instance, has slightly negatively charged oxygen on one side and the two positively charged hydrogens on the other. When polar molecules mix, the negative sides of some molecules line up with the positive parts of others, bonding them together into an even mix.

Oils are non-polar. They have a core of negatively charged carbons, but it is covered evenly with lots of positively charged hydrogen, which all balances out. When you put oil and water together, the water bonds to itself, but cannot bond with the oil because there's no charge on the surface to bond with. So the water bonds together into a mass, pushing the oil out.


Question: Why does oil not mix with water?

Explanation: Liquid water is held together by hydrogen bonds. (Liquid water has fewer hydrogen bonds than ice.) Oils and fats not have any polar part and so for them to dissolve in water they would have to break some of water s hydrogen bonds. Water will not do this so the oil is forced to stay separate from the water.


Question: Why does oil not mix with water?

Explanation: The widely accepted model explaining the hydrophobic effect invokes the formation of icelike clathrate hydrate "cages" around nonpolar solute molecules. Water molecules at the surface of these relatively rigid clathrate structures are strongly hydrogen-bonded to one another. The formation of these solvent "cages" explains why both Delta H and Delta S are negative for the solution process, and the endergonicity of solvation is thus due to entropy and not enthalpy.


Question: Why are animals colored in certain ways?

Explanation: Some animals have special colors or markings called protective coloration. These markings protect animals from predators, or animals that will eat them. Some markings are a kind of camouflage, meaning that they help the animal blend in with its surroundings. Others help scare predators away by making the animal appear dangerous.


Question: Why are animals colored in certain ways?

Explanation:
Many of these animals hold clues that could help answer the question of why such colorful displays evolved. Research published in 2022 showed that all brightly colored terrestrial vertebrate species can generally be split into two camps. In the descendants of nocturnal animals, color can communicate to predators that they are poisonous and wouldn't be a good dinner choice — a phenomenon called aposematism. This tracks with their nocturnal history, as bright colors help to frighten opportunistic predators away while these animals are sleeping and vulnerable during the day.

Meanwhile, the study found that descendants of daytime animals, such as some birds, typically use color as a way to attract mates. It's likely that "sexual signals have to evolve in species that can see those colors," said John J. Wiens, professor of ecology and evolutionary biology at the University of Arizona, who co-authored the research. "Warning signals can evolve in species that do not see colors at all — or do not even have eyes — because they are signaling to other species that can see colors, like birds and fish."


Question: Why are animals colored in certain ways?

Explanation: Colours made by animals or by other objects in the environment (such as flowers and fruit) may serve a variety of functions. Humans like colours and therefore naturally want to find functions for them, often imposing our primate colour vision system on a non-primate world. We also forget that, compared to many other animals, we are relatively colour blind and therefore colours may be invisible to us or at least not easy to discriminate compared to other animals. Colours may be functional or non-functional. The rainbow of diffraction colours produced by the comb-rows of deep-sea ctenophores, for example, do not serve a function as these animals never encounter full spectrum light. If colours do serve a purpose, this may be something to do with vision and behaviour, or irrelevant to vision. Visually ‘neutral’ but still functional colour patterns include animals that are or become dark in order to absorb heat and some colour pigments, such as melanin, may aid mechanical strength (see the black tips of seagull wings). The visual function of colours can be divided into two broad categories, conspicuousness or camouflage, and within each of these categories there are different reasons to ‘want’ to stick out or hide. As all biologists know, these reasons essentially collapse into the various forms of sex, violence and defence necessary for survival.


Question: Why does acid rain occur?

Explanation: Acid rain is a form of air pollution. When coal and petroleum are burned in automobiles, electric power plants, and factories, they release certain harmful gases into the air. These gases combine with the oxygen and water in the air. When the water in the air comes down as rain, sleet, hail, or snow, it carries with it these gases. This is known as acid rain. Acid rain is very damaging to all life-forms.


Question: Why does acid rain occur?

Explanation: Acid rain results when sulfur dioxide (SO2) and nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents. The SO2 and NOX react with water, oxygen and other chemicals to form sulfuric and nitric acids.  These then mix with water and other materials before falling to the ground.


Question: Why does acid rain occur?

Explanation: The sources of acidity in rain can come from anthropogenic or natural activities. Even so, anthropogenic sources are the main contributors of acid rain in urban area. Anthropogenic activities such as burning of fossil fuels from transportation or industrial activities will release sulphuric acid and nitric acid into the atmosphere that are known as the inorganic acids. Meanwhile, the sources of rain acidity in rural area will come from biogenic volatile organic carbon emissions are such as isoprene, propene, acetic acid, formic acid and oxalic acid that are more organic acids. Biogenic volatile organic carbon emissions may not directly emit in the form organic acids, but they may form in the atmosphere through secondary reactions. From that point, it means that the acidity of rainwater may not be necessarily from the urban like pollutions such as automobile emissions and industrial combustions, but it can come from natural source such as the biogenic volatile organic emissions from forests, vegetation and livestock manure.


Question: Why do we yawn?

Explanation:
One is that when we are bored or tired, we just don't breathe as deeply as we usually do. As this theory goes, our bodies take in less oxygen because our breathing has slowed. Therefore, yawning helps us bring more oxygen into the blood and move more carbon dioxide out of the blood.
Yawning, then, would be an involuntary reflex (something we can't really control) to help us control our oxygen and carbon dioxide levels.


Question: Why do we yawn?

Explanation: Yawing clearly is associated with sleepiness and boredom. However, almost paradoxically, it is theorized that yawning is not a sign of sleepiness or boredom, but actually a reflex that your brain induces to wake you up or make you more alert. Yawning is associated with some hormones that are released that briefly increase the heart rate and alertness. So actually the reason that one yawns when tired or bored is the body’s attempt to keep you alert and awake — if only for a brief time.


Question: Why do we yawn?

Explanation: Evidence suggests that drowsiness is the most common stimulus of yawn. Boredom occurs when the main source of stimulation in a person's environment is no longer able to sustain their attention. This induces drowsiness by stimulating the sleep generating system. At this moment, the mind has to make an effort to maintain contact with the external environment. The arousal occurring after yawning is being considered to be due to the mechanical stimulation of carotid body. The strategic location of this structure results in its stimulation due to the compressions and movements caused by yawning. The carotid bodies are highly vascularized, and their compressions may thus affect their shunt system, thereby leading to release of hormones such as adenosine and catecholamines, which subsequently mediate the arousal response.


Question: Why are black holes black?

Explanation: A black hole’s gravity, or attractive force, is so strong that it pulls in anything that gets too close. It can even swallow entire stars. Nothing can move fast enough to escape a black hole’s gravity. This includes light, the fastest thing in the universe. That’s why we can’t see black holes in space—they've gobbled up all the light. Though astronomers can’t see black holes, they know they’re there by the effect they have on objects that get too close.


Question: Why are black holes black?

Explanation: Black holes don’t emit or reflect light, making them effectively invisible to telescopes.


Question: Why are black holes black?

Explanation: In the case of the most massive stars (maybe only stars more massive than say, 25 or even 50 solar masses), not even neutron degeneracy pressure can stop the collapse of the core. In this case, at least 3 solar masses worth of matter collapses into a single point with infinite density. This point is referred to as a singularity. At a distance of approximately 9 km from the singularity is a spherical region at which the escape velocity is exactly equal to the speed of light. What this means is that any object that reaches this distance from the singularity (usually referred to as the event horizon or Schwarzschild radius) can never escape, even if it were moving at the speed of light. Thus, even light cannot escape from this object, and it is for this reason we call it a black hole.


Question: Why is latitude measured in 180 degrees?

Explanation:
Longitudes go all the way around the earth, but latitudes all meet at the poles. If your latitudes continued past them, you'd have a latitude that increased moving towards the poles, then increased moving away from the poles on the other side. We could do this, but then we would be double-counting locations on the surface of the earth (e.g., 120 degrees W and 120 degrees N would be the same place as 60 degrees W and 60 degrees N) unless we made the longitudes only go from -90 to +90 degrees instead.

Another way to think about it: make a complete, 360-degree circle out of wire and hang it from a piece of string. If you turn the wire circle around by twisting the string, you only need to turn it around half a turn before the wire will have swept out a complete sphere. If you keep turning it, then one side of the circle will overlap where the other side was. So you need to have 1 360-degree circle and 1 180 degree circle to make a sphere.


Question: Why is latitude measured in 180 degrees?

Explanation:
A cutaway drawing of the Earth demonstrates how latitude is determined. It makes clear that latitude is a measure of the angle between the plane of the equator and lines projected from the center of the Earth. For example, the angle between a line drawn from New Orleans on the 30th line of latitude to the center of the Earth and a line drawn on the plane of the equator is 30 degrees (30°). In each hemisphere the 30th line of latitude connects all points whose projections to the center of the Earth form a 30° angle with the plane of the equator.

The latitude of the equator is zero degrees (0°). Lines of latitude north and south of the equator are numbered to 90° because the angular distance from the equator to each pole is one-fourth of a circle, or one-fourth of 360°. There is no latitude higher than 90°. The North Pole is situated at 90° north latitude, or simply 90° N. The South Pole is at 90° south latitude, or 90° S.


Question: Why is latitude measured in 180 degrees?

Explanation: Two levels of abstraction are employed in the definitions of latitude and longitude. In the first step the physical surface is modeled by the geoid, a surface which approximates the mean sea level over the oceans and its continuation under the land masses. The second step is to approximate the geoid by a mathematically simpler reference surface. The simplest choice for the reference surface is a sphere, but the geoid is more accurately modeled by an ellipsoid of revolution. The definitions of latitude and longitude on such reference surfaces are detailed in the following sections. Lines of constant latitude and longitude together constitute a graticule on the reference surface. The latitude of a point on the actual surface is that of the corresponding point on the reference surface, the correspondence being along the normal to the reference surface, which passes through the point on the physical surface. Latitude and longitude together with some specification of height constitute a geographic coordinate system as defined in the specification of the ISO 19111 standard.


Question: Why is water considered a universal solvent?

Explanation: Water is made up of tiny things called molecules. Each water molecule is like a magnet - one side pulls on one kind of thing while the other side pulls on the opposite kind of thing. Most things are made up of the two different kind of things. So two water molecules pulling in opposite directions will pull many things apart.


Question: Why is water considered a universal solvent?

Explanation: Water is called the "universal solvent" because it is capable of dissolving more substances than any other liquid. This is important to every living thing on earth. It means that wherever water goes, either through the air, the ground, or through our bodies, it takes along valuable chemicals, minerals, and nutrients.


Question: Why is water considered a universal solvent?

Explanation: Water is called the universal solvent because it dissolves a wide variety of substances. Water is polar, so it readily dissolves charged or polar solutes. Water also dissolves some molecules that have nonpolar character, such as aromatics and surfactants. However, water is not a good solvent for nonpolar molecules such as hydrocarbons (oils).


Question: Why is Neptune blue?

Explanation: Its atmosphere is made of hydrogen, helium, and methane. The methane gives Neptune the same blue color as Uranus.


Question: Why is Neptune blue?

Explanation: Neptune's atmosphere is made up of hydrogen, helium and methane. The methane in Neptune's upper atmosphere absorbs the red light from the sun but reflects the blue light from the Sun back into space. This is why Neptune appears blue.


Question: Why is Neptune blue?

Explanation: We now know this blueness comes from a combination of this higher abundance of gaseous methane, which has strong absorption bands in the infrared and red portion of the visible spectrum, and enhanced Rayleigh‐scattering from atmospheres that have low abundances of aerosols.


Question: Why is gravity important?

Explanation: Gravity is the force that pulls things toward the center of the Earth, or towards the center of other physical bodies that have mass (for example, other planets, and even the sun!). Gravity is very important: it's why we have weight, why we naturally stay on the ground, why planes need to generate lift to get up into the air, and even why objects and planets stay in orbit!


Question: Why is gravity important?

Explanation: Gravity is the most significant interaction between objects at the macroscopic scale, and it determines the motion of planets, stars, galaxies, and even light.


Question: Why is gravity important?

Explanation: Gravity is a fundamental interaction that permeates throughout our Universe. On Earth, gravity gives weight to physical objects, and has been a constant presence throughout terrestrial biological evolution. Thus, gravity has shaped all biological functions, some examples include the growth of plants (e.g., gravitropism), the structure and morphology of biological parts in multicellular organisms, to its effects on our physiological function when humans travel into space.


Question: Why do we have day and night?

Explanation:
We get day and night because the Earth rotates on an imaginary line called an axis. During daytime, your part of the Earth is facing the sun. As the Earth rotates you move away from the sun until eventually, the sun is no longer visible. For you, this is now nighttime, but for the other side of the planet, day has just begun.

The Earth rotates on its axis once every 24 hours. We call each 24-hour period 1 day, even though we experience both daytime and nighttime.


Question: Why do we have day and night?

Explanation: The Earth orbits the sun once every 365 days and rotates about its axis once every 24 hours. Day and night are due to the Earth rotating on its axis, not its orbiting around the sun. The term ‘one day’ is determined by the time the Earth takes to rotate once on its axis and includes both day time and night time.


Question: Why do we have day and night?

Explanation: The spins of the terrestrial planets likely arose as the planets formed by the accretion of planetesimals. Depending on the masses of the impactors, the planet's final spin can either be imparted by many small bodies (ordered accretion), in which case the spin is determined by the mean angular momentum of the impactors, or by a few large bodies (stochastic accretion), in which case the spin is a random variable whose distribution is determined by the root-mean-square angular momentum of the impactors, in the case of ordered accretion, the planet's obliquity is expected to be near 0 [degrees] or 180 [degrees], whereas, if accretion is stochastic, there should be a wide range of obliquities. Analytic arguments and extensive orbital integrations are used to calculate the expected distributions of spin rate and obliquity as a function of the planetesimal mass and velocity distributions. The results imply that the spins of the terrestrial planets are determined by stochastic accretion.


Question: Why is the ozone hole a concern?

Explanation:
Ozone is a natural part of Earth’s upper atmosphere. This part of the atmosphere, about 15 miles (24 kilometers) above the surface, is called the ozone layer. It protects people by absorbing harmful rays from the sun. If they reach Earth, these rays can cause skin cancer, eye diseases, and other health problems.

Some chemicals used in industry can destroy this protective ozone. Scientists have found a “hole” in the ozone layer over Antarctica. To preserve the ozone layer, many countries have limited their use of the destructive chemicals.


Question: Why is the ozone hole a concern?

Explanation: Ozone depletion can cause increased amounts of UV radiation to reach the Earth which can lead to more cases of skin cancer, cataracts, and impaired immune systems. Too much exposure to UV is believed to be contributing to the increase in melanoma, the most fatal of all skin cancers.


Question: Why is the ozone hole a concern?

Explanation:
The weak Antarctic vortex in 2019 favoured extreme weather and wildfires in Australia.
The unusual warming of the Antarctic stratosphere in September 2019 favoured the extremely dry conditions observed during the summer of 2019/20 in the Southern Hemisphere [2] that contributed to the devastating “2019/2020 Black Summer'' wildfires in Australia [3]. Additional studies [4–6] have further reinforced the link between the unusually weak Antarctic vortex in 2019 and the ensuing dry weather in the Southern Hemisphere. However, stratospheric warming events, such as that observed in 2019, are less likely in a future climate [6] as increasing concentrations of greenhouse gases (GHG) will cool the stratosphere. Furthermore, modelling studies suggest that summertime precipitation in the Southern Hemisphere, with some regions projected to get drier and others wetter, will be more affected by future increases in the concentration of GHGs and warming of the tropical upper troposphere than by stratospheric ozone recovery resulting from the implementation of the Montreal Protocol [7].


Question: Why are some bacteria beneficial?

Explanation: Some bacteria are good for our bodies — they help keep things in balance. Good bacteria live in our intestines and help us use the nutrients in the food we eat and make waste from what's left over. We couldn't make the most of a healthy meal without these important helper germs!


Question: Why are some bacteria beneficial?

Explanation:
Bad bacteria like salmonella and E. coli can make you sick. Good bacteria like the kind in probiotics play an important role in keeping us healthy.

These good bacteria interact with the intestinal lining to protect the body from harmful invaders. They help the immune system function properly, which means better ability both to fight infections and to dampen chronic inflammation.


Question: Why are some bacteria beneficial?

Explanation: For probiotics, there is an emerging view that well‐studied species known to confer health benefits may do so via the principle of ‘shared benefits’. This principle is based on the knowledge that certain bacterial species have conserved, or core, properties which may be responsible for improving health.


Question: Why do we sleep?

Explanation: Sleep gives your body a rest and allows it to prepare for the next day. It's like giving your body a mini-vacation. Sleep also gives your brain a chance to sort things out. Scientists aren't exactly sure what kinds of organizing your brain does while you sleep, but they think that sleep might be the time when the brain sorts and stores information, replaces chemicals, and solves problems.


Question: Why do we sleep?

Explanation: Sleep is important to a number of brain functions, including how nerve cells (neurons) communicate with each other. In fact, your brain and body stay remarkably active while you sleep. Recent findings suggest that sleep plays a housekeeping role that removes toxins in your brain that build up while you are awake.


Question: Why do we sleep?

Explanation: A number of sleep theories have been put forth and fluctuations in biological patterns have been measured during sleep, but the function of sleep is not yet understood. Sleep can be understood as fulfilling many different functions but intuition suggests there is one essential function. The discovery of this function will open an important door to the understanding of biological processes.


Question: Why are computer viruses harmful?

Explanation:
A computer virus is a program that is able to copy itself when it is run. Very often, computer viruses are run as a part of other programs. Biological viruses also work that way, as they copy themselves as part of other organisms. This is how the computer virus got its name.

In addition to copying itself, a computer virus can also execute instructions that cause harm. For this reason, computer viruses affect security.


Question: Why are computer viruses harmful?

Explanation: A computer virus is a type of malicious software, or malware, that spreads between computers and causes damage to data and software. Computer viruses aim to disrupt systems, cause major operational issues, and result in data loss and leakage.


Question: Why are computer viruses harmful?

Explanation: The emergence of computer viruses traces back to the 1980s and has evolved into a significant threat to both our professional endeavors and daily routines, particularly given the ever-advancing technology landscape. In recent times, rapid progress in fields such as science, technology, and commerce has heightened reliance on computers, the internet, and various software applications. Unfortunately, this increased technological integration has also spawned a growing threat from computer viruses within networked environments. For example, computer viruses possess the capability to compromise sensitive information, including personal bank account details and user passwords, leading to severe consequences for individuals, households, and institutions alike.


Question: Why is pi an irrational number?

Explanation: Pi cannot be represented as a ratio of any two whole numbers, i.e. pi is never equal to a/b, where a and b are whole. This property makes pi irrational.


Question: Why is pi an irrational number?

Explanation: Pi is a mathematical constant that is given as the ratio of the circumference of a circle to the diameter of the circle. Pi is represented by the Greek letter π. The approximate value of Pi is 3.14159263539… which is a non-terminating and non-repeating decimal expansion and we know that the non-terminating and non-repeating decimal is an Irrational Number. Hence, Pi is an irrational number.


Question: Why is pi an irrational number?

Explanation:
Here is Ivan Niven’s proof, which is the first proof of the irrationality of  \pi:
Let $\pi = \frac{a}{b}$, the quotient of positive integers. We define the polynomials
\[f(x) = \frac{x^n (a - bx)^n}{n!},\]
\[F(x) = f(x) - f^{(2)}(x) + f^{(4)}(x) - \cdots + (-1)^n f^{(2n)}(x),\]
the positive integer $n$ being specified later. Since $n! f(x)$ has integral coefficients and terms in $x$ of degree not less than $n$, $f(x)$ and its derivatives $f^{(i)}(x)$ have integral values for $x = 0$; also for $x = \pi = \frac{a}{b}$, since $f(x) = f(a/b - x)$. By elementary calculus we have
\[\frac{d}{dx} \left\{ F'(x) \sin x - F(x) \cos x \right\} = F''(x) \sin x + F(x) \sin x = f(x) \sin x\]
and
\[\int_0^\pi f(x) \sin x \, dx = \left[ F'(x) \sin x - F(x) \cos x \right]_0^\pi = F(\pi) + F(0).\]
Now $F(\pi) + F(0)$ is an integer, since $f^{(i)}(\pi)$ and $f^{(i)}(0)$ are integers. But for $0 < x < \pi$,
\[0 < f(x) \sin x < \frac{\pi^n a^n}{n!},\]
so that the integral in (1) is positive, but arbitrarily small for $n$ sufficiently large. Thus (1) is false, and so is our assumption that $\pi$ is rational.


Question: Why is the Pythagorean Theorem significant?

Explanation: The Pythagorean theorem is a cornerstone of math that helps us find the missing side length of a right triangle. In a right triangle with sides A, B, and hypotenuse C, the theorem states that A² + B² = C². The hypotenuse is the longest side, opposite the right angle.


Question: Why is the Pythagorean Theorem significant?

Explanation: The Pythagorean theorem is crucial in various fields, including construction, manufacturing and navigation, enabling precise measurements and the creation of right angles for large structures.


Question: Why is the Pythagorean Theorem significant?

Explanation:
As a first example, we note that any regular polygon in two dimensions can be viewed as a collection of identical triangles arranged in a certain fashion. Another important observation is that the triangle is intimately related to the circle. For instance, if one considers a Pythagorean triple (i.e. three integers which satisfy a2+b2=c2) one can divide by c2 to obtain
a2/c2+b2/c2=1
which is quickly seen to correspond to a rational point on the unit circle. In fact, this immediately shows that there are infinitely many Pythagorean triples (which are not multiples of any other Pythagorean triple), since the rational points on the circle are dense. This neat little observation (which I got from the first pages of Hatcher's freely available book 'Topology of numbers') shows that the triangle and circle are closely related, a fact which is often expressed using sine and cosine functions.

This, combined with the fact that circles are also known to be the set describing all points equidistant to a single point (the center) hints at another very important thing: One can define a notion of distance by using the Pythagorean theorem. In fact, after making the crucial observation that we can easily generalize to n dimensions by 'decomposing' R^n, n-dimensional Euclidean space, into n copies of R (treating the coordinates independently, so to say), it becomes clear that we can use the Pythagorean theorem to define a notion of distance in any Euclidean space R^n. This is known as the 'Euclidean distance' and is one the most important (early) examples of a metric; the study of metric spaces and related concepts has turned into an entire field of mathematics.


Question: Why can’t we see ultraviolet light?

Explanation: When you turn on a light, you are able to see thanks to light waves. Some light waves are visible to the human eye, but others are not. Ultraviolet rays are shorter light waves that are produced by the sun. People cannot see ultraviolet rays, but some insects like bees can.


Question: Why can’t we see ultraviolet light?

Explanation: Generally, humans can see light with wavelengths between 380 and 700 nanometers (nm). But ultraviolet (UV) light has wavelengths shorter than 380 nm. That means they go undetected by the human eye.


Question: Why can’t we see ultraviolet light?

Explanation: Two major reasons can be considered for this change. First, UV light, even at ≈360 nm, can damage retinal tissues. Indeed, the yellow pigments in the lenses or corneas in many species, including human, are devised to obviate most UV light from reaching the retina. This change in the eye structure must be responsible for the transition from UV vision to violet vision. Second, by achieving violet vision, organisms can improve visual resolution and subtle contrast detection.


Question: Why is absolute zero unattainable?

Explanation:
Heat energy is basically due to molecules zooming around (translation), spinning around (rotation) and stretching/unstretching/bending frequently (vibration).

We remove heat energy by slowing and stopping these three things.

Even if you completely stop the atoms or molecules from moving, they have a small amount of inherent energy that cannot be stopped, called zero point energy.

Why is this the case? When you get very tiny and at very low energies, our universe doesn’t behave the way we normally expect.

Normally we expect that we can smoothly turn up or down the energy of something like a billiard ball by making it go faster or slower. But the universe isn’t that simple when you try to completely stop something very tiny. At very low energies, there are certain energy level that are allowed and some that are not allowed. Why? It’s the nature of our universe.

The universe is probably not actually completely smooth, it’s sort of pixelated at a very tiny scale, especially when it gets to small energy amounts.

So basically imagine a pixel on your phone screen that’s black but still emits the faintest bit of light when powered on.

Atoms are kinda like that, even when powered down, they are never fully “off” similar to the black pixel giving off some light.


Question: Why is absolute zero unattainable?

Explanation: Using classical definitions, temperature is a measure of the average speed of molecules in a substance, and absolute zero is the temperature at which the average velocity of molecules is zero. We can’t go beyond that because there is no velocity slower than zero.


Question: Why is absolute zero unattainable?

Explanation:
The third law postulates that the entropy of a substance is always finite and that it approaches a constant as the temperature approaches zero. The value of this constant is independent of the values of any other state functions that characterize the substance. For any given substance, we are free to assign an arbitrarily selected value to the zero-temperature limiting value. However, we cannot assign arbitrary zero-temperature entropies to all substances. The set of assignments we make must be consistent with the experimentally observed zero-temperature limiting values of the entropy changes of reactions among different substances. For perfectly crystalline substances, these reaction entropies are all zero. We can satisfy this condition by assigning an arbitrary value to the zero-temperature molar entropy of each element and stipulating that the zero-temperature entropy of any compound is the sum of the zero-temperature entropies of its constituent elements. This calculation is greatly simplified if we let the zero-temperature entropy of every element be zero. This is the essential content of the third law.
"It is impossible to achieve a temperature of absolute zero." This statement is more general than the Lewis and Randall statement. If we consider the application of this statement to the temperatures attainable in processes involving a single substance, we can show that it implies, and is implied by, the Lewis and Randall statement.


Question: Why does Earth rotate?

Explanation: As the planets formed, they kept this spinning motion. This is similar to what you see when skaters pull in their arms and spin faster. As material gathered in more closely to form a planet, like Earth, the material spun faster. The Earth keeps on spinning because there are no forces acting to stop it.


Question: Why does Earth rotate?

Explanation:
The Earth's spin rate is appreciably higher than what would be dictated by it simply forming from accretion. And its axial tilt is kind of cockeyed as well,.

The most plausible explanation is the hypothesis that a Mars-sized planet (which they named Theia) smacked us at a particular velocity/angle/location around 4 1/2B years ago--most likely twice, a few hundred thousand years apart.


Question: Why does Earth rotate?

Explanation: The spins of the terrestrial planets likely arose as the planets formed by the accretion of planetesimals. Depending on the masses of the impactors, the planet's final spin can either be imparted by many small bodies (ordered accretion), in which case the spin is determined by the mean angular momentum of the impactors, or by a few large bodies (stochastic accretion), in which case the spin is a random variable whose distribution is determined by the root-mean-square angular momentum of the impactors. In the case of ordered accretion, the planet's obliquity is expected to be near 0° or 180°, whereas, if accretion is stochastic, there should be a wide range of obliquities. Analytic arguments and extensive orbital integrations are used to calculate the expected distributions of spin rate and obliquity as a function of the planetesimal mass and velocity distributions. The results imply that the spins of the terrestrial planets are determined by stochastic accretion.