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Why are some bacteria beneficial? | STEM | Health Science | 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. | High School | https://www.health.harvard.edu/staying-healthy/the-good-side-of-bacteria |
Why are some bacteria beneficial? | STEM | Health Science | 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. | PhD | https://kidshealth.org/en/kids/germs.html |
Why do we sleep? | STEM | Neuroscience | 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. | Elementary | https://kidshealth.org/en/kids/sleep.html |
Why do we sleep? | STEM | Neuroscience | 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. | High School | https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-understanding-sleep |
Why do we sleep? | STEM | Neuroscience | 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. | PhD | https://pmc.ncbi.nlm.nih.gov/articles/PMC7120898/ |
Why are computer viruses harmful? | STEM | Computer Science | 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. | Elementary | https://kids.kiddle.co/Computer_virus |
Why are computer viruses harmful? | STEM | Computer Science | 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. | High School | https://www.fortinet.com/resources/cyberglossary/computer-virus |
Why are computer viruses harmful? | STEM | Computer Science | 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. | PhD | https://www.sciencedirect.com/science/article/pii/S1110016824005969 |
Why is pi an irrational number? | STEM | Mathematics | 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. | Elementary | https://www.reddit.com/r/explainlikeimfive/comments/ngx5hm/eli5_why_is_pi_irrational/ |
Why is pi an irrational number? | STEM | Mathematics | 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. | High School | https://www.geeksforgeeks.org/is-pi-a-rational-or-irrational-number/ |
Why is pi an irrational number? | STEM | Mathematics | 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. | PhD | https://mathematics11.quora.com/Why-is-the-value-of-%CF%80-an-irrational-number
https://projecteuclid.org/download/pdf_1/euclid.bams/1183510788 |
Why is the Pythagorean Theorem significant? | STEM | Mathematics | 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. | Elementary | https://www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-geometry/cc-8th-pythagorean-theorem/v/the-pythagorean-theorem |
Why is the Pythagorean Theorem significant? | STEM | Mathematics | 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. | High School | https://science.howstuffworks.com/math-concepts/pythagorean-theorem.htm |
Why is the Pythagorean Theorem significant? | STEM | Mathematics | 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. | PhD | https://hsm.stackexchange.com/questions/644/why-is-the-pythagorean-theorem-so-ubiquitous |
Why can’t we see ultraviolet light? | STEM | Biology | 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. | Elementary | https://study.com/academy/lesson/ultraviolet-rays-lesson-for-kids-definition-facts.html |
Why can’t we see ultraviolet light? | STEM | Biology | 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. | High School | https://wonderopolis.org/wonder/Why-Can%E2%80%99t-We-See-Ultraviolet-Light |
Why can’t we see ultraviolet light? | STEM | Biology | 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. | PhD | https://pmc.ncbi.nlm.nih.gov/articles/PMC166225/ |
Why is absolute zero unattainable? | STEM | Physics | 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. | Elementary | https://www.reddit.com/r/explainlikeimfive/comments/14whnj3/eli5_ive_often_heard_that_absolute_zero_cannot_be/ |
Why is absolute zero unattainable? | STEM | Physics | 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. | High School | https://www.quora.com/How-do-you-define-absolute-zero-Why-is-absolute-zero-unattainable |
Why is absolute zero unattainable? | STEM | Physics | 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. | PhD | https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Thermodynamics_and_Chemical_Equilibrium_(Ellgen)/11%3A_The_Third_Law_Absolute_Entropy_and_the_Gibbs_Free_Energy_of_Formation/11.13%3A_Absolute_Zero_is_Unattainable |
Why does Earth rotate? | STEM | Astronomy | 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. | Elementary | https://coolcosmos.ipac.caltech.edu/ask/59-Why-does-Earth-spin- |
Why does Earth rotate? | STEM | Astronomy | 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. | High School | https://www.reddit.com/r/askscience/comments/ur1b50/what_caused_the_earths_rotation_and_what_dictated/ |
Why does Earth rotate? | STEM | Astronomy | 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. | PhD | https://www.science.org/doi/10.1126/science.259.5093.350 |
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