# Science Articles

The universe is a strange and fascinating place, from the subatomic all the way up to the astronomical. Study and conduct experiments in any and every branch of science that calls to you.

## Articles From Science

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Cheat Sheet / Updated 03-08-2023

The human body is a beautiful and efficient system that everyone should know a little bit about. In order to study and talk about anatomy and physiology, though, you need to learn the language. You have to have a solid grasp on the directional terms, the body cavities, and the overall organization of the organs and their division of labor. A familiarity with common Latin and Greek word roots will go a long way too.

View Cheat SheetArticle / Updated 02-15-2023

An earthquake is the sometimes violent shaking of the ground caused by movements of Earth's tectonic plates. Most earthquakes occur along fault lines, which is where two tectonic plates come together. Earthquakes strike suddenly and violently and can occur at any time, day or night, throughout the year. Smaller earthquakes might crack some windows and shake products off store shelves, but larger earthquakes can cause death and massive destruction, devastating communities and debilitating local economies. A tectonic shift Earthquakes occur when large sections of the Earths' crust — called tectonic plates — shift. There are seven primary tectonic plates (African, Antarctic, Eurasian, Indo-Australian, North American, Pacific, and South American) and a number of smaller, secondary and tertiary plates. Because of underlying movement in the Earth's mantle, these plates can shift. This shifting of one plate causes it to rub against or push under or over an adjacent plate. The place where two plates meet is called a fault line, and it's at these fault lines that earthquakes occur. Earthquakes are often followed by smaller earthquakes called aftershocks, which can occur over days or weeks as the plates settle into equilibrium. In the United States, California experiences damaging earthquakes most often, but Alaska has the greatest number of large earthquakes. They occur mostly in uninhabited areas, though, and so don't cause as much damage. What can earthquakes do? The violent ground-shaking of earthquakes by itself can cause damage to homes, roads, and bridges; shake products off shelves; and lead to injuries and death, but earthquakes can also lead to other natural disasters: Avalanches and landslides: Earthquakes can shake snow, soil, and rock right off a sloped surface. Landslides have been a particular problem in California, where a number of mountainside homes have ended up in the Pacific Ocean because of them. Surface faulting: Surface faulting is a change in the relative positions of things on opposite sides of a fault line. For instance, a straight section of railroad track that runs across a fault line might have a nasty curve in it after an earthquake, rendering it useless for train travel. Tsunamis: Tsunamis are a series of waves that are caused by the sudden displacement of large amounts of ocean water, usually because of underwater earthquakes. When tsunamis hit land, they can knock over buildings, wash away cars, and cause massive flooding. The most massive tsunamis can reach heights of well over 500 feet. Liquefaction: Liquefaction occurs when water-logged soil acts like a liquid and causes sections of ground to sink or slide. As well as damage to roads and buildings, liquefaction can lead to flash floods. How are earthquakes measured? Seismometers and seismographs sense and record movements in the Earth's surface, showing both the intensity and duration of earthquakes and other tremors. Seismologists then use this information to rate the earthquake on the Richter scale. The Richter scale was developed in 1935 by Charles Richter to show the amount of energy released during an earthquake. It was originally intended not as an absolute measure of individual quakes but as a way to compare the relative strengths of different earthquakes. Though Richter measurements are generally thought of as being between 0 and 10, there are theoretically no limits to the scale in either direction. Earthquakes measuring less than 4.0 magnitude occur in small areas and might not even be noticed, much less cause any serious damage. Earthquakes measuring 4.0–4.9 magnitude cover a larger area. They are felt, but damage is light. You start to see some damage with a 5.0-magnitude earthquake, starting with poorly constructed buildings. Higher up on the Richter scale, you see greater damage over a greater area. The largest recorded earthquake was the 9.5-magnitude Great Chilean Earthquake of 1960. This quake spawned numerous tsunamis that caused damage as far away as Hawaii, Japan, and the Philippines.

View ArticleArticle / Updated 02-07-2023

Many physicists feel that string theory will ultimately be successful at resolving the hierarchy problem of the Standard Model of particle physics. Although it is an astounding success, the Standard Model hasn’t answered every question that physics hands to it. One of the major questions that remains is the hierarchy problem, which seeks an explanation for the diverse values that the Standard Model lets physicists work with. For example, if you count the theoretical Higgs boson (and both types of W bosons), the Standard Model of particle physics has 18 elementary particles. The masses of these particles aren’t predicted by the Standard Model. Physicists had to find these by experiment and plug them into the equations to get everything to work out right. You notice three families of particles among the fermions, which seems like a lot of unnecessary duplication. If we already have an electron, why does nature need to have a muon that’s 200 times as heavy? Why do we have so many types of quarks? Beyond that, when you look at the energy scales associated with the quantum field theories of the Standard Model, as shown in this figure, even more questions may occur to you. Why is there a gap of 16 orders of magnitude (16 zeroes!) between the intensity of the Planck scale energy and the weak scale? At the bottom of this scale is the vacuum energy, which is the energy generated by all the strange quantum behavior in empty space — virtual particles exploding into existence and quantum fields fluctuating wildly due to the uncertainty principle. The hierarchy problem occurs because the fundamental parameters of the Standard Model don’t reveal anything about these scales of energy. Just as physicists have to put the particles and their masses into the theory by hand, so too have they had to construct the energy scales by hand. Fundamental principles of physics don’t tell scientists how to transition smoothly from talking about the weak scale to talking about the Planck scale. Trying to understand the “gap” between the weak scale and the Planck scale is one of the major motivating factors behind trying to search for a quantum gravity theory in general, and string theory in particular. Many physicists would like a single theory that could be applied at all scales, without the need for renormalization (the mathematical process of removing infinities), or at least to understand what properties of nature determine the rules that work for different scales. Others are perfectly happy with renormalization, which has been a major tool of physics for nearly 40 years and works in virtually every problem that physicists run into.

View ArticleCheat Sheet / Updated 01-09-2023

Organic Chemistry II is one of the toughest courses you can take. Surviving isn’t easy — you probably know that from your Organic Chemistry I class. Preparation is key: If you study the basics of organic chemistry the right way, prepare for your tests, and know your aromatic systems, you’re off to a great start!

View Cheat SheetArticle / Updated 01-05-2023

Nuclear fusion is essentially the opposite of nuclear fission. In fission, a heavy nucleus is split into smaller nuclei. With fusion, lighter nuclei are fused into a heavier nucleus. The fusion process is the reaction that powers the sun. On the sun, in a series of nuclear reactions, four isotopes of hydrogen-1 are fused into a helium-4 with the release of a tremendous amount of energy. Here on earth, two other isotopes of hydrogen are used: H-2, called deuterium, and H-3, called tritium. Deuterium is a minor isotope of hydrogen, but it’s still relatively abundant. Tritium doesn’t occur naturally, but it can easily be produced by bombarding deuterium with a neutron. The fusion reaction is shown in the following equation: Major breakthrough in 2022 In December 2022, scientists at the U.S. National Ignition Facility in Livermore, California, achieved a major breakthrough in nuclear fusion research: energy gain. Energy gain, also known in this context as ignition, means that they were able to create a fusion reaction that released more energy than they put in by their lab's gigantic high-powered lasers. The scientists said they proved nuclear fusion can work on Earth, but we are still many years from being able to use it in power plants. Yet, scientists are optimistic that controlled fusion power will be achieved. The rewards are great — an unlimited source of clean energy. Hydrogen bomb was first demonstration The first demonstration of nuclear fusion — the hydrogen bomb — was conducted by the military. A hydrogen bomb is approximately 1,000 times as powerful as an ordinary atomic bomb. The isotopes of hydrogen needed for the hydrogen bomb fusion reaction were placed around an ordinary fission bomb. The explosion of the fission bomb released the energy needed to provide the activation energy (the energy necessary to initiate, or start, the reaction) for the fusion process. Control issues with nuclear fusion The goal of scientists for the last 50 years has been the controlled release of energy from a fusion reaction. If the energy from a fusion reaction can be released slowly, it can be used to produce electricity. It will provide an unlimited supply of energy that has no wastes to deal with or contaminants to harm the atmosphere — simply non-polluting helium. But achieving this goal requires overcoming three problems: Temperature Time Containment Temperature The fusion process requires an extremely high activation energy. Heat is used to provide the energy, but it takes a lot of heat to start the reaction. Scientists estimate that the sample of hydrogen isotopes must be heated to approximately 40,000,000 K. K represents the Kelvin temperature scale. To get the Kelvin temperature, you add 273 to the Celsius temperature. Now 40,000,000 K is hotter than the sun! At this temperature, the electrons have long since left the building; all that’s left is a positively charged plasma, bare nuclei heated to a tremendously high temperature. Presently, scientists are trying to heat samples to this high temperature through two ways — magnetic fields and lasers. Neither one has yet achieved the necessary temperature. Time Time is the second problem scientists must overcome to achieve the controlled release of energy from fusion reactions. The charged nuclei must be held together close enough and long enough for the fusion reaction to start. Scientists estimate that the plasma needs to be held together at 40,000,000 K for about one second. Containment Containment is the major problem facing fusion research. At 40,000,000 K, everything is a gas. The best ceramics developed for the space program would vaporize when exposed to this temperature. Because the plasma has a charge, magnetic fields can be used to contain it — like a magnetic bottle. But if the bottle leaks, the reaction won’t take place. And scientists have yet to create a magnetic field that won’t allow the plasma to leak. Using lasers to zap the hydrogen isotope mixture and provide the necessary energy bypasses the containment problem. But scientists have not figured out how to protect the lasers themselves from the fusion reaction. Another Possible Use of Fusion An interesting by-product of fusion research is the fusion torch concept. With this idea, the fusion plasma, which must be cooled in order to produce steam, is used to incinerate garbage and solid wastes. Then the individual atoms and small molecules that are produced are collected and used as raw materials for industry. It seems like an ideal way to close the loop between waste and raw materials. Time will tell if this concept will eventually make it into practice.

View ArticleCheat Sheet / Updated 12-23-2022

Biology is the study of the living world. All living things share certain common properties: They are made of cells that contain DNA. They maintain order inside their cells and bodies. They regulate their systems. They respond to signals in the environment. They transfer energy between themselves and their environment. They grow and develop; they reproduce. They have traits that have evolved over time.

View Cheat SheetArticle / Updated 12-23-2022

Any physicist knows that if an object applies a force to a spring, then the spring applies an equal and opposite force to the object. Hooke’s law gives the force a spring exerts on an object attached to it with the following equation: F = –kx The minus sign shows that this force is in the opposite direction of the force that’s stretching or compressing the spring. The variables of the equation are F, which represents force, k, which is called the spring constant and measures how stiff and strong the spring is, and x, the distance the spring is stretched or compressed away from its equilibrium or rest position. The force exerted by a spring is called a restoring force; it always acts to restore the spring toward equilibrium. In Hooke’s law, the negative sign on the spring’s force means that the force exerted by the spring opposes the spring’s displacement. Understanding springs and their direction of force The direction of force exerted by a spring The preceding figure shows a ball attached to a spring. You can see that if the spring isn’t stretched or compressed, it exerts no force on the ball. If you push the spring, however, it pushes back, and if you pull the spring, it pulls back. Hooke’s law is valid as long as the elastic material you’re dealing with stays elastic — that is, it stays within its elastic limit. If you pull a spring too far, it loses its stretchy ability. As long as a spring stays within its elastic limit, you can say that F = –kx. When a spring stays within its elastic limit and obeys Hooke’s law, the spring is called an ideal spring. How to find the spring constant (example problem) Suppose that a group of car designers knocks on your door and asks whether you can help design a suspension system. “Sure,” you say. They inform you that the car will have a mass of 1,000 kilograms, and you have four shock absorbers, each 0.5 meters long, to work with. How strong do the springs have to be? Assuming these shock absorbers use springs, each one has to support a mass of at least 250 kilograms, which weighs the following: F = mg = (250 kg)(9.8 m/s2) = 2,450 N where F equals force, m equals the mass of the object, and g equals the acceleration due to gravity, 9.8 meters per second2. The spring in the shock absorber will, at a minimum, have to give you 2,450 newtons of force at the maximum compression of 0.5 meters. What does this mean the spring constant should be? In order to figure out how to calculate the spring constant, we must remember what Hooke’s law says: F = –kx Now, we need to rework the equation so that we are calculating for the missing metric, which is the spring constant, or k. Looking only at the magnitudes and therefore omitting the negative sign, you get Time to plug in the numbers: The springs used in the shock absorbers must have spring constants of at least 4,900 newtons per meter. The car designers rush out, ecstatic, but you call after them, “Don’t forget, you need to at least double that if you actually want your car to be able to handle potholes.”

View ArticleArticle / Updated 12-14-2022

For most interpretations, superstring theory requires a large number of extra space dimensions to be mathematically consistent: M-theory requires ten space dimensions. With the introduction of branes as multidimensional objects in string theory, it becomes possible to construct and imagine wildly creative geometries for space that correspond to different possible particles and forces. It’s unclear, at present, whether those extra dimensions exist or are just mathematical artifacts. The reason string theory requires extra dimensions is that trying to eliminate them results in much more complicated mathematical equations. It’s not impossible, but most physicists haven’t pursued these concepts in a great deal of depth, leaving science (perhaps by default) with a theory that requires many extra dimensions. From the time of Descartes, mathematicians have been able to translate between geometric and physical representations. Mathematicians can tackle their equations in virtually any number of dimensions that they choose, even if they can’t visually picture what they’re talking about. One of the tools mathematicians use in exploring higher dimensions is analogy. If you start with a zero-dimensional point and extend it through space, you get a one-dimensional line. If you take that line and extend it into a second dimension, you end up with a square. If you extend a square through a third dimension, you end up with a cube. If you then were to take a cube and extend into a fourth dimension, you’d get a shape called a hypercube. A line has two “corners” but extending it to a square gives four corners, while a cube has eight corners. By continuing to extend this algebraic relationship, a hypercube would be a four-dimensional object with 16 corners, and a similar relationship can be used to create analogous objects in additional dimensions. Such objects are obviously well outside of what our minds can picture. Humans aren’t psychologically wired to be able to picture more than three space dimensions. A handful of mathematicians (and possibly some physicists) have devoted their lives to the study of extra dimensions so fully that they may be able to actually picture a four-dimensional object, such as a hypercube. Most mathematicians can’t (so don’t feel bad if you can’t). Whole fields of mathematics — linear algebra, abstract algebra, topology, knot theory, complex analysis, and others — exist with the sole purpose of trying to take abstract concepts, frequently with large numbers of possible variables, degrees of freedom, or dimensions, and make sense of them. These sorts of mathematical tools are at the heart of string theory. Regardless of the ultimate success or failure of string theory as a physical model of reality, it has motivated mathematics to grow and explore new questions in new ways, and for that alone, it has proved useful.

View ArticleCheat Sheet / Updated 11-08-2022

Chemistry covers all kinds of stuff. Sometimes you might not be sure where to start when you are first given a set of problems and told to go forth and succeed. Sometimes it’s converting metric units, writing ionic formulas, naming covalent compounds, balancing reactions, or dealing with extensive and intensive properties. This Cheat Sheet is designed to give you some help on a few of the trickier things you might encounter so that when you are done looking it over you can go forth and succeed!

View Cheat SheetArticle / Updated 10-26-2022

A conversion factor uses your knowledge of the relationships between units to convert from one unit to another. For example, if you know that there are 2.54 centimeters in every inch (or 2.2 pounds in every kilogram or 101.3 kilopascals in every atmosphere), then converting between those units becomes simple algebra. It is important to know some common conversions of temperature, size, and pressure as well as metric prefixes. Conversion factor table The following table includes some useful conversion factors. Using conversion factors example The following example shows how to use a basic conversion factor to fix non-SI units. Dr. Geekmajor absentmindedly measures the mass of a sample to be 0.75 lb and records his measurement in his lab notebook. His astute lab assistant, who wants to save the doctor some embarrassment, knows that there are 2.2 lbs in every kilogram. The assistant quickly converts the doctor’s measurement to SI units. What does she get? The answer is 0.34 kg. Let’s try another example. A chemistry student, daydreaming during lab, suddenly looks down to find that he’s measured the volume of his sample to be 1.5 cubic inches. What does he get when he converts this quantity to cubic centimeters? The answer is 25 cm3. Rookie chemists often mistakenly assume that if there are 2.54 centimeters in every inch, then there are 2.54 cubic centimeters in every cubic inch. No! Although this assumption seems logical at first glance, it leads to catastrophically wrong answers. Remember that cubic units are units of volume and that the formula for volume is Imagine 1 cubic inch as a cube with 1-inch sides. The cube’s volume is Now consider the dimensions of the cube in centimeters: Calculate the volume using these measurements, and you get This volume is much greater than 2.54 cm3! To convert units of area or volume using length measurements, square or cube everything in your conversion factor, not just the units, and everything works out just fine.

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