Physical Sciences and Mathematics
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Created by:
amberrolland on March 1, 2012
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67 terms
Terms | Definitions |
|---|---|
 absolute zero | The lowest temperature that can be attained by matter, corresponding to the point at which motion in atoms stops. -273 degrees on the Celsius scales and -460 on the Fahrenheit scale. |
| accelerating universe | A phrase used to refer to the discovery that the Hubble expansion is not slowing down, as one would expect if only gravity were acting on the galaxies, but is actually speeding up as time goes by. |
| acceleration The most familiar kind of acceleration is a change in the speed of an object. An object that says at the same speed but changes direction, however, is also being accelerated. | A change in the velocity of an object. |
| acid | A sour-tasting material (usually in a solution) that dissolves metals and other materials. Technically, a material that produces positive ions in solution. The opposite of a base with a pH of 0 to 7. A given amount of this added to the same amount of a base neutralizes the base, producing water and a salt. Common vinegar, for example, is a weak solution of one kind of this. |
| acute angle | An angle that measures less than ninety degrees but more than zero degrees. |
| adhesion | The molecular attraction that holds the surfaces of two dissimilar substances together. |
| adsorption | The assimilation of a gas, liquid, or dissolved substance by the surface of a solid. |
| aerodynamics A vehicle that has been built to minimize friction with the air is said to be aerodynamically designed. | The branch of science devoted to the study of the flow of gases around solid objects. It is especially important in the design of cars and airplanes, which move through the air. |
| alchemy | A science (no longer practiced) that sought to transform one chemical element into another through a combination of magic and primitive chemistry. The ancestor of modern chemistry. Associated today with wizards, magic, and the search for arcane knowledge. The search for the Philosopher's Stone that would change lead and other base metals into gold was part of this. |
| algebra | A branch of mathematics marked chiefly by the use of symbols to represent numbers, as in the use of a-squared + b-squared = c-squared to express the Pythagorean Theorem. |
| algorithm | A set of instructions for solving a problem, especially on a computer. One of these for finding your total grocery bill, for example, would direct you to add up the costs of individual items to find the total. |
| alkali | A bitter, caustic mineral often found in large beds in the desert. Bases; two common examples are lye and ammonia. Plants have difficulty growing in soil that is rich in these. |
| alloy Brass is an alloy of copper and zinc. Steel is an alloy of iron and carbon. | A material made of two or more metals, or of a metal and another material. Often have unexpected characteristics. |
| alpha radiation | Particles sent out by some radioactive nuclei, each particle consisting of two protons and two neutrons bound together. Alpha particles carry a positive charge. Low penetrating power; can be stopped by clothing. |
| amplitude | In physics, the height of a crest (or the depth of a trough) of a wave. |
| Andromeda galaxy So named because the stars of the constellation Andromeda appear to enclose it. | In astronomy, the galaxy nearest to the Milky Way, usually seen as a large collection of stars arranged in a central core with spiral arms. |
| antimatter | In physics, matter made of antiparticles. |
| antiparticle | In physics, a rare form of subatomic matter that is a mirror image of normal matter. One of these corresponding to an elementary particle has the same mass as the particle but is opposite in all other properties. An example would be electrons and positrons or antiprotons and protons. When matter and antimatter come together, the two particles annihilate each other, converting their mass into energy or into other types of particles. May be possible to make antimatter in particle accelerators. |
| apogee | In astronomy, the point during the orbit of a satellite, such as the moon, at which it is the farthest from the body being orbited. For planets in the solar system orbiting the sun, their farthest point from the sun is referred to as aphelion. |
| Archimedes | An ancient Greek scientist, mathematician, and inventor best known for his investigations of buoyancy. Credited with popularizing the phrase, "Eureka!" Proved that a crown was not dense enough to be made of pure gold by measuring and weighing it. According to the principle of this person, when an object placed in water is weighed, and its weight int he water is compared to its weight out of the water, it seems to lose a definite amount - an amount equal to the weight of the water it displaces. This principle holds not only for water, but also for gases, such as air. Credited with saying, with regard to levers and fulcrums, "Give me the place to stand, and a lever long enough, and I will move the Earth!" |
| asteroid | A small planet that revolves around the sun. The largest asteroid is only about six hundred miles in diameter. |
| asteroid belt | A region of the solar system between the orbits of the planets Mars and Jupiter. Most asteroids are found here. |
| astronomical unit | The mean distance between the Earth and the sun, about 98 million miles or 150 million kilometers. Often abbreviated as AU. |
| astronomy | The science that deals with the universe beyond the Earth. It describes the nature, position, and motion of the stars, planets, and other objects in the skies, and their relation to the Earth. |
| astrophysics | The branch of astronomy devoted to the study of the physical characteristics and composition of objects in the sky. Typical concerns in this field are how much light stars give off and the size, mass, and temperature of planets and stars. |
| atom | A unit of matter; the smallest unit of a chemical element. Each of these consists of a nucleus, which has a positive charge, and a set of electrons that move around the nucleus. Link together to form molecules. |
| atomic clock | The most accurate clock available. Time is measured by the movement of electrons in cesium atoms. The standard second is now defined by measurements on this clock. |
| atomic number | The number of protons or electrons normally found in an atom of a given chemical element. The higher this number is, the heaver the atom is. In a neutral atom, the number of protons and electrons is the same. |
| atomic weight | The mass of a given atom, measured on a scale in which the hydrogen atom has the weight of one. Because most of the mass in an atom is in the nucleus, and each proton and neutron has an atomic weight near one, this is very nearly equal to the number of protons and neutrons in the nucleus. |
| average | A single number that represents a set of numbers. Means, medians, and modes are kinds of this; usually, however, this term refers to a mean. |
| axiom The term axiomatic is used generally to refer to a statement so obvious that it needs no proof. | In mathematics, a statement that is unproved but accepted as a basis for other statements, usually because it seems so obvious. |
| axis The axis of the Earth is an imaginary line drawn through the North Pole and the South Pole. | In geometry, a straight line about which an object may rotate or that divides an object into symmetrical halves. |
| background radiation | Low-level radiation at the surface of the Earth that comes from cosmic rays and from small amounts of radioactive materials in rocks and the atmosphere. |
| Baconian method | A method of experimentation, created by Francis Bacon in the seventeenth century, that derives it conclusions from observed facts rather than from previous conclusions or theories. |
| base | Any of a number of bitter-tasting, caustic materials. Technically, a material that produces negative ions in a solution. Opposite of an acid and has a pH of 7 to 14. A given amount of this added to the same amount of an acid neutralizes the acid; water and a salt are produced. Alkalis and ammonia are common types of these. |
| beta radiation | High-energy electrons, carrying a negative charge, that are sent out by some radioactive nuclei. Has some penetrating power and can pass through clothing and wooden walls. |
| Big Bang theory | In astronomy, a theory according to which the universe began billions of years ago in a single event, similar to an explosion. There is evidence for this theory in the observed red shift of distant galaxies, which indicates that they are moving away from the Earth, in the existence of cosmic microwave background, and from other data. Most accepted theory of the origin of the universe by astronomers today. |
| Big Dipper | A constellation in the northern sky. The two stars on the far end of the bowl of this point toward the North Star. Part of the constellation Ursa Major (the Great Bear). |
| black hole Supermassive and stellar black holes, which are thought to arise from the death of very massive stars, exist. | In astronomy, an object so massive that nothing, not even light, can escape its gravitation. Given their name because they absorb all the light that falls on them. The existence of these was first predicted by the general theory of relativity. Figuratively, this is used to refer to a total disappearance. |
| blackbody | An object that can absorb and send off radiation with complete efficiency - that is, it reflects none of the radiation that falls on it. The higher the object's temperature, the higher the frequency of the radiation it gives off. |
| Bohr atom | The simplest modern picture of the structure of the atom, according to which electrons move in orbits around the nucleus. The electron's orbits can exist only at certain well-defined distances from the nucleus. When an electron changes orbits, it does so in a sudden quantum leap. The energy difference between the initial and final orbit is emitted by the atom in bundles of electromagnetic radiation called photons. Named after the twentieth-century Danish physicist Niels Bohr. |
| Niels Bohr | A Danish physicist of the twentieth century. One of the founders of quantum mechanics and the originator of the Bohr atom. |
| boiling point Water boils at 212 degrees Fahrenheit or 100 degrees Celsius. | The temperature at which a given material changes from a liquid to a gas. This is the same temperature as the condensation point. |
| British thermal unit (Btu) | A unit for measuring heat. One of these raises the temperature of one pound of water one degree Fahrenheit. |
| Brownian motion | The erratic motion, visible through a microscope, of small grains suspended in a fluid. The motion results from collisions between the grains and atoms or molecules in the fluid. First explained by the twentieth-century physicist Albert Einstein, who considered it direct proof of the existence of atoms. |
| buffer | In chemistry, the components of a solution that can neutralize either an acid or a base and thus maintain a constant pH. Often used in medications designed to decrease acidity in the stomach. |
| buoyancy | The force that causes objects to float. According to the principle of Archimedes, when a solid is placed in a fluid (a liquid or a gas), it is subject to an upward force equal in magnitude to the weight of the fluid it has displaced. |
| calculus | The branch of mathematics, usually studied after algebra, that provides a natural method for describing gradual change. |
| Calorie A calorie (with a lower-case c) is a measurement of the heat needed to raise the temperature of a gram of water, rather than a kilogram. | The amount of heat required to raise the temperature of a kilogram of water by one degree Celsius. |
| capillary | A thin tube, such as blood vessel or a straw, through which fluids flow. The interaction between the fluid and the vessel walls produces a force that can lift the fluid up into the tube, a phenomenon known as capillary action. |
| carbon | A chemical element; its symbol is C. The carbon nucleus has six protons and six or more neutrons; six electrons are in orbit around the carbon nucleus. Forms the basis for all living tissue. |
| carbon dioxide (CO2) | A compound made up of molecules containing one carbon atom and two oxygen atoms. Normally found as a gas that is breathed out by animals and absorbed by green plants. The plants, in turn, return oxygen to the atmosphere. Also given off in the burning of fossil fuels. |
| carbon 14 | A radioactive isotope of Carbon. Contains six protons, six electrons, and eight neutrons. Produced when neutrons bombard atoms of nitrogen. Used in a common form of radioactive dating to determine the age of ancient objects. |
| carbon monoxide (CO) | A compound made up of molecules containing one carbon atom and one oxygen atom. Usually formed when materials burn; it is found, for example, in automobile exhaust. Colorless, odorless gas that can be fatal to human beings if inhaled. |
| cardinal numbers | Numbers that indicate the quantity of things in a group or set, but not the order or arrangement of those things. One, two, and one thousand are examples of these numbers. |
| catalyst | In chemistry, a substance that causes a chemical reaction to occur but is not itself involved in the reaction. Often used to refer to the prime agent of any change. |
| cc | An abbreviation for cubic centimeter - the volume of a cube that has edges one centimeter long. |
| Celsius | A temperature scale, also called Centigrade, according to which water freezes at zero degrees and boils at one hundred degrees. |
| centigrade | The Celsius temperature scale. |
| centimeter | A unit of length in the metric system; one-hundredth of a meter, or about two-fifths of an inch. |
| centrifugal force | A force that tends to move objects away from the center in a system undergoing circular motion. Keeps the water in a whirling bucket from spilling or throws a rider in a car against the door when the car goes around a sharp curve. A form of inertia. |
| CFC (chlorofluorocarbon) | Chemical compounds originally developed for use in refrigeration systems, now used widely in industry. When released into the air, these compounds break down and release chlorine, which causes damage to the Earth's ozone layer and is responsible for creating the ozone hole. |
| chain reaction | In chemistry and physics, a self-sustaining series of reactions. For example, when a uranium-based nuclear reactor undergoes one of these, a single neutron causes the nucleus of a uranium atom to undergo fission. In the process, two or three more neutrons are released. These neutrons start more fissions, which produce more neutrons, and so on. Figuratively, any group of events linked so that one is the cause of the next. |
| chaos | A new branch of science that deals with systems whose evolution depends very sensitively upon the initial conditions. Turbulent flows of fluids (such as white water in a river) and the prediction of the weather are two areas where the theory of this has been applied with some success. |
| electrical charge | A fundamental property of matter. Protons and the nuclei of atoms have a positive charge; electrons have a negative charge; neutrons have no charge. Normally, each atom has as many protons as it has electrons and thus is neutral. |
| chemical bond | Any rearrangement of electrons in two atoms that generates a force, causing the atoms to be bound to each other, forming a molecule. |
| chemical equilibrium | A balanced condition within a system of chemical reactions. |
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