Visionlearning Glossary
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Absolute Zero The theoretical lowest temperature possible at which all molecular motion ceases. Absolute zero, 0 K or -273.15°C, has never been reached.
Used in the following modules: Matter: States of Matter, Temperature
Accuracy In science, the term accuracy describes how well a measurement approximates the theoretically correct value of that measurement, for example, how close an arrow strikes to the center of a target. Accuracy provides a measure of the systematic error associated with a value. Compare to precision. See the module Uncertainty.
Used in the following modules: Data: Analysis and Interpretation, Data: Uncertainty, Error, and Confidence, Gravity, Minerals II, Research Methods: Description, Research Methods: Modeling, Using Science News in Teaching
Acid Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different scientists (listed in parentheses). 1) (Arrhenius) a compound that releases hydrogen ions (H+) in solution; 2) (Brønsted-Lowry) a compound capable of donating hydrogen ions, 3) (Lewis) a compound that can accept a pair of electrons from a base.
Used in the following modules: Acids and Bases, DNA I, DNA II, Fats and Proteins, Matter, Minerals II, Research Methods: Modeling, Scientific Communication: Peer Review, The Carbon Cycle, The Nitrogen Cycle
Acid Rain Rain with a pH less than 5.
Used in the following modules: The Nitrogen Cycle
Activation Energy The energy required to initiate a chemical reaction or process, abbreviated Ea. For example, a cigarette lighter requires activation energy (provided in the form of a spark) to initiate the reaction of fuel with oxygen.
Used in the following modules: Chemical Equations, Chemical Reactions
Adams, John Couch Welsh astronomer, born near Launceston, Cornwall (1819-1892). He successfully predicted the existence of a then-unknown planet (Neptune) based on perturbations in Uranus’ orbit. He also studied the Leonid meteor shower, successfully predicting its occurrence and proving its association with Tempel’s Comet. For further information, see John Couch Adams.
Used in the following modules: Gravity
Adsorb To adhere in an extremely thin layer of molecules (as of gases, solutes, or liquids) to the surfaces of solid bodies or liquids with which a substance is in contact.
Aesthenosphere The semi-molten layer of the earth which starts at ~70-200 km depth and ends at 660 km depth. The aesthenosphere is part of the mantle, and is composed primarily of the rock peridotite. The aesthenosphere can flow very slowly, allowing rigid pieces of the lithosphere to move around on top of it.
Used in the following modules: Earth Structure
Agricola, Georgius (Geroge Bauer) German geologist and medical doctor, born in Glauchau, Saxony (1494-1555). Agricola wrote several influential geological manuscripts, including De Natura Fossilium (1546), De Ortu et Causis Subterraneorum (1546) and De Re Metallica (published posthumously in 1556). The later is his most influential work, being a compendium of everything then known about mining, including (but not limited to) equipment, methods of surveying for and extracting minerals, mine administration, and the occupational diseases of miners. For further information, see Georgius Agricola.
Used in the following modules: Minerals I
Alchemy A medieval chemical philosophy concerned principally with the transformation of base metals into gold, and the discovery of an elixir of life.
Alcohol An organic compound containing a hydroxyl group. Common examples include methanol (CH3OH) and ethanol (CH3CH2OH).
Used in the following modules: Organic Chemistry, Temperature
Alhazen The Latinized name for the Muslim scientist Abū ‘Alī al-Hasan ibn al-Hasan ibn al-Haytham who was born in Basra, Mesopotamia (Iraq) (965-1039 CE). Alhazen made significant contributions in the fields of astronomy, mathematics, medicine, and most significantly, optics. His work in optics irrefutably proved that vision is a function of external light rays entering the human eye; and his rigorous and quantitative approach formed the basis of the modern experimental method in science. For further information see Alhazen
Used in the following modules: Light I, Research Methods: Experimentation, Research Methods: The Practice of Science, Scientific Communication: Utilizing the Scientific Literature
Alkanes A group of hydrocarbons with the general formula CnH(2n+2). Alkanes contain no carbon-carbon multiple bonds; common examples include methane and propane.
Used in the following modules: Organic Chemistry
Alkenes A group of hydrocarbons with the general formula CnH(2n). Alkenes contain at least one carbon-carbon double bond; common examples include ethylene.
Used in the following modules: Organic Chemistry
Alkyne A group of hydrocarbons with the general formula CnH(2n-2). Alkynes contain at least one carbon-carbon triple bond; common examples include ethyne also known as acetylene.
Used in the following modules: Organic Chemistry
Allele A variation of a genetic element, usually resulting in a distinct trait.
Used in the following modules: Genetics I
Alpha Particle A type of particle that is ejected from radioactive nuclei. Alpha particles consist of two protons and two neutrons and thus are equivalent to helium nuclei.
Used in the following modules: Atomic Theory I, Nuclear Chemistry
Alternative Hypothesis In statistical testing, an alternative hypothesis (H1) is a statement describing the possibility that an observed result or effect is genuine. The alternative hypothesis is always compared to a null hypothesis (H0), and H1 is not accepted until statistical testing shows that it should be accepted in favor of H0. For example, in an evaluation of data regarding the pain relieving properties of a new drug, the alternative hypothesis would state that the new drug has an effect on pain relief compared to a control. Accepting H1 does not indicate that the observed result or effect is large or important, simply that it is favored in terms of probability of the outcome.
Used in the following modules: The Case of the Ivory-billed Woodpecker
Alveolar Pertaining to an alveolus.
Used in the following modules: Absorption, Distribution and Storage of Chemicals
Alveoli The plural of alveolus.
Used in the following modules: Absorption, Distribution and Storage of Chemicals
Alveolus A small sac-like structure in the body, especially common in the lung. A lung alveolus has extremely thin walls that aid in the exchange of gases including O2 and CO2.
Amino Acid Biochemical molecules that contain at least one amine group (-NH2) and at least one carboxylic acid group (-COOH) and conform to the general formula NH2-R-COOH, where R is an organic molecule. Amino acids are essential basic building blocks of proteins.
Used in the following modules: DNA I, Fats and Proteins
Ampére, Andre French mathematician born in Poleymieux, Lyon (1775-1836). Ampére researched metaphysics, physics, and chemistry, but he focused on mathematics, which he taught at the Ecole Polytechnique in Paris. His key contributions to science include his work on partial differential equations, the discovery of fluorine, and studies on the wave theory of light. His most important work was the Memoir on the Mathematical Theory of Electrodynamic Phenomena, Uniquely Deduced from Experience, in which he described a mathematical derivation for the electrodynamic force law. The Amp (a measurement of electrical current) is named in his honor. For further information see Andre Ampére.
Amphibious Having the ability to live both on land and in water.
Used in the following modules: Adaptation
Andean Margin A convergent plate boundary, where oceanic crust is being subducted beneath continental crust. Named after the Andes Mountains in South America, which are the classic example of a continent-ocean convergence.
Used in the following modules: Plate Tectonics II
Andesite An extrusive igneous rock of intermediate composition, often gray in color. The main minerals present in andesite are plagioclase and hornblende. The word “andesite” comes from the Andes Mountains in South America, where this rock type is common. Around the world, andesitic magma erupts out of volcanoes along convergent boundaries, and its intrusive equivalent is diorite.
Used in the following modules: Minerals III, The Rock Cycle
Angstrom (Ångstrom) A unit of length equivalent to 10-10 meters. 1Å = 0.0000000001 m.
Anion An ion that migrates to the anode in an electrical cell; a negatively charged ion.
Used in the following modules: Minerals II, Minerals III
Anode A positively charged terminal in an electrical cell.
Anomaly A deviation from the normal or expected, sometimes expressed with respect to an average value. Anomalies are described in many kinds of data, and are features of datasets that require explanation.
Anther Male part of a flowering plant that holds pollen.
Used in the following modules: Genetics I, Scientists and the Scientific Community
Aquifer A porous and permeable body of rock or sediment through which groundwater flows.
Used in the following modules: The Hydrologic Cycle
Archimedes Greek mathematician, born in Syracuse, Sicily (287-212 BCE). Little is known about Archimedes’ life, but he is best known for devising the water displacement method of measuring the volume of an irregularly-shaped object (which he possibly conceived of while getting into his bathtub). He is also credited with developing the foundations of integral calculus and mathematical physics. For further information see Archimedes.
Used in the following modules: Density
Aristotle A Greek philosopher born in Stagira (384-322 BCE). He joined Plato’s Academy in Athens (then being run by Eudoxus) at the age of 17. After attending the academy, he taught there for 20 years before founding his own school, the Lyceum. He is remembered primarily for his works on deductive logic and the use of philosophical reasoning to address questions about the natural world. For further information see Aristotle.
Used in the following modules: Charles Darwin I, Charles Darwin III, Light I, Matter, Research Methods: The Practice of Science, Taxonomy I
Arrhenius, Svante Swedish physical chemist born in Vik (1859-1927). Arrhenius is most famous for what is now known as the Arrhenius equation, which relates the rate of chemical reactions to temperature and activation energy. Arrhenius was awarded the Royal Society’s Davy medal and the Faraday medal of the Chemical Society in 1914, and the Nobel Prize for Chemistry in 1903 based on his early work on the conductivity of electrolytes in solution. For further information see Svante Arrhenius.
Used in the following modules: Acids and Bases
Atom The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in combinations with other atoms forming molecules.
Used in the following modules: Atomic Theory I, Atomic Theory II, Carbohydrates, Chemical Bonding, Chemical Equations, Chemical Reactions, Data: Uncertainty, Error, and Confidence, Data: Using Graphs and Visual Data, DNA I, DNA II, Earth's Atmosphere, Fats and Proteins, Matter, Matter: States of Matter, Minerals I, Minerals III, Nuclear Chemistry, Organic Chemistry, Research Methods: Modeling, Scientific Ethics, Teaching Effectively with Multimedia, The Mole, The Nitrogen Cycle, The Periodic Table of Elements, Water
Atomic Mass The average mass of an atom of an element, usually expressed in atomic mass units. The term is often used interchangeably with atomic weight.
Used in the following modules: Atomic Theory I, Atomic Theory II, Nuclear Chemistry
Atomic Mass Unit One atomic mass unit (amu or u) is defined as 1/12 the mass of the standard carbon-12 isotope, or 1.66 × 10-27 kg.
Atomic Number The number of protons in an atomic nucleus.
Used in the following modules: Atomic Theory II, Nuclear Chemistry, The Periodic Table of Elements
Atomic Unit Compare with Bohr radius and hartree.A system of non-SI units used in quantum chemistry to simplify calculations and mathematical expressions. The definitions of atomic units include physical constants (like the speed of light, the rest mass of the electron, and other quantities that never change), so that all constants drop out of expressions when atomic units are used.
Atomic Weight As listed on the periodic table, the atomic weight is a weighted average of the masses of stable isotopes of an element that occur in nature. Given in grams, the atomic weight is the weight of one mole of atoms of an element. Atomic weight is often used interchangeably with atomic mass.
Used in the following modules: Matter, Nuclear Chemistry, The Mole, The Periodic Table of Elements
Attenuation/attenuate The behavior of waves as they radiate out from a source. As distance from the source increases, intensity of the waves decreases. Attenuation occurs because the same amount of energy is being spread out over a larger area.
Avogadro, Amadeo Italian chemist and mathematician born in Turin (1776-1856). Avogadro was schooled to be an ecclesiastical lawyer, but retained an interest in natural philosophy, and studied mathematics and physics on his own. In 1811, Avogadro made the first distinction between molecules and atoms. He further suggested Avogadro’s Principle: equal volumes of gas at the same pressure and temperature contain the same number of molecules. Avogadro’s number, which defines the number of atoms in a mole, is named after him for his disambiguation of molecules. For more information see Amadeo Avogadro.
Used in the following modules: The Mole
Bacon, Francis English statesman and philosopher born in London (1561-1626). In 1620, Bacon published the Novum Organum, in which he argued for a method of scientific inquiry based on inductive reasoning in which the only way to discover the truth was to gather evidence from the real world. He is often referred to as the catalyst for the Scientific Revolution. In 1618, Bacon was appointed Lord Chancellor, and in 1621, he was made viscount St. Albans. For further information see Francis Bacon
Used in the following modules: Research Methods: The Practice of Science, Scientific Institutions and Societies
Basalt A dark, fine-grained igneous rock formed by cooling of iron- and magnesium-rich lava above the surface of the earth. Basalt is the main component of the oceanic crust of the earth.
Used in the following modules: Earth Structure, Minerals I, The Rock Cycle
Base Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different scientists (listed in parentheses). 1) (Arrhenius) a compound that releases hydroxide ions (OH-) in solution; 2) (Brønsted-Lowry) a molecule or ion that accepts hydrogen ions from solution; 3) (Lewis) a molecule or ion that donates an electron pair to an acid.
Used in the following modules: Acids and Bases, DNA I, DNA II, Earth Structure, Scientific Communication: Utilizing the Scientific Literature
BCE An abbreviation for Before the Common Era, which is a designation for the period of time prior to year 1 of the Gregorian calendar. BCE is an alternative to the abbreviation BC, and the numbering of years is identical to the Before Christ system. Compare with CE.
Used in the following modules: Research Methods: Description, Research Methods: Experimentation, Research Methods: The Practice of Science, Scientific Communication: Understanding Scientific Journals and Articles, Scientific Communication: Utilizing the Scientific Literature
Becquerel, Henri French physicist, born in Paris (1852-1908). Becquerel’s most famous work is his study of uranium salts, which he discovered produced rays that caused gas to ionize. This type of radiation was termed Becquerel radiation. In 1903 he was awarded half a Nobel Prize for his discovery of radiation; the other half was awarded to Pierre and Marie Curie for their work on Becquerel radiation. For further information see Henri Becquerel.
Used in the following modules: Nuclear Chemistry
Bernoulli, Daniel Swiss medical doctor and mathematician born in Groningen (1700-1782). His work Hydrodynamica contains the first correct analysis of the dynamics of water flowing through a hole, based on the principle of the conservation of energy. He was a prolific researcher and won the Grand Prize of the Paris Academy 4 times, for topics in astronomy and nautical topics. For further information see Daniel Bernoulli.
Used in the following modules: Matter
Berzelius, Jöns Jakob Swedish chemist and medical doctor born in Väversunda, Ostergötland (1779-1848). While studying for his medical degree, he experimented with the use of electric shock to treat patients with various diseases. He is most famous for a series of experiments that proved that elements in inorganic compounds are bound together in definite proportions. In studying compounds, he discovered cerium, selenium, and thorium. With his experimental results, he was able to determine the atomic weights of nearly all elements then known. For more information, see Jöns Jakob Berzelius.
Used in the following modules: Minerals III
Binomial A formal two word name given to each species, based on the combination of a genus name and a species name.
Used in the following modules: Taxonomy II: Nomenclature
Biodiversity The variety and abundance of life and its ecological context, including the different kinds of organisms, the numbers of species, the variations in their genes, and the complexity of their ecological conditions.
Used in the following modules: Charles Darwin III, Taxonomy I, Taxonomy II: Nomenclature
Biogeochemical of or relating to the partitioning and cycling of chemical elements and compounds between the living and nonliving parts of an ecosystem
Used in the following modules: Earth's Atmosphere, The Carbon Cycle, The Nitrogen Cycle
Biomass The combined mass of living or once-living organisms in a given area.
Used in the following modules: The Nitrogen Cycle
Biosphere The part of the world in which life can exist.
Used in the following modules: Scientific Communication: Utilizing the Scientific Literature, The Carbon Cycle, The Nitrogen Cycle
Bjerknes, Vilhelm Norwegian mathematician, physicist and meteorologist born in Christiana, Norway (now Oslo) (1862-1951). Bjerknes proposed the concept of numerical weather prediction, developed by later scientists as a means of weather forecasting through the use of mathematical modeling. Bjerknes also made fundamental contributions to our understanding of air masses, fronts, and circulation in the atmosphere. He received many honors during his life, and posthumously was honored by a stamp with his image. For further information see Vilhelm Bjerknes
Used in the following modules: Research Methods: Modeling
Bohr, Niels Danish physicist born in Copenhagen (1885-1962). Bohr’s research was mainly theoretical in nature, including an investigation into the absorption of alpha rays and the structure of atoms. He combined Rutherford’s atomic model with concepts from the Quantum Theory, developing the model of the atom that is still used today. He was awarded the Nobel Prize in Physics in 1922 for his work on atomic structure. For further information, see Niels Bohr.
Used in the following modules: Atomic Theory II
Bose, Satyendra Nath Indian Bengali mathematician born in Calcutta (1894-1974). Bose developed an interest in physics and mathematics in high school. He later worked on quantum theory, particularly Planck’s law of black body radiation. His 1924 paper Planck’s Law and the Hypothesis of Light Quanta was strongly endorsed by Einstein, and helped to form the foundation for Bose-Einstein statistics and the theory of Bose-Einstein condensates. The boson, a sub-atomic particle with integer spin, is named in his honor. For more information see Satyendra Nath Bose.
Used in the following modules: Matter: States of Matter
Boyle, Robert English chemist and theologian, born at Lismore Castle, Munster, Ireland (1627-1691). Boyle published on a broad array of topics, including chemistry, physics, medicine, and theology. He is best known for Boyle’s Law, from which the ideal gas law is derived. In 1661, Boyle published The Sceptical Schymist or Chymico-Physical Doubts and paradoxes, which is considered a conerstone in the field of modern chemistry. Boyle was also one of the founding members of the Royal Society of London. For further information see Robert Boyle
Used in the following modules: Acids and Bases, Matter, Scientific Institutions and Societies, Waves and Wave Motion
Brahe, Tycho Danish astronomer, born in Knutstorp Castle (1546-1601). He is famous for his geocentric theory of the solar system, as well as for his meticulous astronomical observations concerning the positions of planets. He made his observations over 20 years, from the island of Hven. He later was appointed Imperial Mathematician to the Holy Roman Emperor, Rudolph II, in Prague. For further information see Tycho Brahe.
Used in the following modules: Gravity
Brønsted, Johannes Danish physical chemist born in Varde (1879-1947). In 1906, Brønsted published his first paper on electron affinity. In 1923, he suggested the protonic theory of acid-base reactions, and later became an authority on catalysis by acids and bases. The Brønsted catalysis equation is named for him. He also developed the theory of proton donors during ionization. For further information see Johannes Brønsted.
Used in the following modules: Acids and Bases
Buffer A substance that when added to solution compensates for any change in hydrogen ion concentration following the addition of an acid or a base, and thus maintains a relatively constant pH. Buffers can react with and neutralize small amounts of either acids or bases.
Buoyant Force The upward pressure exerted on an object by a fluid in which the object rests.
Used in the following modules: Density
Bush, Vannevar American scientist and statesman, born in Everett, Massachusetts (1890-1974). Bush did seminal work in analog computing, and founded the American Appliance Company, later renamed Raytheon. In 1939 he was appointed chairman of the National Advisory Committee for Aeronautics and began advocating for the establishment of a federal agency to coordinate scientific research, especially as related to military and defense needs. The effort would eventually lead to the creation of the National Science Foundation in 1950. For further information see: Vannevar Bush.
Used in the following modules: Scientific Communication: Utilizing the Scientific Literature, Scientific Institutions and Societies
Calcareous Containing calcium.
Calibrate To determine or check the accuracy of an instrument used for quantitative measurements, or to make corrections in or to adjust an aspect of a system.
Carbonic Acid The weak acid formed when CO2 dissolves in water.
Used in the following modules: Acids and Bases, The Carbon Cycle
Carpel (also called Pistil) Female part of a flowering plant consisting of ovary with ovules and stigma/stamen structures to receive pollen.
Used in the following modules: Genetics I
Cartesian Plane The Cartesian plane, named after the mathematician Rene Descartes, is a plane with a rectangular coordinate system that associates each point in the plane with a unique pair of numbers in an ordered pair of the form (x,y). The x value is the horizontal coordinate and the y value is the vertical coordinate.
Used in the following modules: Wave Mathematics
Cathode A negatively charged terminal in an electrical cell.
Used in the following modules: Atomic Theory I, The Process of Science
Cathode Ray A negatively charged beam of particles (electrons) that are emitted from the negative terminal in a vacuum tube.
Used in the following modules: The Process of Science
Cation An ion that migrates to the cathode in an electrical cell; a positively charged ion.
Used in the following modules: Minerals III
Cavendish, Henry English chemist and physicist born in Nice, France (1731-1810). Cavendish’s most important work was isolating hydrogen and describing its properties. He also researched electrical capacitance and used a torsion balance (now named for him) to measure the gravitational constant (G), which allowed him to calculate the mass of the Earth. For further information, see Henry Cavendish.
Used in the following modules: Gravity
CE An abbreviation for Common Era, which is a designation for the period of time beginning with year 1 of the Gregorian calendar. CE is an alternative to the abbreviation AD, and the numbering of years is identical to the Anno Domini system. Compare with BCE.
Used in the following modules: Data: Analysis and Interpretation, Research Methods: Experimentation, Research Methods: The Practice of Science, Scientific Communication: Utilizing the Scientific Literature
Celsius, Anders Swedish astronomer born in Uppsala (1701-1744). In 1742, Celsius invented the centigrade temperature scale, using the freezing and boiling points of water as his reference temperatures. Interestingly, he defined the freezing point as 100° and the boiling point as 0°. The scale was reversed to its present form after his death. Celsius also was the first to suggest that the aurora has a magnetic cause. For further information see Temperature
Chadwick, James English physicist born in Bollington, Cheshire (1891-1974). Chadwick worked with Ernest Rutherford on the disintegration of atoms by bombarding them with alpha particles. He was awarded the Nobel Prize in physics in 1935 for his discovery of the neutron. For further information, see James Chadwick.
Used in the following modules: Atomic Theory I
Chapman, Sydney British-American geophysicist and mathematician born in Eccles, Lancashire (1888-1970). In 1939, Chapman co-authored the classic work The Mathematical Theory of Non-Uniform Gases. The following year, he co-authored the two-volume work Geomagnetism. His most famous work in mathematics was his research in stochastic processes, for which he developed (independently of Andrey Kolmogorov) the Chapman-Kolmogorov equations. For further information see Sydney Chapman.
Used in the following modules: Earth's Atmosphere
Chemical Bond A link between atoms. See ionic bond and covalent bond.
Used in the following modules: Chemical Bonding, Chemical Equations, Chemical Reactions
Chemical Reaction A process in which atoms and molecules recombine by forming or breaking chemical bonds. Chemical reactions form new products that have different chemical properties than the initial reacting material.
Used in the following modules: Chemical Equations, Chemical Reactions, DNA I, Fats and Proteins, Matter, Nuclear Chemistry, Research Methods: Modeling, Research Methods: The Practice of Science, The Rock Cycle
Chlorofluorocarbons Compounds consisting of carbon, chlorine, fluorine, and sometimes hydrogen once used widely as aerosol propellants and refrigerants. The realization that chlorofluorocarbons cause depletion of the stratospheric ozone layer led to a sharp decrease in their use mandated by the Montreal Protocol in 1989.
Used in the following modules: Research Methods: The Practice of Science
Chromosome The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions.
Used in the following modules: DNA I, Genetics I
Classification (biological Classification) The arranging of groups of organisms into sets or divisions on the basis of their evolutionary relationships.
Combustion Commonly referred to as burning, a chemical reaction between a fuel (for example wood) and an oxidizing agent (for example oxygen) that produces heat (and usually, light).
Used in the following modules: Organic Chemistry
Compound A material formed by the chemical combination of elements in defined proportions. Compounds can be chemically decomposed into simpler substances.
Used in the following modules: Acids and Bases, Chemical Bonding, Chemical Reactions, Fats and Proteins, Matter, Minerals I, Minerals III, Research Methods: Experimentation, Research Methods: The Practice of Science, The Mole, The Nitrogen Cycle, Water
Conchoidal Fracture A type of breakage that produces a smooth, curved surface. Conchoidal fracture occurs when a substance has uniform strength in all directions and no pre-existing planes of atomic weakness. This generally occurs in two types of substances: minerals like quartz whose atomic structure consists of equally strong bonds in all directions, and volcanic glass, called obsidian, which has no definitive crystal structure.
Confirmation Bias The tendency to search for or interpret new information in a way that confirms one's preconceptions and avoid information and interpretations that contradict prior beliefs.
Conic Section A curve formed by the intersection of a cone with a plane. This often results in a circle, ellipse or parabola. For more on conic sections, visit Mathworld's Conic Sections lesson.
Used in the following modules: Gravity
Continental Crust The uppermost layer of the earth that forms the continents. Unlike oceanic crust, continental crust is created and destroyed very slowly, so there is some continental crust on the earth as old as 4 billion years. Continental crust ranges from 10-70 km thick and is composed primarily of granite.
Used in the following modules: Earth Structure, Plate Tectonics II
Continental Drift The theory proposed in 1915 by Alfred Wegener, a German geophysicist and meteorologist. The theory stated that the continents had once been joined into one “supercontinent,” called Pangaea. About 200 million years ago, Pangaea broke apart and the continents drifted to their present positions. Wegener based his theory on the similarity of fossils and rock types on the east coast of South America and the west coast of Africa. The theory was widely ridiculed at the time because Wegener had not proposed a driving force for such drift.
Used in the following modules: Plate Tectonics I, Plate Tectonics II
Control In science, a control is a system for which the expected change or outcome is well known and is measured or observed for the purpose of comparing it to a treatment group in scientific research. The control is used as a standard to compare or quantify change in the treatment. For more information, see: Research Methods: Experimentation
Used in the following modules: Adaptation, Charles Darwin II, Data: Statistics, Data: Uncertainty, Error, and Confidence, DNA I, Gravity, Research Methods: Comparison, Research Methods: Experimentation, Research Methods: Modeling, Scientific Communication: Peer Review, Scientific Communication: Understanding Scientific Journals and Articles, Scientific Ethics, Scientists and the Scientific Community, The Carbon Cycle, Using Science News in Teaching
Convection The movement or circulation of a fluid due to variations in its density as a result of the transfer of heat within the fluid.
Used in the following modules: Earth Structure, Plate Tectonics II, The Rock Cycle
Convergent Boundary A plate boundary where two plates are moving towards each other.
Cope, Edward Drinker American paleontologist, born near Philadelphia, Pennsylvania (1840-1897). Cope was a prolific writer and very successful fossil-hunter, publishing over 1200 papers during his career. He developed Cope’s law, stating that mammalian species become larger over time. Cope was especially interested in the natural history of reptiles and amphibians, publishing Bactrachian of North America and The Crocodilians and Snails of North America. Copeia, the leading scientific journal in the field of herpetology is named in his honor. For further information see Edward Drinker Cope.
Used in the following modules: Taxonomy II: Nomenclature
Copernicus, Nicolaus (Mikolaj Kopernik or Nicolaus Koppernigk) Polish astronomer born in Torun in the Royal Prussia region of the Kingdom of Poland (now Poland) (1473-1543). Copernicus was the first European scientist to provide scientific evidence for a heliocentric view of the solar system. In 1543, Copernicus published De revolutionibus orbium coelestium, often considered the origin of the Scientific Revolution. For further information see Nicolaus Copernicus
Used in the following modules: Gravity, Research Methods: The Practice of Science
Core The innermost layer of the earth, which starts at ~2900 km depth. The core is composed mainly of iron and consists of a molten outer core and a solid inner core.
Used in the following modules: Atomic Theory I, Earth Structure, Educational Web Design, Research Methods: Comparison, Scientific Ethics, The Process of Science, Waves and Wave Motion
Correlation Correlation, as measured by the correlation coefficient, provides a measure of the strength and direction of a linear relationship between two random variables. While there are many measures of correlation, among the best known is the Pearson product-moment correlation, which ranges from -1 to 1. A correlation coefficient close to -1 indicates a strong negative correlation; a correlation coefficient close to 0 indicates little correlation; and a correlation coefficient close to 1 indicates a strong positive correlation.
Used in the following modules: Data: Statistics, Research Methods: The Practice of Science, Scientists and the Scientific Community, The Hydrologic Cycle
Coulomb A metric unit of electrical charge equal to the charge on 6.24 × 1018 electrons.
Covalent Bond A very strong chemical bond formed by the sharing of a pair of electrons. Multiple covalent bonds can be formed when multiple pairs of electrons are shared between atoms. Covalent bonds are generally characterized in two types, polar and non-polar covalent bonds. Compare to ionic bond, hydrogen bond.
Used in the following modules: Chemical Bonding
Covalent Molecule A molecule held together by covalent bonds, that is, pairs of electrons shared between atoms. Covalent molecules are true chemical molecules whose interaction with other molecules is influenced by whether a polar molecule or non-polar molecule is formed.
Used in the following modules: Chemical Bonding, Water
Crick, Francis English molecular biologist, physicist, and neuroscientist, most noted for being one of the co-discoverers of the structure of the DNA molecule in 1953. He later contributed to the successful deciphering of the genetic code of DNA. For further information see Francis Crick
Used in the following modules: DNA II
Crust The uppermost 5-70 km of the earth. There are two types of crust: continental and oceanic. Continental crust ranges from 10-70 km thick and has a composition approximating that of granite. Oceanic crust, on the other hand, is approximately 5 km thick and has a composition similar to basalt, making it significantly denser than continental crust.
Used in the following modules: Earth Structure, Minerals I, Minerals II, Minerals III, Plate Tectonics I, Plate Tectonics II, The Rock Cycle
Crystal A solid of defined shape that is bound by plane surfaces (facets) that intersect at characteristic angles. The shape of a crystal is defined by the bonding and/or interaction between atoms, ions, or molecules that make up the solid. The substances, planar angles and defects in a crystal affect the electrical and optical properties (including color) of the crystal.
Used in the following modules: Chemical Bonding, Matter: States of Matter, Minerals I, Minerals II, Minerals III, Plate Tectonics I, Research Methods: Description, The Rock Cycle, Water
Crystallize/Crystallization The process through which crystals form, resulting in the change from a liquid or vapor to a solid. Crystallization can happen in two basic ways:
1. By lowering the temperature of a melted material like magma or water, atoms and ions start to aggregate into crystals, forming solid rock or ice. This can also happen from a vapor, as is the case with the formation of snowflakes, but it is much less common.
2. By evaporating water from a solution, the saturation point of the water is reached and a solid begins to precipitate out as crystals (for example, salt flats in the desert have been precipitated out of lakes that dried up).
Curie, Marie French-Polish physicist and chemist born in Warsaw (1867-1934). Curie was the Head of the Physics Laboratory at the Sorbonne. Working with her husband, Pierre Curie, and inspired by Becquerel’s discovery of radiation, Curie isolated and named the element polonium. She also developed techniques for isolating radium from radioactive residues in order to study its properties. Curie was awarded, with Pierre, half a Nobel Prize in Physics in 1903, for their study of Becquerel radiation. After her husband’s death in 1906, she succeeded him as Professor of General Physics, and was the first woman to hold the post. In 1911 she was awarded a Nobel Prize in Chemistry for her work in radioactivity. For more information see Marie Curie.
Used in the following modules: Nuclear Chemistry
Curie, Pierre The French physicist born in Paris, France (1859 – 1906 CE). Pioneer in the fields of crystallography, magnetism, and piezoelectricity, he shared the 1903 Nobel Prize in Physics with his wife Marie Curie and with Henri Becquerel for research on the “radiation phenomena.” For further information see: Pierre Curie
Cytoplasm The internal fluid of a cell (called cytosol) along with all dissolved materials and cellular organelles except for the nucleus. The cytoplasm is the primary site for chemical activity in the cell.
Used in the following modules: Cells
Dalton, John English physicist, chemist and meteorologist born in Eaglesfield, Cumberland (1766-1844). Dalton published Experimental Essays on the Constitution of Mixed Gases; on the Force of Steam or Vapour from water and other liquids in different temperatures, both in a Torricellian vacuum and in air; on Evaporation; and on the Expansion of Gasses by Heat, in which he details his theory of partial pressures in gas mixtures. He is most famous for his investigation of relative atomic weights, and for founding atomic theory. For further information see John Dalton.
Used in the following modules: Atomic Theory I, Earth's Atmosphere, Matter, Research Methods: Modeling
Dana, James Dwight American geologist, mineralogist, and naturalist, born in Utica, New York (1813-1895). Dana published A System of Mineralogy in 1837, which remains a standard in the field. He served as geologist and mineralogist on the U.S. Antarctic and South Seas expedition in 1838-1842. On returning to the states, he published Zoophytes (1846), Geology (1849), and Crustacea (1852-55). He served as coeditor of the American Journal of Science. His other publications include Manual of Geology (1862), Manual of Mineralogy (1843), Corals and Coral Islands (1872), and Characteristics of Volcanoes (1890). For more information see James Dwight Dana.
Used in the following modules: Minerals II
Darwin, Charles English naturalist and geologist born in Shrewsbury, Shropshire (1809-1882). While serving as naturalist aboard HMS Beagle, Darwin developed his theory of evolution through natural selection based on his detailed observations of species, most famously, the variety of finches. He published his theory in 1859 in his book On the Origin of Species. His other works include The Descent of Man, and Selection in Relation to Sex and The Expression of the Emotions in Man and Animals. For further information, see Darwin Online.
Used in the following modules: Adaptation, Authoring Modules I, Charles Darwin I, Charles Darwin II, Research Methods: Comparison, Taxonomy I
Data (plural form of datum) A collection of pieces of information, generally taking the form of numbers, text, bits, or facts, that are related either by the method in which they are collected or the manner in which they are stored. For more information, see: Data: Analysis and Interpretation
Used in the following modules: Authoring Modules I, Bone Changes in Rock Climbers, Charles Darwin II, Data: Analysis and Interpretation, Data: Statistics, Data: Uncertainty, Error, and Confidence, Data: Using Graphs and Visual Data, Earth's Atmosphere, Genetics I, Plate Tectonics I, Plate Tectonics II, Research Methods: Comparison, Research Methods: Description, Research Methods: Experimentation, Research Methods: Modeling, Research Methods: The Practice of Science, Scientific Communication: Peer Review, Scientific Communication: Understanding Scientific Journals and Articles, Scientific Communication: Utilizing the Scientific Literature, Scientific Ethics, Scientific Institutions and Societies, Scientists and the Scientific Community, The Carbon Cycle, The Case of the Ivory-billed Woodpecker, The Process of Science, Using History and Biographies in Science, Visionlearning Teaching Modules
Daughter A material that is derived from the breakdown or division of another. For example, a product of the radioactive decay of an element; or a cell or cells that are derived from the division of a parent cell.
Used in the following modules: Charles Darwin II, Data: Uncertainty, Error, and Confidence, Nuclear Chemistry
Daughter Product In nuclear physics, the decay product of radioactivity.
Used in the following modules: Data: Uncertainty, Error, and Confidence
Decompose To break up into constituent parts by or as if by a chemical process, to rot.
Used in the following modules: Research Methods: The Practice of Science
Delta Deltas form where rivers reach lakes, seas, or the ocean, and deposit their remaining sediment in a broad, flat plain as the river slows and eventually stops. The name comes from the Greek letter delta, shaped like a triangle, as these features are often triangular with one point at the river mouth.
Used in the following modules: Research Methods: Modeling, The Rock Cycle
Democritus Greek natural philosopher born in Thrace (ca. 460-370 BCE). With his teacher, Leucippus, Democritus developed the atomist concept of the cosmos, which held that the world is composed of invisible, minute particles suspended in a void. For further information, see Democritus.
Denitrification The loss or removal of nitrogen or nitrogen compounds; specifically: reduction of nitrates or nitrites commonly by bacteria (as in soil) that usually results in the escape of nitrogen into the air.
Used in the following modules: The Nitrogen Cycle
Density A measure of the compactness of a substance given by the mass per unit volume (d = m/v). Common units of density include g/ml, g/cm3, and kg/L. A measure of lead is not heavier than an equivalent measure of styrofoam, it is denser.
Used in the following modules: Density, Earth Structure, Earth's Atmosphere, Matter: States of Matter, Minerals I, Minerals II, Research Methods: Modeling
Deoxyribonucleic Acid (DNA) A double-stranded, helical polymer of the sugar deoxyribose, phosphate, and one of four nucleotide bases (Adenine, Cytosine, Guanine, and Thymine). The molecule is the primary carrier of genetic information in all cells.
Dependent Variable In science, a dependent variable refers to a condition or parameter that may change as a result of an experimental treatment on an independent variable. The change in the dependent variable is then observed or measured toward understanding the underlying processes involved in the change. For more information, see: Research Methods: Experimentation
Used in the following modules: Research Methods: Experimentation
Descartes, Rene French mathematician and philosopher born in Indre-et-Loire, France (1596-1650). Descartes invented analytical geometry and developed what is now called the Cartesian coordinate system, which describes geometry in term of algebra. He was an influential philosopher as well, famously stating, “Cogito ergo sum” (I think therefore I am). For further information see Rene Descartes.
Used in the following modules: Light I, Wave Mathematics
Deuterated The isotopic labeling of a compound that contains hydrogen through the substitution of deuterium for some or all of the hydrogen in the molecule.
Used in the following modules: Scientific Ethics
Deuterium A stable isotope of hydrogen (written 2H) that contains one neutron in its nucleus and has a natural abundance of 0.015%.
Used in the following modules: Atomic Theory II, Scientific Ethics
Diatomic A molecule that contains two atoms. All of the non-inert gases occur as diatomic molecules: H2, O2, N2, F2, and Cl2.
Used in the following modules: Chemical Equations
Differential Equation An equation relating a variable that changes over time (referred to as a function), to its rate of change (referred to as its derivative). Many fundamental relationships in the natural world are described by differential equations, for example Newton’s Second Law relates the force on a particle to the rate of change of that particle’s linear momentum: F = d (mv) / dt. In this equation, the force on a particle (F) is equal to the rate of change over time (expressed by the derivative designation d / dt) of the particle’s momentum (which is a product of the particle’s mass [m] and velocity [v]).
Used in the following modules: Research Methods: Modeling
Diffract To undergo the process of diffraction.
Used in the following modules: Light I
Diffraction The bending or spreading of waves when they meet an obstruction.
Used in the following modules: DNA II, Light I, Minerals I, Minerals III, Research Methods: Description
Diffusion The movement of atoms or molecules from one part of a medium to another caused by their random thermal motion. The result of diffusion is a tendency for particles to move from an area of higher concentration to an area of lower concentration.
Used in the following modules: Absorption, Distribution and Storage of Chemicals
Diorite An intrusive igneous rock of intermediate composition, often called “salt-and-pepper” rock because of its speckled black and white appearance. The main minerals present are plagioclase and hornblende. Around the world, diorite forms below volcanoes along convergent boundaries, and its extrusive equivalent is andesite.
Used in the following modules: The Rock Cycle
Dipole An asymmetrical distribution of electrical charge across an object. Polar molecules contain a dipole.
Used in the following modules: Chemical Bonding, Water
Dipole-dipole Interaction An interaction between two or more molecular dipoles resulting from the attraction between oppositely charged ends of the molecules.
Dissociate The breaking apart of a molecule, especially in the presence of heat or a polar solvent. For example, the ionic compound sodium chloride dissociates in water by separating into positively charged sodium ions and negatively charged chlorine atoms.
Divergent Boundary A plate boundary where two plates are moving away from each other.
DNA Deoxyribonucleic Acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding genetic information in most organisms. Specifically, a template for the synthesis of proteins and enzymes in most organisms.
Used in the following modules: DNA I, DNA II, Genetics I, Research Methods: Comparison, Research Methods: Description, Research Methods: The Practice of Science, Scientists and the Scientific Community, The Nitrogen Cycle, The Process of Science
Earthquake 1. The sudden motion or slip along a fault. 2. The ground shaking that results from the release of seismic energy either by (1) or by other means, such as the movement of magma beneath the surface of the earth.
Used in the following modules: Data: Statistics, Data: Using Graphs and Visual Data, Earth Structure, Matter: States of Matter, Plate Tectonics II, The Process of Science, The Rock Cycle, Wave Mathematics, Waves and Wave Motion
Eclogite A metamorphic rock that forms from mafic rocks (like basalt and gabbro) under extremely high pressure. The main minerals present are garnet and a green pyroxene, giving the rock a characteristic, mottled red and green appearance. The most common environment where ecolgites form is deep in subduction zones, where subducted oceanic crust is put under very high pressures.
Used in the following modules: The Rock Cycle
Ecosystem The complex of a community of organisms and its environment, functioning as a unit.
Used in the following modules: The Nitrogen Cycle
Einstein, Albert Theoretical physicist, born in Württemberg, Germany (1879-1955) who became an American citizen in 1940. While working as a patent clerk in Zurich, he developed theories on the photoelectric effect and relativity, for which he won a Nobel Prize in physics in 1921. He was also associated with the Manhattan Project, which resulted in the development of the atomic bomb. In 1999, Time magazine named Einstein “Person of the Century.” For further information see Albert Einstein
Used in the following modules: Gravity, Light I, Light II, Matter: States of Matter, Research Methods: Experimentation, Scientific Institutions and Societies
Electrical Charge A fundamental property used to explain attraction and repulsion between certain particles. Two types of charge exist: negative charge, which is generally conveyed as an excess of electrons; and positive charge, which is generally conveyed as a lack of electrons and excess of protons. The interaction of opposite charges produces an attractive electrical force, and the interaction of like charges produces a repulsive electrical force.
Used in the following modules: Atomic Theory I, Atomic Theory II, Chemical Bonding, Chemical Reactions, Water
Electrical Force A fundamental force produced by the interaction of electrical charges. Sometimes called the ‘electromagnetic’ force, electrical force is several billion times stronger than gravitational force.
Used in the following modules: Light II
Electrolyte A substance that dissociates into 2 or more oppositely charged ions in water. Electrolytic solutions conduct electricity because the charged ions can carry electrons in water.
Electromagnetic Radiation A series of waves that are propagated by simultaneous, periodic variations of electrical and magnetic fields. Examples of electromagnetic radiation include radio waves, light, X-rays, gamma rays and others.
Used in the following modules: Light II
Electron A sub-atomic particle with a negative charge of 1.60 × 10-19 coulombs and a mass of 9.11 × 10-31 kg. Electrons are generally found around the nucleus of an atom, but may be gained or lost during ion formation. Compare to the proton.
Used in the following modules: Acids and Bases, Atomic Theory I, Atomic Theory II, Chemical Bonding, Chemical Equations, Chemical Reactions, Data: Using Graphs and Visual Data, Matter: States of Matter, Minerals III, Nuclear Chemistry, Organic Chemistry, Research Methods: Modeling, Research Methods: The Practice of Science, Teaching Effectively with Multimedia, The Mole, The Periodic Table of Elements, The Process of Science, Water
Electron Shell The orbitals around the nucleus of an atom where electrons reside. Also called electron orbitals and energy levels.
Used in the following modules: Atomic Theory II, Chemical Bonding, Chemical Reactions, The Periodic Table of Elements
Electronegativity A relative measure of the affinity (or attraction) that atoms of an element have for electrons. The higher the electronegativity of an atom, the stronger will be its affinity for electrons. The type of bond formed between two atoms (ionic or covalent) can be predicted by the difference in electronegativities of the two bonding atoms.
Element One of less than 118 pure chemical substances. An element is a substance composed of atoms with identical atomic number.
Used in the following modules: Absorption, Distribution and Storage of Chemicals, Atomic Theory I, Atomic Theory II, Cells, Chemical Bonding, Chemical Equations, Chemical Reactions, Data: Uncertainty, Error, and Confidence, Data: Using Graphs and Visual Data, DNA I, DNA II, Educational Web Design, Matter, Matter: States of Matter, Minerals II, Minerals III, Nuclear Chemistry, Organic Chemistry, Research Methods: Modeling, The Carbon Cycle, The Mole, The Nitrogen Cycle, The Periodic Table of Elements
Empedocles Greek philosopher born in Acragas (490-430 BCE). He is credited (by Aristotle) with inventing rhetoric, and by the philosopher Galen with founding the science of medicine. Empedocles is remembered for his belief that all matter was composed of four elements: earth, air, fire and water. He also proved experimentally that air was a substance, rather than empty space, and deduced that light travels at a finite velocity. For more information see Empedocles.
Used in the following modules: Matter, Research Methods: Experimentation, Research Methods: The Practice of Science
Endocytosis The uptake by a cell of material from its environment by a process in which the cell surrounds the material and engulfs it with a vesicle formed by its plasma membrane.
Used in the following modules: Absorption, Distribution and Storage of Chemicals
Endothermic A process or reaction that absorbs heat. For example, ice melting is an example of an endothermic process because it absorbs heat from its surroundings.
Used in the following modules: Chemical Reactions
Energy An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear and radiant (light).
Used in the following modules: Absorption, Distribution and Storage of Chemicals, Atomic Theory II, Carbohydrates, Cells, Chemical Equations, Chemical Reactions, Data: Using Graphs and Visual Data, Earth Structure, Earth's Atmosphere, Energy, Fats and Proteins, Light II, Matter: States of Matter, Nuclear Chemistry, Plate Tectonics II, Research Methods: Modeling, Research Methods: The Practice of Science, Scientific Ethics, Scientific Institutions and Societies, Temperature, The Carbon Cycle, The Hydrologic Cycle, The Nitrogen Cycle
ENIAC Short for Electronic Numerical Integrator and Computer; the first general-purpose electronic computer. It was the first high-speed, digital computer capable of being reprogrammed to solve a broad range of computing problems.
Used in the following modules: Research Methods: Modeling
Entropy A measure of disorder or randomness in a system. The 2nd law of thermodynamics states any spontaneous change is accompanied by an overall increase in entropy overall. For example, when water evaporates molecules are dispersed over greater distances resulting in an increase in entropy.
Used in the following modules: Energy
Enzyme Molecules produced by living organisms that help catalyze biochemical reactions. Enzymes are predominantly protein or protein-based molecules and are highly specific in their mechanism of action as well as the reactants that they work upon (called substrates).
Used in the following modules: Carbohydrates, DNA I, Fats and Proteins
Epidemiology The scientific study of epidemics and epidemic diseases, especially the patterns, causes, and control of diseases in human populations.
Used in the following modules: Data: Statistics, Research Methods: Comparison
Epistemology (from the Greek episteme, ‘knowledge’, and logos, ‘theory’) the study of the nature of knowledge; a branch of philosophy investigating the origin, nature, methods, and limits of human knowledge.
Erosion The action or process of eroding: wearing away by the action of water, wind, glacial ice, etc.
Used in the following modules: The Rock Cycle
Eugenics A social philosophy that advocates for the control of heritable characteristics in humans through various forms of intervention including selective breeding, sterilization, and others.
Excited State An energy state for an atom in which electrons exist above the minimum or ground state configuration. In general, excited states are unstable and will quickly relax back to ground state through the emission of a quantum of energy.
Exothermic A process or reaction that releases heat. For example, wood burning in the presence of oxygen is an example of an exothermic reaction.
Used in the following modules: Chemical Reactions
Extensive Property A property of matter that is dependent on the amount of material present. Common extensive properties include mass, volume, length and charge.
Extrusion A process by which viscous magma is emitted from below the surface of the earth to cool on the surface.
Used in the following modules: Plate Tectonics I
Fahrenheit, Daniel Gabriel German physicist born in Danzig, Poland (1686-1736). Fahrenheit invented the alcohol thermometer in 1709, and the mercury thermometer in 1714. He also developed the temperature scale now known as Fahrenheit, which defines freezing as 32°F, boiling as 212°F, and body temperature as 98.6°F. For more information see Daniel Gabriel Fahrenheit.
Used in the following modules: Data: Analysis and Interpretation, Temperature
Faraday, Michael British chemist and physicist born in London (1791-1867). In 1831, Faraday discovered electromagnetic induction, the principle by which electric transformers and generators function. The farad, a unit of electrical capacitance, is named in his honor. For further information, see Michael Faraday.
Used in the following modules: Light II
Fermat, Pierre A French lawyer and mathematician, born in Beaumont-de-Lomange (1602-1665 CE). Fermat had a very successful career in the criminal court, but retained a deep interest in mathematics. He made contributions toward the development of calculus and analytical geometry; and along with Blaise Pascal he laid the foundations of probability theory which led to development of statistical methods. For further information see Pierre de Fermat; also see our module Data: Statistics.
Used in the following modules: Wave Mathematics
Feynman, Richard American physicist, born in Queens, New York (1918-1988). Feynman is best known for his work on quantum mechanics, quantum electrodynamics, and particle theory. In 1965, he was the joint recipient of the Nobel Prize in physics (with Julian Schwinger and Shin-Ichiro Tomonaga) for his work on quantum electrodynamics. Feynman also worked on the Manhattan Project, and participated on the panel that investigated the Space Shuttle Challenger disaster. In addition, he published several popular semi-autobiographical books. For further information see Richard Feynman.
Filial In science, filial is commonly used to designate the sequence of generations following the parental generation. For example, the first filial generation (abbreviated as F1) would be the direct offspring of a parental generation, the second filial generation (F2) would be the offspring of the first filial generation.
Used in the following modules: Genetics I
Fisher, Ronald English statistician, geneticist and evolutionary biologist born in London (1890-1962). He is considered the father of modern statistics. In 1919, Fisher began working at the Rothamsted Experimental Station. Six years later, he published Statistical Methods for Research Workers, drawing on his experience in creating statistically valid experiments. In 1935, Fisher published The Design of Experiments. Both works are still considered standards in the field of statistics. Fisher also contributed extensively to understanding population genetics, and was a staunch promoter of eugenics. For further information see Research Methods: Comparison, Research Methods: The Practice of Science
Fixity Of Species An idea popular among 16th and 17th century European zoologists and botanists that reflected Western religion and the story of creation as laid out in the Bible. A key feature of the argument for "fixity" was the notion that the structure of each species was based on a model, ideal form and never changed. With the publication of Darwin’s and other scientists’ work on evolution, the idea is no longer considered by scientists. For more information, see our module Charles Darwin I.
Used in the following modules: Charles Darwin I, Scientists and the Scientific Community
Floodplain The relatively flat land adjacent to a river channel that is underwater when the river floods. The floodplain is the site of deposition of sediments carried down the river and are often occupied by farms, due to the proximity of irrigation water, fertile soils, and flat topography.
Used in the following modules: The Rock Cycle
Folk Taxonomy The names given to organisms and phenomena on the basis of cultural tradition as opposed to scientific study.
Used in the following modules: Taxonomy I
Force The result of an interaction that is capable of changing the state of motion of an object. A 'push or pull' on an object resulting from its interaction with another object.
Used in the following modules: Adaptation, Chemical Bonding, Density, Earth Structure, Energy, Gravity, Light I, Light II, Matter: States of Matter, Minerals I, Nuclear Chemistry, Plate Tectonics I, Plate Tectonics II, Research Methods: Experimentation, Research Methods: Modeling, The Carbon Cycle, The Scientific Method, Unit Conversion
Franklin, Benjamin American inventor, scientist, and politician, born in Boston (1706-1790). Franklin was a prolific scientist and humanitarian. In Philadelphia, he founded America’s first subscription library, the city hospital, and the American Philosophical Society. He was also an inventor, designing a heat-efficient stove, swim fins, and bifocals. His experiments with electricity and lightening brought him global recognition. In the political scene, he was elected to the continental congress, signed the Declaration of Independence, and—one of his last acts before dying—wrote an antislavery treatise. For further information see Benjamin Franklin.
Franklin, Rosalind English biophysicist and x-ray crystallographer born in London (1920-1958). Franklin discovered that DNA crystallizes into two forms, and, working with Maurice Wilkins, used x-ray crystallography to determine the molecular structure of one of these forms. Her work was instrumental in allowing James Watson and Francis Crick to determine the complete structure of DNA. Her results were shared with them without her knowledge, and her contributions were not acknowledged. When Watson, Crick and Wilkins won a Nobel Prize for their work on the structure of DNA in 1962, Franklin was again overlooked, because the Nobel Prize cannot be awarded posthumously. For further information see Rosalind Franklin
Used in the following modules: DNA II
Frequency The rate at which a vibration occurs that constitutes a wave, either in a material or in an electromagnetic field, usually measured in hertz (Hz).
Used in the following modules: Research Methods: Description, Research Methods: Modeling, The Hydrologic Cycle, Waves and Wave Motion
Fry Richardson, Lewis English meteorologist born in Newcastle upon Tyne, Northumberland (1881-1953). Richardson was the first to apply mathematics (the method of finite differences) to predicting the weather. He published his results in Weather Prediction by Numerical Process (1922). This work laid the foundations for modern weather modeling and prediction. Richardson was a Quaker and a conscientious objector, and spent a significant amount of time, in his later years, analyzing the causes of war. He attempted to use differential equations to model factors like the psychology of a population, believing these factors to outweigh any single decision by a leader in determining if a country would go to war. For more information, see Lewis Fry Richardson.
Used in the following modules: Research Methods: Modeling
Gabbro A dark-colored intrusive igneous rock that consists mostly of the minerals plagioclase, pyroxene, and olivine. Gabbro has a similar composition to basalt, which is extrusive. Both gabbro and basalt are mafic rocks, composed of minerals high in iron and magnesium.
Used in the following modules: The Rock Cycle
Galileo Galilei The Italian physicist, mathematician, and astronomer born in Pisa in the Grand Duchy of Tuscany (1564-1642 CE). Among other things, Galileo studied the acceleration of objects and discovered the four largest moons of the planet Jupiter. His work significantly advanced the use of quantitative experimentation in science, and he made noteworthy contributions in the development of technology: he invented the refracting telescope, perfected the compound microscope, and improved compass design. Galileo was famously jailed during the Inquisition for his support of Copernicus’s heliocentric view of the cosmos. For further information see Galileo Galilei
Used in the following modules: Gravity, Research Methods: The Practice of Science, Scientific Institutions and Societies, Temperature, Waves and Wave Motion
Gamete A reproductive cell having half the number of chromosomes (a haploid) of a mature cell, e.g. a sperm or egg cell.
Used in the following modules: Genetics I
GCM see General Circulatin Model
Used in the following modules: Research Methods: Modeling
Gene Material (usually DNA) that is inherited from a parent and which encodes for a cellular component important for some cellular function.
Used in the following modules: Genetics I, The Case of the Ivory-billed Woodpecker
General Circulation Model (GCM) Also referred to as General Climate Models; a class of computer models used for weather forecasting, and understanding or projecting climate change. GCM's designed for applications on the scale of decades to centuries were originally created by Syukuro Manabe and Kirk Bryan at the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. For more information, see: Research Methods: Modeling
Genotype The genetic determinants of a specific phenotype.
Used in the following modules: Genetics I, Genetics II
Genus A taxonomic category one rank or step above Species in the Linnaean system, and which may include one or many species in it.
Used in the following modules: Adaptation, Charles Darwin III, Taxonomy II: Nomenclature, The Nitrogen Cycle
Geocentric Having or representing the Earth as the center, as in the heliocentric concept of the universe. Compare to heliocentric.
Used in the following modules: Research Methods: The Practice of Science
Geosphere The part of the world in which there are rocks and minerals.
Used in the following modules: The Carbon Cycle, The Nitrogen Cycle
Gilbert, Grove Karl American geologist born in Rochester, New York (1843-1918). Gilbert participated in the Wheeler geologic survey of the American West. His field studies resulted in the publication on The Geology of the Henry Mountains, which established his preeminence as a geologist. In 1879, he was appointed the Senior Geologist at the newly created U.S. Geological Survey. In addition to his study of the Henry Mountains, Gilbert investigated the Pleistocene Lake Bonneville. He is considered a major founder of the field of geomorphology, having investigated and published on erosion, river incision and sedimentation. For further information see Grove Karl Gilbert.
Used in the following modules: Research Methods: Description, Research Methods: The Practice of Science
Glacial Period Any of those parts of geologic time from Precambrian onward when a much larger portion of the earth was covered by glaciers than at present.
Used in the following modules: The Carbon Cycle
Glossary Terms Terms highlighted in red in the main lesson text are hyperlinked to a pop-up glossary to provide easy access to definitions.
Used in the following modules: Authoring Modules I, Visionlearning, Visionlearning Teaching Modules
Goodall, Jane English primatologist and anthropologist, born in London (1934-). Goodall is famous for her ground-breaking 45-year study of chimpanzee family and social interactions in the Gombe Stream National Park, Tanzania. She founded the Jane Goodall Institute and remains a leader in global effort to protect chimpanzees. Goodall revolutionized the field of primatology by discovering tool-making among wild chimpanzee populations, and remains the only human ever accepted into chimpanzee society. Interestingly, Goodall suffers from prosopagnosia, a neurological condition that makes it difficult for her to recognize human faces. For further information, see Jane Goodall.
Gould, Stephen Jay American paleontologist born in New York City, New York (1941-2002). With Niles Eldridge, he co-created and championed the concept of evolution via punctuated equilibrium, and wrote many popular books about evolution, paleontology, and the history of science. For further information see Stephen Jay Gould.
Granite A light-colored, coarse-grained igneous rock formed by cooling of silica-rich magma below the surface of the earth. Granite is considered to be the average composition of the continental crust of the earth.
Used in the following modules: Earth Structure, Minerals I, Minerals II, Minerals III, Scientific Communication: Utilizing the Scientific Literature
Greenhouse Effect The greenhouse effect is created by gases like carbon dioxide in the earth's atmosphere. Carbon dioxide and other greenhouse gases allow radiation from the sun to pass through the atmosphere; the earth then absorbs this radiation and emits heat. That heat is absorbed by the
greenhouse gases, resulting in atmospheric warming.
Used in the following modules: Earth's Atmosphere
Greenhouse Gas A greenhouse gas is a component of the atmosphere that absorbs heat radiated by the earth and subsequently warms the atmosphere, creating what is commonly known as the greenhouse effect. Common greenhouse gases include carbon dioxide (CO2), methane (CH4), water vapor, amd sulfate (SO4).
Used in the following modules: Data: Analysis and Interpretation, Research Methods: Comparison, The Nitrogen Cycle
Ground State The lowest energy state for an atom or molecule. When an atom is in its ground state, its electrons fill the lowest energy levels before they begin to occupy higher orbitals.
Used in the following modules: Atomic Theory II
Groundwater Water that fills pore space in rocks and sediments and forms a subsurface aquifer. Groundwater is distinct from soil moisture, which does not completely fill pore spaces and is immediately beneath the surface.
Used in the following modules: Research Methods: Modeling, The Hydrologic Cycle, The Nitrogen Cycle, The Rock Cycle
Gutenberg, Beno German geophysicist, born in Darmstadt (1889-1960). Gutenberg is best known for precisely determining the depth to the core of the Earth and describing its elastic properties. He also described the differences in structure of oceanic and continental crust, discovered a low-velocity zone within the mantle, created a magnitude scale for earthquakes, and studied the distribution of temperature in the Earth. For further information, see Beno Gutenberg.
Used in the following modules: Earth Structure
Haber, Fritz German chemist born in Breslau (1868-1934). Haber began his career in chemistry with investigations on the decomposition and combustion of hydrocarbons. In 1898, he published his textbook Electrochemistry, and followed this with increasing investigations of electrochemical phenomena. Among these experiments, he researched the electrolysis of solid salts, and energy loss by steam engines. In 1918, Haber was awarded a Nobel Prize in Chemistry for his research on nitrogen fixation from the air, a key component in the development of nitrogen fertilizers. For further information see Fritz Haber.
Used in the following modules: The Nitrogen Cycle
Half-life The time required for half of the original amount of a substance to undergo a process. For example, the time required for half of the atoms of a radioactive substance to undergo decay; or the time required for half of a ingested substance to be excreted from the body.
Used in the following modules: Nuclear Chemistry
Halley, Edmund English astronomer born in Derbyshire (1656-1742). He observed transits of Mars and Venus to determine the distance from the Earth to the Sun, and accurately predicted the return of a comet, now named after him. For further information see Edmund Halley.
Used in the following modules: Gravity, Scientific Communication: Utilizing the Scientific Literature
Hau, Lene Danish physicist born in Vejle (1959-). Her most famous work consisted of experiments in slowing down light. In 1999, she and several colleagues succeeded in slowing light to 17 m/s, and in 2001, they managed to very briefly stop a light beam. In 2007, she and her research team transformed light into matter and back into light using Bose-Einstein condensates. For further information, see Lene Hau.
Used in the following modules: Research Methods: Experimentation
Hawking, Stephen British cosmologist and theoretical physicist, born in Oxford (1942-). His most important contributions to science have been his study of quantum gravity and black holes. He also authored the extremely popular A Brief History of Time, which spent 237 weeks on the British Sunday Times best-sellers list. Hawking suffers from amyotrophic lateral sclerosis, a degenerative motor neural disease, which was diagnosed during his graduate studies. He is confined to a wheelchair and speaks through a voice-box. As part of an ongoing effort to popularize science and space-travel, Hawking went on a sub-orbital flight, during which he became the first quadriplegic to experience antigravity.
For further information see Stephen Hawking
Used in the following modules: Scientific Communication: Peer Review, Scientific Institutions and Societies
Heat A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures are placed into contact. Heat is a process, not a property of a material.
Used in the following modules: Adaptation, Atomic Theory II, Chemical Equations, Chemical Reactions, DNA I, Earth Structure, Earth's Atmosphere, Energy, Fats and Proteins, Matter: States of Matter, Minerals I, Minerals III, Nuclear Chemistry, Scientific Ethics, Temperature, The Carbon Cycle, The Hydrologic Cycle, The Rock Cycle
Heliocentric Having or representing the sun as a center, as in the heliocentric concept of the universe. Compare to geocentric.
Used in the following modules: Research Methods: The Practice of Science
Heraclitus A Greek philosopher from Ephesus (535-475 BCE). His philosophy consisted of a belief that everything is in a constant state of flux, and that opposites are not only necessary in life, because they provide balance, but are also, in fact, identical. For further information see Heraclitus.
Used in the following modules: Energy
Herschel, John Scottish astronomer born in Slough (1792-1871). Herschel studied double star systems, made a comprehensive map of the celestial Southern hemisphere, and was a pioneer and strong proponent of the use of photography in astronomy, now a staple of astronomical research. His book Outlines of Astronomy was a standard textbook for decades after its publication, and the modern New General Catalog (the best-known catalogue of deep sky objects in amateur astronomy) is derived largely from his General Catalogue of Nebulae and Clusters. For more information, see John Herschel.
Used in the following modules: Data: Using Graphs and Visual Data
Herschel, William English astronomer and composer born in Hanover, Germany (1738-1822). Hershcel worked closely with his sister, Caroline. Their most important contribution was the discovery, in 1781, of the planet Uranus. They also discovered two moons of Uranus in 1787, and two of Saturn’s moons. William Herschel’s work on double stars showed that gravity acts outside of the solar system. He also studied sunspots and their connection to weather. For further information see William Herschel.
Hess, Harry American marine geologist born in New York, New York (1906-1969). Hess was key scientist in the establishment of the theory of plate tectonics in the early 1960’s. From observations he made of the sea floor while serving in the U.S. Navy during World War II, he developed the idea of sea-floor spreading, which he published in 1962 in the paper “History of Ocean Basins.” For more information see Harry Hess.
Used in the following modules: Plate Tectonics I, Plate Tectonics II
Heterogeneous Mixture A mixture of two or more substances that can be easily separated by common physical means (i.e. settling, filtration, etc.). A mixture in which the components can be visibly distinguished. For example, oil and water. Compare to homogeneous mixture.
Hipparchus Greek astronomer, mathematician and geographer born in Nicaea (ca. 190-120 BCE). Hipparchus made the oldest surviving quantitative and accurate models for the motion of the Sun and Moon. He also developed a method for accurately predicting solar eclipses and compiled the first comprehensive star catalogue of the western celestial hemisphere. For further information, see Research Methods: Description, Wave Mathematics
Homeothermic Of, or pertaining to, the maintenance of a uniform temperature regardless of the temperature of the surroundings. In biology, synonymous with warm-blooded.
Used in the following modules: Adaptation
Homogeneous Mixture A mixture of two or more substances that cannot be easily separated by common physical means (i.e. settling, filtration, etc.). A mixture with no visible separation between its components. For example, salt and water. Compare to heterogeneous mixture.
Hooke, Robert An English physicist, born on the Isle of Wight (1635-1703). Hooke’s studies were extremely diverse, encompassing biology, geology, physics, chemistry, and astronomy. He was also an accomplished inventor: he designed the universal joint, the iris diaphragm, and a prototype of a respirator, and the balance spring. In 1662, he became the first Curator of Experiments for the Royal Society of London. Hooke discovered the theory for combustion and devised an equation for elasticity, which is now known as Hooke’s Law. He also made important contributions in biology by describing and naming cells, which he observed with a compound microscope that he designed. For further information see Robert Hooke.
Used in the following modules: Cells, Gravity, Light I, Research Methods: Experimentation, Scientific Institutions and Societies
Hot Spot A fixed plume of hot magma which rises through the mantle and creates volcanoes on the earth’s surface. The Hawaiian Island chain is an example of a hot spot. Because the plumes are fixed, the hot spots record past plate motions.
Hugo De Vries Dutch botanist and geneticist, born in Haarlem, Holland (1848-1935). He is known for “rediscovering” Gregor Mendel’s 1850s laws of heredity in the 1890s. Based in part on that rediscovery, he suggested the concept of genes, and developing a theory of evolution based on mutations. For further information, see Hugo de Vries.
Used in the following modules: Genetics II
Hutton, James Scottish geologist, chemist and naturalist born in Edinburgh (1726-1797). Hutton is considered to be the father of modern geology. From his geologic observations, Hutton became convinced that the Earth was older than the bible suggested. He also belonged to the uniformitarian school of thought, which held that changes to the Earth’s surface did not happen in sudden catastrophes, but rather occurred slowly, by processes that were continuously in effect. In 1795, he published his ideas in The Theory of the Earth, which was later popularized by John Playfair. For further information see James Hutton.
Used in the following modules: The Rock Cycle
Huxley, Thomas Henry English biologist born in Ealing, Middlesex (1825-1895). While serving in the Navy as an assistant surgeon, Huxley collected and studied marine invertebrates. He was so fierce a proponent of Darwin’s theory of evolution by natural selection that he earned the nickname “Darwin’s Bulldog”. Huxley’s most famous work is Evidence on Man’s Place in Nature, published in 1863, which is the first attempt to apply the concept of evolution to the human race. For further information see Thomas Henry Huxley.
Used in the following modules: Charles Darwin I, Research Methods: Comparison
Huygens, Christian Dutch mathematician born in The Hague, (1629-1695). Huygens ground and polished his own telescope lenses, and in 1655, he detected the first moon of Saturn using one of them. He also proposed the theory that Saturn has rings. Huygens worked on a variety of other mathematical, scientific, and engineering problems, including the development of accurate pendulum clocks and gravitational theory. In 1678, he published his “Theory of Light” in which he argued that light is a wave, not a particle. For further information see Christian Huygens.
Used in the following modules: Light I
Hydrocarbon An organic compound that contains only hydrogen and carbon.
Used in the following modules: Organic Chemistry
Hydrogen Bond A strong dipole-dipole attraction between two or more molecules, at least one of which has a hydrogen atom bonded to an electron-withdrawing atom. More specifically, a weak bond formed between a hydrogen atom on one molecule which has developed a partial positive charge because of its bonding to an electronegative atom (commonly N, O, or F) and an electronegative atom on another molecule.
Used in the following modules: Carbohydrates, DNA II, Matter: States of Matter, Minerals II, Water
Hydrophilic Literally meaning water loving, a substance that readily associates with water. Often polar molecules or some ionic molecules that easily dissolve in or form solutions with water. Compare to hydrophobic.
Hydrophobic Literally meaning water fearing, a substance that has little affinity for water. Generally, non-polar molecules that do not dissolve in or form solutions with water. Compare to hydrophilic.
Used in the following modules: Fats and Proteins
Hydroxyl An -OH group within a molecule.
Used in the following modules: Organic Chemistry
Hypothesis From the Greek word hypothesis meaning assumption or the basis of an argument, a hypothesis is a proposal intended to explain certain observations or phenomenon. In science, hypotheses represent the basis of scientific research, which is pursued to objectively determine whether or not a hypothesis is correct. For more information, see: Ideas in Science: Theories, Hypotheses, and Laws
Used in the following modules: Charles Darwin I, Data: Analysis and Interpretation, DNA II, Genetics I, Genetics II, Research Methods: Comparison, Research Methods: Description, Research Methods: Experimentation, Research Methods: Modeling, Research Methods: The Practice of Science, Scientific Communication: Understanding Scientific Journals and Articles, Scientific Ethics, Scientists and the Scientific Community, The Case of the Ivory-billed Woodpecker, The Mole, The Process of Science, The Scientific Method
Igneous Formed from the cooling and crystallization of a magma. Igneous rocks can be extrusive, meaning that they cooled on or very near the earth’s surface, or intrusive, meaning that they cooled below the earth’s surface.
Used in the following modules: Minerals III, Research Methods: Description, The Rock Cycle
Independent Variable In science, an independent variable is a condition or parameter that is consciously manipulated in some way in the course of scientific research with the goal of observing the outcome of this manipulation on a second variable, referred to as a dependent variable. For more information, see: Research Methods: Experimentation
Used in the following modules: Research Methods: Experimentation
Inert Deficient in active properties; especially: lacking a usual or anticipated chemical or biological action.
Used in the following modules: Chemical Reactions, Research Methods: The Practice of Science, The Nitrogen Cycle
Intensive Property A property of matter that is independent of the amount of material present. Common intensive properties include boiling point, color, density, melting point, and solubility.
Used in the following modules: Density
Interglacial Period Any of those parts of geologic time from Precambrian onward when a similar or lesser portion of the earth was covered by glaciers than at present.
Used in the following modules: The Carbon Cycle
Intergovernmental Panel On Climate Change (IPCC) A scientific body created to evaluate the risk of human-caused climate change. The panel was established in 1988 by two organizations of the United Nations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP).
Interstitial Pertaining to or located between the small spaces and gaps between tissues in an organism.
Ion An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion that has lost electrons and acquired a positive charge. An anion is an ion that has gained electrons and acquired a negative charge.
Used in the following modules: Absorption, Distribution and Storage of Chemicals, Acids and Bases, Atomic Theory II, Cells, Chemical Bonding, Chemical Reactions, Earth's Atmosphere, Matter: States of Matter, Minerals III, The Carbon Cycle, The Nitrogen Cycle, Water
Ionic Bond A chemical bond characterized by electrostatic attraction between ions of opposite charge. The formation of an ionic bond involves a complete transfer of electrons between atoms, and can be predicted when one bonding atom has a much higher electronegativity than the other. Compare to covalent bond, hydrogen bond.
Used in the following modules: Chemical Bonding
Ionic Compound A chemical compound held together by ionic bonds, that is, electrostatic attraction between positive and negative ions. Ionic compounds generally form ordered structures in which each cation is surrounded by several anions and vice versa. Thus ionic compounds commonly form complex lattices rather than true molecules.
Used in the following modules: Chemical Bonding, Water
Isomers Molecules with identical molecular formulas but differing in the sequence of bonding or arrangement in space of their atoms, i.e. their structural formulas.
Used in the following modules: Organic Chemistry
Isotope Atoms of the same element with different numbers of neutrons in their atomic nucleus. Isotopes have the same chemical properties and atomic number but different atomic masses. Isotopes can differ greatly in nuclear stability.
Used in the following modules: Atomic Theory II, Data: Analysis and Interpretation, Data: Uncertainty, Error, and Confidence, DNA I, Matter, Nuclear Chemistry
Iteration One step in an iterative process. Iteration refers to a single component of a process in which multiple, repeating steps are used to determine a solution.
Used in the following modules: Data: Uncertainty, Error, and Confidence
Iterative Repetitive in a cyclical fashion. An iterative process or method in science is one in which a sequence of steps is repeated in order to solve a problem, and each repetition of the steps brings one closer and closer to the solution. For more information, see: Data: Uncertainty, Error, and Confidence
Used in the following modules: Research Methods: Description, Research Methods: Modeling, Scientific Communication: Utilizing the Scientific Literature
John Tyndall Irish physicist born at Leighlin Bridge, County Carlow (1820-1893). Tyndall was one of the first scientists to recognize the natural greenhouse effect and to identify the relative importance of various greenhouse gases. He also showed that ozone is an oxygen cluster (O3), not a hydrogen compound. In addition, Tyndall was a prolific an inventor, devising a respirator for fireman, the foghorn, and the light pipe, which was the progenitor of fiber optics. For further information, see John Tyndall.
Used in the following modules: The Hydrologic Cycle
Joliot-Curie, Frederic The French physicist born in Paris, France (1900 – 1958 CE). Shared the 1935 Nobel Prize in Chemistry with his wife Irène Joliot-Curie for their discovery of artificial radioactivity. For further information see: Frederic Joliot-Curie
Joliot-Curie, Irene The French scientist born in Paris, France (1897 – 1956 CE). Daughter of Marie Curie and Pierre Curie, Irène shared the 1935 Nobel Prize in Chemistry with her husband Frédéric Joliot-Curie for their discovery of artificial radioactivity. For further information see: Irene Joliot-Curie
joule A metric unit of work and energy. 1 joule (J) = 1 kg·m2/s2.
Used in the following modules: Energy
Joule, James Prescott English physicist born in Salford (1818-1889). In 1840, Joule published a paper detailing what is now called Joule’s Law, which describes the relationship between the current through a resistor and the heat lost from the system. He continued his studies on heat and its relationship to mechanical work, concluding that heat is a form of energy. He developed the theory of conservation of energy, and, subsequently, the first law of thermodynamics. The joule, an SI unit of energy, is named after him. For further information see James Prescott Joule.
Used in the following modules: Energy
Keeling, Charles David American marine geochemist born in Scranton, Pennsylvania (1928-2005). Keeling researched the greenhouse effect and subsequent changes in the earth’s atmosphere. Keeling helped establish a station on Mauna Loa in 1958 where monthly atmospheric CO2 measurements have been taken ever since. His dedication to producing a long-term record was critical to showing that atmospheric carbon dioxide levels have been increasing over time. His work resulted in a greater awareness of the human impact on global climate. For further information see Charles David Keeling.
Kelvin, William Scottish physician and mathematician born in Belfast, Ireland (1824-1907). In 1867, Kelvin published Treatise on Natural Philosophy (later republished as Principles of Mechanics and Dynamics), which established the role of energy in the theory of mechanics. Kelvin also championed the idea that the entropy of the universe constantly increases, and will eventually reach a state of uniform temperature and maximum entropy, where no further work is possible: this uniform temperature will be absolute zero, or 0° Kelvin (-237°C). For more information, see William Kelvin.
Used in the following modules: Temperature
Kepler, Johannes German mathematician and astronomer born in Weil der Stadt, Württemburg (now part of Stuttgart, Germany) (1571-1630). Kepler is best known for outlining his laws of planetary motion, which defined the paths of the planets as orbits that could be mathematically represented as an ellipse. He was a champion if the Copernican model of the universe, publishing the Mysterium Cosmographicum in defense of it. For further information, see Johannes Kepler
Used in the following modules: Gravity, Research Methods: The Practice of Science
Kinetic Energy The energy an object possesses by virtue of its motion.An object of mass m moving at velocity v has a kinetic energy of ½m·v2.
Used in the following modules: Energy
Lamarck, Jean Baptiste French zoologist and botanist, born in Bazentine le Petit (1744-1829). While working as a professor of invertebrate natural history at the Musée National d'Histoire Naturelle, Lamarck developed his theory of evolution, which stated that organisms could change in response to changes in their environment and could pass these changes on to their offspring, a theory later proven largely incorrect. For further information see Jean Baptiste Lamarck.
Used in the following modules: Adaptation
Laplace, Pierre-Simon French mathematician and astronomer born in Normandy, France (1749-1827). Laplace made significant contributions in mathematics and error quantification and is credited with founding the field of mathematical astronomy. In addition, he predicted the existence of black holes and the concept of gravitational collapse. For more information, see Pierre-Simon Laplace.
Used in the following modules: Data: Uncertainty, Error, and Confidence
Lattice A characteristic pattern formed by the spatial distribution of repeating units.
Used in the following modules: Water
Lavoisier, Antoine French chemist, born in Paris (1743-1794). He is famous for proving that air is composed of several gases - he thought 2. He also experimentally established the Law of Conservation of Mass, devised the system of chemical nomenclature that is currently in use, and authored the first modern chemistry textbook, Traité Élémenaire de Chimie (Elementary Treatise of Chemistry). For further information see Antoine Lavoisier.
Used in the following modules: Matter
Lawes, John Bennet English gentleman farmer, born at the Rothamsted Manor House in Hertfordshire (1814-1900). He investigated the effects of various fertilizers on crops. Rothamsted Station is still now the oldest functioning agricultural research station in the world, and some experiments (termed Rothamstead Classical Experiments) have been running since it was founded. For further information, see John Bennet Lawes.
Used in the following modules: Data: Statistics
Le Verrier, Urbain French astronomer, born in Saint-Lô, (1811-1877). He worked primarily on celestial mechanics and, like John Couch Adams, predicted the existence of Neptune based on perturbations in the orbit of Uranus. He also—incorrectly—predicted the existence of a planet inside the orbit of Mercury, which he named Vulcan, based on perturbations in Mercury’s orbit. For further information, see Urbain Le Verrier.
Used in the following modules: Gravity
Leaching Dissolving out by the action of a percolating liquid.
Leclerc, Georges French mathematician, naturalist and biologist, born in Montbard, Côte-d’Or (1707-1788). In 1727, Leclerc discovered the binomial theorem. In the 1730’s, he published Mémoire sur le jeu de franc-carreau (Thesis on the game of franc-carreau), which combined differential and integral calculus with probability theory. His most famous works are in natural history, where his ideas influenced the thinking of Lamarck and Darwin. His great work, Histoire naturelle, générale et particulière (General and specific natural history) consists of 36 volumes, published in 1749-1778, plus 8 more volumes published after his death. For more information, see Adaptation
Lehmann, Inge Danish physicist born in Osterbro by the Lakes (1888-1993). In 1925, Lehmann became interested in seismology while working as assistant to Professor N.E. Norlund. Three years later, she was appointed chief of the seismological department at the Royal Geodetic Institute. Because Denmark is seismically stable, Lehmann focused her research on small earthquakes and explosions and the microseismic wave motions generated by Arctic and North Sea storms. From refractions of seismic waves, she discovered the Earth’s inner core 1936. In 1971, Lehmann was awarded the Bowie Medal by the American Geophysical Union for her contributions to the fields of seismology and earth science. For more information, see Inge Lehmann.
Used in the following modules: Earth Structure
Lenticular Shaped like a lens, of or related to a lens; often referring to clouds, galaxies, rock bodies, or small features within rocks.
Used in the following modules: Research Methods: Description
Lewis, Gilbert Newton American chemist born in Weymouth, Massachusetts (1875-1946). Lewis’s early work, carried out as a faculty member at MIT, involved the determination of electrode potentials of elements, conductivity and thermodynamics. Most of his later work focused on thermodynamics and chemical equilibrium, electron-pair bonding of atoms and molecules, isotopes, and light-matter interactions. During his 34-year tenure at UC Berkeley, Lewis was renowned as a remarkable teacher and advisor. In 1923 he published Valence and the Structure of Atoms and Molecules, still considered a classic work and a vital contribution to modern bonding theory. For more information see Gilbert Newton Lewis.
Used in the following modules: Chemical Bonding
Light A form of electromagnetic radiation. Visible light is that associated with stimulating the organs of sight, which for normal human vision ranges in wavelength from 3900 to 7700 ångstroms.
Used in the following modules: Atomic Theory II, Cells, Charles Darwin I, Chemical Equations, Chemical Reactions, Data: Using Graphs and Visual Data, DNA I, Educational Web Design, Energy, Genetics I, Gravity, Light I, Light II, Matter: States of Matter, Minerals II, Minerals III, Nuclear Chemistry, Research Methods: Comparison, Research Methods: Experimentation, Research Methods: Modeling, Research Methods: The Practice of Science, Scientific Communication: Peer Review, Scientific Communication: Understanding Scientific Journals and Articles, The Carbon Cycle, Wave Mathematics
Limestone A sedimentary rock composed mainly of calcite (CaCO3). Limestone forms through chemical precipitation in warm, shallow seas, and often contains marine fossils.
Used in the following modules: Plate Tectonics I, The Carbon Cycle
Limiting Reactant A reactant that limits the amount of product produced in a chemical reaction.
Line Spectra An emission spectrum of light that contains very sharply defined lines. Line spectra are given off when matter is heated or excited in some way and each line corresponds to a wavelength of light given off during an electron transition from an excited state to the ground state.
Used in the following modules: Atomic Theory II, Data: Using Graphs and Visual Data
Linnaean Hierarchy The seven major categories of biological classification based on Linnaeus’ system: Kingdom, Phylum, Class, Order, Family, Genus, and Species.
Linnaeus, Carolus (also Carl Linnaeus or Karl von Linné) Swedish physician, naturalist and taxonomist born in Stenbrohult (1707-1778). Inspired by the work of John Ray, Linnaeus developed a system for classifying organisms, a modified version of which is still in use. In 1735, he published the first edition of Systema Naturae, which detailed his classification system. He was also the physician to the Royal Family of Sweden. For more information see Carolus Linnaeus.
Used in the following modules: Taxonomy I, Taxonomy II: Nomenclature
Lipids A diverse group of organic molecules that contain long hydrocarbon chains or rings and are hydrophobic. Examples are fats, oils, waxes, and steroids.
Used in the following modules: DNA I, Fats and Proteins
Lithosphere The rigid upper layer of the earth consisting of the crust and the upper mantle. The earth’s tectonic plates are composed of pieces of the lithosphere. The lithosphere ranges in thickness from 10-12 km underneath the oceans to 70-200 km at the continents.
Used in the following modules: Earth Structure
Loschmidt, Johann Josef Austrian chemist and physicist, born in Pocerny (now part of the Czech Republic) (1821-1895). He worked in thermodynamics, optics and electrodynamics. One of his many contributions to science was the accurate calculation of the average size of the gas molecules that make up air. For further information see Johann Josef Loschmidt.
Used in the following modules: The Mole
Lovelock, James British chemist, born in Letchworth Garden City (1919-). He developed the Gaia Hypothesis, which proposes that the biosphere and all physical components of the Earth are coupled together in a complexly interacting system. The hypothesis is frequently paraphrased as describing the Earth as a single living organism. Lovelock was also an inventor: his most famous invention is the electron capture detector, which provided valuable information on the distribution of halogen-bearing chemicals and CFCs in the atmosphere. For further information see James Lovelock.
Used in the following modules: Research Methods: The Practice of Science
Lunar Eclipse A celestial event occurring when the Moon passes through some portion of the Earth's shadow. This only occurs when the Sun, Earth, and Moon are aligned so that the Earth is between the Sun and the Moon.
Used in the following modules: Research Methods: Description, Scientific Communication: Utilizing the Scientific Literature
Lyell, Charles A British geologist born in Scotland (1797-1875 CE). His most important work was The Principles of Geology: An Attempt to Explain the Former Changes of the Earth's Surface by Reference to Causes now in Operation. Lyell championed the theory of uniformitarianism, which states that the same processes we see on Earth today were active throughout the past and shaped the earth as we know it, including slow processes like sedimentation. This opposed the leading view at that time, catastrophism, which states that changes to the earth’s surface occur in sudden, discrete events. He also wrote Elements of Geology, which is still considered a seminal work on stratigraphy and paleontology. His third major, though now lesser known, work was The Antiquity of Man, in which he supports Darwin’s theories regarding the origins of species. The Lyell Medal is now awarded yearly by the Council of the Geological Society to a significant contemporary geologist. For further information see Charles Lyell; also see our module The Rock Cycle.
Used in the following modules: Charles Darwin II
Magma Molten rock below the surface of the earth.
Used in the following modules: Minerals I, Minerals II, Plate Tectonics I, Plate Tectonics II, Research Methods: Description, The Rock Cycle
Malthus, Thomas Robert English ordained minister and economist born in Dorking, Surrey (1766-1834). In 1798 he published his Essay on Population, suggesting that a given population will always exceed its food supply, and it would therefore be counterproductive to provide starving populations with food. Instead, he argued, social equality must be achieved through other means, such as universal suffrage and state-funded education for the poor. For further information see Thomas Robert Malthus.
Used in the following modules: Charles Darwin II
Manhattan Project A United States project initiated in August 1942 that was responsible for developing atomic technology, and specifically an atomic bomb, during World War II.
Mantle The middle portion of the interior of the earth, starting below the crust at 5-70 km below the earth’s surface and continuing to a depth of 2900 km. The mantle is composed mainly of the rock peridotite.
Used in the following modules: Earth Structure, Minerals I, Minerals III, Plate Tectonics II
Mass a fundamental property of matter which is a numerical measure of the inertia of an object or the amount of matter that an object contains. The mass of an object is different from its weight as mass is independent of the gravitational field exerted on an object.
Used in the following modules: Adaptation, Atomic Theory I, Atomic Theory II, Chemical Equations, Data: Uncertainty, Error, and Confidence, Density, Earth's Atmosphere, Gravity, Matter, Minerals I, Minerals II, Nuclear Chemistry, Research Methods: Description, Research Methods: The Practice of Science, Scientific Communication: Peer Review, Scientific Institutions and Societies, The Metric System, The Mole, The Scientific Method
Mass Spectrometer A spectrometer that measures the composition of samples by analyzing the mass to charge ratio (m/z) of components in the sample. To do this, the sample introduced into the spectrometer is ionized under high energy, and the various ions are then seperated in a magnetic field and measured. The specific m/z signature of each ion is then used to identify the parent element or compound. For additional information, see the Wikipedia's definition of mass spectrometry.
Used in the following modules: Minerals I, Minerals II, Research Methods: Description
Matthews, Drummond English marine geophysicist, born in Porlock, Somerset (1931-1997). In 1962, Matthews participated in the International Indian Ocean Expedition and made a detailed survey of a submarine ridge that showed that the pattern of magnetic polarity of sea floor rocks surrounding the ridge was symmetric. This discovery contributed to the widespread acceptance of the plate tectonic theory. He also studied the structure and evolution of continental crust using deep crustal seismics. For further information, see Drummond Matthews.
Used in the following modules: Plate Tectonics I
Maxwell, James Clerk Scottish theoretical physicist and mathematician born in Edinburgh (1831-1879). Maxwell developed the classical electromagnetic theory, which synthesized previously unrelated observations, experiments and equations of electricity and magnetism. In 1864, Maxwell wrote A Dynamical Theory of the Electromagnetic Field, in which he proposed that light is a wave. He also described what is now known as Maxwellian distribution, a statistical way of describing the kinetic theory of gases. For further information see James Clerk Maxwell.
Mean In statistics, mean commonly refers to the arithmetic mean, also called the average, which is one measure of the mid-point of a dataset. The mean and median approach one another in datasets that approach a normal distribution, but can differ substantially in datasets with skewed distributions. Compare to median. The mean is calculated by obtaining the sum of the values in a dataset and dividing that sum by the number of data points, as in the formulas:
Used in the following modules: Absorption, Distribution and Storage of Chemicals, Acids and Bases, Cells, Charles Darwin I, Charles Darwin II, Charles Darwin III, Chemical Equations, Data: Analysis and Interpretation, Data: Statistics, Data: Uncertainty, Error, and Confidence, Data: Using Graphs and Visual Data, Density, Earth's Atmosphere, Educational Web Design, Energy, Minerals I, Minerals II, Research Methods: Comparison, Research Methods: Experimentation, The Carbon Cycle, The Hydrologic Cycle, The Nitrogen Cycle, Unit Conversion, Wave Mathematics
Median In statistics, the median is the value separating the upper half from the lower half of a dataset. In other words, it is the middle value of the data when they are arranged in order of magnitude. The median is a characteristic of a dataset comparable to the mean. The median and mean approach one another in datasets that approach the normal distribution, but can differ substantially in datasets with skewed distributions.
Used in the following modules: Data: Statistics
Mendel, Gregor Austrian Augustinian monk and scientist born in Heizendorf (now Hynice, Chech Republic)(1822-1884). In 1856, Mendel wrote Versuche über Pflanzen-Hybride (Treatises on Plant Hybrids), which detailed his observations on the inheritance of various traits in cross-bred pea plants and presented his principles of hereditary transmission. Unfortunately, the importance of his work was not recognized until after his death. For further information see Gregor Mendel.
Used in the following modules: DNA I, Genetics I, Genetics II, Scientific Institutions and Societies, Scientists and the Scientific Community
Mendeleev, Dmitri Russian inventor and chemist born in Tobolsk, Siberia (1834-1907). Mendeleev’s most famous work is the development of the periodic table of elements, and his prediction of properties of elements that were, at that time, not yet discovered. In 1869, Mendeleev helped found the Russian Chemical Society. He researched in many fields including physics, hydrodynamics, meteorology, and chemical technology. For further information see Dmitri Mendeleev.
Used in the following modules: The Periodic Table of Elements
Mesosphere 1. The lowermost portion of the mantle. 2. The layer of the atmosphere above the stratosphere, where temperature decreases with altitude.
Used in the following modules: Earth Structure, Earth's Atmosphere
Metabolism A sequence of biochemical reactions in living organisms that converts food into energy used to drive other biological processes. Also, the sequence of transformations foreign compounds undergo inside a living cell.
Used in the following modules: Adaptation, Carbohydrates, Cells, Research Methods: Experimentation, The Carbon Cycle
Metamorphic Formed through the processes involved in metamorphism, which include deep burial, exposure to high temperatures and pressures, and interactions with hydrothermal fluids. Metamorphic rocks are generally considered to have a parent rock, or protolith, which can be any rock type. The minerals and textures that are produced through metamorphism are indicative of both the protolith and the metamorphic environment.
Used in the following modules: Minerals III, The Rock Cycle
Metamorphism Physical and chemical changes to rocks that occur below the earth’s surface. These changes are caused by increased temperature, increased pressure, and the presence of hydrothermal fluids, and result in the growth and reorientation of crystals in the rock. Metamorphism does not include melting - once magma forms, the resulting rock will be igneous.
Michell, John English natural philosopher and geologist, born in Nottinghamshire, (1724-1793). In 1750 he published A Treatise of Artificial Magnets, detailing his observations on the variations in forces between magnetic poles. He also demonstrated radiation pressure, adding support to Christian Huygens’ argument that light consists of waves. For further information see John Michell.
Used in the following modules: Gravity
Michelson, Albert American physicist, born in Strelno, Prussia (1852-1931). He is remembered for his work in optics, particularly for his early, extremely accurate experiments to determine the velocity of light. Michelson invented the interferometer, which he used to determine the effect of Earth’s motion on the observed velocity of light. He was also interested in astronomy, and, using his interferometer, accurately measured the diameter of the star Betelgeuse. He was awarded a Nobel Prize in physics in 1907. For further information see Albert Michelson.
Used in the following modules: Light II
Mid-ocean Ridges A linear, elevated region of the ocean floor where magma is upwelling, extruding, and new crust is forming. The ridges are often referred to by their more specific names: Mid-Atlantic Ridge, East Pacific Rise, etc.
Used in the following modules: Earth Structure, Plate Tectonics I, Plate Tectonics II
Millibar (mb) A unit of measurement of atmospheric pressure equivalent to 1 gram per square centimeter. Average sea level pressure is 1013 mb, equivalent to one Atmosphere.
Mineral A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO2), salt (also called halite, NaCl), graphite (C). Rocks are formed of one or more minerals.
Used in the following modules: Charles Darwin I, Data: Statistics, Matter, Matter: States of Matter, Minerals I, Minerals II, Minerals III, Plate Tectonics I, Research Methods: Description, The Carbon Cycle, The Rock Cycle
Mineralization Conversion into an inorganic form.
Used in the following modules: The Nitrogen Cycle
Moho The commonly used abbreviation of the Mohorovicic Discontinuity, the boundary between the crust and the mantle.
Used in the following modules: Earth Structure
Mohorovicic Discontinuity The boundary within the earth between the crust and the mantle, as indicated by the refraction and velocity change of seismic waves recognized by Andrija Mohorovicic. The depth of the Mohorovicic Discontinuity is ~5-7 km below oceanic crust and ~10-70 km below continental crust.
Used in the following modules: Earth Structure
Mohorovicic, Andrija Croatian meteorologist and geophysicst born in Volosko (1857-1921). In 1901, Mohorovičić was appointed head on the meteorological service of Croatia and Slavonia. He upgraded the services to European standards, and expanded the work of the observatory into seismology, geomagnetism and gravitation. Mohorovičić discovered the existence of S and P seismic waves, which propagate through the Earth at different velocities. From seismic refractions, Mohorovičić discovered a discontinuity between the less dense rocks of the crust and denser rocks of the mantle, now called the Mohorovičić discontinuity (known more commonly as the Moho). For more information, see Andrija Mohorovicic.
Used in the following modules: Earth Structure
Mohs, Friedrich German geologist and mineralogist born in Gernrode (1773-1839). In 1802, after studying at the Mining Academy in Freiberg, Saxony, Mohs moved Austria, where he was hired to identify minerals in a private collection. In order to do this, he classified the minerals by their physical characteristics, rather than their chemical compositions (as was usually done). He developed the Moh’s hardness scale, a relative scale of the hardness of minerals that remains a useful way to identify minerals in the field. For further information, Friedrich Mohs.
Used in the following modules: Minerals II
Mole An amount equal to Avogadro’s number or 6.02 × 1023. One mole of atoms is equal to 6.02 × 1023atoms.
Used in the following modules: Acids and Bases, Chemical Equations, The Mole
Molecular Weight The formula weight of a compound, given by summing the atomic weights of atoms in the compound. Given in grams, the molecular weight is the weight of one mole of molecules in a compound.
Used in the following modules: Absorption, Distribution and Storage of Chemicals, Chemical Equations, The Mole
Molecule A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a chemical compound that retains the chemical properties of the compound.
Used in the following modules: Absorption, Distribution and Storage of Chemicals, Acids and Bases, Carbohydrates, Cells, Chemical Bonding, Chemical Equations, DNA I, DNA II, Earth's Atmosphere, Fats and Proteins, Matter: States of Matter, Minerals I, Nuclear Chemistry, Organic Chemistry, Research Methods: Description, Research Methods: Modeling, Scientists and the Scientific Community, The Carbon Cycle, The Metric System, The Mole, The Nitrogen Cycle, Water
Monomer Any molecule that may become chemically bonded to other molecules of the same type to form a larger molecule called a polymer.
National Science Foundation A United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. For more information see http://www.nsf.gov .
Used in the following modules: Data: Using Graphs and Visual Data, Scientific Institutions and Societies, Visionlearning, Visionlearning Teaching Modules
Negative Control In science, a negative control refers to a system that is identical to a treatment in all ways with the specific exception of the treatment itself. Thus, the negative control provides a measure of the natural fluctuations of a dependent variable due to factors other than the experimental treatment. For more information, see: Research Methods: Experimentation
Used in the following modules: Research Methods: Experimentation
Neutral Generally defined as neither one thing nor another. 1. Electrically neutral refers to having no net electrical charge, usually achieved by having an equal number of positive and negative charges, atoms are electrically neutral. 2. In acid/base chemistry, neutral refers to a solution that is neither acid nor base. A neutral solution contains equal concentrations of H+ and OH-, and has a pH = 7.
Used in the following modules: Acids and Bases, Atomic Theory I, Atomic Theory II
Neutralization The chemical process of making a solution of acid or base into a neutral solution by adding either base or acid, respectively. A process represented by the reaction:Acid + Base --> H2O + Salt
Used in the following modules: Acids and Bases
Neutron A sub-atomic particle with no charge and a mass of 1.675 × 10-27 kg. Neutrons are found in the nucleus of atoms. Compare to the proton.
Used in the following modules: Atomic Theory I, Atomic Theory II, Nuclear Chemistry, Scientific Ethics, The Mole
Newton, Isaac English alchemist, physicist, astronomer and mathematician born in Woolsthorpe-by-Colsterworth, Licolnshire (1643-1727). In 1672, Newton offered an experimental proof that light is composed of particles, and developed a theory of color based on the separation of white light through a prism. This theory was broadly (though not universally) accepted until the 18th century. In 1687, he published the Philosophiae Naturalis Principia Mathematica, which many considered the most influential book in the history of science. In it, Newton presents his theories of universal gravitation and the laws of motion. He is credited, along with Gottfried Leibniz, for the development of calculus, and he demonstrated a consistency between Kepler’s laws of planetary motion and his theory of gravity, dispelling the final doubts in the scientific community over a heliocentric view of the solar system. He also contributed significantly to the development of new technology, inventing the reflecting telescope. For further information see Isaac Newton
Used in the following modules: Charles Darwin II, Data: Using Graphs and Visual Data, Energy, Gravity, Light I, Minerals I, Research Methods: Description, Research Methods: Experimentation, Research Methods: The Practice of Science, Scientific Communication: Understanding Scientific Journals and Articles, Scientific Institutions and Societies, The Scientific Method, Waves and Wave Motion
Nightingale, Florence English nurse and statistician born in Florence, Italy (1820-1910). Nightingale observed that poor sanitation was the leading cause of deaths in field hospitals during the Crimean War, and became a key activist for hospital sanitation. She was a skilled statistician, and used statistical observations to convince the Members of Parliament of the medical conditions during the Crimean War. Nightingale was also extremely influential in the field of nursing: the Nightingale School of Nursing still teaches her care-giving principles. For further information, see salts to nitrites and the further oxidation of nitrites to nitrates.
Used in the following modules: The Nitrogen Cycle
Nitrogen Fixation The assimilation of atmospheric nitrogen into ammonia, most commonly through metabolic processes of soil microorganisms. Other agents of nitrogen fixation include lightning,forest fires, and the industrial process used to manufacture synthetic fertilizers.
Used in the following modules: The Nitrogen Cycle
Nobel Prize Awards made annually, beginning in 1901, from funds originally established by Alfred B. Nobel for outstanding achievement in physics, chemistry, medicine or physiology, literature, and the promotion of peace. A Nobel Prize in economics was established from private funds in 1969.
Used in the following modules: DNA II, Minerals III, Nuclear Chemistry, Research Methods: The Practice of Science, Scientists and the Scientific Community
Non-polar Covalent Bond A covalent bond in which electrons are equally shared between bonding atoms. A non-polar covalent bond is formed when both atoms participating in a bond have an equal or nearly equal affinity for electrons (electronegativity). A non-polar bond will result in a symmetric distribution of electron charge across the bonding pair. Compare to polar covalent bond, polar molecule.
Non-polar Molecule A molecule that has an equal distribution of bonding electrons across it. Non-polar molecules are formed by non-polar covalent bonds or when polar covalent bonds result in a symmetric distribution of electrical charge, the configuration + - - + for example. Compare to polar molecule.
Normal Distribution Also called a Gaussian distribution or a bell curve, the normal distribution is one of a family of continuous probability distributions in which the probability of observing any specific value is evenly distributed about the mean (µ) of the dataset and falls off continuously as one moves away from the mean value in either direction. The standard deviation (σ) of the dataset describes the spread of a normally distributed set of data as seen in the figure below:
Nucleic Acid A group of polymers made of repeating units of phosphoric acid and sugar to which nucleotide bases are attached. The two most common examples are DNA and RNA.
Used in the following modules: DNA II
Nucleotide Base A nitrogen containing base that is a constituent of a nucleic acid. Examples are adenine, guanine, thymine, uracil, and cytosine.
Used in the following modules: DNA I
Nucleus 1. [Atomic] A tiny, dense positively charged mass at the heart of an atom. The nucleus is composed of protons and neutrons, and contains nearly all of the mass of the atom while occupying only a tiny fraction of the volume. 2. [Cellular] The internal structure present in some cells that contains genetic material.
Used in the following modules: Atomic Theory I, Atomic Theory II, Cells, DNA II, Nuclear Chemistry, Research Methods: Modeling, The Periodic Table of Elements
Null Hypothesis In statistical testing, a null hypothesis (H0) commonly takes the form of a statement suggesting that an observed result or effect is due to random chance. The null hypothesis is put forward as the counterpart to an alternative hypothesis (H1), and is presumed correct until statistical testing shows otherwise. For example, in an evaluation of data regarding the pain relieving properties of a new drug, the null hypothesis would state that the new drug has no effect beyond that of a control. The null hypothesis is never proven by statistical testing; either H1 is accepted in favor of H0, or H0 is “not rejected.”
Used in the following modules: Research Methods: Comparison, The Case of the Ivory-billed Woodpecker
Nuremberg Doctors’ Trial Officially United States of America v. Karl Brandt, et al., was the first of the Trials of War Criminals held before U.S. military court in the aftermath of World War II. Twenty of the defendants were medical doctors and three were Nazi officials who were all accused of having been involved in Nazi human experimentation. Of the 23 defendants, seven were acquitted and seven received death sentences; the remainder received prison sentences ranging from 10 years to life imprisonment.
Used in the following modules: Scientific Ethics
Oceanic Crust The uppermost layer of the earth beneath the ocean basins. Oceanic crust is constantly forming at mid-ocean ridges and is constantly being destroyed at subduction zones, thus the oldest oceanic crust on the earth is about 160 million years old. Oceanic crust is composed of basalt and is 5-7 km thick.
Used in the following modules: Earth Structure, Plate Tectonics II
Ockham’s Razor A principle that states that the explanation of any phenomenon should make as few assumptions as possible, eliminating those that make no difference in the observable predictions of the explanatory hypothesis or theory. Attributed to the 14th-century English logician and Franciscan friar William of Ockham.
Oersted, Hans Christian Danish physicist and chemist born in Langeland (1777-1851). He experimentally demonstrated the relationship between electricity and magnetism. For more information, see Hans Christian Oersted.
Used in the following modules: Light II
Oldenburg, Henry German natural philosopher and diplomat, born in Bremen (1619-1677). Oldenburg was an original fellow of the Royal Society, served as its first secretary, and was the founding editor of the Philosophical Transactions of the Royal Society. For further information see Henry Oldenburg.
Used in the following modules: Scientific Communication: Understanding Scientific Journals and Articles
Organic Molecule Organic molecules are molecules that contain carbon bonded to hydrogen. Organic molecules may contain other elements as well, especially O, N, Cl, and others. Use of the term 'organic' dates to the 19th century, when it was believed that organic molecules could only be derived from living organisms.
Used in the following modules: Carbohydrates, Organic Chemistry
Organism A living being.
Used in the following modules: Adaptation, Cells, Charles Darwin I, Charles Darwin II, Charles Darwin III, Data: Uncertainty, Error, and Confidence, DNA I, DNA II, Earth's Atmosphere, Genetics I, Genetics II, Light II, Organic Chemistry, Plate Tectonics I, Research Methods: Description, Research Methods: Experimentation, Research Methods: The Practice of Science, Scientists and the Scientific Community, Taxonomy I, The Carbon Cycle, The Nitrogen Cycle, The Rock Cycle
Osborn, Henry Fairfield American geologist and paleontologist, born in Fairfield, Connecticut (1857-1935). In 1900, Osborne joined the US Geological Survey, and became the senior paleontologist in 1925. He participated in fossil-hunting expeditions to the American Southwest, and described and named several species, including Tyrannosaurus Rex in 1905 and Velociraptor in 1924. In 1918, he founded the Save the Redwoods League. For further information see Henry Fairfield Osborn.
Used in the following modules: Taxonomy II: Nomenclature
Ovule Gamete of a flowering plant, similar to egg cells in mammalian organisms.
Used in the following modules: Genetics I
Oxidation State The effective charge of an atom or element that indicates the extent or possibility of its oxidation.
Used in the following modules: The Nitrogen Cycle
Ozone Layer A layer of higher than average concentrations of ozone within the stratosphere. Within the ozone layer, concentration are still in the range of 8-12 parts per million (ppm); concentrations outside of the ozone layer are around 0.02 ppm.
Used in the following modules: Earth's Atmosphere, Research Methods: The Practice of Science, The Nitrogen Cycle
P-wave A compression wave produced by an earthquake. The “P” is from the Italian “primero,” indicating that the P-waves were the first to arrive at seismic stations.
Used in the following modules: Earth Structure
Paleomagnetic Reversals The history of reversals in polarity of the earth’s magnetic field, as recorded in magnetic minerals within igneous rocks.
Used in the following modules: Plate Tectonics I
Pangaea The supercontinent which existed from about 300-200 million years ago. During this time, all of the continents were gathered into a single land mass.
Used in the following modules: Plate Tectonics I, Plate Tectonics II
Parent the material or source from which something is derived.
Used in the following modules: Adaptation, Charles Darwin III, Chemical Bonding, Genetics I, Genetics II, Nuclear Chemistry
Parsimony The concept that the simplest explanation that fits all of the data is the most likely (and therefore the best) explanation. In different disciplines, the most parsimonious explanation may require the fewest assumptions, the fewest number of steps in a process, or the fewest interacting components in a system. Related to Ockham’s Razor.
Used in the following modules: Data: Analysis and Interpretation
Parsimony, The Principle Of A principle in science and philosophy that suggests that the simplest of two or more compatible theories is generally preferable to explain a phenomenon