Visionlearning Glossary

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

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

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

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

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

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, DNA III, Earth Structure, Earth's Atmosphere, Energy, Fats and Proteins, Ideas in Science: Theories, Hypotheses, and Laws, Matter: States of Matter, Minerals I, Minerals III, Nuclear Chemistry, Scientific Ethics, Temperature, The Carbon Cycle, The Hydrologic Cycle, The Rock Cycle

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

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

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

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.

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

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.

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 Hipparchus.

Used in the following modules: Research Methods: Description, Wave Mathematics

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

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.

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

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.

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

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: Ideas in Science: Theories, Hypotheses, and Laws, The Rock Cycle

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

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

An organic compound that contains only hydrogen and carbon.

Used in the following modules: Organic Chemistry

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, DNA III, Matter: States of Matter, Minerals II, Water

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.

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

An -OH group within a molecule.

Used in the following modules: Organic Chemistry

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, DNA III, Genetics I, Genetics II, Ideas in Science: Theories, Hypotheses, and Laws, 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