Visionlearning Glossary

A “ripple” wave produced by an earthquake. The “S” is from the Italian “Segundo,” indicating that S-waves arrived at seismic stations after the P-waves.

Used in the following modules: Earth Structure

American astronomer and astrochemist, born in Brooklyn, New York (1934-1996). Sagan was a pioneer in astrobiology, and championed the Search for Extra-Terrestrial Intelligence (SETI). He was also a prolific researcher: he was key in the determination of Venus’s high surface temperature, he was an early proponent of oceans on Titan and Europa, and studied planetary atmospheres. He is best remembered for hosting a TV series Cosmos, and for writing a widely popular companion book by the same name. For further information see Carl Sagan.

Used in the following modules: Scientific Communication: Peer Review

Generally, any ionic compound except those that contain hydroxide or hydrogen ions. Specifically, any compound other than water formed by the reaction of an acid and a base. In common usage, the term salt, or table salt, refers to the ionic compound sodium chloride, NaCl.

Used in the following modules: Acids and Bases, Minerals I, Scientific Communication: Peer Review, Water

German botanist born in Hamburg (1804-1881). Schleiden determined the importance of the nucleus in cellular propagation and, with Theodor Schwann, is credited with establishing the foundations of the cell theory. For further information, see Matthias Jacob Schleiden.

Used in the following modules: Cells

German physiologist and histologist born in Neuss, Germany (1810-1882). Schwann cofounded (with Matthias Schleiden) the cell theory. He elaborated on Schleiden’s work and showed that cells are the basis of both plant and animal tissue. He also demonstrated that yeast is an organism, and published Microscopical Researches in the Structure and Growth of Animals and Plants (1839, translation 1847). For further information see Theodor Schwann.

A term first coined by Alexandre Koyré in 1939, it refers to the period remarkable of scientific advances roughly extending from the publication of De Revolutionibus Orbium Coelestium by Nicolaus Copernicus in 1543 to the death of Isaac Newton in 1727. For more information, see: The Practice of Science

Used in the following modules: Research Methods: The Practice of Science, Scientific Institutions and Societies, The Rock Cycle

The mechanism proposed by Harry Hess which drives plate tectonics. According to this theory, new magma is formed at divergent boundaries, pushing plates away from each other as if on a conveyor belt.

Used in the following modules: Plate Tectonics I, Plate Tectonics II, The Carbon Cycle

An extinct volcano which has been eroded by ocean waves, resulting in a flat-topped feature just beneath the surface of the ocean. 

Used in the following modules: Plate Tectonics II

Loose, unconsolidated material of the following compositions: 1. Rock fragments (also called clasts) transported by wind, moving water, or moving ice, such as sand 2. Chemical precipitates from solution, such as salt 3. Organic secretions or accumulation, such as coal

Used in the following modules: Minerals I, Research Methods: Comparison, Research Methods: Modeling, Scientific Communication: Utilizing the Scientific Literature, The Carbon Cycle, The Hydrologic Cycle, The Nitrogen Cycle, The Rock Cycle

Formed from the deposition or precipitation of sediments. Sedimentary rocks consist of sediments that have been compacted and cemented together.

Used in the following modules: Minerals III, Research Methods: Comparison, Research Methods: Description, Research Methods: Modeling, Scientific Communication: Utilizing the Scientific Literature, The Rock Cycle

A form of sound waves that travel away from the source of an earthquake. There are several types of seismic waves, but S-waves and P-waves are the most commonly measured and recognized.

Used in the following modules: Earth Structure

A scientist who studies earthquakes and the behavior of seismic waves in the earth.

Used in the following modules: Data: Statistics, Earth Structure

A mineral formed from hydrothermal metamorphism of basalt. The rock “serpentinite” is composed entirely of serpentine, and is very common in Northern California, and it weathers to create a nutrient-poor, heavy metal-rich soil.

Used in the following modules: The Nitrogen Cycle

Although it is commonly called a "volcanic neck," Shiprock (located near the Four Corners of Utah, Colorado, Arizona, and New Mexico) is a remnant of a single explosive volcanic eruption rather than a long-lived volcano. The magma involved in the eruption started more than 100 km below the earth's surface, in the mantle. For more information, see this link

Used in the following modules: Earth Structure

Le Systéme Internationale (SI) is a system of standard units introduced to remove barriers to international trade, based on the older metric system.

Used in the following modules: Temperature, The Metric System

In statistics, a skewed distribution is one that exhibits asymmetry in the probability distribution of a random variable. Large differences in the mean compared to the median of a dataset can indicate a skewed distribution of data values. Compare the graph at left below to the normal distribution graph at right.

Danish medical doctor born in Lemvig, Denmark (1918-). Skou’s early work in local anesthetics led him to investigate the sodium-potassium pump. In 1997, Skou was awarded a Nobel Prize for his work on cation transport across cell membranes. For more information see Jens Christian Skou.

Used in the following modules: Absorption, Distribution and Storage of Chemicals

A photochemical haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen.

Used in the following modules: The Nitrogen Cycle

British physicist born in Eastbourne, Sussex (1877-1956). He studied radioactivity with Ernest Rutherford, jointly concluding that radioactivity consisted of atomic disintegration (of parent atoms) and the formation of new kinds of matter (daughter products). Soddy articulated the Displacement Law, which states that an element which emits an alpha particle moves two places back on the Periodic Table. He also came up with the concept of isotopes. In 1921, he was awarded the Nobel Prize in Chemistry. For further information see Frederick Soddy.

Used in the following modules: Nuclear Chemistry

A celestial event occurring when the Moon passes between the Sun and the Earth such that the Sun is wholly or partially obscured. At least two and up to five solar eclipses occur each year on Earth, with between zero and two of them being total eclipses.

Used in the following modules: Research Methods: Description

A mixture of more than one substance with properties that do not vary within the sample. Commonly used to describe a solid dissolved in a liquid, solutions of two or more gases, liquids, solid metals or other materials also exist. Also called a homogeneous mixture.

Used in the following modules: Acids and Bases, Chemical Bonding, Taxonomy II: Nomenclature, Water

The most abundant component in a homogeneous mixture of two or more substances.

Used in the following modules: Chemical Bonding, Water

Italian microscopist and biologist, born in Scandiano (1729-1799). He investigated spontaneous generation of microorganisms in broth and herbal infusions. Spallanzani also studied the circulatory system, pioneered artificial insemination, and proposed that bats navigate by echolocation. For further information, see Lazzaro Spallanzani.

Used in the following modules: Research Methods: Experimentation

The inquisition, initiated in 1478 by King Ferdinand and Queen Isabella, which protected the orthodoxy of Catholicism in Spain.

1. In biological classifications, it is the lowest and most basic unit of the Linnaean taxonomic hierarchy (although it is also divisible into subspecies), and one of the two required titles of a binomial name. In nature, a species is a group of organisms that breed only amongst themselves and produce offspring that are also capable of reproducing. 2. In chemistry, a group of constituents or molecules, that share major chemical similarities. For example, Hg⁰ and Hg⁺², or CO and CO₂.

Used in the following modules: Adaptation, Charles Darwin I, Charles Darwin II, Charles Darwin III, Data: Using Graphs and Visual Data, DNA II, Genetics I, Genetics II, Scientific Communication: Utilizing the Scientific Literature, Scientific Ethics, Scientists and the Scientific Community, Taxonomy I, Taxonomy II: Nomenclature, The Carbon Cycle, The Nitrogen Cycle

An instrument that measures the intensity of radiation, including light, as a function of its wavelength. Because different substances, including elements and compounds, both absorb and emit specific wavelengths of radiation, spectrometers can be used to measure the composition of distant stars and planets, as well as the composition of various samples on earth including soil, water, minerals and gases.

Used in the following modules: Earth's Atmosphere, Minerals I, Minerals II, Research Methods: Description

The study of the interaction of radiation (electromagnetic or particle radiation) and matter. An analytical technology used for the identification of substances based on the spectrum of radiation absorbed or emitted by different substances. For further information see: Spectroscopy

Used in the following modules: Scientists and the Scientific Community

A process that occurs without external influence or excitement. For example, the rusting of metal is a spontaneous process because no force is required to start the process.

Used in the following modules: Chemical Reactions, Research Methods: Experimentation, Research Methods: The Practice of Science

The standard deviation (σ) is a measure of the variability of values in a dataset. Standard deviation is one of the most common measure of statistical dispersion. If many data points are close to the mean of the dataset, the standard deviation is small; if many data points are far from the mean, then the standard deviation is large.

Used in the following modules: Data: Statistics, Data: Uncertainty, Error, and Confidence, Data: Using Graphs and Visual Data

Also called random error, statistical error refers to the inherent variability of a measurement. Statistical error is caused by random fluctuations or natural variability within a system or of a measurement, and describes the precision of measurement. Compare to systematic error. See the module Uncertainty.

Used in the following modules: Data: Uncertainty, Error, and Confidence

Statistical significance provides a measure of the statistical probability for a result to have occurred, and quantifies the likelihood that a result occurred by chance. Statistical significance does not define whether a difference or relationship is large or small, nor does it speak to the practical significance of an occurrence. The significance level (α) is reported as a percentage (10%, 5%, 1% …), where the lower the level, the higher the probability that an occurrence was not due to chance. For more information, see: Data: Statistics

Used in the following modules: Data: Statistics, Research Methods: Comparison

Danish geologist and anatomist, born in Copenhagen (1638-1686). He was deeply interested in mineralogy, formulating the Law of Interfacial Angles. Steno was also appointed the Royal Anatomist for Denmark. For further information, see Nicolaus Steno.

The layer of the atmosphere above the troposphere, where temperature increases with altitude because of the presence of the ozone
layer. Only the highest clouds are within the stratosphere, but there is very little wind.

Used in the following modules: Earth's Atmosphere, Research Methods: The Practice of Science

The process by which one tectonic plate moves beneath another.

Used in the following modules: Plate Tectonics I, Plate Tectonics II, The Carbon Cycle, The Rock Cycle

A region where one plate is being subducted beneath another, manifesting in a deep, linear trench, frequent earthquakes, and a chain of volcanoes. The western coast of South America is a subduction zone, as are the Marianas, the Phillippines, and the Aleutian Islands.

Used in the following modules: Plate Tectonics I, Plate Tectonics II

a very fast, powerful mainframe computer, used in advanced military and scientific applications.

Used in the following modules: Research Methods: Modeling

The name of the fund established by the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980, which was enacted in the wake of the discovery of toxic waste dumps such as Love Canal and Times Beach in the 1970s. The fund is overseen by the U.S. Environmental Protection Agency (EPA) to clean up toxic waste sites and to compel responsible parties to perform cleanups or reimburse the government for sites remediated by EPA.

The cohesive force exerted at the surface of a liquid that makes it tend to assume a spherical shape. Surface tension is related to the interactive forces between molecules of a liquid, and is caused by the fact that molecules at the surface are not surrounded by molecules on all sides and consequently they interact more strongly with those directly adjacent to them on the surface.

Used in the following modules: Water

The intimate living together of two dissimilar organisms in a mutually beneficial relationship.

Used in the following modules: The Nitrogen Cycle

A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for a given problem: in modeling, a system may be defined as the entire earth or a single organism.

Used in the following modules: Absorption, Distribution and Storage of Chemicals, Adaptation, Atomic Theory I, Authoring Modules I, Authoring Modules II, Carbohydrates, Charles Darwin I, Chemical Bonding, Data: Analysis and Interpretation, Data: Statistics, Data: Uncertainty, Error, and Confidence, Data: Using Graphs and Visual Data, DNA I, Energy, Fats and Proteins, Genetics I, Gravity, Matter, Matter: States of Matter, Minerals I, Minerals II, Plate Tectonics I, Research Methods: Comparison, Research Methods: Description, Research Methods: Experimentation, Research Methods: Modeling, Research Methods: The Practice of Science, Scientific Communication: Peer Review, Scientific Ethics, Taxonomy I, Taxonomy II: Nomenclature, Teaching Effectively with Multimedia, Temperature, The Hydrologic Cycle, The Metric System, The Mole, The Nitrogen Cycle, Using History and Biographies in Science, Using MyClassroom for Students, Using MyClassroom for Teachers, Visionlearning, Visionlearning and the National Science Education Standards, Visionlearning Teaching Modules, Wave Mathematics

Systematic error describes a bias or uncertainty in a measurement introduced by an instrumental, human, or environmental variable. Systematic error is due to an unknown, but non-random fluctuation; however, if the source of a systematic error can be identified, it can often be eliminated or controlled. Systematic error affects the accuracy of a measurement. Compare to statistical error. See the module Uncertainty.

Used in the following modules: Data: Statistics, Data: Uncertainty, Error, and Confidence