[noun] The radian is the SI unit for angular measure. One radian is equal to the angle at the center of a circle made by a slice of that circle in which the distance around the circumference is equal to the radius of the circle (one arc length). One complete circle equals 2π radians.

• Appears in modules:

• Wave Mathematics

[noun] Energy emitted as particles, waves, or rays.

• Appears in modules:

• Atomic Theory II
• Atomic Theory III
• Composition of Earth's Atmosphere
• Confidence Intervals
• Creativity in Science
• DNA II
• DNA III
• Ellen Ochoa
• Energy
• Factors that Control Earth's Temperature
• Factors that Control Regional Climate
• France Anne-Dominic Córdova
• Franklin Chang Díaz
• Gene Expression
• History of Earth's Atmosphere II
• Kevin Arrigo
• Light and Electromagnetism
• Luis Walter Alvarez
• Mario Molina
• Nuclear Chemistry
• Origins of Life I
• Uncertainty, Error, and Confidence

[noun - atoms & subatomic particles, chemical reactions] The spontaneous emission of radiation, due to a nuclear reaction or direct emission from an unstable atomic nucleus. Radioactivity takes several different forms, including the emission of alpha particles, electrons, or gamma rays.

• Appears in modules:

• Atomic Theory II
• Cell Division I
• DNA I
• DNA III
• Nuclear Chemistry
• Properties of Minerals
• The Piltdown Hoax

[person - physical & chemical properties, thermodynamics] Scottish chemist born in Glasgow (1852-1916). Ramsay began his career working in organic chemistry. In the 1880s he became more interested in physical chemistry, working mainly in stoichiometry and thermodynamics. In the late 1880s, Ramsay investigated nitrogen oxides and discovered argon, helium, neon, krypton and xenon. He was awarded a Nobel Prize in Chemistry in 1904.

[noun - biomolecules, atoms & subatomic particles, matter, physical & chemical properties, atoms & subatomic particles, matter] The erratic movement of molecules during diffusion as they move from areas of high to low concentration. Molecules do not move in a straight path, instead they have a random path due to their interaction with the medium through which they are moving and from bumping into other molecules and environmental barriers. See also Brownian motion.

• Appears in modules:

• Diffusion I

[noun] The region in a longitudinal wave where the particles are farthest apart.

[noun] The relationship between two or more quantities; relative amounts of two or more values expressed as a proportion.

• Appears in modules:

• Atomic Theory I
• Chemical Bonding
• Chemical Equations
• Composition of Earth's Atmosphere
• Density
• Early Ideas about Matter
• History of Earth's Atmosphere I
• History of Earth's Atmosphere II
• Linear Equations in Science
• Mendel and Independent Assortment
• Mendel and Inheritance
• Percy Lavon Julian
• Population Genetics
• Properties of Solids
• Scientific Notation and Order of Magnitude
• Solutions, Solubility, and Colligative Properties
• Stoichiometry
• The Mole and Atomic Mass
• The Phosphorus Cycle
• Uncertainty, Error, and Confidence
• Unit Conversion
• Wave Mathematics

[person - genetics & inheritance, organisms, taxonomy & systematics] English naturalist, philosopher and theologian, born in Black Notley, Essex (1625-1705). Ray developed a classification scheme for organisms based on physical traits, and was the first to differentiate by monocotyledonous and dicotyledonous plants.

• Appears in modules:

• Taxonomy I
• Taxonomy II

[noun - seismology & plate tectonics, mechanics] A type of seismic wave with a retrograde elliptical motion that travels along the surface of the earth or along a subsurface interface.

[noun - chemical reactions] The initial material that participates in a chemical reaction. Written on the left side of a chemical equation. Compare to product.

• Appears in modules:

• Chemical Equations
• Chemical Reactions
• Early Ideas about Matter
• Photosynthesis I

[noun - chemical reactions] A chemical change when substances come into contact with each other.

• Appears in modules:

• Acids and Bases I
• Acids and Bases II
• Atomic Theory II
• Carbon Chemistry
• Cell Division I
• Cellular Organelles I
• Chemical Equations
• Composition of Earth's Atmosphere
• DNA III
• Early Ideas about Matter
• Energy Metabolism I
• Energy Metabolism II
• Exponential Equations in Science I
• Exponential Equations in Science II
• Franklin Chang Díaz
• Gene Expression
• History of Earth's Atmosphere II
• Lipids
• Mario Molina
• Membranes II
• Modeling in Scientific Research
• Nuclear Chemistry
• Origins of Life I
• Origins of Life II
• Photosynthesis I
• Properties of Minerals
• Scientific Ethics
• Solutions, Solubility, and Colligative Properties
• Stoichiometry
• The Carbon Cycle
• The Mole and Atomic Mass
• The Nitrogen Cycle
• Thermodynamics I

[noun - chemical reactions] Thel reaction rate is the speed with which reactants are converted to products.

[adjective - genetics & inheritance] Designating a genetic trait that is hidden when an organism has inherited two different variations (alleles) of a gene for that specific trait; unexpressed.

• Appears in modules:

• Barbara McClintock
• Gene Expression
• Mendel and Independent Assortment
• Mendel and Inheritance
• Population Genetics

[noun - data, research methods] A written account or description.
[verb] To write an account or description.

• Appears in modules:

• Animal Behavior
• Barbara McClintock
• Biodiversity I
• Cellular Organelles I
• Confidence Intervals
• Craig Lee
• Data Analysis and Interpretation
• Description in Scientific Research
• Discovery and Structure of Cells
• Early Ideas about Matter
• Exponential Equations in Science I
• Franklin Chang Díaz
• History of Earth's Atmosphere II
• Introduction to Paleoanthropology
• Linear Equations in Science
• Mario Molina
• Origins of Plate Tectonic Theory
• Plates, Plate Boundaries, and Driving Forces
• Scientific Controversy
• Scientific Ethics
• Sergio Avila
• Taxonomy I
• The Carbon Cycle
• The Nature of Scientific Knowledge
• The Practice of Science
• Theories, Hypotheses, and Laws
• Uncertainty, Error, and Confidence
• Understanding Scientific Journals and Articles
• Utilizing the Scientific Literature

[verb - human impacts on the environment] To cause to appear again in a new form or function; to adapt to a new use, form, or function.

[noun - forces, stellar and galactic astronomy, forces, modern physics] Occurs when the observed light from an object appears to be of a longer wavelength (redder) than what is actually emitted. Redshift may be caused by the Doppler Effect, when emitting source of light moves away from an observer. Cosmological redshift, by comparison, is caused by the stretching of space in which light rays travel due to the expansion of the universe. See also blueshift.

• Appears in modules:

• The Nature of Scientific Knowledge

[verb - light & optics] To change direction in response to hitting a surface; to bounce off in a different direction.

• Appears in modules:

• Animal Behavior
• Chemical Equations
• Confidence Intervals
• Earth Structure
• Factors that Control Earth's Temperature
• Factors that Control Regional Climate
• Light and Electromagnetism
• Linear Equations in Science
• Photosynthesis I
• Properties of Minerals

[noun - light & optics, mechanics] The change in direction and usually speed of a wave as it crosses a boundary between two different media, for example, a solid and a liquid.

• Appears in modules:

• Light I

[noun - equations] A measurement of the association between a dependent variable and an independent variable usually written as an equation which enable future values of the dependent variable to be predicted.

• Appears in modules:

• Exponential Equations in Science I

[adjective - atoms & subatomic particles, atoms & subatomic particles, modern physics] A particle or condition that is subject to the general theory of relativity because the velocity of the system is a significant portion of the speed of light.

[noun - modern physics, scientific concepts] In science, relativity usually refers to the general theory of relativity, formulated by Albert Einstein in 1915. Einstein's general theory of relativity states that gravity affects both space and time. The gravity of a massive object warps space and time near it, so that the rules of geometry with which we are familiar (such as the interior angles of a triangle always adding up to 180°) are no longer true, and time passes more slowly (a clock near a massive object ticks more slowly than a clock far away from that object).

• Appears in modules:

• Charles Darwin I
• Gravity
• The Nature of Scientific Knowledge
• Theories, Hypotheses, and Laws

[person - cells, scientific concepts] Polish microscopist and doctor (1815-1865) who lived and worked primarily in Berlin, Germany. Under his microscope, Remak discovered that new cells are generated through division of existing cells. Remak made numerous additional contributions to cell theory, but was continuously denied a professorship because of his Jewish religion.

• Appears in modules:

• Creativity in Science
• Discovery and Structure of Cells

[verb - atoms & subatomic particles, compounds, physical & chemical properties] To drive away, to force back, to resist, to ward off.

• Appears in modules:

• Kinetic-Molecular Theory
• Light and Electromagnetism
• Lipids
• Membranes I
• Water

[noun - anatomy & physiology, cells, genetics & inheritance, research methods] In science, quality research studies are designed such that the exact procedures and methods followed by the scientists are clear and can be replicated, allowing other scientists to recreate the investigation under similar conditions to test whether similar results are obtained. For more information, see our module Statistics in Science.

• Appears in modules:

• Cell Division I
• Cell Division II
• Discovery and Structure of Cells
• DNA III
• Meselson and Stahl
• Scientific Ethics
• Scientists and the Scientific Community
• Statistics in Science

[noun - evolution & adaptation] Any separation of a group of individuals from the larger population of the same species, such that members of the separated group can mate only with one another. Consequently, the gene pool is isolated group is isolated from that of the rest of the species. This can occur due to migration, climate change, or other factors.

• Appears in modules:

• Future of Human Evolution

[noun - research methods] A study or an investigation.

• Appears in modules:

• Animal Behavior
• Barbara McClintock
• Bernardo Houssay
• Biodiversity I
• Blood Biology I
• Bone Changes in Rock Climbers
• Carlos J. Finlay
• Cell Division I
• Cell Division II
• Cellular Organelles I
• Charles Darwin I
• Charles Darwin II
• Chemical Bonding
• Comparison in Scientific Research
• Confidence Intervals
• Craig Lee
• Creativity in Science
• Data Analysis and Interpretation
• David Ho
• Description in Scientific Research
• Discovery and Structure of Cells
• DNA I
• DNA II
• DNA III
• Earth Structure
• Ellen Ochoa
• Energy Metabolism I
• Energy Metabolism II
• Experimentation in Scientific Research
• Fabiola León-Velarde
• France Anne-Dominic Córdova
• Franklin Chang Díaz
• Future of Human Evolution
• Gene Expression
• Gravity
• History of Earth's Atmosphere I
• Introduction to Inferential Statistics
• Introduction to Paleoanthropology
• Kevin Arrigo
• Linear Equations in Science
• Lipids
• Louis Tompkins Wright
• Luis E. Miramontes
• Luis Walter Alvarez
• Mario Molina
• Membranes I
• Membranes II
• Mendel and Independent Assortment
• Meselson and Stahl
• Modeling in Scientific Research
• Origins of Life I
• Origins of Life II
• Peer Review in Scientific Publishing
• Percy Lavon Julian
• Plates, Plate Boundaries, and Driving Forces
• Properties of Solids
• Ruth Benerito
• Santiago Ramón y Cajal and Camillo Golgi
• Scientific Controversy
• Scientific Ethics
• Scientific Institutions and Societies
• Scientists and the Scientific Community
• Sergio Avila
• Statistics in Science
• Taxonomy I
• Temperature
• The Case of the Ivory-billed Woodpecker
• The How and Why of Scientific Meetings
• The Nature of Scientific Knowledge
• The Nitrogen Cycle
• The Phosphorus Cycle
• The Piltdown Hoax
• The Practice of Science
• The Process of Science
• The Scientific Method
• Theories, Hypotheses, and Laws
• Thermodynamics I
• Uncertainty, Error, and Confidence
• Understanding Scientific Journals and Articles
• Utilizing the Scientific Literature

[noun - anatomy & physiology, cells, organisms] The physical and chemical processes by which an organism supplies its cells and tissues with the oxygen needed for metabolism and relieves them of the carbon dioxide formed in energy-producing reactions, or any of various energy-yielding oxidative reactions in living matter.

• Appears in modules:

• Cellular Organelles I
• Composition of Earth's Atmosphere
• Energy Metabolism I
• The Carbon Cycle
• Uncertainty, Error, and Confidence
• Y-Chromsome and Mitochondrial DNA Haplotypes

[noun - cells] The voltage, or charge, difference across the cell membrane when the cell is at rest.

[adjective - scientific tools & techniques, research methods] In science, retrospective research refers to the study of events that have already occurred, or data that have already been set or collected. Retrospective studies are common in fields that study historical data or events, for example, paleontology. For more information, see our module Comparison in Scientific Research.

• Appears in modules:

• Comparison in Scientific Research

[person - atmospheric science, weather & climate, data, research methods] 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.

• Appears in modules:

• Modeling in Scientific Research

[adjective - hydrology & fresh water, landforms & geologic formations, bioregions, biomes & ecosystems, natural resources] Related to or located in or adjacent to (near) a river, stream, wetland, or other fresh water body. The areas around the edges of these water bodies, called riparian corridors or zones, are often home to unique plants and animals.

• Appears in modules:

• Sergio Avila

[noun - cells, genetics & inheritance] Ribonucleic acid. A single-stranded nucleic acid containing the sugar ribose. In most organisms, a molecule responsible for transfer of the genetic information encoded in DNA to the manufacture of proteins. In some organisms such as viruses RNA is the primary carrier of genetic information.

• Appears in modules:

• César Milstein
• David Ho
• Discovery and Structure of Cells
• DNA I
• DNA III
• Gene Expression
• The Nitrogen Cycle
• The Phosphorus Cycle

[noun - evolution & adaptation, biodiversity & ecological relationships, bioregions, biomes & ecosystems, organisms] A breeding place or colony of birds or mammals. Rookeries are typically occupied for decades to centuries, or until some outside force causes the animals to move. A rookery may consist of hundreds to thousands of individuals.

[noun - cells] A system of membranes present in most eukaryotic cells that separates the cytoplasm into compartments. In comparison to the smooth endoplasmic reticulum, the rough version is evenly covered with ribosomal granules and specializes in synthesizing and transporting proteins.

• Appears in modules:

• Cellular Organelles I

[noun - landforms & geologic formations] A vehicle used for exploring the surface of the moon or a planet.

• Appears in modules:

• Confidence Intervals
• History of Earth's Atmosphere I
• Properties of Minerals

[organization - research methods, science & decision making, science communication] The longest continuously existing scientific society, established at Cambridge University in 1660. More information about the Royal Society is available on their website.

• Appears in modules:

• Discovery and Structure of Cells
• Experimentation in Scientific Research
• Scientific Institutions and Societies
• Utilizing the Scientific Literature

[person - atoms & subatomic particles, atoms & subatomic particles] New Zealand-English physicist born in Nelson, New Zealand (1871-1937). Rutherford classified radiation into three types: alpha, beta, and gamma ray. In 1903, he experimentally showed that alpha rays could be deflected with both electric and magnetic fields. Rutherford also described and named the half-life, the way in which radioactivity decreases over time. Rutherford was awarded a Nobel Prize in Chemistry for his work in 1908. In 1917, he experimentally discovered the proton, having predicted and named it three years earlier.

• Appears in modules:

• Atomic Theory I
• Atomic Theory II
• Modeling in Scientific Research
• Uncertainty, Error, and Confidence