Science Dictionary

Day, in astronomy, the average length of time between successive noons. Noon is defined as the instant when the sun is highest in the sky.

Double Star, a pair of closely-spaced stars that to the unaided eye usually appear as a single star.

Hourglass, a device for measuring time. In its usual form it consists of two cone-shaped or oval glass receptacles joined by a narrow neck.

Magnitude, in astronomy, a unit of measurement of the brightness of stars. The scale of magnitude extends from negative numbers (for example, the minus first magnitude) for very bright stars to positive numbers (for example, the fourth magnitude) for dimmer ones.

Midnight Sun, a name given the sun when it can be seen at midnight during the Arctic or Antarctic summer.

The nebular theory, also known as nebular hypothesis, presents one explanation of how the solar system was formed, proposed by Pierre Simon de Laplace in 1796.

By Yara Simón

Nova, (plural: Novae), a star that rapidly increases in brightness and then fades again.

Perihelion and Aphelion, The perihelion is the point on the orbit of a planet or comet that is closest to the sun.

Perturbation, in astronomy, is a disturbance in the orbit or motion of a heavenly body.

Planetarium, is an educational device for showing the locations and movements of the planets and other objects in the universe.

Planetesimal hypothesis is a theory of the origin of the solar system. It was proposed by Forrest R.

Solar wind is a continuous stream of mostly hydrogen and helium that flows outward from the sun in all directions. It does everything from disrupt GPS signals to create the aurora borealis.

By Mark Mancini

Twilight is the light diffused over the sky from sunset to darkness and from darkness to sunrise.

Van Allen Radiation Belts, two zones encircling the earth in which there are relatively large numbers of high-energy (fast-moving) charged particles.

By Yara Simón

He may have been born in Brooklyn, but Carl Sagan was gunning for the stars as soon as he arrived in this world. Get to know the scientist whose infectious delight in the universe still holds us spellbound.

By Marianne Spoon

Is this famous primatologist atheist, agnostic or theistic? Find out as we bravely explore whether science and religion must always collide.

By Marianne Spoon

Bessey, Charles Edwin (1845-1915), an American botanist and administrator, developed world-class botanical programs in the United States.

Just, Ernest Everett (1883-1941) was an internationally known American biologist, zoologist, and physiologist who made major contributions to the field of biology through his pioneering research into fertilization, experimental parthenogenesis, and cell physiology.

Rowley, Janet (1925-) is an American geneticist, a scientist who investigates the structure, function, and transmission of genes.

Margulis, Lynn Alexander (1938-), an American biologist, helped advance the study of the origins of cells.

Meyerhof, Otto Fritz (1884-1951), a German-born American biochemist, shared the 1922 Nobel Prize in physiology or medicine for his research into oxygen consumption by muscles, and the relationship of oxygen consumption and the metabolism of lactic acid (a chemical produced in the body by muscular activity) and carbohydrates within the muscle.

Berg, Paul (1926-), an American biochemist and molecular biologist, has been at the forefront of genetic engineering, both as an inventor of a pioneering procedure and as an advocate concerned about the risks of genetic research.

Hubbard, Ruth (1924-) is an Austrian-born American biologist and biochemist whose contributions to the study of the biochemistry and photochemistry of vision in vertebrates and invertebrates have greatly advanced the understanding of the field.

Benzer, Seymour (1921-), an American geneticist, is one of the founders of modern behavioral geneties.

Modern science allows us to break atoms down into tiny components. But can scientists use their mighty machines to recreate the foundation of the universe?

By Jonathan Strickland