antimatter—a substance identical to ordinary matter except that the electrical charges of particles are opposite. I.e., an antiproton has a negative charge whereas a proton is positive.

astronomy—the branch of science that deals with celestial objects, space, and the physical universe as a whole.

astrophysics—the branch of astronomy concerned with the physical nature of stars and other celestial bodies, and the application of the laws and theories of physics to the interpretation of astronomical observations.

baryon—a class of particles that are composed of exactly three quarks. Baryons participate in strong nuclear force interactions and include such particles as protons and neutrons.

baryon number problem—the fact that the universe is matter-dominated, rather than having an equal amount of antimatter as would be expected if the big bang were true.

bias—prejudice in favor of or against one thing, person, or group compared with another, usually in a way considered to be unfair.

biblical creation—the origin of the universe, earth, and life according to a straightforward reading of the book of Genesis.

big bang—secular theory of the origin of the universe which proposes that all mass, energy, and space were contained in a point which rapidly expanded to become stars and galaxies over billions of years.

cosmic microwave background (CMB)—an invisible source of electromagnetic radiation (microwaves) which seems to be coming from all directions in space. Big bang supporters interpret the CMB as radiation left over from the big bang.

differential rotation—the condition in which different parts of an object rotate at different speeds; one example would be a spiral galaxy whose inner regions rotate faster than its outer regions.

dipole—a pair of equal and oppositely charged or magnetized poles separated by a distance.

doppler effect—an increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move toward (or away from) each other.

electromagnetic radiation—a kind of radiation including visible light, radio waves, gamma rays, and X-rays, in which electric and magnetic fields vary simultaneously.

epicycles—a small circle whose center moves around the circumference of a larger one.

extra-solar planet—An extrasolar planet (or exoplanet) is a planet which orbits a star other than the Sun, and therefore belongs to a planetary system other than our solar system.

fusion—a nuclear reaction in which the nuclei of atoms combine to form more massive nuclei which releases energy in the process.

galaxy—a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction.

general relativity—a theory of gravitation developed by Albert Einstein in which gravity is described as a geometrical curvature in space and time. One prediction of this theory is that gravitational fields slow the passage of time—a phenomenon that has been verified using atomic clocks.

geocentrism—having or representing the earth as the center, as in former astronomical systems.

heliocentrism—is the theory that the Sun is at the center of the Universe and/or the Solar System.

inflation—a variation of the big bang theory in which the universe experiences an accelerated phase of expansion shortly after the big bang.

Local Group—the cluster of a few dozen galaxies of which our galaxy is a member.

magnetic field—a region around a magnetic material or a moving electric charge within which the force of magnetism acts.

materialism—the philosophy that all that exists is material.

Milky Way—a faint band of light crossing the sky, made up of vast numbers of faint stars. It corresponds to the plane of our Galaxy, in which most of its stars are located in the galaxy in which our sun is located.

naturalism—a philosophical viewpoint according to which everything arises from natural properties and causes, and supernatural or spiritual explanations are excluded or discounted.

plasma—an ionized gas consisting of positive ions and free electrons in proportions resulting in more or less no overall electric charge, typically at low pressures (as in the upper atmosphere and in fluorescent lamps) or at very high temperatures (as in stars and nuclear fusion reactors).

presupposition—a thing tacitly assumed beforehand at the beginning of a line of argument or course of action.

Ptolemy—Greek astronomer and geographer of the 2nd century A.D.

Pythagoras—c. 580–500 B.C., Greek philosopher; known as Pythagoras of Samos. Pythagoras sought to interpret the entire physical world in terms of numbers and founded their systematic and mystical study. He is best known for the theorem of the right-angled triangle.

redshift—the displacement of spectral lines toward longer wavelengths (the red end of the spectrum) in radiation from distant galaxies and celestial objects.

remanent magnetism—the magnetization left behind in a medium after an external magnetic field is removed.

singularity—the initial condition in the big bang theory in which the entire universe (including space, time and mass) is contained in an infinitesimal volume.

terminator—the dividing line between the light and dark part of a planetary body.

uniformitarianism—the theory that changes in the earth’s crust during geological history have resulted from the action of continuous and uniform processes. Often contrasted with catastrophism.

Virgo Cluster—the massive cluster of about 2000 galaxies that lies in the constellation Virgo

worldview—a particular philosophy of life or conception of the world: the Christian worldview is based on the Bible.

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