Unit 1 Universe, Models, and Solar System

astronomy

Study of everything in the universe beyond Earth's atmospheres

Big Bang Theory

Hypothesis that all matter and energy were at one time compressed into a very small volume; then there was a rapid expansion that sent everything moving outward, causing the universe to expand.

evidence

Evidence that serves to either support or counter a scientific theory or hypothesis.

galaxy

A very large group of stars held together by gravity; few million to a few billion stars.

geocentric

Model used by the ancient Greeks that puts the Earth at the center of the universe.

heliocentric

Model proposed by Copernicus that put the Sun at the center of the universe.

law

A summary of many experimental results and observations; a law tells how things work.

Milky Way Galaxy

The spiral galaxy in which Earth and our solar system reside.

orbit

To travel in a circular or elliptical path around another object.

revolution

The Earth's movement around the Sun in an orbital path.

rotation

The motion of the Earth spinning on its axis.

solar system (planetary system)

The Sun and all the objects that revolve around the Sun as a result of gravity.

technology

Use of knowledge to invent new devices or tools. Throughout history, technology has made people's lives easier.

telescope

An instrument that allows people to see distant objects.

theory

A hypothesis that has been repeatedly tested that has no significant evidence against it.

universe

Everything that exists; all matter and energy; also includes all of space and time.