Nj

Ptolemaic system

A model proposed by Ptolemy where planets move in small circles (epicycles) while orbiting Earth.

Geocentric model

The cosmological model proposed by Aristotle which states that Earth is at the center of the universe with concentric spheres carrying the planets and stars.

Phases of Venus

Evidence observed by Galileo that supports the heliocentric model proposed by Copernicus.

Elliptical orbits

The type of orbits proposed by Johannes Kepler, which indicates that planets move in ellipses rather than circles.

Kepler’s laws of planetary motion

A set of laws formulated by Johannes Kepler that describe the motion of planets around the Sun, including that they move in elliptical orbits.

Geo-heliocentric model

A cosmological model proposed by Tycho Brahe where planets orbit the Sun, but the Sun orbits the Earth.