Heliocentric vs Geocentric Models

Front

A model of the universe where Earth is at the center. Earth-centered, historical model, replaced by heliocentric model. What is this model called?

Back

Geocentric

Front

A model of the universe where the sun is at the center. Sun-centered, modern model, replaced geocentric model. What is this model called?

Back

Heliocentric

Front

The action of moving around something in a path that takes a full circle. Involves a complete orbit. Takes place in a regular cycle. What is this called?

Back

Revolution

Front

Shaped like an oval or a flattened circle. In astronomy, planets’ orbits are this shape, not perfect circles. Related to planetary motion. Describes the shape of orbits. Different from a perfect circle. What is this term?

Back

Elliptical

Front

The curved paths that celestial objects follow as they move around larger objects due to gravity. Elliptical or circular paths. Governed by gravitational forces. What is this called?

Back

Orbit

Front

A well-supported explanation of a natural phenomenon based on a body of evidence. Based on repeated testing. Broad in scope. Predictive power. What is this called?

Back

Theory

Front

In the geocentric model, this is a small circular path that a planet follows while also moving along a larger circular orbit around Earth. Related to the geocentric model. Explains the apparent 'looping' or retrograde motion of planets. Part of Ptolemy’s explanation of planetary motion. What is this called?

Back

Epicycle

Front

The apparent backward motion of a planet when observed from Earth, caused by differences in orbital speeds. Observable phenomenon. Caused by Earth overtaking other planets in orbit. Led to confusion in the geocentric model. What is this called?

Back

Retrograde

Front

The change in light waves to longer wavelengths as objects in space move away from the observer. Evidence for expanding universe. Related to Doppler effect

Back

Redshift