Module 2. Vocab Review

Orbit that does not stay in a specific region of space, but where an object escapes the gravitational field of another.

______________ motion is the backward, westward loop traced out by a planet with respect to the fixed stars.

Small shift in the observed direction to a star, caused by Earth’s motion perpendicular to the line of sight.

One-half of the major axis of an ellipse and is the way in which the size of an ellipse is usually quantified.

The time needed for an orbiting body to complete one revolution about another body is known as a period.

The basic motion laws explaining all of the complex dynamical behavior found on Earth and elsewhere in the universe.

A large circle within the geocentric model necessary to explain observed planetary motions that smaller ones ride on.

Focus is one of two special points within an ellipse, whose separation from each other indicates the eccentricity.

A model of the solar system that is centered on the Sun, with Earth in motion about the Sun.

The speed necessary for one object to escape the gravitational pull of another.

This model was developed in the 2nd century that predicted with great accuracy the positions of the then known planets.

The center of mass is the “average” position in space of a collection of massive bodies, weighted by their masses.

A model of the solar system where Earth is at the center of the universe and all other bodies are in orbit around it.

Three laws derived by Kepler describing the motion of the planets around the Sun.

Force exerted on one body by another due to the effect of gravity.

A measure of the flatness of an ellipse equal to the distance between two foci divided by the length of the major axis.

A small circle within the geocentric model necessary to explain observed planetary motions that rides on a larger one.

An ellipse is an geometric figure resembling an elongated circle.

The realization that Earth is not at the center of the universe from the 16th Century is called:

The attractive effect that any massive object has on all other massive objects.