The Copernican Revolution-BHS-Astro-2017 part 1

Deferent

A construct of the geocentric model, a large circle encircling Earth, on which an epicycle moves.

Ptolemaic Model

A geocentric solar system model developed by Ptolemy. It predicted with great accuracy that positions of the known planets.

Geocentric Model

A model of the solar system that holds the Earth at the center of the universe with all other bodies orbiting around it.

Describe the astronomical contributions of Copernicus.

Copernicus believed in the heliocentric model of the universe. He believed that the Earth spun on an axis, and like all other planets, orbited the sun.

Astronomical Unit

The average distance of Earth from the Sun. (AU)

Retrograde Motion

The backward westward loop traced out by planets in respect to the fixed stars.

Greatest Eastern Elongation

The greatest elongation of an inferior planet in the eastern direction.

Greatest Western elongation

The greatest elongation of an inferior planet in the western direction

Geocentric explanation of retrograde motion of planets

The planets moved along small circles (epicycles) that moved on larger circles (deferent) around the Earth.

Heliocentric explanation of retrograde motion of planets

The planets orbit the Sun at different speeds, retrograde motion is natural and it occurs when the Earth appears to overtake or pass another planet in its orbit. More distant planets move more slowly across the sky than planets that are closer.

Copernican Model

The realization toward the end of the 16th century that Earth is not at the center of the universe.

Synodic Period

The time needed for an orbiting body to complete one revolution about another body.

Quadrature

When a superior planet makes a right angle with the earth and sun.

superior conjunction

When and inferior planet is on the other side of the sun as seen from earth. Elongation is 0 degrees

opposition

When the earth is directly between the sun and a superior planet. Elongation 180 degrees

inferior conjuction

When the inferior planet is between the earth and sun. Elongation is 0 degrees.

Galileo's observations supporting the Heliocentric model.

-The sun has sunspots -Venus has phases. -The moon has mountains, valley's, and craters -Jupiter has moons

Epicycle

A construct of the geocentric model that was necessary to explain observed planetary motions. Each planet rides on a small epicycle whose center, in turn, rides on a larger circle (the deferent).

Heliocentric Model

A model of the solar system that is centered on the sun with Earth orbiting around the Sun.

Inferior Planet

A planet that orbits closer to the Sun than the Earth

Superior Planet

A planet that orbits farther from the Sun than the Earth.

Describe the astronomical contributions of Ptolemy.

Ptolemy created the Ptolemaic model of the universe. The Ptolemaic model was geocentric and the most accurate model of the time. His model of the solar system made sufficiently accurate predictions of planetary positions and remained in use for many centuries