They describe how (1) planets move in elliptical(oval) orbits with the Sun as a focus, (2) a planet covers the same area of space in the same amount of time no matter where it is in its orbit, and (3) a planet's orbital period is proportional to the size of its orbit (its semi-major axis).Aphelion is the greatest distance between a planet or other body and the Sun. Perihelion is the closest distance from the Sun. Objects move slowest in their orbits when they are aphelion and fastest when at perihelion.

Kepler’s first law is that planets move in oval or elliptical orbits with the sun as the focus. All planets move on the oval shape of ellipses. All ellipses have something called eccentricity. Eccentricity is the measurement of how elongated a closed circle is and is measured from the foci(points) to the length of the major axis.every ellipse has two points. One foci is the sun and the other is symmetrically located at the opposite end of the ellipse

Keplers second law states a planet divers the same area of space in the same amount of time no matter where it is in its orbit.

Keplers third and final law states that a planets orbital period is proportional to the size of its orbit.

Astronomy is the study of the universe.

Aristotle was the first to conclude that earth is shaped like a sphere

Aristotle’s evidence is that earth casts a curved shadow on the moon when it passed between the sun and the moon.

Ancient Greeks believed in a geocentric model of the solar system. Geocentric means revolving around the earth. In the geocentric model the moon,sun and known planets revolve around the sun in a perfectly circular orbit.

Aristarchus was the first Greek to propose that the solar system is heliocentric.

The retrograde movement is an apparent westward drift.

Ptolemy created epicycles or smaller circles planets move around the sun when in retrograde.

Copernicus created the first detailed heliocentric model.

Copernicus was also the first to propose: that earth was a planet, earth orbits the sun annually, and earth rotates on a daily basis.