Definitions

Rotation-one of the most basic motions of Earth (spin) Orbit-yearly revolution around the sun -rotates from west to east Astronomical unit-Earth?s average orbital distance, equivalent to 150 million kilometers Ecliptic Plane-Earth?s orbital path that defines a flat plane Axis tilt-happens to be orientated so that it points almost directly to Polaris Edin Hubble said: Virtually every galaxy outside the Local Group is moving away from us The more distant the galaxy, the faster it appears to be racing away Circumpolar-stars that never rise or set but make daily counterclockwise circles around the north celestial pole Summer solstice-around June 21st, each year is the moment when the northern hemisphere receives its most direct sunlight Winter Solstice- occurs around Dec.21st, is the moment when the northern hemisphere receives its least direct sunlight Spring Equinox-occurs around March 21st, at the moment when the northern hemisphere goes from being tipped slightly away from the sun to being tipped slightly towards the sun Fall Equinox-occurs around Sept.22nd, and marks the opposite change when the northern hemisphere first starts to be tipped away from the sun -equinoxes occur on the only 2 days of the year on which the sun rises precisely due east and sets precisely due west Precession-a gradual wobble that changes the orientation of Earth?s axis in space Lunar phases-both the moon?s appearance and time which it rises and sets changes with the cycles Lunar eclipse-occurs when the Earth lies directly between the sun and the moon so that Earth?s shadow falls on the moon Solar eclipse-occurs when the Moon lies directly between the Sun and Earth, so that the moon?s shadow falls on Earth Nodes-the two points in which each orbit at which the moon crosses the surface of the moon?s orbit