| A | B |
|---|
| geocentric | Earth is at the center of the universe |
| heliocentric | the sun is at the center of the universe |
| blue shift | a shift in wavelength when object is moving towards you |
| red shift | a shift in wavelength when object is moving away from you |
| universe | all space matter, all energy |
| lunar eclipse | when the Earth is between the sun and the moon, moon is coppery red |
| solar eclipse | when the moon is between the Sun and the Earth blocking the view of the Sun |
| ellipse | shape of the Earth's orbit not a perfect circle |
| light year | the distance light travels in one year |
| luminosity | the brightness of stars compared to brightness of Sun |
| eccentricity | measurement of how close to a perfect circle an orbit is |
