1. Light Year A unit of distance in astronomy; distance that light travels in one year or about 5.88 trillion miles (9.46 trillion kilometers)

2. Galaxy Any of the very large groups of stars and matter that are found throughout the universe

3. Big Bang Theory Theory that states that the universe originated billions of years ago in an explosion from a single point of nearly infinite energy density

4. Magnitude A star’s brightness.

5. Nebula A cloud of dust and gas in space.

6. Main Sequence Contains most of the stars visible to the naked eye; stars where there is a direct relationship between brightness and size, includes our Sun

7. H-R Diagram A chart that plots the data of stars according to their surface temperature and brightness.

8. Doppler Effect Change in the frequency of a wave due to motion of the source.

9. Visible Light Electromagne tic radiation that can been seen with the unaided eye

10. Frequency The number of complete waves that pass a given point in a certain amount of time

11. Wavelength The distance between the crest of one wave and the crest of the next

12. Amplitude The maximum distance the particles of a medium move away from the rest positions as wave passes through the medium

13. Electromagnetic Wave A transverse wave that transfers electric and magnetic energy

14. Spring Tide Large rise and fall of the tide at or near the full moon.

15. Neap Tide Occurs during first and third quarter moon. Little change between high and low tide.