## Section Review

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### Vocabulary

astronomical unit light year

### Review Questions

1. The fastest plane can travel at about 4400 kilometers/hour. How long would it take to travel to the Sun? Convert your answer to the number of days and then the number of years. (The time it takes to travel a given distance = (distance travelled)/speed, or in the notation used in the chapter: t = D/v.)
2. Compared to the distances between the planets in the solar system, how far apart are the stars from each other? For this comparison find out how many astronomical units there are between two typical stars (e.g., the Sun and Proxima Centauri). Is the answer closer to 10, 100, 1000, 10000, 100,000, 500,000, or 1,000,000?
3. How far away is the nearest star outside of the solar system in kilometer units and light year units?
4. In a manner similar to how the light year is defined, define a ``car day'' as how far a car will travel in one day (24 hours) moving at a speed of 105 kilometers/hour (= 65 miles/hour). How far would a ``car day'' be in kilometers? How many ''car days'' across is your home state (specify if it is the north-south size or the east-west size)?
5. How many kilometers would a light year be if it was discovered that the speed of light was two times slower than previously thought?
6. Where is our solar system in the Milky Way Galaxy?
7. How old is the Earth compared to the age of the universe?
8. How many times older is the Earth than the first civilizations?

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last updated: 03 May 2001