1. Section 9.1 Measuring Distances Beyond the Solar System

2. Scientific Notation Do you know this number, 300,000,000 m/sec.? – It's the Speed of light ! Do you recognize this number, 0.000 000 000 753 kg. ? – This is the mass of a dust particle! Scientists have developed a shorter method to express very large or very small numbers. This method is called scientific notation. Scientific Notation is based on powers of the base number 10. – 3.0 x 10 8 m/s – 7.53 x 10 -10 kg

3. How to Write things in Scientific Notation The number is: 123,000,000,000 Put the decimal after the first digit and drop the zeroes. So the coefficient will be 1.23 To find the exponent count the number of places from the decimal to the end of the number. In 123,000,000,000 there are 11 places. Therefore we write 123,000,000,000 as:

4. Some More Examples 46600000 0.00053 0.00044 5,720,000,000

5. 1 AU – 1.5 x 10 11 m (used to measure planetary distances) The light year is the distance that light travels (in a vacuum) in 1 year (365.25 days) – Light travels 3.0 x 10 8 m/s – Light year= 9.46 x 10 15 m (or 9.46 x 10 12 km) The Light Year

6. ly Examples If Proxima Centauri is 4.3 ly from Earth what is its distance in km? If the Andromeda Galaxy is approximately 2.46 x 10 19 km from Earth. How many light years is this?

7. Today’s Tasks ProbeDistance from Earth (Dec. 5, 2010) Check your Answers! New Horizons (heading to Pluto) 19.42 AU3.08 x 10 -4 ly Voyager 2 (to Jupiter & Saturn)94.6 AU1.5 x 10 -3 ly (0.0015) Cassini (around Saturn)1.5 x 10 9 km1.58 x 10 -4 ly Dawn (orbiting 2 asteroids)3.04 AU4.8 x 10 -5 ly Stardust-NExT3.3 x 10 8 km3.5 x 10 -5 ly All information from: http://www.jpl.nasa.gov/missions/index.cfm?type=Currenthttp://www.jpl.nasa.gov/missions/index.cfm?type=Current 1.Convert all distances in light years from Earth. 2.The Sun is 1.0 AU from Earth, calculate this distance in light years. (1.6 x 10 -5 ly) (1 AU = 1.5 x 10 11 m or 1.5 x 10 8 km) Page. 369 #2, 3, 6, 7, 8, 11