These practice calculations should be completed by 9:00 PM on Thursday February 7, 2008. Given below are three useful conversion factors.

1 LY = 63,240 AU
1 AU = 9.29 x 10⁷ miles = 1.50 x 10⁸ km
1 LY = 5.88 x 10¹² miles = 9.46 x 10¹² km

1. How long does it take a beam of light to reach the Earth from Mars, a distance of about 35,000,000 miles (56,000,000 km) at its closest?

2. How many years would a car moving at 60 miles/hour (100 km / hour) need to cover the above distance?

3. If a radar beam, moving at the speed of light, needs 12 seconds to go from the Earth to a comet and back, then how far away is the comet?

4. M33, alias the Triangulum Galaxy, is about 2,400,000 light years away. (a) How many AU away is M33? (b) How many miles away is M33?

5. Sirius, the brightest night-time star, is 8.58 light years from the Earth. (a) How many AU from the Earth is Sirius? (b) How many years would a beam of red laser light need to reach Sirius?

If you would like credit for your efforts, e-mail your answers, showing and explaining your work, to hudsonrl@eckerd.edu by 9:00 PM on Thursday February 7, 2008.