1. Measuring Distances in Space The Light-Year (ly)

2. Light-year (ly) distance light travels in one year

3. Reminders... Light travels in a straight line. The speed of light is 300,000 km/s The Sun is 150 million km away –by car @ 100 kph, 165 years to the Sun –by 747 @ 600 kph, 27.3 years to the Sun –by shuttle @ 28,000 kph, 215 days to the Sun –by Apollo @ 53,000 kph, 113 days to the Sun –by light speed, it would take 8 minutes to the Sun

4. Next Closest Star Proxima Centauri 4.3 ly away If it went supernova today (it won’t)… –You would see it at graduation * Takes light 4.3 years to get here!

5. The Milky Way Our galaxy… ~ 7,000 ly thick ~ 100,000 ly diameter Light takes 100,000 years to travel from one side to the other Earth about 26,000 ly from the core

6. Your Turn… Just how far does light travel in 1 year? Your group will need paper & pencil (you may use a calculator) With your team, calculate the distance to Proxima Centauri, 4.3 ly away…raise your hand when you think you are done and I will check it. HINT: need to use Speed of light and time

7. distance light travels in 1 s300,000 km/s x 60 s in 1 minx 60 s/min 18,000,000 km/min x 60 min in 1 hrx 60 min/hr 1,080,000,000 km/hr x 24 hr in 1 dayx 24 hr/day 25,920,000,000 km/day x 365.25 days in 1 yearx 365.25 days/yr 9,467,280,000,000 km/yr=1 ly x 4.3 ly to Earth from PCx 4.3 ly distance to Proxima Centuari40,709,304,000,000 km

8. Hubble Deep Field Academy: Distance Wizard… Distance Wizard 1.Explain why you arranged the objects as you did. Be sure to mention any particular trait upon which you based your decision. 2.Explain how the object labeled “F” can be smaller, yet closer, than the object labeled “C.” 3.How is your explanation regarding estimating distances in space similar/different than the astronomers’ explanation?