There are various methods that scientists use to measure distances in space. Using miles or kilometers would require using such large numbers that we would not be able to understand it. The astronomical unit (AU) and the light year (l.y.) are very useful methods. Click on the links to learn what each of these means.

Let’s examine how long it would take to get to other areas of our universe.

• Pluto (our farthest planet) = 327 light minutes (0.000624 light years)
• Alpha Centauri (our next closest star) = 4.35 light years away
• Andromeda (our neighboring galaxy) = 2,000,000 light years away

 Planet / Star Light Years Mercury 0.000006 (3 light minutes) Venus 0.000011 (6 light minutes) Earth 0.000016 (8 light minutes) Mars 0.000024 (12.5 light minutes) Jupiter 0.000082 (43 light minutes) Saturn 0.000151 (79 light minutes) Uranus 0.000304 (160 light minutes) Neptune 0.000476 (250 light minutes) Pluto 0.000624 (327 light minutes) Alpha Centauri (nearest star other than Sun) 4.35 light years

Analysis:

Use the chart above to answer the following questions:

1. What is the difference in light years between Pluto and Earth?
2. Which planets would you pass if you traveled for 45 light minutes from the sun?
3. How does the distance between the inner planets compare with the distance between the outer planets?
4. About how many trips could you make to Earth in the time it would take you to travel to Jupiter?

 319 Minutes Mercury, Venus, Earth, Mars,and Jupiter The inner planets are closer together 5 trips

Extension Activity

Space Travel is Not a Walk in the Park!

Materials:

• Timer (needs to display seconds)
• Light time travel chart (below)

Procedures:

1. Review information about light years.
2. Using the light time travel chart and a timer, begin walking to Mercury. Pretend YOU are moving at the speed of light.
3. Stop and discuss how far you have walked with a friend.
4. Repeat Steps 2 and 3 for each planet. You might not end up walking all the way to Pluto.

Analysis Questions:

1.      Why did you not visit all the planets?

2.      Why did you not leave our solar system, and walk to Alpha Centauri?

 Planet/Star Light Years Mercury 0.000006 (3 light minutes) Venus 0.000011 (6 light minutes) Earth 0.000016 (8 light minutes) Mars 0.000024 (12.5 light minutes) Jupiter 0.000082 (43 light minutes) Saturn 0.000151 (79 light minutes) Uranus 0.000304 (160 light minutes) Neptune 0.000476 (250 light minutes) Pluto 0.000624 (327 light minutes) Alpha Centauri (nearest star other than Sun) 4.35 light years
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