1. Measuring the Very Large

2.  For distance that is.  The Kilometer  What exactly *is* a kilometer?  1000 meters  We walk at about 5 km/hr, or 0.0015 km/s  The Moon (closest object), is 400,000 km away  How long to walk there?  What about driving? (~100 km/hr)  Flying? (1000 km/hr)

3.  Lunar

4.  The distance to the *nearest* planet, Venus  38,000,000 km ▪ (at its closest, but it can be up to 228,000,000 km away)  How long to walk that?  From the earth to the sun is 150,000,000 km  This is used as a new unit of distance  The Astronomical Unit (A.U.)

5.  Solar

6.  In the solar system:  Jupiter is 4 A.U. from us  Neptune, 30 A.U.  Pluto, 50 A.U.  Edge of the solar system, 100,000 A.U.  Nearest Star (Alpha Centauri), 268,000 A.U.  Clearly, the A.U. quickly loses its usefulness.

7. oort

8.  Light travels faster than anything else in the universe.  300,000 km/s (186,000 mi/s, or 670,000,000 mi/hr)  In one year, light will travel 10 trillion km  This is called the LIGHT YEAR (ly)  It is the BASIC unit of distance for astronomy

9.  Local Stars

10.  Nearest Star  4.2 light years  Thickness of the milky way galaxy  1,000 ly  To the center of our galaxy  27,000 ly  Diameter of our galaxy  120,000 ly  Distance to the nearest major galaxy (Andromeda)  2,000,000 ly

12.  Nearest Star  4.2 light years  Thickness of the milky way galaxy  1,000 ly  To the center of our galaxy  25,000 ly  Diameter of our galaxy  120,000 ly  Distance to the nearest major galaxy (Andromeda)  2,000,000 ly

13. Ultra