1. The Scale of the Universe Lancelot L. Kao Updated: Jan 18, 2010

2. 2 Heavenly Bodies Angular Measurements Powers-of-Ten, etc Our Solar System Our Sun Stars & Nebulae Galaxies Observable Universe

3. 3 Angular Measurements Angle & Angular Measure Angular Size Angular Distance Interesting Facts

4. 4 Angular Size

5. 5 Angle & Angular Measure 1 degree = 60 arcminutes (minutes of arc) = 60’ 1 arcminute = 60 arcseconds (seconds of arc) = 60”

6. 6 Angular Distance

7. 7 Interesting Facts

8. 8 Powers-of-Ten Large Number 10 = 10 =10 1 100 = 10 x 10 = 10 2 1,000 = 10 x 10 x 10 = 10 3 1,000,000 = 10 6 1 = ? Small Number 0.1 = 1/10 = 10 -1 0.01 = 1/100 = 10 -2 0.001 = 1/1000 = 10 -3 0.000001 = ?

9. 9 Example of Powers-of-Ten 1,000 x 10,000 = 10,000,000 = 10 3 x 10 4 = 10 7 100,000 x 0.0001 = 10 = 10 5 x 10 -4 = 10 1

10. 10 Our Solar System

11. 11 Distance Units in Astronomy 1 astronomical unit = 1 AU = the average distance between the Earth and the Sun 1 light-year = 1 ly = the distance travelled by light in a year 1 parsec = 1 pc = the distance at which 1 AU perpendicular to the observer’s line-of-sight subtends an angle of 1 arcsecond

12. 12 Units of Length, Time, & Mass Length –English System (inches, feet, yards, miles} –Metric System (centimeters, meters, kilometers) –Astronomy Units (astronomical units, light-years, parsecs, etc) Time –Metric System (seconds, minutes, hours, days, years) Mass –Metric System (grams, kilograms) –Astronomy Units (solar masses)

13. 13 New Solar System (IAU Resolution 5 for GA-XXVI) IAU General Assembly will vote on this resolution on August 24, 2006 at Prague.

14. 14 New Solar System!

15. 15 Our Sun A “typical” star Diameter = 1.39 million kilometers Surface Temperature ~ 5,800 Kelvin Age ~ 4.5 Billion Years Energy Source – thermonuclear fusion

16. 16 Stars and Nebulae

17. 17 The Milky Way

18. 18 Galaxies Stars Star Clusters Gas & Dust Nebulae

19. 19

20. 20 Observable Universe

21. 21 Spaceship Earth