1. Welcome to Astronomy! Introduction to the Universe Astro 1105/1107 Prof. Julia Kregenow

2. A large, glowing ball of gas that generates heat and light through nuclear fusion Star

3. Galaxy A great island of stars in space, all held together by gravity and orbiting a common center M31, The Great Galaxy in Andromeda

4. Universe The sum total of all matter and energy; that is, everything within and between all galaxies

5. Your Goals: Brief Survey What do you want to learn about astronomy? Write down a few things.

6. My Goals: on Syllabus On course website: www.astro.cornell.edu/academics/courses/astro105/ Please read it carefully!

7. Homework for TOMORROW Read Syllabus online -- quiz tomorrow! –The syllabus is our CONTRACT Register on “MasteringAstronomy” website –Instructions on our course webpage www.astro.cornell.edu/academics/courses/astro105/ –Enroll in our course: (ID# given on syllabus) First online assignment due tomorrow 10:30am –“Introduction to MasteringAstronomy” (see HW page)

8. SOME REALLY BIG IDEAS Science Light Lookback time Gravity Star stuff Expanding universe Space is big. And empty.

9. Chapter 1 Our Place in the Universe

10. How did we come to be? Pg. 4

11. The Universe is Dynamic Everything is moving Some terminology: Expansion Revolve vs. Rotate

12. What motion does the Earth undergo?

13. What motion does the Sun undergo?

14. There are over 100,000,000,000 stars in our galaxy. ?

15. Thought Question Suppose you tried to count the more than 100 billion stars in our galaxy, at a rate of one per second… How long would it take you?

16. Unit Conversion Convert 100 Billion seconds to years Seconds -> Minutes -> Hours -> Days -> Years

17. Lookback Time We see objects as they were in the past: Light travels at a finite speed (300,000 km/s). The farther away we look in distance, the further back we look in time. Allows us to study the history of the Universe.

18. Example: Our nearest neighbor. This photo shows the Andromeda Galaxy as it looked about 2 1/2 million years ago. Question: When will be able to see what it looks like now? M31, The Great Galaxy in Andromeda Fig. 1.4

19. Light-year: the distance light travels in one year. (But how far is that?)

20. Scientific Notation Multiply and Divide powers of 10 Convert Units Rearrange an equation to solve for another variable Plug numbers in for variables in an equation and calculate Math Skills Summary

21. Scientific Notation –e.g. 300,000,000 = ? –e.g. 4x10 -5 = ? Multiply and Divide powers of 10 –e.g. 10 8 / 10 -5 = ? Convert Units –e.g. How many inches in a mile? Rearrange an equation to solve for another variable –e.g. b = L / 4  d 2. Solve for d. Plug numbers in for variables in an equation and calculate –e.g. L = 3.8x10 26 watts, d = 1.5x10 11 m, b = ? Math Skills Summary

22. (show coolpics.ppt)