1. The Dark Side of the Universe Scott Watson Dept. of Physics Brown University watson@het.brown.edu http://www.het.brown.edu/people/watson/

2. Cosmic Conundrums How will the Universe end? How old is the Universe? How did the Universe begin? What is the Universe made of?

3. Are we smart enough to answer these questions?

4. Cosmic Timeline

5. Observational Cosmology Cosmic Background Radiation (CMB) Large Scale Structure (LSS) Supernovae Ia

7. The Earth is one of nine planets orbiting our Sun. It is the third closest to the Sun, and so far it is the only place in the universe where we know there is life.

10. Large Scale Structure Analyzing large scale structure provides information about the physics of the early universe!

11. Large Scale Structure Quantum fluctuations in the early universe result in the large scale structure we see today!

12. Cosmic Microwave Background Quick Facts: Cosmic microwave background (CMB) primordial light. 3 degrees above absolute zero (-270 degrees celcius) mm-cm wavelength 400 photons per cubic centimeter 10 trillion photons per second per squared centimeter Few percent of TV "snow" Temperature slightly different on different patches of the sky - 1 part in 100,000.

13. Cosmic Microwave Background Fluctuations in density give rise to cold and hot spots in the photon fluid

14. Cosmic Microwave Background Quantum fluctuations also lead to temperature fluctuations in the CMB

15. Not Just a Bunch of Pretty Pics Power spectrum characterizes and provides a testing of theoretical models Power spectrum measures the strength of the fluctuations verses their angular size of the sky

16. Type Ia Supernovae Type Ia Supernovae are exploding stars all of which behave in the same way. This allows us to deduce their distance from us and how fast they are moving away from us.

17. Type Ia Supernovae

18. The Universe is Flat! The Universe will live forever! The Universe is made of 65% unknown energy! This is the so-called, DARK ENERGY! The Universe is approximately 15 Billion years old!

20. Putting it All Together What is the Dark Energy? Why has it taken over the expansion today?

21. More to come… How are we going to figure this one out? The Dark Energy must have the following properties, –Non-luminous (DARK) –Relativistic energy-like (ENERGY) due to large negative pressure p<-1/3 –Can only clump on scales beyond horizon –Couples to matter ONLY gravitation –Dominates only recently z ~ few (can not interfere with LSS, BBN)

22. Detecting the Dark Energy is a SNAP! SuperNova Acceleration Probe SNAP will allow us to “weigh” the Dark Energy and deduce its properties

23. Keep an Eye on the Dark Energy!