Lecture 24
Cosmic microwave background, inflation, dark energy
Friday August 8, 2008
Slides on Angel
Concepts:
- Cosmic microwave background: CMB is redshifted relic radiation from big bang. Isotropic and homogenous to 1/100,000; small fluctuations indicate structure growing in early universe
- Horizon problem: Areas out of causal contact show similar properties. Solved by inflation: they were close by before universe rapidly expanded
- Flatness problem: Universe that isn't exactly flat tends to quickly diverge towards extremely open or extremely closed. Solved by inflation: whatever initial curvature, rapid expansion smoothed out universe
- Inflation: Exponential growth of universe immediately after the big bang, lasted only 10^-32 seconds but universe increased in size by factor of 10^50
Vocabulary:
- CMB spectrum: The CMB spectrum is blackbody thermal emission with a temperature of only 2.7 K. Has been cooling/redshifting since after BB
- Curvature: How spacetime is shaped. Positive curvature (like sphere) corresponds to high density, negative curvature (like saddle) to low density, and flat (like plane) to "just right" density -- our universe appears to be flat
- Dark energy: Something that is driving the acceleration of the universe, with odd properties like negative pressure. Not well understood yet
Activity:
Worked in groups to brainstorm about some of the issues relevant to searching for intelligent life in the universe.
Answered questions about prospects for life in the solar system and elsewhere and the most efficient way to
try to establish contact. Each group also came up with a question to ask another group. Used mics/cameras in class
to present answers, ask questions.
Random link:
Excerpt from Fox News article titled "Western U.S. to Have Best Glimpse of Next Week's Perseid Meteor Shower"
In 2008, the Perseids are expected to reach their maximum on Aug. 12.
The exact time of maximum should be about 7 a.m. EDT on Aug. 12, according to Margaret Campbell-Brown and Peter Brown in the 2008 Observer's Handbook of the Royal Astronomical Society of Canada.
If so, the timing is very good for meteor watchers observing before dawn in North America, especially in the western states. And that morning, the waxing gibbous moon sets around 1:30 a.m. local daylight-saving time, leaving a dark sky for the next 3 hours.