Summary III
The Universe is Expanding
- Found by Hubble in 1927-29
- Measured by “Doppler Shift”
- Expanding in all directions as if it came from a point
- Estimate for age of universe ~ 15 billion years
- Compare to estimate of age of the earth ~ 5 billion years
The BIG BANG
- Evidence is the expanding universe
- The “Cosmic Background” of radiation observed (1964)
- “3 degree background” remnant of BIG BANG
Future?
- A. Universe keeps expanding (becomes cold and empty)
- B. Expansion slows to a stop (becomes cold and dead)
- C. Reverses and collapses to the BIG CRUNCH
- Depends upon the total mass
- We do not know the mass well enough to know the answer!