Lecture 25
May 8, 2008
Fate of the Universe
Key Concepts:
- What is wrong with the Standard Big Bang Theory?
- What is inflation and how does it offer some of the solutions?
- What exotic possibilities does the inflation offer?
- Is this universe open or closed?
- What is the geometry of the universe?
- What is ultimate fate of our universe?
Shortcomings of the Standard Big Bang Theory
- smoothness problem: why is there so little variation in the CMB background?
- flatness problem: why does the universe appear geometrically flat?
- anti-matter problem: for every ordinary particle, there should be an anti-particle. Where are they?
- structure problem: what caused the galaxies and large scale structure form and grow?
Inflation (A Scenario): Salvation of the Big Bang Theory and Its Smoothness Problem?
- Everything with our cosmic horizon were in contact previously: answer to the smoothness problem
- Inflation flattened out all curvature: answer to the flatness problem
| Fate of the Universe |
Curvature |
| closed |
positive |
| flat |
zero |
| open |
negative |
|
|
- Inflation spread matter out in a large volume and create room to grow structures?: answer to the structure problem (partly)
Grand Unified Theory (GUT): What Triggered the Inflation?
The Four Forces
| Force |
Acts on |
Examples |
| Strong |
quarks |
holds nuclei together |
| Weak |
quarks,electrons,neutrinos |
radioactivity |
| Electromagnetic |
charged particles |
atoms and molecules, electric fan |
| Gravity |
everything |
solar system, your chair on the floor |
- all four forces were one at the beginning
- phase transition: forces separate themselves out
==> separation of strong force from the GUT force triggered inflation?
-
vacuum energy is the source behind the inflation? Quantum theory requires empty space to be filled with particles and anti-particles being continually created and annihilated.
Some Exotic Possibilities with Inflation
- parallel/other universes ("multiverse")?
- a closed universe saved by inflation?
Ultimate Fate of the Universe: What will Happen to the Universe ("Open" or "Closed") ?
- Positive (kinetic) energy of expansion
- Negative (potential) energy of gravitational attraction
Depending on how much energy the Big Bang started with (or how
much matter the universe contains), the universe will either
expand forever or collapse on itself.
Geometry (Curvature) of the Universe
| Fate of the Universe |
Curvature |
| closed |
positive |
| flat |
zero |
| open |
negative |
|
|
The Latest News from the Cosmological Fronts
BOOMERANG experiment (2003): Universe is Flat!
WMAP
_
- The age of the universe is 13.7 billion years old.
- The Hubble constant is 71 km/s/Mpc.
- Universe is flat. Really.
- Only a small fraction of "matter" is baryonic (ordinary).
- The dark matter that accounts for several times larger fraction is "cold" in nature.
- The rest of the density of the universe is something mysterious called "dark energy" for the moment. This dark energy works like a repulsive force (i.e., Einstein's cosmological constant) that balances gravity.
Cosmological Constant: Universe Expansion is Speeding Up?
- Einstein's Biggest Blunder?
- Repulsive effect to resist gravity
- Possible speeding up in the Hubble expansion observed by Type Ia supernovae
- Universe older than inferred from the Hubble flow?
|
 |
The Future of the Universe (Looking into the Crystal Ball)
- Big Crunch: if the universe has enough matter in it (closed), the gravity
wins and the universe collapses on itself.
- A critical, coasting, or accelerating universe will exist "forever".
The universe will continue to change:
- more and more matter gets locked up into low mass stars,
planets, WDs, NSs, and BHs, and not recycled
- in one trillion years, even the longest-lives stars will burn out,
and the galaxies will fade into darkness - only cold WDs, NSs,
and BHs remain
- in 1020 years, these stellar remnants are either drifting in
the intergalactic space or sink into the supermassive BHs formed in
the centers of galaxies
- in 1040 years, all remaining atomic matter will have
disintegrated into radiation and subatomic particles
- in 10100 years, the only remaining objects (BHs) would have
evaporated by Hawking radiation or quantum-tunneled into pure energy.
Quiz 25D: Your More Immediate Future...
Web Resources on Cosmology
