The Inflationary Theory Estimates Age of Universe

I took this information directly from Harrison Prosper's paper because it is more clear than what I think I could generate on my own for this course.


The Big Bang Theory Successes
The big bang theory is able to account for the following facts:

Universal expansion
Microwave background radiation
Abundance of light elements

Big Bang Theory Problems
It fails to account for:

Why the microwave background so uniform (Horizon Problem).
Why the galaxies are distributed in vast sheets (Structure Formation Problem).
Why spacetime is so flat (Flatness Problem).
Why there are no monopoles (Monopole Problem).
How something can be created, apparently, from nothing (Creation Problem).

This theory is a modification of the standard big bang theory. One postulates the existence of a vacuum endowed with a (still mysterious) form of energy. It is mysterious in that the vacuum still looks empty, that is, devoid of ordinary matter and energy. In the beginning, one assumes the vacuum energy density to be huge. This caused the universe to expand at an exponentially fast rate: the universe doubles its size every one trillion trillion trillionth of a second (10e-36 s)! This period of hyper-expansion is called inflation.

The universe is thereby stretched by an absolutely enormous factor, so much in fact that any relatively small region of the universe, for example the entire visible universe, would appear flat, just as a small patch of the Earth's curved surface appears flat. This solves the Flatness Problem.

Any weird things, like monopoles, that may have been created at the start would have been so enormously dispersed that we would expect no more than one in our visible universe! This solves the Monopole Problem.

What we call the visible universe was once confined to a single bubble no more than 3 x 10e-26 cm across; the distance light can travel in the 10-36 seconds since the beginning. Therefore, every part of the visible universe was once in contact. This solves the Horizon Problem.

Finally, somehow, after a very short time, the inflation ceases abruptly. It is assumed that the vacuum energy during inflation has been rapidly decreasing. Whatever vacuum energy remains after inflation transforms explosively into ordinary matter and energy, thereby making the universe extremely hot. The regular big bang expansion takes over thereafter.

The following time-line describes what is predicted by the theory.

10e-43 seconds--This is called the Planck Time.
For shorter times all our current theories break down. Even the very notions of space and time cease to make sense.

10e-36 seconds--Temperature about 10e28 K.
This is the era of hyper-expansion called inflation. The maximum distance that light could have traveled since the beginning is a mere 3 x 10e-26 centimeters! This defines the size of the "visible universe" at that time. The universe expands from this microbubble by a factor of 10 trillion trillion (10e25) in about one 1 billion trillion trillionths of a second (10e-33 seconds). This is surely expansion with a vengence! The universe is now about 3 mm across. The tiny quantum vacuum energy density fluctuations that existed in the original microbubble have also been expanded by this huge factor. They will form the seeds of galaxies. The remaining vacuum energy is transformed explosively into ordinary matter and energy causing the universe to become extremely hot and to expand at a leisurely pace.

10e-6 seconds--Temperature about 10 trillion K.
Quark and anti-quarks form out of pure energy and immediately annihilate back to energy. But, owing to an asymmetry between the behavior of matter and antimatter, an excess of quarks over anti-quarks of one part per billion builds up. Thus, most of the antimatter disappears from our universe.
The quarks stick together to form neutrons and protons. The conversion of protons into neutrons and vice versa maintains an equilibrium with equal numbers of each.

1 second
Because neutrons are slightly heavier than protons it is easier to convert neutrons into protons than to convert protons into neutrons and so the number of protons increases relative to neutrons, giving a final proton to neutron ratio of about 7 to 1.

5 seconds--Temperature about one billion K.
Electron and positron pairs are created. Matter creation ceases.

3 minutes--Temperature about 100 million K.
Nuclear reactions occur at a furious rate. Protons now move slowly enough to fuse into helium nuclei. Helium, deuterium, lithium created.

300,000 years--Temperature about 10,000 K.
The radiation density is now low enough that the universe becomes transparent. It is cool enough now for electrons and nuclei to stick together to form atoms of hydrogen and helium. This is called the recombination era.

1 to 5 billion years--Temperature a few Kelvin.
The density fluctuations (lumpiness) in the matter distribution, caused by the original quantum fluctuations in the vacuum energy, form the seeds of galaxies, which form in huge web-like sheets spanning the universe. It is these initial density fluctuations that the COBE satellite detected.

12 billion years--Temperature a few Kelvin.
Dawn of life on at least one tiny blue planet.

15 billion years--Temperature 2.7 K.
More-or-less intelligent life exists on this blue planet!

Big Bang beginning, or return to Red-Shifting, or the Cosmology Introduction, or go to the Syllabus .

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