Rate of Expansion of The Universe
Plugging this information to the Friedmann-Lemaître-Robertson-Walker equations of motion and neglecting both the cosmological constant and the curvatue parameter, which is justified for the early universe, one gets the following equation:
is the energy density, and one finds the following behavior:
- In a radiation-dominated universe:
- In a matter-dominated universe:
One can further show that the universe was radiation-dominated as long as the energy density was of the order of 10 eV to the fourth, or higher. Since the energy density keeps going down, this was no longer true when the universe was 70,000 years old, when it became matter dominant.
In the universe today, matter is mainly in forms of galaxies and dark matter, while the radiation is the cosmic microwave background radiation, the cosmic neutrino background (if the neutrino rest mass is high enough then the latter is formally matter), and finally, mostly in the form of dark energy.
Read more about this topic: Thermodynamics Of The Universe
Famous quotes containing the words rate of, rate, expansion and/or universe:
“At this very moment,... the most frightful horrors are taking place in every corner of the world. People are being crushed, slashed, disembowelled, mangled; their dead bodies rot and their eyes decay with the rest. Screams of pain and fear go pulsing through the air at the rate of eleven hundred feet per second. After travelling for three seconds they are perfectly inaudible. These are distressing facts; but do we enjoy life any the less because of them? Most certainly we do not.”
—Aldous Huxley (1894–1963)
“All of us failed to match our dreams of perfection. So I rate us on the basis of our splendid failure to do the impossible.”
—William Faulkner (1897–1962)
“The fundamental steps of expansion that will open a person, over time, to the full flowering of his or her individuality are the same for both genders. But men and women are rarely in the same place struggling with the same questions at the same age.”
—Gail Sheehy (20th century)
“All the universe over, there is but one thing, this old Two- Face, creator-creature, mind-matter, right-wrong, of which any proposition may be affirmed or denied.”
—Ralph Waldo Emerson (1803–1882)