Why does higher density of the early universe result in a faster expansion rate?

In summary, the conversation discusses the relationship between the density of the early universe and its expansion rate. The inflation theory suggests that the universe underwent a fast expansion due to a higher density, which has since slowed down. However, the current expansion rate is increasing despite the lower density. This is believed to be due to the gravitational forces of matter, which were stronger when the density was higher.
  • #1
lwymarie
90
1
I heard from a TV program that higher density of the early universe resulted in a faster expansion rate, and the lower density of the present universe has a lower expansion rate. Could anyone please expalin to me why? Thanks =)
 
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  • #2
earlier when the universe was "smaller" and the amount of matter was the same or more ( some of the previous matter could have turned into energy). According to inflation theory which was devised to iron out some bugs in the previous theory the universe underwent a fast expansion. An expansion which has slowed. if the expansion is still slowing down then it must have been higher before, the ultimate expansion beginning with the big bang. Matter's graviational forces could slow down this expansion and are believed to have slowed it down in the past. Just in the past the rate of this slowdown was higher than it is now because they higher density meant a greater gravitational force per unit area, or volume than currently
 
  • #3
Although right after the big bang there was this inflation period, where the universe expanded at an extremely raid rate, followed by a slowdown to "normal" expansion, at the present time the expansion rate is increasing.
 

1. Why is the density of the early universe important in determining the expansion rate?

The density of the early universe is important because it determines the strength of the gravitational force acting on matter. This force is what drives the expansion of the universe, so a higher density means a stronger gravitational pull and therefore a faster expansion rate.

2. How does the density of the early universe affect the speed of light?

The density of the early universe does not directly affect the speed of light. However, the expansion of the universe can cause the wavelength of light to stretch, making it appear to travel at a slower speed. This phenomenon, known as cosmological redshift, is a result of the increasing distance between galaxies due to the expansion of the universe.

3. Can the expansion rate of the universe change over time?

Yes, the expansion rate of the universe can change over time. In fact, it is believed that the expansion rate has been increasing since the early universe due to the presence of dark energy, a mysterious force that is causing the universe to accelerate its expansion.

4. How does the density of the early universe compare to the density of the current universe?

The density of the early universe was much higher compared to the current universe. In the first few seconds after the Big Bang, the universe was incredibly dense and compact, with temperatures reaching trillions of degrees. As the universe expanded and cooled, the density decreased, allowing for the formation of galaxies and other structures.

5. What would happen if the density of the early universe was lower?

If the density of the early universe was lower, the expansion rate would be slower. This would mean that the universe would take longer to reach its current size and would have a different structure, potentially affecting the formation of galaxies and other large-scale structures. Additionally, a lower density would also mean a weaker gravitational force, possibly resulting in a different fate for the universe.

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