Can anyone explain what is meant by the critical density of the Universe?

Answer 1

The critical density is the calculated density at which the universe will NOT expand forever, but will eventually come to a halt & go into the "big crunch". The actual density of the universe is not known with sufficient accuracy to determine if its density is or is not critical. This depends on the total amount of "dark matter" in the universe and whether or not neutrinos do, in fact, have mass.

Answer 2

When the universe came into existence it had no density,
For the first thirty billionths of a second its density increased,
When the radial expansion equaled the speed of light the density was at a maximum.
As matter formed the density decreased.The time line from there is pure speculation.but the minimum critical density will arrive and the universe will begin to go out of existence.

Answer 3

To add to the previous poster's answer:

While the density of the universe is not known, the fact that the expansion of the universe is accelerating suggests the density is not enough to keep the universe from expanding indefinitely. Either the universe expands until all the black holes disintegrate in 10^100 years, or there is a force to reverse the expansion that we haven't figured out yet.

Answer 4

it particularly is stressful to assert, because of the fact we are nevertheless uncertain the place a extensive fraction of the universe's mass is. as quickly as all of us be conscious of extra approximately what "darkish be counted" is surely composed of, we will have a extra effective thought of the universe's density. on condition that the universe's enlargement is at the instant accelerating nonetheless, i'd wager no.

Answer 5

The Big Bang pieces may or may not have enough gravity to cause a Big Crunch. I logically know that the universe Bangs and Crunches, over and over, like your heart.