I heard that the universe is still expanding, and it will come back in. when?

Question

My science teacher said that the universe is still expanding, even today, and that it will come back in. like if you streched a piece of rubber, then let go, it would go back to it's original shape. When will the universe do that? I'm interested =)

Answer 1

The Universe does appear to be expanding; but the jury's still out on when, or even if, it will ever collapse again.

The "rubber band" in this case is gravity, which works over very, very long distances, even between galaxies. If there's enough matter in the Universe, then there will be enough gravity to overcome the original expansion, and everything will start collapsing in again. (Imagine throwing a ball up in the air. The moment it leaves your hand. gravity starts pulling it down. The ball rises more and more slowly, comes to a stop, then starts speeding up towards the ground.)

If there is *not* enough matter in the Universe, then gravity won't be able to stop the expansion, and the galaxies will spread further and further apart forever. (Throw the ball in the air *really* hard, and the ball keeps going before gravity can pull it back down.)

It's very hard to estimate how much matter there is in the Universe, though. One way scientists are trying to answer this question is to measure how fast the expansion is slowing down, which will give them an idea of how much gravity is "winning." But recent studies reveal something very surprising -- it looks like the expansion of the Universe *isn't* slowing down. It's speeding up!! (Toss the ball in the air. Something seems to catch the ball, and it goes up faster and faster!)

So, we really don't know at this point. But if the Universe collapses, it will have to take at least as long as the Universe has existed so far, which seems to be somewhere between 10 and 20 billion years.

Answer 2

Tell your science teacher his statement is far from fact. The universe is indeed expanding, but the question of whether it will come back in is still an open one.
There are basically three possible scenarios for the fate of the universe, all dependent on a certain critical density.
1. The universe could expand and eventually stop and just stay like that. This happens if the density in the universe is equal to the critical mass. Gravity will stop the universe from expanding further but will not be able to make it come back in.
2. The universe could expand forever. This happens if the density of the universe is less than the critical density, and gravity can't counteract the expansion.
3. The universe comes back in. This happens if the density of the universe is greater than the critical density and gravity is sufficiently strong enough to pull the universe back in.
Research has now suggested that much of the mass in the universe may be in the form of dark matter, which can't be detected directly. So now we don't even know exactly how much mass is in the universe, so we can't accurately calculate its density.
As if this weren't enough, there may be dark energy in the universe, and since Einstein's equation equates energy with mass, this would also be a factor in determining the density of the universe. Of course, we can't detect this stuff either.
So the question of where the universe is going is still very much an open question.

Answer 3

Your teacher is making a statement of certainty that most
astronomers wouldn't make.

Yeah, the universe is expanding, but we don't know if it
will contract again or not. Its rate of expansion is slowing
faster than would be predicted by the amount of matter
we know about - causing many scientists to believe
that there is a lot of "dark matter" that we can't detect.

That dark matter would mean that there is more mass
attracting the edges of the Universe back - so presumably
the Universe would contract again ... in BILLIONS of years.


In any case, welcome to the forefront of astronmy.

Answer 4

not each galaxy is purple shifted merely maximum of them. The universe is increasing at a fee of 70 unusual km/s/Mpc (won't be able to be stricken to seem it up) it is declared as Hubble's consistent, which potential the extra distant a galaxy the swifter this is receeding. Andromeda is so on the brink human beings (and gravitationally absolute to us) that the gravitational acceleration is inflicting us and Andromeda to head via area in the direction of one yet another swifter than the area between us is increasing. in order that which you get what Hubble's consistent and the growth of the universe potential: permit's pretend my parent of approximately 70 km/s/Mpc is real: 2 products a million MegaParsec (3.25 million gentle years aside) will recede faraway from one yet another because of the fact the area between them is increasing at a fee of 70 km/s. 2 products 2 MegaParsecs(6.5 million gentle years aside) will recede faraway from one yet another because of the fact the area between them is increasing at a fee of one hundred forty km/s. etc... the extra aside 2 issues are the swifter the area between them is receding. It stands to reason then there'll be a element the place products are so far aside that the area between them is increasing swifter than the fee of sunshine (because of the fact not something that has mass can exceed the fee of sunshine does not mean the vacancy of the area between products won't be able to advance swifter than gentle) which potential galaxies that distant are effectively decrease off from one yet another. So no rely how massive a telescope we build there is an side to the observable universe yet that's not the fringe of the completed universe. desire this explains slightly extra concerning the fee of growth of the universe.

Answer 5

actually "dark matter" has been detected, see here:
http://www.nasa.gov/vision/universe/starsgalaxies/dark_matter_proven.html
Its the more elusive "dark energy" which is fueling the expansion of the universe (and also predicted makes up 75% of the universes by mass) that scientists are having trouble finding so far.
And the expansion of the universe IS NOT SLOWING DOWN, but is actually accellerating due to the anti-gravitational effects of "Dark Energy" on our universe.

Answer 6

In few billion years maybe but then again our knowledge about the universe is contrary to its vastness…so we can go on making all shorts of hypothesises and look at Hubble’s pictures with amazement and awesome….

Answer 7

As the universe expansion seems to be speeding up again, we seem to be in an open one that will never collapse. ~

Answer 8

the whole thing will end up as one black hole.
then a big bang.

no matter how wordy an answer is given, the fact is the weak force of gravity will win

even so there's only one way to find out for sure

Answer 9

Not for billions of years under this theory.