Fate of universe

The beginning of the universe started with the cosmic background, which gets us back to the stage when the universe was 380,000 years old. Then, original chemical elements, found that helium had been formed when the universe was only three minutes old. Than dark matter got us further back when the time of the universe was like a ten billionth of a second, and Higgs boson frozen into the universe when it was only like a trillionth of a second.

Antimatter, if this idea with the neutrinos would work out, gets us back to the very beginning, right after the inflation, we don't know exactly what the time scale is.

the inflation itself when the for the structure we see today, that led to the formation of stars and galaxies, that right at inflation, and that's as far as we can get back to the beginning of the universe right now. Now we'll switch our gears to think about the future of the universe.

And that's one of the really basic questions when think about the universe.

What we have on the end?

Or does it go on forever?

What is the fate of the universe?

The expansions of the universe as told by Einstein as holding a ball give it a thrust upwards. So the way the ball is, has a thrust at the beginning corresponds to big bang. How the ball keeps going up into the sky, is also how the universe expands. This analogy tells that the ball should become more and more slowly as it goes up because the gravity only pulls it never pushes. So we always felt, the universe should decelerate should slow down instead of accelerate or speed up. This is what the prediction of Einstein's theory of relativity was and that's what we believed for seven decades actually.

So believing this is the case, and then universe could have had only three possible phases.

1. If there is a sufficient gravitational pull, so if I hold a ball, thrust it upwards, then it keeps going up for a while but eventually stops, and keeps coming, and then comes back down and boom, falls on the ground. That is one possible fate of the universe.

It goes up for a while, slows down, and stops. Comes back down and boom. That’s the big crunch.

2. If we actually put initial thrust with the rocket, then the ball may escape the gravity from the earth and then may keep going forever. So in this case, universe would not have an end. Just keeps expanding forever, as sort of a free motion.

3. Exactly in the middle of two cases, this is exactly the right kind of initial thrust.

That would barely let escape the gravity of the Earth and sort of roll to a stop toward the end. The universe would not have an end in this case.

We would like to measure which curve we are on by looking far away, which means look far back into the past. By looking at how the universe expands nearby that measures how the universe is expanding more recently. If you measure how universe was expanding far away, you're measuring how universe expanding far back in time.

Once we know which curve you are on, you can forecast the future and tell the fate of the universe and that's what we are would love to do. It turns out that these three cases correspond to three different shapes of the universe.

1. If the universe is flat, we're supposed to be on this curve.

2. If the universe is curved in a strange way, we're supposed to be on that curve.

3. If the universe is sort of like a sphere, then we're supposed to be on this curve.

In this case, not only the time is limited that we would have a big crunch.

It will be very interesting to know, which kind of shape we have for the universe which is related to the fact that which kind of fate we have in the future for the universe too. So that's why this question has attracted lot of attention. People wanted to measure which curve we on, by measuring the expansion speed. Far away and nearby, and compare them. That’s the kind of measurement indeed people have done.

One thing which is clear though, if the universe is slowing down, is the future observers would have a really good time because more and more objects would come into our sight. So, the future observations will be even more fun than the fun we are having today. But, everything changed in 1998, it was discovered the universe is actually accelerating, and we would like to talk about it. So, what is this Dark Energy thing?