Do you think the universe is cyclic in nature? If not, what is it?

Question

Don't just mean expanding and contracting, I mean if it has one discrete state that it keeps returning to.

Answer 1

Good thing you're asking for opinions rather than facts as this is one of the most pressing questions in astrophysics today. Since the recent revelation that the expansion of our universe is accelerating, our current understanding of cosmology would lead us to believe that the universe is not cyclical and will expand forever.

Before we discovered this runaway universe effect, cosmologists assumed that our universal expansion was slowing down--no known science at the time allowed for any other possibility. Then the question was whether the rate of expansion was gradual enough so that the total mass of the universe--all the stars and galaxies, gases and dust--would exert enough total gravity to stop the expansion and begin a long collapse, or was only weak enough to gradually slow the expansion forever and ever but not quite be able to stop it completely. Even if the universe ultimately collapsed this wouldn't answer the question of whether or not it was cyclic, that is, whether after the collapse it would explode again into another big bang or just sit there as a compressed blob for eternity. But the chances were certainly better.

With the stunning discovery that the universe is accelerating, cosmologist have had to discard many of their old beliefs and postulate the existence of strange things like dark matter and dark energy. But the science at this point certainly seems to point to a single, one-shot universe and not the cyclic expanding and contracting one cosmologists have considered for decades.

You may be comforted to hear that other theories, a few of them quite well-established and extensively studied in the physics community, open the possibillity that our universe may just be one of an inifinite number. String theory postulates that our universe may be just one of an infinity of "branes" floating in a kind of giant megaverse. Certain interpretations of quantum mechanics suggest that for every possible action, from your decision to cross the street, to the decay of an elementary particle, other possible actions not taken "split off" into a new universe. Here you have crossed the street but "over there" in the new universe you decided to continue on to the next crosswalk further up the road. Every second of existence an almost inifinite number of universes is created.

These are not just "metaphysical" theories spun off by quacks and new age pop cultural authors, but serious areas of scientific study being undertaken in some of our leading universities.

So although our own little universe may be careening off into a slow gradual death, never to be reborn, all bets are off in any other universes which may exist. Physical laws there may result in the repeated expansion and collapse and rebirth you ask about in your question.

Answer 2

Thanks largely to the work of Hubble, we know that the universe is expanding. We are not yet sure whether the expansion will continue indefinitely, or whether it will some day stop expanding and begin contracting. The answer is in the value of the Hubble Constant. It's the same idea as throwing a ball in the air and wondering if it will come back down or escape earth's gravity.

If it expands forever, clearly it will never again be in a state from earlier in history.

If it contracts, it will also never again repeat an earlier state. We know the physical processes involved in the formation and decay of stars, and they are not reversible or symmetric with time.

This is one answer that I think every knowledgable scientist would agree with. Perhaps the only one!

Answer 3

An important open question of cosmology is the shape of the universe. Mathematically, which 3-manifold represents best the spatial part of the universe?

Firstly, whether the universe is spatially flat, i.e. whether the rules of Euclidean geometry are valid on the largest scales, is unknown. Currently, most cosmologists believe that the observable universe is very nearly spatially flat, with local wrinkles where massive objects distort spacetime, just as the surface of a lake is nearly flat. This opinion was strengthened by the latest data from WMAP, looking at "acoustic oscillations" in the cosmic microwave background radiation temperature variations.

Secondly, whether the universe is multiply connected, is unknown. The universe has no spatial boundary according to the standard Big Bang model, but nevertheless may be spatially finite (compact). This can be understood using a two-dimensional analogy: the surface of a sphere has no edge, but nonetheless has a finite area. It is a two-dimensional surface with constant curvature in a third dimension. The 3-sphere is a three-dimensional equivalent in which all three dimensions are constantly curved in a fourth.

If the universe is indeed spatially finite, as described, then traveling in a "straight" line, in any given direction, would theoretically cause one to eventually arrive back at the starting point.

Strictly speaking, we should call the stars and galaxies "views" of stars and galaxies, since it is possible that the universe is multiply-connected and sufficiently small (and of an appropriate, perhaps complex, shape) that we can see once or several times around it in various, and perhaps all, directions. (Think of a house of mirrors.) If so, the actual number of physically distinct stars and galaxies would be smaller than currently accounted. Although this possibility has not been ruled out, the results of the latest cosmic microwave background research make this appear very unlikely.

Answer 4

Many varieties in nature stick with the fractal kinds, that's, it has an same type from the very small to the very large, a recursive function which will nicely be defined mathematically. And because it takes position, the Universe is complete of math.

Answer 5

Given just what we know today, that the expansion of the Universe is accelerating, we can only conclude that the Universe do not have any cycles. Our Universe is doomed to expand ever larger and the galaxies around us will become ever fainter and fewer until we become totally isolated spatially and temporally.

However, it is possible, given M-Theory, that our Universe is but one tiny bubble in a vast ocean of Universes. There may be cycles on the order of trillion trillion trillion years that are not apparent to us due to our lack of understanding of the fundamental laws of physics.

Now in your question, you mentioned if the Universe has one discrete state that it possibly keeps returning to. Well, usually we talk about discrete states when we discuss quantum mechanics in relation to sub-aomic particles. That's because we are dealing with one or several particles where quantum mechanical effects are dominant, and their quantum states can be determined. The problem with talking about discrete states of the Universe is that the Universe has on the order of 10^85 particles (that's 1 followed by 85 zeros). So to define a particular discrete quantum state of the Universe, you will need to determine what are all the possible states for 10^85 particles to be in. That's a daunting task, so we usually don't use discrete quantum states to describe the Universe, or even anything close to the size of a speck of dust. The number of states to determine is just too many. So what do we use? Tpically, we use macroscopic variables, like size, temperature, speed, energy, density, etc to describe macroscopic objects.

Answer 6

I'm not really sure what you mean, besides the expanding it's doing now and the contracting it did before we got here is there some other state to complete the cycle? well, yea there might be. We already know that virturally everything else in nature recycles itself so I'll get on board the theory that the universe does that.

Answer 7

I think the universe has a boundary. Judging from the cycles of seasons, planets,stars,moons and comets it is safe to assume the universe is much like a clock. It's not an unlikely conclusion that the laws that apply to what we see must apply to the laws we don't see with the exception of other dimensions. I believe the universe to be sphere shape. As far as the expanding contracting theory goes: what evidence do you have we can see? It rather appears to be revolving, rotating, living, and dieing...

Good question, thanks...

Answer 8

to me the defination of universe is that if ther is mass n energy it z called universe n so the universe is simply cyclic in nature cause it z the nature's law of making everything symmetrically so whatever is happening rightnow,exactly the opposite of this might have happened before or will happen in the future.....

Answer 9

i like the old STEADY STATE theory - always has been always will be - mass and energy created to replace mass and energy loss - infinite !

WOULDN'T IT BE POLITE for people who 'paste' answers to give credit ( or are they genius speed typers ? LOL sadly )

and even better if the 'paste' contained the answer ( at least READ IT FIRST )