How big is the universe? What is beyond the universe? Does it just go on forever?

Question

How big is the universe? What is beyond the universe? Does it just go on forever?

Answer 1

Nobody knows for sure how big the universe is.  There is no "beyond" the universe, because the word "universe" means "everything that is".

Some scientists think the universe goes on forever, but most think it is about 65 billion light-years across.  But it could be 45 billion, or 145 billion light-years.  The part of the universe that we can see is about 14 billion light-years across.

Answer 2

nobody knows how big the universe is but an opinion that has been circulated is that the universe is still growing and that one day it will start to shrink into the tiny ball of matter that caused the big bang

Answer 3

By definition there cannot be anything beyond Universe. People may say there may be parallel universes. Then logically there is no connection between them or there may be a connection. If here is connection then they all will form one big universe. If there is no connection I do not know How shall we experimentally discover it and Hence it would remain only a theoretical  possibility which cannot be falsifiable, hence will not be considered as a scientific theory.

Answer 4

The universe is infinite and constantly expanding, the exact date of the universe is not known. As for whats beyond it, "nothingness" its hard to picture because your mind cannot think of nothing. We as humans do not have the senses to percieve what is beyond the universe therefore we cannot see it. Maybe when we die then we will be able to see everything - all the dimensions, parallel universes and the bigger picture.

Answer 5

We do not know how big the universe is.

The only thing we know is that it is at least as big as the portion we can see.

A 2-dimension surface can be folded on itself (like the surface of a sphere, for example) so that it has no end, but it is still finite in size.  For example, on Earth's surface, if you start off in one direction, you can continue in that direction forever without ever arriving at the end of the surface.  However, every 40,000 km (25,000 miles) you will pass over your starting point.

It is possible that a 3-D space could be "wrapped" around itself so that you could go forever in the same direction forever, by passing through your starting point over and over again.

The probe WMAP was sent to analyze the Cosmological Microwave Background (CMB) radiation.  Among other things, it was looking for signs that the universe was wrapped around on itself.  If the total universe was actually smaller than the distance we can see (14 billion light-years), there there would be some telltale signs in the CMB.

(billion = thousand million)

WMAP did not find these signs, so the only thing we know is that the total universe is at least as big as what we see.

Also, when we look very far, we are in fact looking into the past.  We do not see the real shape of the universe.  The universe we see is wrapped onto itself because its shape is dictated by space-time (which is known to be warped onto itself -- the visible universe in the past was much smaller than it is today, so the further out we look in opposite directions, the closer together the objects are ... go figure).

If we could see the universe everywhere as it is now (e.g., if light travel were instantaneous), we would see objects at their comoving distance.

The portion of the universe we see today has a radius of 14 billion light-years in "proper distance" (a.k.a. look-back time, the distance traveled by light from the object we see).  This corresponds to a bit less than 80 billion light-years in comoving distance.

So when cosmologists give a distance of around 160 billion light-years as the size of the universe, they mean the minimum size (diameter) that the universe can have in comoving coordinates. (Actually, the last figure I remember seeing is somewhere around 156 billion l-y.)

What we do not know is if the "comoving" universe is flat.  There are signs that it could be, but it is difficult to prove.  If the universe is flat, then it could very well be infinite in spatial extent.  The only reason we do not see objects at infinite distances is that the light has not had enough time to make it all the way here (therefore, we cannot see them).

And with the expansion increasing in speed, it is possible that we would never see them:  the distance between us and the object grows faster than the distance traveled by the light it emits.

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An infinite universe does solve a few problems.  For example, we would not need to ask what does the universe expand into.  It simply expands into itself.

Take any distance in the present universe.  Take it as big as you want.  Then multiply it by 2 (or even by 10).  The expanded distance would still fit in the universe.

At the Planck Time (the earliest time we can understand), the universe would have already been infinite.  No need to imagine a single point expanding into a universe.  The "singularity" would simply be the state of the energy density at that moment (every single point would have been a black hole), with that state existing everywhere in an infinite universe.

No need to imagine the possibility of going over the starting point over and over again.  No need to imagine extra dimensions that would be needed if the universe were wrapped onto itself.  And so on.

(I did not say that it was easier to understand, only that it solved a few mathematical problems).