# Thread: Where does the universe end?

1. ## Where does the universe end?

What theories do you have?

Or

What is the theory your religion has given?

2. That question keeps on coming to my mind once every 4 years which makes me travel the stars in my head to go on and on and on and on to imagine all possibilities of an end.

But the end never comes. And then I forget the question for the next 4 to 5 years, for it to come, back haunt and nag me again.

3. Where does the earth end? It does not. The middle is everywhere!

4. It does not end in a specific place, because outside the bounds of our universe the concept of space as we known it is non-existant. So, it never ends.

5. If you mean if there is an edge to the universe where you cannot go any further(maybe like a wall or something), then probably not. But space could be finite in size, therefore it could curve in on itself(like the surface of a sphere) so if you were to travel in a straight line eventually you'd arrive at your start point.

6. Not sure. I like to think the rips and holes they have found lead to something else that is important outside of us, but maybe just to the black space. I think about this a lot more than I should, and come up with a lot of funny things. (I feel like a four year old with these funny things, but it's fun for me anyway.) Usually I picture it like a balloon being blown up or pulled open by a vacuum type atmosphere. Other universes. Black space that is surrounded by something else and something else and so on. So in short, not sure. Sometimes reading helps me understand better, and other times it creates more funny thoughts. Maybe I should go for a physics class sometime soon. or I could just keep dreamin'.

7. The outer lair of the universe is God's beard.

8. I was always more comfortable with the hyperspherical model (which Jock alludes to, by analogy with the 3spherical earth). So in any direction you travel straight in, you would circle back around to the starting point; only in 3 dimensions, it would actually be a straight line. In hyperspace, you would see the path was really a "great circle".

For some reason, scientists tie the shape of the universe to the rate of expansion. since it's not slowing down, but rather speeding up, they seem to go with a hyperbolic model, where parallel straight lines diverge instead of converging.
(That would almost insinuate that the 4th dimension is time, and they do treat it as such in the equations, but when we speak of 3-space as the surface of a 4D object like a hypersphere, then the 4th dimension is also spatial, and the shape has nothing to do with the rate of expansion, as you could have a closed hypersphere that expands faster).

After reading Brian Greene's treatment of string theory, where he mentions spacetime as itself having strings as its quanta, then it becomes conceivable for there to be an end to space. What would happen, is once you reach a certain point, the strings stop, and you are no longer in space or time. That of course also means your matter (also made of strings, of course) instantly disappears as well. Everything just ceases to exist past this edge. The same thing actually happens if you decrease size to below the Planck length. The strings are embedded in a medium that is not spacetime, so there is actually no space between them. (I've just seen that the theory of this kind of geometry is attributed to mathematician Alain Connes).

In any case, I myself was always uncomfortable with the notion of infinite space. It would have been hard for me to explain why, but as I eventually heard someone else put it; if space is infinite, then everything in it is reduced to zero. Locating a given point in the whole universe, like earth, or even the galaxy, would be like identifying a single point in a line.

One theory is that in an infinite space, eventually, there will be no more possible arrangements of matter, so stuff will only be able to begin repeating itself, until you arrive at an exact copy of our world. The same thing is posited in infinite time as well.
But another point is that if it were uniformly filled with matter and energy, then total matter and energy would be infinite.

9. Originally Posted by JocktheMotie
Where does the earth end? It does not. The middle is everywhere!
IOW, we are in the creamy white filling (instead of the crunchy wafers) of an Oreo cookie?

That's a tasty answer, if true.

10. The observable Universe is currently estimated at about Ninety some odd billion light years across, the age around 13 and 3/4 billion years old. (Space expands faster than light).

So the real size of the universe is probably at least 150% of the observable size, but likely even larger. We'll probably never know, considering that, yes, space is expanding faster than light from end to end, and we'll never be able to see further than the age of the universe in light years.

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