Introductory Question

[TheGeckomancer]

Hello all, I spend a LOT of time learning random bits of science, math, etc. But this is my form of entertainment, not a hobby or profession. But that leaves tons of gaps. So I decided to finally start asking some of the weird questions I have in my head. I am sure some will be dumb or have obvious answers but whatever.

 

So the main 2 that compelling me right now. First one is: If (and I know this is entirely impossible) I was able to pick a direction and start traveling BILLIONS of time the speed of light WITHOUT traveling backwards in time, (maybe through a warp funnel or something), and I was able to continue forever, at a rate of movement faster than the expansion of the universe. Again, I know it's not possible. Basically I am asking whats at the edge of the universe. Or does it fold on itself like a crazy klein bottle?

 

My second question... I am not sure if this goes here or not. If you draw 4 boxes next to each other, 2 side by side and 2 just below also side by side (so they make one bigger box), all of the inner edges will be touching with no gaps. If you draw 4 hypothetical circles (they are not real and the lines that make up the circles have no dimensions), the edges of the circles will touch but they will leave diamond shaped gaps in between them. If you then draw a circle in that gap, it will create more smaller gaps around it. Continue this forever. Is there a moment when these hypothetical circles become points? I guess another way of asking, is there a smallest quantifiable amount of space?

[Strange]

Basically I am asking whats at the edge of the universe. Or does it fold on itself like a crazy klein bottle?

 

Currently, we don't know what the overall topology of the universe is. It is generally thought that it doesn't have an edge, but it could be infinite or finite. In the first case, you will just keep going forever. In the second case, you could end up where you started (but you might not). Imagine you set off on a trip round the Earth. If you happen to travel on a great circle (the equivalent of a straight line) such as the equator, then you will end up where you started after one circle. But you might go round on a crazy spiral.

 

 

I guess another way of asking, is there a smallest quantifiable amount of space?

 

Again, no one knows. (In other words: good questions!) There are theories where space is "quantized" at some level. But there are theories where it isn't ...

[imatfaal]

Two interesting questions - neither of which can be answered with certainty. To add to Strange's point on the smallest space it is worth noting that there are no signs that space is quantised at the levels which we can measure so far - the theories which relate to quantised space are at unimaginably small scales that we do not have the energy to probe and may never do so (ie current tech cannot just be scaled up - we need newer ideas). Your nice illustration of the gaps between circles is a sort of fractal and reminded me of Sierpinski Carpets and Menger Sponges - both of which are worth a look at; they are pretty great at a physical / realisable level but it is when taken to non-physical / theoretical levels they become seriously weird.

[TheGeckomancer]

This made me think of a branching question for the smallest space. To me it would seem that if space continued infinitely downward AND upward in scale, than our perspective is inherently limited in such a way to where we can't know the universe. I mean theoretically couldn't there be another set of particles, infinitely smaller than the ones we interact with that make up microcosms we could never observe? Similarly going upward?

Actually to add a point to that. We know that nature abhors a vacuum, even in empty space virtual particles pop into and out of existence all the time. Wouldn't that same rule have to apply on the infinitely decreasing scales of the universe? I know we don't know the answer to any of these questions. I am more asking if there is any logical reason why this wouldn't be true.

Edited November 24, 2015 by TheGeckomancer

[zapatos]

I mean theoretically couldn't there be another set of particles, infinitely smaller than the ones we interact with that make up microcosms we could never observe? Similarly going upward?

I am more asking if there is any logical reason why this wouldn't be true.

Many things are possible, but barring any evidence to support your conjecture you are just having fun speculating.

[TheGeckomancer]

Not exactly. Sometimes you can discern if something is true or not by assuming it is or isn't then looking at the what if repurcussions. I may not be able to discern anything with those assumptions, but that doesn't mean it was wasted.

[zapatos]

Not exactly. Sometimes you can discern if something is true or not by assuming it is or isn't then looking at the what if repurcussions.

You still need evidence at some point.

 

I may not be able to discern anything with those assumptions, but that doesn't mean it was wasted.

I didn't mean to imply the speculation was a waste. Speculating is a good thing. I do it all the time.

[swansont]

Not exactly. Sometimes you can discern if something is true or not by assuming it is or isn't then looking at the what if repurcussions.

 

So what are the repercussions?

[MigL]

OK, I'll take the bait.

 

Suppose the universe was not finite but unbounded ( such as the surface of a sphere is ), so that it never folded back on itself.

Also suppose that it was literally infinite, such that there is no outer edge, because that outer edge would make a 'mess' of things.

 

And suppose that it has always been infinite , even at the time of the Big Bang.

Well light and causality information only travels so fast.

There would be a causality disconnect between various parts of this infinite universe and information could not be shared amongst all areas of the early universe.

What would guarantee that all these areas are at the same temperature/energy ?

Would all the symmetry breaks encountered on the way down of the vacuum energy all occur simultaneously ?

Would all the inflation events occur at the same rate ?

Or would all these domains, having evolved separately, give rise to 'domain walls' or discontinuities in the present universe ( and the resultant magnetic monopoles ) ?

What happens to the isotropic principle ?

 

So you see, an always infinite universe again gives rise to boundary problems and 'messes' things up.

Does that mean we can eliminate it as a possibility ?

I don't believe so.

 

Sorry if my post has more questions than answers, but that's what happens when you speculate.

Edited November 24, 2015 by MigL

[Strange]

And suppose that it has always been infinite , even at the time of the Big Bang.

 

Note that if "at the time of the big bang" is referring to a singularity, then that would be zero size, even if the universe is (and always has been) infinite.

 

What would guarantee that all these areas are at the same temperature/energy ?

Would all the symmetry breaks encountered on the way down of the vacuum energy all occur simultaneously ?

Would all the inflation events occur at the same rate ?

 

Do we know they are (were) the same everywhere?

[MigL]

Sorry Strange, been away sulking for a while.

 

"Do we know they are ( were ) the same everywhere ?"

Yes, we have a principle which takes advantage of this property ( isotropy ) to enable us to discuss Cosmology and the Universe.