Space questions

m83

Hi first time visitor to this board, astronomy n00b, looking for clarification on some things:

1. Are the empty vacuums of space entities in their own right, ie are they created in a similar manner as astronomical objects? Do they have mass? Are there an theories suggesting that the empty vacuums of space could account for dark matter?

2. Is there an edge of the universe whereby that which is universe per say could be differentiated from that which is not universe? Or does this question even make since, like speaking about the 'time before the big bang?'


Any help with these question would be sincerely appreciated.

The Roach

Right, I can't claim to be an expert on this, but here's my take on it.

The empty vaccuums of space are just that, empty. They are part of the universe in the same way that the holes between the strings are part of a net. And being empty there is no mass associated with them. I think what you're hinting at with the mention of dark matter is Einstein's original theory of general reletivity. In this, to make everything balance out, he added what he called a cosmological constant, which was necessary for his calculations to balance. He later discarded this idea. However, one of the suggestions as to where the missing mass of the universe is kinda goes back to a similar idea; that is that the empty space has some sort of latent energy, and that it is this that makes up the "missing" parts of the universe. However, the dark matter/energy theory is by far the more popular.

As regards the edge of the universe, that's one of those things that's a bit difficult to get you head around. As you suggested, trying to think about space outside the universe is about as impossible as time before the big bang. The easiest way I find to think about the size/expansion of the universe is like this: take an ordinary un-inflated balloon and draw 2 points on it about 1cm apart with a marker. Now imagine they are 2 galaxies in space at this very moment. Now if you start to inflate the balloon, you'll notice that the points start to move further away from each other. However, the actual amount of matter that makes up the balloon isn't changing, just the way it's spread out. If you can picture the entire universe as the SURFACE of the balloon (not the whole balloon, as this still gives the idea of inside and outside the balloon) you're thinking the right way. As the universe expands, it still contains the same amount of matter, it's just the distance between objects is getting larger.

Ok, I admit at this point I may be starting to ramble a bit, but it's 4.30am and I'm a bit knackered! Hope this helps a little bit, and people, feel free to correct me!

Son Goku

m83 wrote:

1. Are the empty vacuums of space entities in their own right, ie are they created in a similar manner as astronomical objects? Do they have mass? Are there an theories suggesting that the empty vacuums of space could account for dark matter?

The vacuum is a "thing" like matter and not just a stage for matter to act in. It does posses a mass, in a certain way. However this doesn't have anything to do with Dark Matter. Dark Matter is difficult to detect forms of matter.

m83 wrote:

2. Is there an edge of the universe whereby that which is universe per say could be differentiated from that which is not universe? Or does this question even make since, like speaking about the 'time before the big bang?'

It doesn't make sense in General Relativity. The universe in all our present models is either infinite or unbounded. Unbounded means the universe would be like the surface of the Earth, you could travel in one direction and return to the same point.

jessop1

..a couple of articles that might be of interest

Dark Matter
http://news.independent.co.uk/world/science_technology/article2134891.ece

Universe is Finite, "Soccer Ball"-Shaped, Study Hints (or more precisely, a dodecahedron)
http://news.nationalgeographic.com/news/2003/10/1008_031008_finiteuniverse.html

jessop1

..a couple of articles that might be of interest

Dark Matter
http://news.independent.co.uk/world/science_technology/article2134891.ece

Universe is Finite, "Soccer Ball"-Shaped, Study Hints (or more precisely, a dodecahedron)
http://news.nationalgeographic.com/news/2003/10/1008_031008_finiteuniverse.html

Kevster

Son Goku wrote:

Unbounded means the universe would be like the surface of the Earth, you could travel in one direction and return to the same point.

I think that is most likely. I mean, isn't that inferred by the fact that the CMB can be observed from every direction?


However, if the Universe IS like the Earth's surface, then we are already at the edge of the Universe, right? ...Just like we are already on the Earth's edge (surface).


For those that think that the universe is flat - And not bent back upon itself by gravity - The edge could be viewed as the point at which light has not yet reached.

Kevin.

Son Goku

Kevster wrote:

I think that is most likely. I mean, isn't that inferred by the fact that the CMB can be observed from every direction?

It's by far the most likely actually. The strongest piece of evidence is that there are what is called standing waves observed in the cosmos. These are "sound" waves* in the universe which look exactly like how sound waves look in a tube, i.e. They carry the tell tale signs of having travelled around their container and constructively interfering with themselves.

The evidence is strongly in favour of our spacetime being finite but unbounded.

Kevster wrote:

However, if the Universe IS like the Earth's surface, then we are already at the edge of the Universe, right? ...Just like we are already on the Earth's edge (surface).

Yeah, pretty much.


*I say "sound" because it would take an entity with a 800 light year eardrum and a life span of millions of years to hear a single note, but it is still basically the same phenomena. If you could listen to these sounds, this is what the universe's first 1,000,000 years would sound like:
Early Universe

Kevster

Son Goku wrote:

It's by far the most likely actually. The strongest piece of evidence is that there are what is called standing waves observed in the cosmos. These are "sound" waves* in the universe which look exactly like how sound waves look in a tube, i.e. They carry the tell tale signs of having travelled around their container and constructively interfering with themselves.

...Very interesting and I never knew that. Are these separate from the CMB or are they tied-into it?