Increased rate of Universe expansion

I think I am missing something...
It seems that astrophysicists and theoretical physicists alike seem to have a problem with the rate of the expansion of the universe accelerating.
If I understand it correctly, this problem is what has led to people postulating "dark" matter or energy... or the collective mass of antimatter (or would that be antimass?) or SOMETHING counteracting the effects of gravity on the universe as a whole.
As I understand the theory, the universe is expanding due to inertia from "The Big Bang" and scientists expected the expansion rate to be falling over the years due to gravity essentially being the "brakes" of the system.
When we discovered that the further out you go in the universe, the faster the universe is expanding, things got turned on its head.

I hope I am right so far.

If so, then I am confused as to why this is a problem.
I would have fully expected the outer fringes of the universe to be expanding at a greater rate than the more "internal" areas.

Space is a "vaccuum" with no resistance.
There is nothing in space to slow the expansion down via friction.
The only thing that is acting as the "brakes" of the system would be gravity.
Gravity is a force that interracts with massive bodies (please forgive the lay terminology).
The inverse square law applies to gravity.
If there WAS a "Big Bang" and all matter started out at a single point, and expanded from that single point, the further you get away from that point, the more sparcely populated that area of space is bound to be, correct?

If a ball explodes and the pieces spread out from the point of explosion in even a remotely uniform fashion (and nothing impedes the oieces from traveling) wouldn't you expect the pieces towards the origin of the blast to be much closer together than the pieces, say a mile away?

If that is the case, wouldn't the bodies that are closer to the outer edge of the universe be affected less by gravity, therefore be slowed down less than the rest of the universe?

(I apologize that this isn't written more succinctly. I didn't really put the thoughts together before posting them.)

What am I missing?
Why is this a problem at all?
Why did scientists expect the outer part of theuniverse to be slowing down more than the inner part? :bugeye:

 

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Hmmm. Go back to step 1. Matter is not expanding into a space vacuum or void. The BB created space at the same time. So it is not matter moving out into space it is space expanding.

 

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Regardless of whether that's true or not, I still don't understand what the problem is.
What, other than gravity, is supposed to be slowing down the expansion?
If it is nothing but gravity, I would expect space at the internal most parts of the universe, where it is more densely populated, to be slowing more rapidly than the outer fringes.

 

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It seems to me (again, correct me if I am wrong) that we do not know if the outer edge (let's say 10 billion light years away) is expanding any faster than it was five billion years ago. We simply know that it appears to be expanding slower than than the area 1 billion light years away.

That's exactly what I would expect to see.
A star 10 billion light years away is in an area of space with much less matter in its immediate and surrounding area than a star 1 billion light years away.
Therefore there would be much less of an effect of the "gravity brake" on it, and the speed it is travelling away from "Universal Central Point" (if there is such a thing) would have been impeded much less than the stars and galaxies that are in a much more densely populated area.

 

We are in agreement with your general premis. My view extends a bit farther to mean that you have gravity at the interior regions and accelerated expansion at the exterior regions. All caused by the same source.

 

The expansion is accelerating, not decelerating as I think you are implying. The accelerated expansion is the unaccounted for phenomena for which dark energy was introduced.

 

As I understood the research, we don't actually have evidence that "Galaxy X" at 10 billion light years away is accelerating at greater rate than it was 2 billion years ago, rather we have evidence that "Galaxy X" at 10 billion light years away is accelerating at a greater rate than "Galaxy Y" at 4 billion light years away.

We did this by measuring the brightness of Supernovae at different distances in space.
Is this correct?
If not, how exactly did we determine that "Galaxy X" is, in fact, accelerating at a greater rate than it was 2 billion years ago?

 

I believe that the primary principle is the assumption that red shift is recession related. The problem is that there are other theoretical explanations for a red shift, i.e. the "Tired Light Theory".

I believe in the accelerating expansion for other reasons than doppler shift based on my own work in the area of gravity.

 

I am not sure the universe is accelerating, sure things farther are receding faster, but that just means its expanding, not, necessarily, that is it accelerating.

last I heard (from my physics teacher) was that it is too early to tell, the data points we have are incredibly close to linear (which would mean a constant rate of expansion), but it just so happens that our data points would look almost exactly the same whether or not there were an acceleration (either way) or constant expansion. we will be able to tell for sure a couple of billion years from now.

 

Can you do me a favor and leave yourself a note to email me then?

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I do think you physics teacher is a bit behind the times on this. I think the red shift data, expecially after hubble, has made the acceleration commonly accepted.

 

As I understood it, it had nothing at all to do with redshift.
The numbers were arrived at solely through the brightness of supernovae.
I would love to learn more about this.

 

I believe you are correct in that there have been other indicators but red shift was the initial, if not primary, basis for believing the expansion was accelerating.

 

You are all missing one small concept. There is no "internal most" part or "outer edge" to the universe. You are taking the pictures you see in books and on TV to literally. As Mac pointed out, the BB was an explosion OF space, not IN space. It happened everywhere, at the same time. The universe is not a ball of expanding space. The universe is most likely infinite in extent and we only see the portion limited by our hubble horizon. Remember, every non-local region is expanding from every other. The acceleration is still a mystery (dark energy) and it was indeed detected by the observing the spectra of very distant (old) supernovae.

 

So, is the Universe expanding or is the our local observable space expanding into the Universe?

If the Universe itself is expanding:
A.) It can not be Infinite.
B.) There is an outer edge.

If the Universe itself is NOT expanding (rather our observable space is expanding into the Universe) is it viewed as expanding radially outward from a central point?

 

Space is expanding. Matter is not moving into any new space. The expansion of space itself is carrying matter away from us and every other point simultaneously. This is what causes the cosmological redshift.

Yes, it can. It my be infinite and unbounded or finite and unbounded.

The example is of a 2D being living on an infinite plane or sphere. It cannot fathom the 3rd dimension. On the plane, it will travel forever in any direction and never pass the same point again. On a sphere, it can travel such that it returns to its original point. However, if the sphere is expanding such that the "space" between the being and it's destination expands faster than light, it will never reach it. (yes, space itself is expanding faster that 'c'. This defines the Hubble horizon).

No, there isn't. See above.

See above. There is no central point, just like there is no "central" point on the surface of a sphere. The sphere surface is a poor metaphor for the 3D volume that we call space. Impossible to visualize really.

 

I'm not saying this in any demeaning way but you have a very common problem concieving of a finite universe without an egg shell edge.

The way I view it is to assume the universe is formed of time and space.

Nothingness is the absence of time and space. What you want to call an edge or shell assumes something beyond what you call the universe and "Nothing" (not as in a void) exists beyond the finite dimensions of the universe.

What could exist in the absence of time space?

 

OK, I have two questions...
1.) Can an infinitely long string get longer?
2.) What reason do we have to believe that the Universe itself is expanding rather than the Big Bang being an explosion of matter IN space (as opposed to an explosion that created space) and that matter is traveling outwards from that point of explosion radially?

 

Actually, upon reading wikipedia they say that the big bang resulted in the explosion of spacetime from a single point as shown:
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link to image</center>

Which goes back to what I said when I tried to put together a synopsis of Stephen Hawking's thoughts but gave up when it appeared his opinions changed with the wind.

 

1) Meaningless question. A change in length (i.e."get longer") implies a finite length that can be added to to increase length. You stated that the string was already infinetly long. Question is flawed.

2) Lots and lots of megawatt powered brains working for decades. And:

- Uniform distribution of mass in the observable universe.