Where Does Space End? It Must End Somewhere!

[YT2095]

Our universe floats about in a conceptually-impossible void of nothing, impossible in the sense you cannot describe it in any sense which is like having no apples, to some. This nothingness is by definition, something that should not be considered at all. You can say, that if you where a tachyon travelling a little faster than the superluminal speed the universe is now receeding the distant galaxies, you will eventually reach a part of spacetime which is so heavily curved, you will come back on yourself. You will always remain in spacetime, because there is nothing according to physics which exists, other than everything contained within spacetime.

 

Therefore, clearly said, there is no edge to the universe.

 

actually real Void Space, the tachyon or Photon would be able to travel through but lose much more energy than it would traveling through Normal space (based upon the the assumption that tachyons actually exists and there is no evidence for this yet).

but I agree, it is almost indescribable/unexplainable in it`s nature, and we don`t have to go to the edge of the Universe to observe it (or rather Not observe it).

I would also like to see evidence to support that space would "turn back on itself", there seems to be non that support it so far?

[Royston]

No it hasn't been answered, because i haven't answered it.

 

Tom, as Mooey has pointed out, whatever you aspire to is irrelevant to the discussion. My education is geared towards cosmology and astrophysics, but so what. Plus, although I agree with your conclusion, parts of your reasoning, I have to say, are poorly conveyed. Also, it's not hard to provide citations and references, I really can't understand why this is an issue, for instance...

 

However, Albert Einstein, one of the greatest physicists that had ever lived, showed that everything that 'counts' must be contained within the expansion of space and time - thus - the edge of the universe is the boundary between nothing and everything; and it also suggests that nothing quite literally is 'nothing,' so there is no edge, and no true boundary between two things.

 

Citation please. As for the OP, I took the liberty to plough through this thread and here are some model answers, (there are other good answers from other people)...

 

Example 1

 

Example 2

 

I completely agree with Severian's point here...

 

Yes, this has been a free-for-all for posting nonsense

 

Therefore, clearly said, there is no edge to the universe.

 

I have no argument with this, (though I disagree it was 'clearly said') and I doubt anyone, with a rudimentary understanding of the subject will argue with your conclusion.

 

My contention with this thread is the abundance of hand waving, stated as fact. For passers by on this forum, they're going to walk away with some very strange ideas of astronomy and cosmology.

 

I hope you can see why this is irritating, hence my post. There's a place for ideas that are outside the widely accepted models, and that's speculations. If they really do have something substantial (which is sadly rare) then it deserves a place here.

[YT2095]

good point about the Citations, although most of you probably already know about Void Space anyway, for those that don`t have a look at this: http://news.bbc.co.uk/1/hi/sci/tech/6962185.stm

 

it`s a bit "Spooky" but pretty cool at the same time

[Tom Vose]

actually real Void Space, the tachyon or Photon would be able to travel through but lose much more energy than it would traveling through Normal space (based upon the the assumption that tachyons actually exists and there is no evidence for this yet).

but I agree, it is almost indescribable/unexplainable in it`s nature, and we don`t have to go to the edge of the Universe to observe it (or rather Not observe it).

I would also like to see evidence to support that space would "turn back on itself", there seems to be non that support it so far?

 

I could argue the energy of the tachyon but i never really made a references to the photon.

 

If you want evidence to the curved spacetime, around the (so-called boundary of a universe, hold on please).

[someone]

Will not everything ends and numbers also never ends u could just count for ever and u will never get to the last number. And some of that time you need some of it to name the numbers that have no names yet (if u get to those numbers) so not everything really ends.

[north]

space ends at the edge where energy/matter is no longer created

[Sovereign]

Ever since I was a young boy, I have wrestled with trying to understand space. In particular, I have never really understood how space is supposed to never end. I really don't see how that's possible. Everything ends somewhere. Where one thing ends the next begins.

 

Can people please provide thoughts on this?

 

That depends how you define space. If I define space as that which doesn't have shape, then space has no borders, since borders only apply to objects(that which has shape).

 

For anyone who claims space has shape, what gives shape to space? What contours it?

[north]

That depends how you define space. If I define space as that which doesn't have shape, then space has no borders, since borders only apply to objects(that which has shape).

 

For anyone who claims space has shape, what gives shape to space? What contours it?

 

energy/matter shapes and contours space

 

think three dimensions , 360 degrees

[electricman6913]

Would the edge of space be curved so that we could never reach it.

[npts2020]

Would the edge of space be curved so that we could never reach it.

 

My understanding of current cosmological thinking says there is no "edge" of the universe per se only a limit to what is observable.

[mooeypoo]

I believe I heard somewhere that the universe is best compared (in shape) to a doughnut.

In that case, there shouldn't be any edges. Anywhere... just edge to what we see, maybe, like npts2020 suggested.

 

Any astrophysics experts to the rescue? *cough*martin*coughcough*

[Cap'n Refsmmat]

From what I understand, the actual shape is still up for discovery, but a doughnut is one of the possibilities.

[npts2020]

If we had accurate enough measuring devices, we might possibly be able to tell where there is mass outside our currently visible universe by detecting perturbations of the most distant galaxies we can see directly. IMO there is no logical reason to believe the earth is the center (or even near) of the universe, even if there is such a thing.

[Martin]

My understanding of current cosmological thinking says there is no "edge" of the universe per se only a limit to what is observable.

 

That's right. And current mainstream cosmo is essentially what this particular subforum is about, not the more speculative scenarios. Educational function.

 

In that case, there shouldn't be any edges. Anywhere... just edge to what we see, maybe, like npts2020 suggested.

 

Right! We seem to have agreement. Thanks npts2020, Moo.

Toroid (donut) type is one possibility among several, like Cap'n says.

 

From what I understand, the actual shape is still up for discovery, but a doughnut is one of the possibilities.

 

I agree! Space could be flat-out infinite, or it could be finite volume in which case the 3D analog of the 2D surface of a sphere is one that gets a lot of consideration----or the 3D analog of the 2D donut surface as was mentioned.

 

For practical purposes the issue boils down to measuring Omega, sometimes written Omega_total, the total energy density as a ratio to the energy density needed for spatial flatness.

 

The most recent 95% confidence interval* for Omega is [.992, 1.018].

You can see it is roughly [0.99, 1.02].

 

More accurate measurement is on the way (a new satellite observatory is scheduled for launch this year.) If Omega turns out to be over one, like 1.01, then it is the finite volume case---probably the 3D sphere.

Otherwise most likely infinite.

 

The key thing is how that 95% confidence interval develops. It incorporates CMB temperature data, Supernova data---data of various sorts. It keeps narrowing down. But no one can say if it will narrow down on the up side of one.

 

npts2020 has basically right message.

 

If we had accurate enough measuring devices, we might possibly be able to tell where there is mass outside our currently visible universe by detecting perturbations of the most distant galaxies we can see directly. IMO there is no logical reason to believe the earth is the center (or even near) of the universe, even if there is such a thing.

 

More precision data will narrow the range of possibilities for model of the universe.

 

*Currently the best most up-to-date source is this paper by Komatsu, Dunkley, Wright etc etc (Ned Wright was in on it. )

http://arxiv.org/abs/0803.0547

Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation

E. Komatsu, J. Dunkley, M. R. Nolta, C. L. Bennett, B. Gold, G. Hinshaw, N. Jarosik, D. Larson, M. Limon, L. Page, D. N. Spergel, M. Halpern, R. S. Hill, A. Kogut, S. S. Meyer, G. S. Tucker, J. L. Weiland, E. Wollack, E. L. Wright

---

Merged post follows:

Consecutive posts merged

I think this thread has gotten out of hand. Any new posts that sound mystical, refer to undefined concepts outside mainstream cosmology can be moved to Speculations forum. Have to either lock it or keep it on track.

 

We can't keep on hosting stuff that sounds like the BAUT "Against the Mainstream" forum. Doesn't jibe with main purpose. Dis-educational. Confuses newcomers.

Edited January 6, 2009 by Martin
Consecutive post/s merged.

[Phi for All]

Warning: This is a large thread on current mainstream cosmological concepts. Any speculative additions will be moved to the proper section. If you are posting to this thread rather than starting a new one in Speculations, please keep to the original intent.

Edited January 7, 2009 by Phi for All
punctuationalness

[DJBruce]

I was under the impresion that the universe was flat, "The simplest version of the inflationary theory, an extension of the Big Bang theory, predicts that the density of the universe is very close to the critical density, and that the geometry of the universe is flat, like a sheet of paper. That is the result confirmed by the WMAP science."

 

http://map.gsfc.nasa.gov/universe/uni_shape.html

[Martin]

I was under the impresion that the universe was flat, "The simplest version of the inflationary theory, an extension of the Big Bang theory, predicts that the density of the universe is very close to the critical density, and that the geometry of the universe is flat, like a sheet of paper. That is the result confirmed by the WMAP science."

 

http://map.gsfc.nasa.gov/universe/uni_shape.html

 

Near flatness is an observational fact. For instance before WMAP it was inferred from galaxy counts---redshift surveys. The fact that the number of galaxies within a large volume increases as the cube of the radius. This represented a puzzle called the "flatness problem"

 

Inflation scenarios were invented (around 1980) and got astronomers' attention because they addressed the flatness problem, and several other puzzles (notably the near uniform temperature of the CMB.)

 

One cannot argue that inflation implies space is flat.

Any logical connection goes the other way!

The observed near flatness is one of a handful of reasons we have for taking the idea of inflation seriously. Inflation scenarios are adjusted to produce the observed degree of flatness and CMB temperature uniformity.

 

Inflation has not been proven, and would depend on undiscovered physics---require some exotic entirely speculative "inflaton" mechanism to make it work. What lends it some degree of credibility is the fact that it offers one possible explanation for why space is nearly flat, and observed features of the CMB.

 

Near flatness does not imply perfect flatness.

The situation is summed up in the 95% confidence interval in that WMAP paper I cited. We could have a finite spatial volume and a slight positive spatial curvature. That would fit the data and constitute near flatness.

 

Or we could have infinite spatial volume and exactly zero spatial curvature.

("Like a sheet of paper" in the words of that NASA popularization website.)

That would also fit the data---perfect flatness as a special case of near---I hope this makes sense to you: near includes the possibility of perfect?

 

That WMAP paper is the latest official report on the WMAP results bearing on cosmology, by the scientists themselves. It says what you need to know. The popularization stuff from the PR department is often misleading and poorly written, best to just leave it alone.

 

You might be interested in the figure they give for the radius of curvature in the finite volume case. As I recall they give a lower bound of some 101 billion LY. In other words if space is a hypersphere---the 3D analog of the surface of an expanding balloon---then the circumference of that hypersphere is at least 2 pi times 101 billion LY. It's nice---they give us a rough handle on the size---a lower bound estimate.

 

Neither the finite volume nor the infinite volume case is ruled out at present.

For convenience, here's that WMAP link again:

http://arxiv.org/abs/0803.0547

Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation

Edited January 6, 2009 by Martin

[Mr Skeptic]

For practical purposes the issue boils down to measuring Omega, sometimes written Omega_total, the total energy density as a ratio to the energy density needed for spatial flatness.

 

The most recent 95% confidence interval* for Omega is [.992, 1.018].

You can see it is roughly [0.99, 1.02].

 

More accurate measurement is on the way (a new satellite observatory is scheduled for launch this year.) If Omega turns out to be over one, like 1.01, then it is the finite volume case---probably the 3D sphere.

Otherwise most likely infinite.

 

Is it possible for the value of Omega to vary depending on where it is measured from? I know that the universe is supposed to be homogeneous at large scales (though I've heard that it might also be fractal), but what if it is not homogeneous at the scale of the observable universe? If the value of Omega is different in different places, could one big chunk of space curve one way, and another curve the other way?

[Martin]

... could one big chunk of space curve one way, and another curve the other way?

 

Certainly!

 

All sorts of weird stuff might be true. Your idea of largescale inhomogeneities is pretty mild compared with some of the other stuff people talk about.

 

David Wiltshire (prominent Kiwi cosmologist) tried vigorously for several years to promote largescale inhomog as a substitute for dark energy. We may have talked about this...I don't recall. I was interested in Wiltshire's arguments for a while. At one point I think there were perhaps a halfdozen people writing papers exploring the idea.

 

My impression is that cosmologists frequently have a kind of loner or revolutionary mentality. The crew appears orderly and wellbehaved but there is always mutiny brewing below the surface. They love challenge to the main assumptions of their field and whenever somebody comes up with a reasonable sounding challenge there is a stir or ruckus for a while. It either catches on or it doesn't. Wiltshire's didn't, at least so far.

 

A governing factor here is Occam razor a.k.a. economy. It is a pragmatic mathematical field where you want a mathematical model that gives the best fit to the data with the fewest adjustments. You want it simple.

 

A major assumption is uniformity. People keep looking for evidence that will challenge uniformity but they don't find it. So the simplest thing to do is assume largescale homogeneity. Of course there's going to be some minor fluctuation about the average, and that gets intensely studied. (For an example, check out Baryon Acoustic Oscillation---a huge ripple in the distribution of galaxies believed to stem from early universe.)

 

But so far the uniform model is working out. That means simple, just two equations. One timeline. One Newton constant G. One Hubble rate H(t). One critical density, rhocrit(t), calculated directly from G and H(t).

One overall average density rho(t). And therefore just one Omega(t).

Omega is simply the ratio (rho/rhocrit) of actual largescale average density to the critical density one calculates from G and H(t). So if it is reasonable to assume these things are uniform then Omega can be taken to be uniform as well.

 

So far the data is running with the simple model. People keep proposing and trying out more complex models---like Wiltshire's. They turn out not to fit, or they take too much fine adjustment, tweaking too many knobs. They drop out of sight. Maybe all we can say about standard is "so far it's working out."

 

Some day another revolution will happen, like the one in 1998. Some alternative will be proposed, the old model will choke on some new data, the new model will catch on----and then that will be the standard. And then it too will work out OK for a while.

[jamey2k9]

this is more theory than fact but you have to think what was here before time what was there before space what was there.com think of it like this im guessing yes the universe has boundaries but the boundaries have no boundaries if there was a place before time and space surely the universe can expand into that

[NowThatWeKnow]

this is more theory than fact but you have to think what was here before time what was there before space what was there.com think of it like this im guessing yes the universe has boundaries but the boundaries have no boundaries if there was a place before time and space surely the universe can expand into that

 

Hi "12 year old boy with a 1200 IQ". Could you use some punctuation so us folks with a lower IQ don't have to work so hard?

[jamey2k9]

Yes sorry my punctuation is terrible (and can you even get an IQ of 1200)

[ydoaPs]

Yes sorry my punctuation is terrible (and can you even get an IQ of 1200)

 

/me points to your signature

[devrimci_kürt]

martin,I like the stuff you write

[mooeypoo]

martin,I like the stuff you write

There's a link saying "(say thanks for this post)" at the bottom of each post. Use it ! He deserves it, and it'll have even more effect