What Is Beyond The Observable Universe?

[DaveC426913]

But NOT any Mass that may be near the 'edge', that can NOT be traveling away from us that fast?

Yes, galaxies are receding from us at speeds greater than the speed of light.

No, that does not violate SR.

 

[Max™]

They aren't traveling away from us through space, they're being dragged along with the expansion of the Universe.

Locally they aren't moving that rapidly, it is only when you examine scales approaching that of the observable horizon that you see this apparently forbidden motion.

Nothing can move THROUGH spacetime faster than light, spacetime itself is not moving through spacetime, it has different constraints.

 

[sylas]

They aren't traveling away from us through space, they're being dragged along with the expansion of the Universe.

This depends, I suggest, on what analogies or similes you like. But IMO the technical descriptions do not really correspond to anything "dragging" things. "Dragging" suggests some kind of force, which pulls objects along in some way. But there is no "force" corresponding to a drag that is forcing things apart. There's dark energy of course, which is a bit like a pressure that accelerates expansion; but you still get all the same superluminal proper recession velocities in a universe where there is no dark energy and the expansion is slowing down. You get superluminal expansions in a model where the expansion rates are linear, without any acceleration or deceleration. That is, no forces at all, just expansion of things with recession velocities for co-moving objects remaining constant.

That is -- you STILL get superluminal recessions whether the expansion is being pushed to increase or dragged to slow down, or if it is just coasting.

So for this reason, I feel that speaking of space "dragging" things is really misleading.

Personally, I think might be better to say that space is being dragged along by all the stuff that is expanding, if we speaking of anything being "dragged". Any sufficiently large volume withing boundaries that are locally not superluminal will be increasing in total volume. That is, there's more space between things as time goes by.

Locally they aren't moving that rapidly, it is only when you examine scales approaching that of the observable horizon that you see this apparently forbidden motion.

That's definitely incorrect on two counts.

The most unambiguous problem is with the suggestion that superluminal recession velocities have anything to do with being at boundaries of the observable universe. That just isn't true. You get superluminal proper recession velocities for galaxies that are "now" something like 14 billion light years away in proper distance, or only about a third of the way to the edge of the observable universe. Roughly speaking.

More subtly, I don't think it is really meaningful to say "locally they aren't moving that rapidly".

Of course, everything out at some distant location is all moving locally with respect to each other at small velocities, much like in our own neighbourhood. But that's simply not bothering to look at expansion of the universe at all. The expansion of the universe is not a local effect. It really means that density of things is falling as everything moves apart from everything else (on sufficiently large non-local scales).

The proper distance between things IS increasing that rapidly. Whether you speak of this as things moving apart, or as the space between things increasing; it still isn't any object being dragged.

The precise way to describe expansion of the universe is GR, of course. The rest is analogies or similes, and all too often they end up being actively misleading if you are not careful to remain consistent with the underlying GR account.

Cheers -- Sylas

 

[Max™]

I didn't mean to imply that it had to do with being at the edge of the observable Universe, as symmetrically we would expect our current position to appear the same from the perspective of an arbitrarily distant point.

I use the term dragging out of habit, as the space in which you are located itself is moving, you aren't going to observe forces relative to it, you would only notice red shift from everything else moving away from you.

I'm only speaking of the GR description, I take that for granted in such discussions.

 

[Mihael@@/&]

Things have changed since Mar8-06, 06:08 AM :)

http://en.wikipedia.org/wiki/Observable_universe

"No evidence exists to suggest that the boundary of the observable universe corresponds precisely to the physical boundary of the universe (if such a boundary exists); this is exceedingly unlikely in that it would imply that Earth is exactly at the center of the Universe, in violation of the Copernican principle. It is likely that the galaxies within our visible universe represent only a minuscule fraction of the galaxies in the Universe. According to the theory of cosmic inflation and its founder, Alan Guth, the lower bound for the diameter of the entire Universe could be at least in the range of 10^23 to 10^26 times as large as the observable universe."

 

[heusdens]

Is it just black space extending forever? Or perhaps black space for a finite distance until another universe?

I find it hard to believe our universe is just the only universe. I don't see how it wouldn't extend for eternity instead. What is so special about our universe and the space we are in?

What do you think?

You didn't mention this option in the poll, but the most serious candidate for the universe outside the horizon, since the horizon is just an arbitray limit, is that the universe outside of the horizon is simply more of the same, and in fact not anything different then we see here.

All other assumptions are speculations. Why would it be that the universe outside of the horizon (which used to be bigger in the past and will be smaller in the future) would be any different then the part we see?

That needs an explenation.

So the only serious option is that the universe outside of the horizon is the same (same homogeneity and isotropy) as the part we see.

 

[heusdens]

.. On the other hand, the total universe is is still finite, but there is no such thing as outside.

How do you know that?

 

[heusdens]

But most evidence points to the universe being flat. In that case a what would happen if you reach the end of the universe? If it were a spherical universe then we would just reach the other side. But what would happen if you reach the end of the universe? Would their be like a giant hard barrier that you can hit but not explode? Sounds to mythical to me. The universe seems to complex for it to be just finite.

The universe isn't infinitely big and infinitely small?

The current assumption or basic premise is that the universe has no edge or boundary.

You will never see a sign in space "end of universe, turn back now" there will simply be "more universe" after such a (fictional) sign.

For practical measurements, the universe we can observe only exists in finite parts and measurements, but this does not imply the universe must be finite and spatially closed (like a 2d surface on a 3D sphere, but then for the 3D analogous situation).

But from a more philosophical point of view I would think that by necessity the university (the totality of it) must be infinite, yet at the same time this infinity only exists in the form of finitudes. Indespite that this seems a contradiction, it is not as can be seen from this analogy: you can pick arbitraily any natural number, and you will always come up with a definite finite (and countable) quantity, yet the number set itself is infinite, you can always draw more numbers and larger numbers, no matter how long you draw a number.

Our measurements are like the numbers we can draw, the universe is like the complete set.

Notice also that the finitude and/or the infinitude of the world form a dialectical unity, you can not determine one without the other, they are like the two sides of the same coin, or the two poles of a magnet.

 

[heusdens]

...

Both those regions are at the edge of our observable universe... and we are the edge of their observable universe as measured now. But those two regions at opposite sides of the sky are OUTSIDE the observable universe for each other.

Cheers -- sylas

Good argument, and when we invoke the cosmological principle, that the universe looks (at sufficient large scale) the same in all parts of the universe, we arrive at the conclusion that beyond the horizon of observation there is just more universe that looks about the same as the stuff and structure we see.

 

[zahero_2007]

there is a multiverse

 

[TheTechNoir]

there is a multiverse

Care to elaborate?

And my answer is that what exists beyond the visible universe is the exact same as what exists here. I find it an unlikely possibility that somewhere far off the laws of physics change.

I believe that the universe has no boundary and therefore I also believe that outside the observable universe you see the same thing there as we see here (speaking on a large, far away view that is - obviously locally there are lots of differences but broadly speaking the universe is quite uniform). Because of no boundary, this means that a spatially flat universe with a finite size, a spatially flat universe with infinite size (seems to currently be a lot of people's preferred belief whereas flat/finite seems to be more fringe), the closed universe or 2d surface of sphere anology universe, the saddle, and all other known possibilities would all lead me to believe that in any given region of space outside of our observable universe you would observe roughly the same thing as we do here.

EDIT: Question: I understand it, but am I the only one who finds it a bit difficult to mentally visualize the step up from 2d analogue to full 3d closed universe?

EDIT 2: Lastly, I find it EXCEEDINGLY unlikely that just past the exact tip of our observable universe at any given time all matter disappears and space becomes utterly empty. Heck if from ANYONE'S perspective this were to be the case I would be beyond shocked. But for it to happen to be exactly/perfectly around us, no less? Me thinks the poll options are both completely crackpot.

 

[cristo]

EDIT: Question: I understand it, but am I the only one who finds it a bit difficult to mentally visualize the step up from 2d analogue to full 3d closed universe?

I think it's perfectly normal not to be able to visualise in 4D

 

[mistergrinch]

Beyond the observable universe it's turtles all the way down -- aka the "turtleverse". Turtleverse Theory is about to revolutionize the field of cosmology!

 

[harcel]

Beyond the observable universe there is lots and lots of unobservable universe,

 

[Radrook]

Beyond the observable universe there is lots and lots of unobservable universe,

Where is the universe located?

 

[Jake4]

Beyond the observable universe there is lots and lots of unobservable universe,

I like this answer the best.

 

[DevilsAvocado]

Where is the universe located?

Here.

 

[rinardman]

Is the universe infinite? If it isn't infinite, then how much bigger is it than the observable universe? How would humans ever be able to answer the second question?

I can't imagine the universe being finite, because that would mean besides there being a "here", there would have to be a "there". (At least in my mind)

And, I can't imagine a universe that is infinite, because my human brain, as magnificently constructed as it is, is woefully underpowered to do that job.

I pondered this a lot in my younger days, but now that I'm getting old I've decided to just be as happy as I can, in my little corner of whatever the universe really is.

*

 

[Gold333]

I don't understand this question.

If the poll asks what the change in structure is that the boundary of the observable universe represents (e.g. photon decoupling, looking back into the past up until close to the big bang, etc)

...that would put Earth at the centre of this sphere (at the "edges" of which something changes).

How can the Earth be at the centre of the universe? (or at the centre of the sphere at whose "edges" something changes?

 

[Radrook]

If indeed the universe is infinite then how can it grow? You cannot add to the inifinite because if you do then it wasn't infinite to begin with.

 

[Nabeshin]

If indeed the universe is infinite then how can it grow? You cannot add to the inifinite because if you do then it wasn't infinite to begin with.

This is a very fundamental misconception of what something means to be infinite. I do not really feel like writing a very long post explaining precisely why this is wrong (perhaps someone else will), so I suggest you google around for a short while and come to understand infinity a little better.

 

[periot123]

universe is not flat it has three and some say it has four dimentions philosophically we can call it infinite. No one can measure its boundary if we say that the universe is finite its like counting sand in the shore ^_^ in the end even if the universe is finite or infinite we cannot measure its boundary ....

 

[JaredJames]

universe is not flat it has three and some say it has four dimentions philosophically we can call it infinite. No one can measure its boundary if we say that the universe is finite its like counting sand in the shore ^_^ in the end even if the universe is finite or infinite we cannot measure its boundary ....

What does any of that mean?

There are four basic dimension of the universe, not three - don't know where you pulled that from.

The number of grains of sand on a shore line is a finite number and nothing to do with infinity so I don't know where that comparison comes from.

We've already estimated the size of the universe, although it's only based on our current knowledge we are "measuring the boundary" if you will.

 

[Tanelorn]

What is black space? And what is blacks space? Do you mean empty space?

I believe that the observable universe is just a tiny (like 10-30 or far smaller) part of the whole universe. I think Penrose proposes this. I also ask if the observed homogeneity of our observable universe only appears that way because we are looking at just a tiny grain of sand part of the whole. I also sometimes wonder if given the above scenario whether the universe could still be undergoing continuous inflation at some point now a very great distance away, pushing the expansion of space everywhere else, including here. This would also be the same point that our observable universe inflated from 13.7B years ago. I recall that the Inflation and/or dark energy expansion of space can apparently separate any two points in space at a rate many, many times faster than the speed of light. However I am probably talking complete nonsense because I have little understanding of GR or advanced mathematics, I probably get my ideas from the water cycle here on earth!

So I guess I have to vote other!

 

[DevilsAvocado]

...that would put Earth at the centre of this sphere (at the "edges" of which something changes).

How can the Earth be at the centre of the universe? (or at the centre of the sphere at whose "edges" something changes?

Where is the center on the surface of a sphere?

https://www.youtube.com/watch?v=I9Cjxd4Mjog

https://www.youtube.com/watch?v=17jymDn0W6U


See these threads for further info:

https://www.physicsforums.com/showthread.php?t=365912"

https://www.physicsforums.com/showthread.php?t=368057"

 

[Isaacsname]

Wow, I wish I understood more of this, it's fascinating even based on conjecture.

I found this site recently that shows the assumed scales of things in our universe as well as the size of what is unobservable ( Planck scale to 900m light years ) They say the observable is 190m light years, and the unobservable is 900m light years.

http://primaxstudio.com/stuff/scale_of_universe/

How does one come to the conclusion of the size of the unobservable areas ? Or is it a necessary to satisfy some cosmological model ?

Thanks,

Isaac

 

[JaredJames]

I found this site recently that shows the assumed scales of things in our universe as well as the size of what is unobservable ( Planck scale to 900m light years ) They say the observable is 190m light years, and the unobservable is 900m light years.

How big?

Try 93 billion light years in size, with the observable universe being ~48 billion light years if my memory is correct.

 

[Isaacsname]

What is black space? And what is blacks space? Do you mean empty space?

I believe that the observable universe is just a tiny (like 10-30 or far smaller) part of the whole universe. I think Penrose proposes this. I also ask if the observed homogeneity of our observable universe only appears that way because we are looking at just a tiny grain of sand part of the whole. I also sometimes wonder if given the above scenario whether the universe could still be undergoing continuous inflation at some point now a very great distance away, pushing the expansion of space everywhere else, including here. This would also be the same point that our observable universe inflated from 13.7B years ago. I recall that the Inflation and/or dark energy expansion of space can apparently separate any two points in space at a rate many, many times faster than the speed of light. However I am probably talking complete nonsense because I have little understanding of GR or advanced mathematics, I probably get my ideas from the water cycle here on earth!

So I guess I have to vote other!

No, I think you are correct, at least according to what I understand so far myself.:tongue2:

Have you checked out Leonard Susskind's Stanford lectures on FLRW standard cosmology ? They're on Youtube, 8 of them , iirc, and he explains how the relative velocity of two galaxies in an expanding space traveling apart from each other can excede c by some factor, lecture 7 or 8 I think.

Good stuff, sometimes Susskind gets a little derailed with a train of thought, but still worth watching imho.

Isaac

 

[DevilsAvocado]

How does one come to the conclusion of the size of the unobservable areas ? Or is it a necessary to satisfy some cosmological model ?

Here is good info on the Observable universe:

http://en.wikipedia.org/wiki/Observable_universe

The diameter of the observable universe is estimated to be about 28 billion parsecs (93 billion light-years),[3] putting the edge of the observable universe at about 46–47 billion light-years away.

If you are puzzled by the fact the universe can be 93 billion light years 'wide', while it is 'only' 13.75 billion years old!?

The answer is: There is no speed limit for the expansion of the universe, but any object moving inside the universe is always limited to the speed of light.


EDIT:
Check out this thread for info expansion of the universe: https://www.physicsforums.com/showthread.php?t=365912"

 

[Isaacsname]

How big?

Try 93 billion light years in size, with the observable universe being ~48 billion light years if my memory is correct.

Yoikes, reminds me to always check the source. Had I just looked on the wiki page for " Observable universe " I would have found that the ~ 180/190m lightyear estimation originated from a model that stated an age of 15.8b years for the age of the universe. ( ...under " misconceptions " )

I guess the idea was flawed..:tongue2: and shown to be incorrect.

http://en.wikipedia.org/wiki/Observable_universe

from

http://www.astro.ucla.edu/~wright/old_new_cosmo.html#05Aug06

" The claim that the Universe would be 15% larger is partially incorrect. Even though relatively nearby galaxies would be 15% further away the actual size of the Universe would go from infinite (flat) to finite (closed) but very big, which is a smaller Universe. The distance to distant quasars at redshift z=6 would increase by only 4%, and the distance to the last scattering surface changes less than 0.5% because this is what is fixed by the CMB. "

Thank you, I just learned some things.

 

[pibb]

could antimatter lay beyond the universe?

 

[JaredJames]

could antimatter lay beyond the universe?

Judging by your two posts you have something for antimatter.

The answer to this one is basically no, but we could also say who knows.

I'd be swinging against that option though.

 

[awhalen]

Listen to yourself! Do events we can never know about exist or not? How the hell can you or I or anyone ever know? It's just a fantasy!

If a tree falls in a forest and nobody is there to hear it, see it, feel it, or observe it does it still fall and affect its surroundings?

Yes it does even though nobody knows about it. and if you go back to the spot at which it fell you could figure out what happened.

So asking the questions about this universe may lead us to understand what's outside our space time even though we will never observe it it still occurs

As Einstein said "everything is relative"

 

[Darken-Sol]

sorry i just jumped to the end. how about a process like quarks. is it possible all light sent out pops back to feul the big bang? i came to this conclusion with wild speculation and the use of a magic 8 ball.

 

[DaveC426913]

As Einstein said "everything is relative"

And Ted Stevens said "the internet is a series of tubes".

Spurious out-of-context quotes don't help much.

sorry i just jumped to the end. how about a process like quarks. is it possible all light sent out pops back to feul the big bang? i came to this conclusion with wild speculation and the use of a magic 8 ball.

Magic 8 ball.