Science Questions

What would we see at the edge of the universe?

Sun, 5th Jun 2011

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Question

Neil Henis asked:

Let's say we develop warp drive..say warp 1,000,000,000. We start at earth and travel 13.7 billion light years in any direction. When we get there-what will we see? Will there be a sign saying danger..slow down, universe ends in 10,000 light years, or will we simply see similar space and stars like we see here, with a further 13.7 billion light year limit in any direction. How far could we go like this?

Answer

Dominic -   Wherever you are in the universe, if you look at the distribution of galaxies and galaxy clusters around you, you will find that the sky looks more or less the same as anywhere else, and that's because you can think of the universe as being a bit like a sphere, only a three-dimensional surface of a sphere.  So on a sphere, you can go all the way around and come back to where you started again.  The universe is not a two-dimensional surface.  It’s a sort of three-dimensional surface or four-dimensional sphere if you want to think of it that way.  So, wherever you are on the surface of that sphere, you've got 13.8 billion light years worth of universe that you can see in any direction, full of galaxy and galaxy clusters.

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The universe does not have an edge, it is infinite, and it is essentially the same everywhere. Pikaia, Sun, 5th Jun 2011

Look at it from the viewpoint of topology. Then you could have a sphere, so as you move you return to your point of origin, there is also the doughnut which introduce two types of 'rotations', as it seems to me? As it has this 'hole' in the middle.



I wonder?

What the he* is infinity?

The *.gif is from: We are the doughnuts :) :Which in its turn lended it from Wikipedia commons: Which in its turn lended it from ? Which in its turn ?? Which .. yor_on, Sun, 5th Jun 2011

A complication that arises when talking about the hypothetical "warp drive" is that by definition this device moves us through a great deal of "space" in a very short "time". When talking about things cosmological, Einstein's theory of relativity requires that we specify what we mean by these terms. Involved in the issue not only of "what" is at the edge of the universe, but "when". We may get different answers depending on what we mean by "when". Atomic-S, Mon, 6th Jun 2011

@NakedScientists Space and time are curved... so if you could see all the way around... you'd see you again looking for yourself. was tweeted by @EvilEyeMonster @EvilEyeMonster, Mon, 6th Jun 2011

@NakedScientists The edge of the universe? HA... you'd see your own back. was tweeted by @EvilEyeMonster @EvilEyeMonster, Mon, 6th Jun 2011

Neil Henis asked the Naked Scientists: Let's say we develop warp drive..say warp 1,000,000,000. We start at earth and travel 13.7 billion light years in any direction. When we get there-what will we see? Will there be a sign saying danger..slow down, universe ends in 10,000 light years, or will we simply see similar space and stars like we see here, with a further 13.7 billion light year limit in any direction. How far could we go like this? What do you think? Neil Henis, Tue, 7th Jun 2011

Another Universe. Incognito, Wed, 8th Jun 2011

Spheres and Toroids for the shape of the Universe are all very speculative.

I don't believe anybody has been able to look out and see a primordial view of the Milky Way or Andromeda as reflected around a sphere or toroid. 

If one believes in a point-source Big Bang theory, then there would be no reason to think that there wouldn't be an edge out there somewhere, but that we just happen to be in the middle of a relatively high density region of the Universe.

It is possible that one would reach a place where stars and galaxies just start becoming rarer and rarer...  until there are just no more, and half the night sky would just be empty.

Or...  it is an equally likely argument that it is truly infinite. CliffordK, Wed, 8th Jun 2011

dont matter where, if theres no light u aint gonna see?as per optical BUT if theres an antilight thing out there u might get ur eyes pulled out of ur head? CZARCAR, Wed, 8th Jun 2011

Now, that is a model of a universe that might worry me slightly Czarcar. Remind me to take no star trips before your model has beeen invalidated. yor_on, Sun, 12th Jun 2011

http://news.discovery.com/space/feeding-black-holes-discovered-at-the-dawn-of-time-110615.html    hungry black holes & no comment from me CZARCAR, Thu, 16th Jun 2011

Of course, all these hypotheses are just that, hypotheses, be it doughnut, sphere, hecatohedron or twin doughnuts joined at the........... alright, a figure of 8 then.

The problem I have with all of them, is that they all suggest a boundary. Even if the centre of the universe is wherever you are, with 13.7b light years all around, it still suggests a limit of the universe. A boundary.

Though it is impossible for humans to comprehend, I am much happier with the concept of the universe (as we call it) being a mass of varying density expanding into an infinite void. Look beyond the limits of our universe and you will see nothing whatsoever. A total and boundless void. Don_1, Thu, 16th Jun 2011

Don - that boundary is considered more as a horizon than anything physical.  It has many of the same characteristics as the event horizon of a black hole - incl an analogue of Hawking radiation.  It is very complicated and frankly I struggle to get my head around it imatfaal, Fri, 17th Jun 2011

Yes, I see this term 'horizon' bandied around quite a lot and though the concept of a (or should that be 'an') horizon is easy enough to grasp, it still has me in a quandary. I know that there is something beyond the detectable horizon and if I move toward the horizon, I will be able to detect it, but the horizon has now moved and there is still something beyond it.

I think part of the problem with understanding the terminology of the universe is the inability of language to describe it and, as I have said before, the fact that we and our world are finite.

Perhaps I should describe my notion of the universe as being an inverted sphere. Now I must try to get my head around that idea. Don_1, Fri, 17th Jun 2011



A horizon (if you pronounce the h) An horizon (if you don't) - what you do when writing it - I dunno.  The horizon is the division between the part of the universe with which you can interact and those which you cannot (even at light speed communication).  Your second sentence is incorrect if I am reading it as intended.  Stuff outside your horizon is lost to you forever ( just as if you fall through the event horizon of a black hole then the outside is lost forever).

You point about language is very well made and correct - it is for this reason that much of physics and science in general requires the use of maths.  Our language and instinct are classical, small scale, slow speed, and low energy; when we move out of our comfort zone then language struggles to keep up and mathematical definitions/explanations are the only way of continuing. imatfaal, Fri, 17th Jun 2011

I think you can actually get to the edge, because if you keep going straight and not turning, you won't actually go around the sphere. You know what I mean? ???, Thu, 28th Jul 2011

It is difficult for man to contemplate eternity,but that is what it is, there is no beginning or end to the universe, so you could not reach the end of it,no more than you could find the beginning or end of time. It's just something which we don't have enough brain power to understand. grumpy10, Thu, 18th Aug 2011



I guess that would make you a Cosmic-Agnostic then, if that's what you believe. peppercorn, Thu, 18th Aug 2011

As a firm believer in empirical study..I went to the end of the universe this morning and this is what I found !




neilep, Thu, 18th Aug 2011

This is what you would find syhprum, Sat, 20th Aug 2011

I know it has been said in other ways but to put it simply, light rays travel a straight line in curved space.  Rather like a light ray follows the curves of a fibre optic.
That curvature stops it from effectively having an observable or definable edge.  It's a very similar concept to being inside the event horizon of a black hole.  In this case we are within the event horizon of the Universe. MikeS, Sun, 21st Aug 2011

I do not think the universe has an edge. I think it is infinite in size in all directions without looping back on itself. Robro, Tue, 23rd Aug 2011



But if it's already infinite in size how can it be expanding?
If it's infinite in size, would that not imply that it was always infinite in size in which case it could not have started with the big bang. MikeS, Wed, 24th Aug 2011

In a similar vein according to Alan Moore scripting as Tharg (of 2000AD comic fame) the end of the unioverse has "Big George was here" written across it in massive letters... Mazurka, Wed, 24th Aug 2011

In a similar vein according to Alan Moore scripting as Tharg (of 2000AD comic fame) the end of the unioverse has "Big George was here" written across it in massive letters...


Didn't Killroy beat him to it? MikeS, Wed, 24th Aug 2011



That's not true.  The big bang model actually says that if the universe was infinite, it was still infinite at the big bang, but it was also infinitely dense.  In other words, if the universe is infinite in size now, you can squeeze it as much as you want so it gets really dense and it will still be infinite in size.  You can keep squeezing forever, so it's density increases without bound (towards infinity) and it will still be infinitely large. 

Here's a reference: http://www.astro.ucla.edu/~wright/infpoint.html

This is definitely not intuitive, but we're dealing with an infinitely large universe, so our intuition, which is based on visualizing finite objects, breaks down here. 

Of course, we don't know if the universe is infinite, but it's one possibility that so far agrees with what we've observed.  We haven't ruled out all the other possibilities yet. jpetruccelli, Wed, 24th Aug 2011



That's not true.  The big bang model actually says that if the universe was infinite, it was still infinite at the big bang, but it was also infinitely dense.  In other words, if the universe is infinite in size now, you can squeeze it as much as you want so it gets really dense and it will still be infinite in size.  You can keep squeezing forever, so it's density increases without bound (towards infinity) and it will still be infinitely large. 

Here's a reference: http://www.astro.ucla.edu/~wright/infpoint.html

This is definitely not intuitive, but we're dealing with an infinitely large universe, so our intuition, which is based on visualizing finite objects, breaks down here. 

Of course, we don't know if the universe is infinite, but it's one possibility that so far agrees with what we've observed.  We haven't ruled out all the other possibilities yet.


But if it was infinite in size and density at the moment of the big bang because of the horizon problem the big bang could not have been an instantaneous event over all of the universe.  This would surely have left the universe less than homogeneous and isotropic as it appears to us?  Also if it was already infinite in size what purpose did inflation serve?  How does quantum mechanics account for the void being able to instantly cough up an infinite amount of energy?  This would seem to imply it was at no cost.  If our observable universe started from a point is that the same as a singularity?  If so there must have been an infinite number of singularities.  Why didn't they combine?  If it was infinitely large and infinitely dense then it must have been an infinitely large black hole not multiple ones?

This maybe the mainstream view but honestly, to me it sounds more like magic and unicorns mushrooms, or perhaps just desperation. MikeS, Wed, 24th Aug 2011

Well, Mike, my post was to point out that you were misleading someone about what the big bang model allows or doesn't allow.  It's pretty clear you don't understand the model, despite the fact that you continually post and tell others why it's wrong.  This is your modus operandi on a lot of areas of physics on this forum. 

If you'd shown any desire to engage in actually learning physics in the past, I'd be more helpful, but you've made it clear that you're here to evangelize, not to learn.  So I'll just say that all your objections listed above are answered by realizing that the singularity of the BB need not be a point.  The universe can remain infinite in size but grow infinitely in density as you move back in time towards the big bang.  The singularity if where the density becomes infinite and the models break down.  It may not be comfortable to think of things (energy, size, density) being infinite in the early universe or the modern universe, but the theory is about matching observations, not feeling comfortable.


Sure, you're welcome to believe any theory you want.  We have an entire new theories section forum for discussing non-mainstream theories.  We don't even require that you learn about the reasons why the mainstream theories are so widely accepted before you go promoting an alternative. 

You're not welcome to continue to mislead other posters by offering bad science in order to trash mainstream theories (and thereby promote your alternatives). jpetruccelli, Wed, 24th Aug 2011



But if it's already infinite in size how can it be expanding?
If it's infinite in size, would that not imply that it was always infinite in size in which case it could not have started with the big bang.


That's just it, no one has proven the Universe is expanding. I can more easily say it is infinite, than to say the Universe has an edge. And no I'm not implying that it could not have started with a big bang, I am stating that I do not think that the big bang ever existed. No one has proven that it did exist.

I mean, come on guys and gals, just THINK about it, really THINK. How is it possible to get something out of nothing, no space, no matter, no time, no potential, all this equals NO BIG BANG. No matter how many times you force a math equation on zero, if zero equals zero, you end up with zero. It is so simple. Robro, Thu, 25th Aug 2011

And to add to my last post. If you only concentrate on things that can be observed in nature, and you interpret your observations to the very best ability of modern science, you will ultimately come to the conclusion that the Universe has no edge. The big bang idea necessitates an effect without a cause. It throws real science out the door. I mean it's a cool fantasy, bringing in all the added dimensions and special relativity, the needed dark matter and dark energy to make the big bang Universe mostly all work out. But it does not all work out. Every time there is a problem with the big bang theory, a gang of physicists pile onto it and conjure up some new phantom particle or other dimension, or something that nobody can see, to fix it. They stack theories upon theories to keep it on life support. But it is taking it's last gasping breaths before it dies. It is sad that many good scientists stake their reputation on the theory and concept, rather than being able to keep their integrity and move on to better things. They feel that if the big bang dies, they die. So sad it is.        Robro, Thu, 25th Aug 2011


Sure, you're welcome to believe any theory you want.  We have an entire new theories section forum for discussing non-mainstream theories.  We don't even require that you learn about the reasons why the mainstream theories are so widely accepted before you go promoting an alternative. 

You're not welcome to continue to mislead other posters by offering bad science in order to trash mainstream theories (and thereby promote your alternatives).


JP
Lets just correct a few issues in your tirade.
If you had actually read my posts I seldom mention the big-bang and I agree with most of it anyway.
There was nothing evangelical in that post.  I was querying how the universe could have been of infinite size at its birth.
I wasn't offering any science, let alone bad science. I was not trashing any mainstream idea, it was initially a query.

quote JP
"The big bang model actually says that if the universe was infinite, it was still infinite at the big bang, but it was also infinitely dense." "The universe can remain infinite in size but grow infinitely in density as you move back in time towards the big bang"

"Our universe is thought to have begun as an infinitesimally small, infinitely hot, infinitely dense, something - a singularity."
http://big-bang-theory.com/
"According to the theory, the universe was once in an extremely hot and dense state that expanded rapidly (a "Big Bang").:
http://en.wikipedia.org/wiki/Big_Bang

This does not say the universe was infinite in size at its birth, quite the opposite in fact.
The original big-bang theory certainly believed the universe originated from a singularity.  If, that part of it has been modified then it's a patch. MikeS, Thu, 25th Aug 2011

Mike

Modnote!  Enough is enough - stop taking every opportunity to argue and to advance non-mainstream theories.  Please restrict your posting in the Physics forum to established and agreed ideas and theories - feel free to proselytise to your hearts content in New Theories.

Do not continue to derail this thread by responding to this note within the thread.

imatfaal, Thu, 25th Aug 2011



Rob - to most academic physicist's standard of proof we have shown that the universe is expanding, we don't agree why and that means we argue about whether it will continue, but the consensus is that it is expanding; it's the simplest way to explain observations.  An expanding universe does not imply an edge by the way. 

How is it possible to get something out of nothing - read up on the Casimir effect, it seems to document the non-zero vacuum energy.

  This is an open question


Firstly - you are misrepresenting the theory, this is strawman argument.  Secondly, the paradigm shift model of science is very interesting but only really models extreme instances of entrenched views; the vast array of competing ideas in cosmology means that it is unlikely that dogmatism will have any real hold.  And lastly, whilst Occam's razor is useful, it has no power to disprove a working theory that suffers from being too complicated - there is nothing in the the "rules of the universe" that say it should be simple; it is human nature to presume it must be beautiful and elegant, but there is no basis for this in fact.


imatfaal, Thu, 25th Aug 2011

@ imat
Yes, I see your point, and forgive me for being so forward on the issue. But it is to my understanding that the big bang concept is based on red shift of distant objects. The farther the object, the greater the red shift. My concern is that certain objects in space do not conform to this standard of distance. So, the interpretation of red shift must be inaccurate. Science will never be able to dig deep enough to describe conditions inside a singularity, which is in itself something and not able to exist prior to the bang.

And here is another item that confuses me. If red shift is no longer a Doppler observation :) and it is now an expanding space observation, then space should have expanded everywhere equally in all directions, right. The photons traveling through the expanded medium of space would also take on that expansion, as would every area in space everywhere. So, while we here on Earth are waiting for the photon to arrive, we are expanding at the same rate for billions of years, our ability to detect the expansion has also expanded, so we would detect no red shift since we have expanded equally with the rest of space, right. But I'm sure that the counter for this will be said to be gravity, right? But gravity should pull the expanded photons back to normal as they arrive, there again, no red shift. Because in BBT, when the photons arrive they would have to expand at an even much higher rate to overcome the local gravity field in order to maintain their red shift. Robro, Thu, 25th Aug 2011

Sorry again, not trying to advance a non mainstream idea, just trying to better understand the current theories. With that I must say that an edge to the Universe has not been detected, Galaxies stretch out as far as the most powerful telescopes can see. I have a suspicion that when telescopes are developed that look into longer and longer wavelengths, we will see the same thing, Galaxies. So, when it is discovered that Galaxies are out there at 20 - 30  billion light years, the BBT will have to be adjusted to fit the observation, again. And what an eyebrow raising adjustment that will be. Robro, Thu, 25th Aug 2011



But when we do look back, the furthest galaxies (which are around 1 billion years old), look different from the galaxies we see around us which are far older.  This isn't just a redshift thing--the types of stars that make up these galaxies are younger, for example, than those around us.

If we do somehow look past these galaxies and see more galaxies, including old galaxies, then there is indeed a problem with the big bang theory and it will have to either be fixed (if the problem is relatively minor) or discarded (if the problem is major).  jpetruccelli, Thu, 25th Aug 2011



There's a couple points to be made here.  First, it's not gravity that holds our telescopes (or us) together to make the observation.  It's (primarily) electromagnetism. 

Second, you're making a good observation.  If the universe were static, and our twin earth were sending light to us, you'd be right.  The light would redshift climbing out of the gravity well of the twin earth, and it would blueshift back to normal when it arrived at earth.  The problem is that the universe's expansion happens during the light's travel and it's not reversible simply by falling back into a gravity well.  Consider the earth II -> earth case again.  The light redshifts a little climbing out of earth II's gravity well, then as it travels to earth it's constantly stretched (redshifted) by the expanding universe.  When it reaches the earth, it's blueshift undoes it's original redshift, but it doesn't undo the stretching. jpetruccelli, Thu, 25th Aug 2011

@ JP

That's a good analogy, but my confusion rests in the time during transfer.

The light leaves Earth-2 and is initially red shifted a little, and then travels 12 billion years. DURING the 12 billion year transfer, Earth-1 undergoes the same amount of expansion as the light did during the transfer, wouldn't this negate the transfer expansion as far as observation is concerned. Upon arrival at Earth-1 the light is blued up and returns to normal, thus no red shift. But red shift is observed, and is more or less determined by the distance from the object. I am wondering how or by what method that it is proven that expansion, if real, is what accounts for this.

Question: Is it at all possible for red shift to be caused by something other than expansion? And if so, how would this act as a barrier to hide the far reaches of the Universe, or the edge? Robro, Thu, 25th Aug 2011



"Earth-1 undergoes the same amount of expansion as the light did during the transfer" Uh-uh - the gravitational forces and the electromagnetic forces of the earth are far greater than any background expansionary action.  Universal expansion is not everything getting bigger - it is a background expansion. if a star is 4 million light years from us now it will take 3.78421136 × 10^22 metre-sticks to bridge the gap.  At a later date those 3.78421136 × 10^22 metre-sticks will no longer bridge the gap, you will need more metre-sticks ; the electromagnetic forces between the atoms in the metre-stick will have held them at the same length but the gap will have increased. 

"Question: Is it at all possible for red shift to be caused by something other than expansion? And if so, how would this act as a barrier to hide the far reaches of the Universe, or the edge?"  Yes. In physics we are simply unable to prove things beyond all doubt and to the exclusion of other, as yet unknown theories; by its nature physics is an ongoing search for ever more accurate models.  But at present the best, simplest and most accurate explanation is that the universe is expanding. imatfaal, Fri, 26th Aug 2011

I think we cannot comprehend infinty, so we start to make models and concepts like multidimensional space. If there would actually be a boundry , I would think of it like the end of space-time. Wherever there is no matter or any form of energy/gravity, it is possible that time stops as well. No matter how fast you go, you would eventually be standing still. At least, that concept is something we can grasp with our feeble minds. Unfortunately, we can only concider something to be true or false, if we can understand it. So, I suppose a concept like the absence of time is a credible theory, and if we can understand it, it must contain some truth. That's silly, of course, but that's the way we think. Just like the way we knew for a fact, that the earth was flat. Werner, Wed, 28th Sep 2011

Most unsatisfying answer ever given. The Earth is a sphere and we can travel off of it. So let's say the galaxy IS a sphere and were in the middle of it (hypothetically) if we traveled straight in one direction we would have to hit an edge at one point. That is what I would like to know. What would it look like? ThatOneGuy, Wed, 30th Apr 2014

If this was the case how does this explain the red-shift effect that suggests the universe is flying apart. I understand that the universe feels/is fractal in nature but (and I’m no expert so maybe looking very stupid at this point in time) red-shift would suggest a force either pulling or pushing galaxies apart. So if you can only see 13.8 billion light years in any given point in space-time that would suggest a static form folding in on itself. I know the analogy is like an expanding balloon but what’s expanding space? What’s pushing the galaxies apart in a finite 13.8 LY block of 3D space. I agree with ‘that one guy’ the whole thing smacks of 'well if' & ‘imagine this’. If we hypothesize a big bang then the universe has an edge which is the cool down of the expansion. if the universe just is then I can believe that its so big no one could ever find the end let alone see it. But redshift has to be suggesting that we are expanding into something which again would suggest it has an edge. The balloon theory doesn't stack up and if it is expanding space who the jinglebutts is blowing the balloon? Nomad_Wizard, Fri, 1st May 2015

I would like to know where, roughly we are in the universe. I know that through math, we can approximate where it all began, and safely assume that things are more concentrated together, and given how spaced apart everything gets from that point on, and up to where we are, but also by what we are able to see and lose sight of(referencing the fact that each day, we lose sight of certain stars, as things grow apart and fade). Marlon Lee, Wed, 22nd Jul 2015

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