The edge of the universe

luckyfrank · 13-12-2009 11:43pm #1

It's hard to believe that the universe is not infinite, i mean there is a place where the universe just stops and then there in nothing

no matter no space no time, but surly if the universe is expanding it must be expanding into something that wasnt there before

Ive read before that it's not the universe that's expanding just that the space within it is expanding if that makes sense

Hypothetical question : If i was standing on the very edge of the universe with a tennis ball in my hand and threw that ball over the edge what would happen to the ball ?

Brian CivilEng · 14-12-2009 1:13pm

luckyfrank wrote: »

Hypothetical question : If i was standing on the very edge of the universe with a tennis ball in my hand and threw that ball over the edge what would happen to the ball ?

The ball would not move as fast as the universe is expanding, so the ball would not leave the universe. The universe will have expanded and where you are standing will no longer be the edge.

Mena · 14-12-2009 1:22pm

abitofacomedian wrote: »

The ball would not move as fast as the universe is expanding, so the ball would not leave the universe. The universe will have expanded and where you are standing will no longer be the edge.

All well and good, but what if you had a really strong arm, and managed to throw said ball faster than the universe is expanding?

Interesting question by the way.

Rockshamrover · 14-12-2009 1:29pm

What would happen if there was another universe expanding towards ours and they met each other? Would they just merge or repulse each other?

marco_polo · 14-12-2009 1:36pm

luckyfrank wrote: »

It's hard to believe that the universe is not infinite, i mean there is a place where the universe just stops and then there in nothing

no matter no space no time, but surly if the universe is expanding it must be expanding into something that wasnt there before

Ive read before that it's not the universe that's expanding just that the space within it is expanding if that makes sense

Hypothetical question : If i was standing on the very edge of the universe with a tennis ball in my hand and threw that ball over the edge what would happen to the ball ?

Because something is finite does not mean that is has an edge, the surface of a sphere is a finite 2D space yet it has no edges.

Try to imagine a 3D shape that has such a property, without your head exploding, and you have a finite universe with no edge.

A finite n-dimensional (3 or more) space is called a torus

A nice introduction paper here that is not too technical
http://www.maths.lse.ac.uk/Personal/mark/topos.pdf

r3nu4l · 14-12-2009 1:38pm

Mena wrote: »

All well and good, but what if you had a really strong arm, and managed to throw said ball faster than the universe is expanding?

Interesting question by the way.

I'm not sure we could to be honest. The tennis ball would have to comply with our laws of physics and these laws are the only frame of reference that we have for what may be 'outside' our universe. So I don't know what Physicians or astrophysicists have to say about that. It's a great question

Rockshamrover wrote: »

What would happen if there was another universe expanding towards ours and they met each other? Would they just merge or repulse each other?

Again, I think that depends on the properties of that other universe. If it was composed mostly of anti-matter then we might enjoy a huge explosion or something, if it was largely the same as our own universe then perhaps different gravitational effects would come into play to decide what would happen...

Flamed Diving · 26-12-2009 2:43am

Why does it have to be expanding into something? For all we know, the universe is all the space there is, and by expanding more space is created. No "outside" space should be required.

A7X · 05-01-2010 6:38pm

Flamed Diving wrote: »

Why does it have to be expanding into something? For all we know, the universe is all the space there is, and by expanding more space is created. No "outside" space should be required.

The problem is the human mind (at least mine) can't comprehend absolute nothing.

It's so hard to think of absolute nothing. I said it to one of my friends before and all i got was him replying without think " Well there would just be nothing". But can you imagine it? I can't.

Flamed Diving · 05-01-2010 6:46pm

A7X wrote: »

The problem is the human mind (at least mine) can't comprehend absolute nothing.

It's so hard to think of absolute nothing. I said it to one of my friends before and all i got was him replying without think " Well there would just be nothing". But can you imagine it? I can't.

I can't remember the philosophical argument that explains why nothing, by definition, cannot exist, and therefore is merely an abstraction and does not require you to imagine it. Anyone?

Ingenuist · 15-01-2010 7:53pm

Question of the century OP

Capt'n Midnight · 16-01-2010 2:58am

It's handy to think of the universe as the observable universe. It doesn't matter what is out there if there is no interaction with it.

My understanding of it is that if there is anything further away than 13 Billion light years we will see more of it as time goes on since some of the universe isn't expanding at the speed of light. But it would take a LONG time for that to be apparent.

stevenmu · 19-01-2010 4:44pm

The way I think of it, and I've no idea how correct this is, is that objects which occupy space conform to the shape and nature of the space they occupy. A little bit like one of those distorting mirrors, except instead of distorting just your reflection it distorts absolutely everything. So when you throw your ball it would appear to just go straight off towards infinity but would actually be following the curves around the edge of the universe.

It's hard to explain but it was well illustrated by M.C. Escher (who had a knack for illustrating tricky concepts

). Take a look at the main picture on this page. One of the basic concepts in it is that the angels in it are all actually the same size, the look smaller the closer to the edge they get from our perspective, but from the angel's own perspective they are the same size, what we see is the distortion of the 2D space they are represented in. If you were an angel in that picture and threw a tennis ball it would continue to infinity (the edge we see would be infinitely far away to them), from our outside perspective it would seem to get smaller and smaller never reaching the edge.

Hope that makes some kind of sense.

Akrasia · 28-01-2010 10:46am

Capt'n Midnight wrote: »

It's handy to think of the universe as the observable universe. It doesn't matter what is out there if there is no interaction with it.

My understanding of it is that if there is anything further away than 13 Billion light years we will see more of it as time goes on since some of the universe isn't expanding at the speed of light. But it would take a LONG time for that to be apparent.

If the universe is expanding slower than the speed of light, what happens to the light that is moving towards the edge of the universe?
does it just get bounced or turned back?
If it was bounced or turned back then the edge of the universe would look like some kind of mirror?

Capt'n Midnight · 10-02-2010 2:43am

Akrasia wrote: »

If the universe is expanding slower than the speed of light, what happens to the light that is moving towards the edge of the universe?
does it just get bounced or turned back?
If it was bounced or turned back then the edge of the universe would look like some kind of mirror?

as I understand it a lot of the light will be red-shifted to the microwave background of 3K

time is relative to the observer, if you shine a light towards an object travelling away at 0.5c it will take a long time to get to the object and a lot longer to get back , if the object is travelling near the speed of light you won't see the light for a very long time, this is why there is a limit to the observable universe and as time goes on we can see further into the universe. Only a long time will tell if we can see further away than now.

we can see objects 13.1 billion light years away or rather we can see what it looked like 13.1 billion years ago , it wasn't 13.1 billion light years away back in those days
http://www.newscientist.com/article/dn17035-most-distant-object-in-the-universe-spotted.html

pug_ · 18-02-2010 8:30pm

I remember when I was in school, a long time ago now, our physics teacher was telling us about a theory. The basic idea was if you had a hypothetical telescope that could see to the edge of the universe without being restricted by the laws of physics what you would see is the back of your own head.

I always liked that idea as it suggests the universe has no edge as such so isn't expanding the same way say a balloon when blown up. In this hypothetical scenario if a ball was thrown from your current position (as there is no edge of the universe to throw it from) and again could break all known laws of physics (hypothetical ball here folks) it would eventually hit you in the back of the head having travelled in a straight line across the entire universe to bring it right back where it started.

Kidchameleon · 23-02-2010 10:52pm

r3nu4l wrote: »

we might enjoy a huge explosion

Cant imagine id enjoy that myself!

20goto10 · 05-03-2010 2:48pm

luckyfrank wrote: »

Hypothetical question : If i was standing on the very edge of the universe with a tennis ball in my hand and threw that ball over the edge what would happen to the ball ?

The universe is donut shaped, so it would come out the other side. But because we see the universe in only 3 dimensions it will appear to disappear and reappear on the other side as if by magic. The same concept applies for a 2D world. If you go off the screen in space invaders you magically appear back from the other side. But if it was seen in 3D you'd simply be looping around a conical.

Capt'n Midnight · 06-03-2010 1:16pm

20goto10 wrote: »

The universe is donut shaped, so it would come out the other side. But because we see the universe in only 3 dimensions it will appear to disappear and reappear on the other side as if by magic. The same concept applies for a 2D world. If you go off the screen in space invaders you magically appear back from the other side. But if it was seen in 3D you'd simply be looping around a conical.

AFAIK wwe aren't 100% sure of the shape of the universe
it may be finite
it may be far larger than we can see
it may be infinite
but I doubt it's a torus

academic anyway, because if you shone a light at the edge of the universe it would take 13.7 Bn years to get there and 13.7 Bn years to arrive from the other side ( or be reflected ) even if the light was still visible in 27Bn years time, the universe would have still expanded further so my understanding is that we would never see the light we shone, just the light emitted from there.

20goto10 · 07-03-2010 11:29am

Capt'n Midnight wrote: »

AFAIK wwe aren't 100% sure of the shape of the universe
it may be finite
it may be far larger than we can see
it may be infinite
but I doubt it's a torus

academic anyway, because if you shone a light at the edge of the universe it would take 13.7 Bn years to get there and 13.7 Bn years to arrive from the other side ( or be reflected ) even if the light was still visible in 27Bn years time, the universe would have still expanded further so my understanding is that we would never see the light we shone, just the light emitted from there.

True it's only theory so far. There's a $1mill prize for the first scientist to prove the shape of it and apparently all the signs are the results will be its torus. I saw a documentary on it, I think it was horizon so I'm sure the information is out there on the google. One scientist even went so far as to suggest one of the stars in the night sky could well be light from Earth millions or billions of years ago.

Besides that, one thing's for sure its not as it seems to us in our 3 dimensional universe.

Capt'n Midnight · 07-03-2010 3:16pm

20goto10 wrote: »

One scientist even went so far as to suggest one of the stars in the night sky could well be light from Earth millions or billions of years ago.

If that were true the Hubble should have found symmetry in the skies because our sun is only 1/3rd the age of the universe so the light would have gone around at least 3 times

Also the microwave radiation background seems to be damn close to the age of the universe, so nah that doesn't add up for me

Alvin T. Grey · 19-04-2011 9:21am

The universe = everything. Therefor the property of "outside" has no meaning. It's like asking what happened before the big bang. You are trying to describe something in terms of a property that it does not have.

I like to think of the universe as a train that lays it's own track as it goes along. And where does it lay those tracks? - strictly speaking the answer is "custard" (or any other term not even distantly related to the question). I know it makes no sense but to hairless monkeys like ourselves it wouldn't.

So a comfortable lie that we can deal with, the answer would be "right where it laid them".

Remember in terms of the edges of cosmology, we are using brains developed for spotting ripe fruit, and a language developed for telling other monkies where that is.

the culture of deference · 25-05-2011 12:28pm

So if our universe is 27 to 28 billion light years wide and is shown to be torus shape, my question is will we ever get to see the opposite side of the big bang.

Will we ever be able to physically visit or communicate with our nearset star systems in our own galaxy. Even if we do manage to design something that could get us there in 4 years, the time that will have passed on earth will mean that we will never be able to communicate simultaneously.

amen · 27-05-2011 11:33pm

Even if we do manage to design something that could get us there in 4 years, the time that will have passed on earth will mean that we will never be able to communicate simultaneously

nor could most of the planet for most of recorded history.. thats why we had diplomats. could do the same thing here.

FTGFOP · 28-05-2011 1:11am

The idea of the Universe looping back on itself makes me claustrophobic, even though it's billions of light years wide!

the culture of deference · 28-05-2011 5:48pm

amen wrote: »

nor could most of the planet for most of recorded history.. thats why we had diplomats. could do the same thing here.

If I visited proxima centauri as a diplomat and it took me 4 years to get there and 4 years back, hundreds of thousands of years would have passed on earth. It's not like the old days where your reps were only 5 years max away.

Think of the changes on earth that could happen in than timeframe.

himnextdoor · 02-01-2012 9:01pm

I imagine the Universe as being a sphere of space which I imagine as being a vast number of points with a repulsive property such that every point in space is trying to move away from every other point and as a consequence, the Universe expands.

It is the distribution of energy that is interesting here. Firstly, it will be seen that there is no possible state of equilibrium for such a system or, to put it another way, the state of constant expansion is equilibrium for such a system.

But it is the relationship between the centre of the Universe and the edge of the Universe that gives rise to all the characteristics that we can observe.

Imagine if we were able to confine a large number of electrons in close proximity to each other in the shape of a spere using some kind of field; imagine that the density of the electrons was such that they were almost touching each other. Since all the electrons are negatively charge they repel each other and under confinement, the stress caused by this force is more or less evenly distributed. Then we remove the confinement field.

At that moment, the distribution of forces changes; electrons located at the centre feel a crushing force while electrons at the surface of the sphere are easily liberated from the system with a certain amount of energy. There is an energy gradient, centre to surface, that ensures that the sphere decomposes dissipating energy over time.

Since electrons are being removed from the system, over time the strength of the repulsive force diminishes which means that electrons tend to leave the system with decreasing energy over time.

Also, it should be noted that since there is no possible way to arrange a collection of spheres into a larger sphere such that there is an even distribution of forces throughout the system, (during confinement, our system would have generated heat at the centre), not all the forces will be acting perpendicular to the centre. This results in the development of structure within the sphere which evolves as the sphere 'evaporates'.

In the electron model, the first electrons liberated represent the edge of the Universe and they define the volume of the Universe. Although the force of these electrons is still an active part of the overall system they cannot be overtake by others; the energy put into liberating the first electrons is slightly greater than the energy put into subsequent liberations. If you were able to recede from the system so as to maintain a particular perspective then you would observe it to have constant volume but also having a dynamic internal structure. No matter how much the system expands, there will be interaction between the parts.

The thing is, matter can't exist at the edge of the Universe; matter consists of bound space which would rapidly expand at the edge instantly decomposing it into EMR, or perhaps neutrinos, energy which then goes to shape the edge of the Universe.

I think this model neatly demonstates why galaxies near the edge of the Universe are accelerated to a higher velocity than ones closer to the centre too.

Hijpo · 02-01-2012 9:47pm

luckyfrank wrote: »

no matter no space no time

if humans didnt measure it, would time exist?

Allosaur · 04-01-2012 5:12pm

Hijpo wrote: »

if humans didnt measure it, would time exist?

From a humans point of view, no. The rest of the universe might have something to say about that, but heck, their opinion doesn't matter.

himnextdoor · 05-01-2012 8:06am

Hijpo wrote: »

if humans didnt measure it, would time exist?

Time is an effect of a constantly changing Universe; if we couldn't measure time then the Universe would be static.

Measuring time is simply a process of counting events. Accurately. But 'time' is not intrinsically of any value to nature. Rather, it provides a measurement system that allows us to plot graphs that record rates of change and this in turn allows us to deduce interesting things about nature. Time is one of those interesting things.

The three dimensions of space are easy to visualise; they correspond to the set of all points in the Universe. All deterministic processes have degrees of freedom in those dimensions.

But the Universe does seem to have another directional component, things change in a particular direction, hot to cold, but seems unlike any of the other directions in space; a fourth dimension. But determinism has no degrees of freedom along this direction; this direction is a property of space itself and is the source of determinism. This property of space causes change that would occur even in the absense of deterministic processes and this underlying force of change determistically creates a 'sub-space climate' from which reality emerges.

The fourth dimension, the t-axis, has a fundamental relationship with the Universe and could possibly represent the oldest law but what does that direction actully represent? And what is actually moving?

When we observe the world around us we see processes at work that cause 'aging'. Things that are well used get worn out; life moves toward decay; entropy at work. We notice that we can relate periodic motion to rate of change; the number of sunsets per moon cycle is a very useful piece of information and thusly, we have a concept if 'time'.

When we built our telescopes and peered out into the Universe, we realised that the cyclic nature of the Universe was extensive and, well, universal. Eventually, after assigning the fourth dimension as time, we were able to accurately model the behaviour of the Universe.

But it may be that the 'time' designation is misleading to the extent that although the concept of time allows us to build accurate physical models, it fits so well that another more basic principle of the Universe could remain hidden from us.

For instance, if the t-axis were related to the radius of the Universe, then just by thinking of the t-axis in terms of the radius you can show a relationship with the volume of the Universe and would be on the way to accurately defining a cosmological constant from which things like speed of light, gravitational constant and electron charge could be derived.

By thinking in terms of time, albeit a useful concept, we may fail to see such a relationship.

Plus it could be that the fourth dimension is a real direction and a real distance; the distance between in and out.

That would be cool, wouldn't it?

krd · 05-01-2012 6:40pm

Could it be, that what's on beyond the edge of the universe is simply the emptiness of the vacuum.

Capt'n Midnight · 06-01-2012 2:21am

krd wrote: »

Could it be, that what's on beyond the edge of the universe is simply the emptiness of the vacuum.

Nope

even vacuum can produce energy fluctuations and create new particles

The edge of the universe

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