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Astrodob

If the universe is infinite why can't i see stars everywhere I look?

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If the universe is infinite why can't i see stars everywhere I look?
Yeasterday i went for a walk in the woods.
I was thinking as usual :).
Suddenly i got this idea:If the universe is infinite as they say why can't I see stars in absolutely every part of the sky ?
Because in a wood u have trees the trees fill out the space because theres more and more of them,but they don't fill out every space because they don't go on forever.Think of the wood as the universe and trees as stars.
Is it because the universe isn't infinite?
Is it because stars get into the red to infra-red spectrum? (so they're not so noticeable).

Is it because stars are far away from each other?

Is it because the light from the other stars still hasn't travelled to us?

Please try to tell me and share your opinions on this.

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I think you have it mainly nailed down with the 'Is it because the light from the other stars still hasn't travelled to us?' part. Which is also why we can only really see the observable universe, just how far and big the universe stretches out beyond that we can't tell because the light hasn't reached us. Amongst other things.

Also I don't think anybody can say for sure at this point if the universe is infinite or finite, this has not been confirmed as of yet.

It may just be infinite though.... http://newscenter.lbl.gov/2014/01/08/boss-one-percent/

Edited by JB80

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It is not infinite, big yes but not infinite.

Some of the light has not reached us.

You can only see the observable universe, you cannot see the rest of it.

There is more then stars, look at the CMB, that is everywhere and that is the universe.

Dark matter is another big part of the universe and there is 6x more of that then what we refer to as matter.

Get a good book on astrophysics and cosmology.

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Good video,but i absolutely hate when people say the universe had a begining.Nobody knows that and possibly no one will ever know that.How do u get the whole universe from nothing?It's either the universe goes into a big crunch by time and explodes again or something had to get that material into the universe so there could be a big bang.

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It is not infinite, big yes but not infinite.

Some of the light has not reached us.

You can only see the observable universe, you cannot see the rest of it.

There is more then stars, look at the CMB, that is everywhere and that is the universe.

Dark matter is another big part of the universe and there is 6x more of that then what we refer to as matter.

Get a good book on astrophysics and cosmology.

I'm not stupid enough to not know that.I have read a lot of books and everyone knows what dark matter and dark energy is aspecially that galaxy'es are out there and other stuff.

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It is not infinite, big yes but not infinite.

Some of the light has not reached us.

You can only see the observable universe, you cannot see the rest of it.

There is more then stars, look at the CMB, that is everywhere and that is the universe.

Dark matter is another big part of the universe and there is 6x more of that then what we refer to as matter.

Get a good book on astrophysics and cosmology.

How can u even say something like that? Nobody knows if it is infinite or not.Nobody knows if there is a multi-universe.The universe is made out of 4 percent normal matter,but still  the universe is really big and those spots should be filled out. 

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It's either the universe goes into a big crunch by time and explodes again or something had to get that material into the universe so there could be a big bang.

Intuitively those might seem like the only logical possibilities.  I'm far from convinced that people who think about these things for a living would agree that they are the only two possibilities.  My understanding from reading Brian Greene's "The Elegant Universe" is that they're certainly not the only possibilities allowed by our best current understanding, but I'm no expert.

James

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At the end of the day, we just don't know. It's that simple. We have theories, ideas, models and maths...but we just don't know. Science and our understanding of space is always evolving and changing as we learn new things. A few hundred years ago we, as a species, "KNEW" that the earth was flat and that the sun revolved around the planet...what will we "KNOW" to be true in a few hundred years from now? No-one knows, and that is precisely what makes it all so very exciting and interesting.

Phil

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If the universe is infinite why can't i see stars everywhere I look?

Yeasterday i went for a walk in the woods.

I was thinking as usual :).

Suddenly i got this idea:If the universe is infinite as they say why can't I see stars in absolutely every part of the sky ?

Because in a wood u have trees the trees fill out the space because theres more and more of them,but they don't fill out every space because they don't go on forever.Think of the wood as the universe and trees as stars.

Is it because the universe isn't infinite?

Is it because stars get into the red to infra-red spectrum? (so they're not so noticeable).

Is it because stars are far away from each other?

Is it because the light from the other stars still hasn't travelled to us?

Please try to tell me and share your opinions on this.

Well, I might as well throw in my ten pence worth of thought.  I seem to remember a question like this being mentioned in Hawkin's A Brief History of Time.

Being unable to see something does not necessarily mean that it is not there.  Therefore, if the universe stretches on like an endless sea of stars, then you might not be able to see if they go on forever, due to the immense distances involved. 

I don't think it has anything to do with the light not having enough time to reach us, because an endless sea of stars would always have been there, in one form or another, so the light would have reached us (and always would have done).  So, either the stars do not stretch forever, or they become undetectable at a certain distance, as even the remnants of their emitted light cannot be detected by modern methods.

There may well be an infinite amount of stars in existence, but they may not all be in this universe.  If there is indeed a form of multiverse, then this would mean that there are an infinite amount of stars.  Then there is the possibility of there being other dimensions that exist with our own.  When considering all this, I think it's best to just stop and have a nice cup of tea.

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because some star (many) aren't bright enough for us to see and there's plenty of stuff blocking them (light pollution, dust, atmostphere etc). eg. look into the middle of the milky way with your eyes, you'll see a band of stars, with lots of gaps, like there's nothing in between. Now go to a really dark site and look at the same patch, you'll now see an almost continuous cloud, but may not be able to resolve the stars in the cloud, but they are there. Then take a long exposure photo and more will be revealed.

Look out of our own galaxy, there are a few stars around the edge which we can see, but there are very large gaps to the next galaxy. Even our closest galaxy, Andromeda, which is huge, it barely visible by the human eye. So we have no change of seeing other galaxies which are much further away.

Look at the hubble deep space photo, the exposure was hundreds of days and it captured hundreds of galaxies, but there are large gaps between the galaxies. Of course we have no hope of seeing these, even with our telescopes.

So basically, we just see local stars through lots of haze and light pollution.

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FIrstly 'infinite' can have at least two meanings. It can mean 'going on without end' or it can mean 'having no boundary.' These are quite different. The surface of a sphere is not infinite in the sense that the sphere can grow, but it is boundless in that there is no point on the surface that can be defined as a starting or finishing point.

So the universe could be finite but not bounded, finite and bounded, or infinite. The universe seems to be expanding so in one sense it can't be infinite but, if it is 'all that there is,' then in another sense it can. I would say that 'finite and unbounded' would be the best guess to date but who knows? This allows us to keep the expanding universe which we seem to observe and keep the idea that it doesn't have an edge.

Why don't we see stars wherever we look? Knight of Clear Skies' video link is excellent.

The redshift of very distant light due to the expansion of the universe means it is no longer visible light when it gets to us. And once the expansion of the universe has added up over a very great distance till it exceeds the speed of light then light from sources at such distances can never reach us. This is the only 'edge' that we know of. This side of such a distance the universe is, in principle, observable. Light can reach us from there. Beyond that distance it cannot, which does not mean that there is nothing there.

Astrodob, whether or not you hate the idea of the universe or time having a beginning, whether or not it seems reasonable to you or not, do remember that nature can do what it likes. It doesn't have to do what you or I think is reasonable. There was a famous conversation between Einstein and Niels Bohr. The following quotation includes the word 'God' but does not refer to God in the normal sense. Both men were using it to mean 'nature' or 'reality' or 'the truth.'

Einstein hated quantum theory because it was (and is) based not on hard cause and effect but on probability. He said, 'God does not play at dice.' And Bohr's reply was pure genius. 'Stop telling God what to do.'

Remember, it seemed totally unreasonable to most people, only 500 years ago, that the Earth could be spinning around on its axis every day and hurtling around the sun once a year. Unreasonable or not, that's what it is doing.

Olly

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 Even if the Universe is infinite, it does not automatically follow that there is infinite matter contained within it. If matter is not infinite, then it follows that the number of stars is also not infinite.

Plus, matter is not evenly distributed. On a macro scale the universe is "clumpy".

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 Even if the Universe is infinite, it does not automatically follow that there is infinite matter contained within it. If matter is not infinite, then it follows that the number of stars is also not infinite.

Plus, matter is not evenly distributed. On a macro scale the universe is "clumpy".

Hmmmm...   Not sure, but thinking aloud;

If the universe is roughly homogeneous on large scales then there will be stars every so often. If space is infinite then every so often there will be matter in a star and the number of 'every so oftens' will be infinite and so, therefore, will be the particles they contain. (If we have an infinite number of matchboxes each with a hundred matches, how many matches are there?)

Even if, somewhere in the Universe, there are no more stars there is still a problem. There is a minimum energy density allowable in quantum theory, causing particles to appear and disppear in any given volume of space. If the volume of space is infinite then so is the number of these particles.

What do you reckon? I hate the word 'infinity' and often doubt whether it has any business existing outside mathematics.

Olly

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Hmmm, what if there was an infinite number of finite universes?

Is that probabilistic or deterministic or both?

Edited by JB80

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Hmmmm...   Not sure, but thinking aloud;

If the universe is roughly homogeneous on large scales then there will be stars every so often. If space is infinite then every so often there will be matter in a star and the number of 'every so oftens' will be infinite and so, therefore, will be the particles they contain. (If we have an infinite number of matchboxes each with a hundred matches, how many matches are there?)

Even if, somewhere in the Universe, there are no more stars there is still a problem. There is a minimum energy density allowable in quantum theory, causing particles to appear and disppear in any given volume of space. If the volume of space is infinite then so is the number of these particles.

What do you reckon? I hate the word 'infinity' and often doubt whether it has any business existing outside mathematics.

Olly

I don't think so, but then again, my grasp of these concepts is pretty poor! Your matchbox analogy doesn't work because there isn't an infinite number of matchboxes. What there is, is an infinite space, but a finite number of matchboxes. Therefore the number of matches is N x100 (where N is the number of matchboxes).

 There is a minimum energy density allowable in quantum theory, causing particles to appear and disppear in any given volume of space. If the volume of space is infinite then so is the number of these particles.

In the main though, these particles self-annihilate, so the net:net is zero. One exception is if the particles appear near the event horizon of a black hole and one particle gets swallowed (Hawking Radiation).

Another way of looking at it is that if the Universe is truly infinite and the amount of matter contained therein is finite, then the average density of the universe is zero.

I need to go and lie in a darkened room with a damp cloth on my forehead.....

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I need to go and lie in a darkened room with a damp cloth on my forehead.....

If you live long enough the universe will be a darkened universe and there will be no lights in need of turning off...  :grin:

The matter-energy distinction is a very human one and belongs to the macro world. Is it really an important one? Is it not more a matter of terminiology than anything else? So if there is a minimum energy density and an infinite amount of space then there has to be an infininete amount of energy. Erm? Well, as I say, not sure. My matchbox point was really just to point up the fact that any non-zero quantity contained in an infinite number of matchboxes is itself infinite. So if the matchboxes are units of  space and the energy in those boxes is non zero then the energy itself is infinite. You're right, lights out!

Olly

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At the end of the day, we just don't know. It's that simple. We have theories, ideas, models and maths...but we just don't know. Science and our understanding of space is always evolving and changing as we learn new things. A few hundred years ago we, as a species, "KNEW" that the earth was flat and that the sun revolved around the planet...what will we "KNOW" to be true in a few hundred years from now? No-one knows, and that is precisely what makes it all so very exciting and interesting.

Phil

The Egyptians knew that the world wasn't flat 3000 years ago.I Suggest to you that you read a History book than just making up ure own stuff since u look like u only focus on astronomy...

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How do u get the whole universe from nothing?It's either the universe goes into a big crunch by time and explodes again or something had to get that material into the universe so there could be a big bang.

The matter does not come from nothing, it comes from energy. E=mc^2.

Edited by Tiny Small

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If you live long enough the universe will be a darkened universe and there will be no lights in need of turning off...  :grin:

The matter-energy distinction is a very human one and belongs to the macro world. Is it really an important one? Is it not more a matter of terminiology than anything else? So if there is a minimum energy density and an infinite amount of space then there has to be an infininete amount of energy. Erm? Well, as I say, not sure. My matchbox point was really just to point up the fact that any non-zero quantity contained in an infinite number of matchboxes is itself infinite. So if the matchboxes are units of  space and the energy in those boxes is non zero then the energy itself is infinite. You're right, lights out!

Olly

Infinite meens either it's too big or we don't know for me.Let's talk about what infinite is for you-neverending.Everything seems to be a small version of something bigger.First people thought that the smallest thing in the world was an atom,now we know it is not.Then they thought it was an electron,than they thought it was a neutrino.So it looks like everything is infinite think about it the universe could just be a proton or something in another world or dimension.atoms are made out of protons,neutrons and electrons molecules are made out of atoms and so on.It goes for quite a while when u get to the planets they are simmiliar the Sun a proton in a bigger world the planets electrons,asteroids neutrinos.... Though planets are nothing like atoms i must say this makes them sound simmiliar to atoms.So it could go like this forever or stop or something else.Black holes could be portals to other dimensions and everything could be anything it is really suited for a bigger post i should do :D.

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The matter does not come from nothing, it comes from energy. E=mc^2.

Energy is movement or some form of output or input some form of stuff that is everywhere.We still don't understand energu completely I'll give u that,but energy needs to come from somewhere :) even E=mc^2 had to come from somewhere (einstein).

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As I understand it, in probability terms if there is nothing then it is more likely to become something rather than remain as nothing. It only takes one 'thing' to be something rather than nothing. I don't know the mechanism for the 'thing' being 'created' but have a book to read soon on this very subject

To the OP bear in mind that all the stars you see are in our galaxy, and that as far as I am aware we cannot see all galaxies and the light from all galaxies in the universe has not yet had time to reach us

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