If there is no end to the space

[HamsterPower]

wouldn't we have to see stars from everywhere during night? Shouldn't the space be so full of light that there is no darkness?

Isn't that what they mean by no end to space? Infinite numbers of stars as well?

OR do they mean space has no end but there are limited number of stars?

Edited January 14, 2011 by HamsterPower

[dragonstar57]

there are some stars that are to faint to see maybe there are many more that can't even be seen by telescopes

[Mr Skeptic]

You are right and that was considered proof of a finite universe some time ago -- the skies would have had to be infinitely bright. However, there's two ways it doesn't really work that way. First, we now know the universe is finite in time (15 billion years, give or take), so that light from some stars would not have been able to reach us. More importantly, however, is that space is expanding. For each unit of space, some time later there will be a little more space there, and the numerical value of that is the Hubble constant. It also means that the distance between two points can increase faster than the speed of light if they are far enough away (this is not motion but expansion of space). And when the distance between two points is increasing faster than the speed of light, nothing can travel from one point to the other, not even light. And so we are limited to the observable universe.

[ajb]

This is known as Olbers' paradox.

[dragonstar57]

so is space really expanding or are the things in it moving away from each other in an already infinite space?

[between3and26characterslon]

I think of it like this (and this is just my thoughts on the matter and not any current theory I have heard of)

 

Imagine your universe is a ruler and you can see 5cm in either direction.

 

So lets say you're at the 6cm mark, you can see 1cm and 11cm but not as far as 0cm or 12 cm.

 

Now let's say that there was an observer at the 8cm mark, they too can see 5cm in either direction so they can see 3cm and 13cm but not 2cm or 14cm.

 

So the observers at 6cm and 8cm can see each other but can also see parts of the universe the other can not.

 

If one were to instnantaneously dissapear from where they are and re-appear where the other one is they would all of a sudden be able to see parts of the universe they had not seen before, however there is a finite speed at which they can travel. If they were to travel at this finite speed to where the other one is then in the time it takes to get there the universe will have expanded to such an extent that they will only observe what they could originally.

 

If A is at 6cm, B is at 8cm and C is at 11cm (the limit of A's observable universe) and A and B are 200mn LY appart then it will take at least 200mn years for A to travel to B. In this time the universe will have expanded to such an extent that A will still only be able to observe as far as C.

 

In this sense space can be infinite but every event can only experience a finite amount of it.

Edited January 16, 2011 by between3and26characterslon

[steevey]

wouldn't we have to see stars from everywhere during night? Shouldn't the space be so full of light that there is no darkness?

Isn't that what they mean by no end to space? Infinite numbers of stars as well?

OR do they mean space has no end but there are limited number of stars?

 

Maybe the universe has infinite space to expand into, but that doesn't mean that matter takes up that space the way we see it.

[HamsterPower]

In order to explain Olbers' paradox, it is necessary to account for the relatively low brightness of the night sky in relation to the circle of our sun. The universe is only finitely old, and stars have existed only for part of that time. So, as Poe suggested, the Earth receives no starlight from beyond a certain distance, corresponding to the age of the oldest stars. Space is sufficiently rarefied that most lines from the Earth do not touch any star within this distance of Earth. -wikipedia-

^ is the mainstream explanation

 

 

 

 

 

 

This is known as Olbers' paradox.

 

 

 

[MR. Science]

This is a question that no one can honestly say they have the answer to, we don't know.... period.

[steevey]

This is a question that no one can honestly say they have the answer to, we don't know.... period.

 

Well we can't know it, but we can come up with something we are very sure is the answer.

[36grit]

Well, I'm a simple minded guy. And ofcourse I have a simple minded explanation that fits the model in my head. Here goes,

Ever drive down a highway on a sunny day and notice that bright spot on the gaurd rail that seems to be cruising along just ahead of you, No matter how fast or slow you go? That spot is the rays of light that are actually hitting your eyes dead on. When you look up at the sky at night and see a star, it's the same thing. You only see the the light rays that directly hit your eyes. Now, the star itself might be a solid ball of light thousands of miles in diameter, but your just seeing a very small section of light rays that's usually millions of light years in diameter. On top of that, those rays probably only took a fraction of a second to be created. Therefore: they are probably less than a couple of hundred thousand miles long. That means that they will only hit your eye for a fraction of a second. That is to say, the light rays are not continious from your eye to the distant star. There's a lot of distance between and inbetween all those rays of light. To make it even darker, the distance between you and star and the rays of light is expanding very fast.

Personally, I think it's amazing that we can see stars at all.

[lemur]

So if there was light from distant stars curving through spacetime to reach Earth from beyond its hubble horizon, we would observe the curved light as an image completely distinct from the image of the star as it appears within our hubble horizon. I.e. if light is contained by the curvature of spacetime within a universe of relatively closed gravitation, we would still not necessarily be inundated with infinite starlight?

[steevey]

This is known as Olbers' paradox.

 

There can be infinite space but only finite matter. That's why the sky is dark. Not to mention all the galactic dust and the fact that an entire galaxy will only look like a single point after a few hundred million light years because of some triangle property of space or that the concentration of light gets weaker by the 4th power of the distance. It may be a paradox, but theres gotta be some reason why the sky isn't white.

Edited January 18, 2011 by steevey

[ajb]

There can be infinite space but only finite matter. That's why the sky is dark.

 

That is a possibility, picking a "straight line" in space will not necessarily hit a star of galaxy. The initial assumption made in Olber's paradox is an infinite number of stars. So, because the night sky is dark we can say that there must be a finite number of starts, finite universe or not.

 

 

 

Not to mention all the galactic dust

 

Assuming that the universe is infinity old and has infinite number of stars, then the dust would heat up and radiate. Galactic dust by itself will not solve the paradox.

 

 

It may be a paradox, but theres gotta be some reason why the sky isn't white.

 

 

The answer is that universe is only finitely old and that stars have not existed through all of the universe's history. This agrees with the standard model of cosmology, which has other observational tests that it has passed.

 

Though we are bathed in radiation that is extremely uniform. The cosmic background radiation, which is probably the best evidence of the big bang.

[owl]

Great topic.

We must distinguish between space and all the cosmic "stuff" in space. Who can imagine an end to space? What kind of boundary would that be, and, of course, what would be beyond that boundary but... more space... ad infinitum.

We are limited in how far we can see, of course. It's called the cosmic event horizon, so what is beyond this limit, no one knows or can know.

Mr Skeptic says that the cosmos is around 15 billion years old, i.e., from the big bang, based on the best information we have. But this "matter of factly" dismisses the possibility of an oscillating or "bang/crunch" cosmos as perpetually cycling. The primary argument against it is the "missing matter argument," i.e., that there is not enough matter out there to gravitationally "net" it all and bring it all back to eventually "crunch" or "bounce" and start another bang cycle. But science is finding more matter all the time... not only the mysterious "dark matter" but lots of ordinary matter like dust, rocks, gas clouds, planets, and black holes, from relatively small to supermassive. The "not enough matter" pronouncement is definitely premature.

 

As for the matter-of-fact statement that "space is expanding," this assumes space as an entity rather than the emptiness in which entities of all kinds exist and expand out from the bang. I agree with Dragonstar in this respect, questioning, "so is space really expanding or are the things in it moving away from each other in an already infinite space?"

 

The ontology of space, time and "spacetime" is not a settled debate, and I question their status as existing entities. So does the International Society for the Advanced Study of Spacetime, which sponsers conferences on the Ontology of Spacetime. (See Dennis Deiks' volumes of papers from those conferences.)

 

Gotta go, but I look forward to further duscussion of these questions here.

 

Owl

[steevey]

 

 

 

 

 

Assuming that the universe is infinity old and has infinite number of stars, then the dust would heat up and radiate. Galactic dust by itself will not solve the paradox.

 

Now that I think about it, the universe can still be infinitely old since we have no way of telling how long the universe existed as a single point or if it wasn't a single point, we have no idea for how long the thing was there that caused the universe to exist (thing isn't necessarily tangible in this context). Maybe the universe is infinite, and its just that nothing caused it to grow in size till a few billion years ago.

[Spyman]

As for the matter-of-fact statement that "space is expanding," this assumes space as an entity rather than the emptiness in which entities of all kinds exist and expand out from the bang. I agree with Dragonstar in this respect, questioning, "so is space really expanding or are the things in it moving away from each other in an already infinite space?"

Why and how do you think "stuff" would be moving away from each other if "space" is not expanding?

[MR. Science]

Well we can't know it, but we can come up with something we are very sure is the answer.

 

 

Wells thats a theory, mention that, dont put extra trouble on yourself, and don't be a smartmouth.

[owl]

Why and how do you think "stuff" would be moving away from each other if "space" is not expanding?

 

If space is emptiness as distinguished from the "stuff" existing in it, then it (space) is not a medium which can expand, have shape, etc. This goes back to the "square one" ontological question, "what is space if not just emptiness or infinite "volume?"

 

So, I see the "bang" (by whaterver dynamic) "launching" all cosmic "stuff" outward omni-directionally, so the further out things get, the further they are from each other and from the locus of the bang.

 

I know that "expanding space" is now mainstream science, but the ontological question as to what, exactly it is supposed to be, as an entity or medium (besides emptiness) is still hotly debated. I've read a lot of well credentialed sources questioning the nature of space, time, and spacetime, and do not accept the matter-of-fact statement, "space is expanding" as if emptiness could have the properties of a malleable medium.

 

Owl

[Spyman]

If space is emptiness as distinguished from the "stuff" existing in it, then it (space) is not a medium which can expand, have shape, etc. This goes back to the "square one" ontological question, "what is space if not just emptiness or infinite "volume?"

Even if space is emptiness and not a medium, it does still exist and have properties like distance.

 

What is distance and how do we know whether the scale we use for measuring it is absolute and not changing?

 

 

So, I see the "bang" (by whaterver dynamic) "launching" all cosmic "stuff" outward omni-directionally, so the further out things get, the further they are from each other and from the locus of the bang.

If that was the case then we should be able to measure surrounding objects speed and trajectories relative us and find discrepancies with those objects moving outward by our sides as those moving outward in a leading or following position.

 

How do you explain why our observations can't find these discrepancies or the location of the locus?

 

Or do you think that Earth is in the center, or very close to, of the Universe?

 

 

I know that "expanding space" is now mainstream science, but the ontological question as to what, exactly it is supposed to be, as an entity or medium (besides emptiness) is still hotly debated. I've read a lot of well credentialed sources questioning the nature of space, time, and spacetime, and do not accept the matter-of-fact statement, "space is expanding" as if emptiness could have the properties of a malleable medium.

Do you also reject the theory of Relativity which has so far passed every unambiguous observational and experimental test?

 

If not then how do you concede with length contraction?

[owl]

Spyman:

 

"Even if space is emptiness and not a medium, it does still exist and have properties like distance.

 

What is distance and how do we know whether the scale we use for measuring it is absolute and not changing?"

 

Maybe I don't understand the question. I assume that we agree on lightspeed as a universal constant (even if the light source is speeding, as per special relativity.) So we we can say that light travels a given distance in a given unit of time. The sun is 8+ light minutes from earth (give or take its position in elliptical orbit.) It is the same distance regardless of time unit used or frame of reference differences among different observers. Relativity stays intact, but that distance doesn't actually vary with observer frame of reference.

Me:

So, I see the "bang" (by whaterver dynamic) "launching" all cosmic "stuff" outward omni-directionally, so the further out things get, the further they are from each other and from the locus of the bang.

 

You:

"If that was the case then we should be able to measure surrounding objects speed and trajectories relative us and find discrepancies with those objects moving outward by our sides as those moving outward in a leading or following position.

 

How do you explain why our observations can't find these discrepancies or the location of the locus?

 

Or do you think that Earth is in the center, or very close to, of the Universe?"

 

I'm sure I don't understand the first two above, just the last. Of course earth is way out from the locus of the bang, like the rest of cosmos "launched" in all directions from the bang. And every bit of "stuff", like fragments from a fireworks display, is getting further from the "launch site" (primordial ball of all-there-is) and from every other bit of stuff. (Your objections to this above make no sense to me.)

You:

"Do you also reject the theory of Relativity which has so far passed every unambiguous observational and experimental test?

 

If not then how do you concede with length contraction?"

 

No to the first. I reject the reification of space as some thing that expands, curves, and has shape, though the contents of space do so. This is an ontological objection to the treatment of "space itself" as such a malleable medium.

 

As for "length contraction:

As a philosopher of science I see this aspect of relativity as subjective idealism*... where the abstract "observer' in each frame of reference is the "subject." (*The belief that the only cosmos/world we can know is what we percieve, and that varies with point of view, inertial frames of reference, etc.) So relativity says that two rods of equal length when side by side change to different lengths when viewed from different frames of reference with signal delay varying what different observers see. Here there is no "objective world" but it actually changes with our perception of it. I am not a subjective idealist and, therfore disagree with this fundamental philosophy within relativity. Same with one rod accellerated and then measured from a different frame of reference. (It stays the same length not matter how, from where, and in what inetial reference frame it is observed.

 

Hope this is clear. Of course, as one who sees relativity as you do, you will not agree. Mine is a philosopical difference with relativity's basic notion of subjective idealism, as above, and with its reification of space, time, and "spacetime."

 

Owl

Edited January 29, 2011 by owl

[Spyman]

Sorry Owl, but I have a hard time trying to make head or tail of your post, maybe it's a language problem since I am not a naitive english speaker, so I apologize if I have misinterpreted you somewhere.

 

 

Your view of Albert Einsteins theory of Relativity seems to be more than a philosopical difference of what the mainstream science hold, I don't think you can accept Relativity and still say that distances stays the same no matter of reference frames. I don't think the consequences of constant lightspeed for all observers allows for rigid absolute distances and durations between different frames.

 

 

Since I was not able to express my question of observations and trajectories good enough, here is a second try:

 

In a rigid not expandable and absolute space, consider the following two examples:

 

1) One million spaceprobes are gathered together in a spherical swarm around an explosive device, at time zero the device goes off and launches all the spaceprobes outward in all directions from the center. After a certain amount of time each and every one of the spaceprobes starts to take measurements and observations of all other spaceprobes in the neighborhood.

 

2) One million spaceprobes are gathered together in a spherical swarm and between every adjacent spaceprobe there is an mechanical extendable arm, at time zero all arms extends simultaneously a equal amount. After a certain amount of time each and every one of the spaceprobes starts to take measurements and observations of all other spaceprobes in the neighborhood.

 

In both examples the size of the swarm would grow an equal amount, but in the first example the swarm would be spread out like a hollow shell of some thickness, whereas the swarm in the second example would spread out homogeneously. The Earth could be viewed as one of the spaceprobes that happens to be deep inside the swarm and not able to view far enough to see any edges of such a swarm, but are still able to observe neighbors and measure their distances and trajectories.

 

Do you agree that in the first example we would be able to pinpoint the center and in the second example we could not?

 

Which one of the two examples does best fit with our current observations?

Edited February 1, 2011 by Spyman

[IM Egdall]

In our current understanding of the universe (based on general relativity), there is no center of the universe. Where did the big bang happen? It happened here, there, and everywhere. It happened on the tip of your nose. It happened at the star most distant from us. That's why physicists use the balloon analolgy to try and picture this. The SURFACE of an expanding balloon represents our universe. And there is no center to the surface of this balloon. The origin of the surface, where it started expanding, is all places on the surface. And no matter where your are located on the balloon surface, you see the rest of the surface moving away from you.

 

This is all to say that space itself expanded from the big bang. Stange stuff, and hard to comprehend (at least for me), but this is what modern cosmolgy is telling us.

[michel123456]

Even if space is emptiness and not a medium, it does still exist and have properties like distance.

 

Somehow, although all evidences show it is a correct statement, logic shouts to me that it must be wrong.

 

 

What is distance and how do we know whether the scale we use for measuring it is absolute and not changing?

 

Indeed: we don't know that.

 

From time to time I am surprised from your statements Spyman, and I really don't understand why we occasionaly disagree. I suspect I read in your text something that you didn't ment to write.

[owl]

Sorry Owl, but I have a hard time trying to make head or tail of your post, maybe it's a language problem since I am not a naitive english speaker, so I apologize if I have misinterpreted you somewhere.

 

 

Your view of Albert Einsteins theory of Relativity seems to be more than a philosopical difference of what the mainstream science hold, I don't think you can accept Relativity and still say that distances stays the same no matter of reference frames. I don't think the consequences of constant lightspeed for all observers allows for rigid absolute distances and durations between different frames.

 

 

Since I was not able to express my question of observations and trajectories good enough, here is a second try:

 

In a rigid not expandable and absolute space, consider the following two examples:

 

1) One million spaceprobes are gathered together in a spherical swarm around an explosive device, at time zero the device goes off and launches all the spaceprobes outward in all directions from the center. After a certain amount of time each and every one of the spaceprobes starts to take measurements and observations of all other spaceprobes in the neighborhood.

 

2) One million spaceprobes are gathered together in a spherical swarm and between every adjacent spaceprobe there is an mechanical extendable arm, at time zero all arms extends simultaneously a equal amount. After a certain amount of time each and every one of the spaceprobes starts to take measurements and observations of all other spaceprobes in the neighborhood.

 

In both examples the size of the swarm would grow an equal amount, but in the first example the swarm would be spread out like a hollow shell of some thickness, whereas the swarm in the second example would spread out homogeneously. The Earth could be viewed as one of the spaceprobes that happens to be deep inside the swarm and not able to view far enough to see any edges of such a swarm, but are still able to observe neighbors and measure their distances and trajectories.

 

Do you agree that in the first example we would be able to pinpoint the center and in the second example we could not?

 

Which one of the two examples does best fit with our current observations?

 

Yes, Spyman, the difficulty in understanding is mutual, but I do understand your two scenarios above.

I will also explain my philosophical difference with the asuumptions implicit in relativity theory.

 

I accept that observation supports a visible cosmos which is isotropic and homgeneous.

If the expanding balloon model of cosmos is true, this does not mean that we can see beyond the "thickness" of "rubber" within our local part of the balloon and locate the center of the balloon (locus of the big bang.) Of course we can not. As you implied, even in the first example the rubber of the balloon membrane will have thickness.

("...in the first example the swarm would be spread out like a hollow shell of some thickness,...")

 

It is entirely possible that our cosmic event horizon is embedded wiithin the thickness of material expanding outward omnidirectionally from the bang.

 

As to the subjective idealism "embedded" in relativity theory, which I previously mentioned (that distance varies with observational perspective), here is a thought experiment for you.

 

If there were no intelligent life in the cosmos, we can probably agree that cosmos would not vanish simply because we were not here to observe it. (Yes?) So, the distance between, for instance, earth and sun would remain as is and sunlight would still take over eight seconds to reach earth. (Yes?)

 

Likewise rods of "equal length" would stay equal no matter how they traveled in relation to each other. Again, with no "observer" to invoke relativity, signal delay, and frame of reference difference, the rods themselves would stay the same length. Do you agree?

 

Same for time as for space and distance: Things would move around on their own and all events would happen without our observation and measurement. An earth rotation and orbit would be the same duration without our clocks disagreeing because of inertial differences in their frames of references... as we observe now, calling it "time dilation."

 

Do you see what I'm getting at here? I do not agree with the subjective idealism implicitly embedded in relativity theory.

Thanks for the converstion. Looking forward to your reply.

Owl