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chriscurtis
2006-Nov-02, 08:51 PM
Hi Gang,

I remember reading of an argument against an infinite universe being that every line of sight would in the the surface of a star and the whole sky would be bright. However, if most of the stars in the universe were black holes, surely the line of sight would end in that surface. If Hawking radiation exists, maybe you would see that. Maybe it would be microwaves or something that isn't bright to our eyes.

Would say the experts? I'm so curious about this one

Cheers and hellos from Auckland, New Zealand where summer is just kicking in
Chris

Squashed
2006-Nov-02, 09:06 PM
Hi Gang,

I remember reading of an argument against an infinite universe being that every line of sight would in the the surface of a star and the whole sky would be bright. However, if most of the stars in the universe were black holes, surely the line of sight would end in that surface. If Hawking radiation exists, maybe you would see that. Maybe it would be microwaves or something that isn't bright to our eyes.

Would say the experts? I'm so curious about this one

Cheers and hellos from Auckland, New Zealand where summer is just kicking in
Chris

You raise an interesting point in regard to Olber's paradox because not every object in the universe is a star and so star light would be blocked by these non-transparent/non-radiating entities - but I don't know if these non-transparent/non-radiating objects would be numerous enough to block that many stars.

01101001
2006-Nov-02, 09:07 PM
Wikipedia: Olbers' paradox (http://en.wikipedia.org/wiki/Olbers'_paradox)

And see many topics in this forum, such as:
Olber's Paradox (http://www.bautforum.com/showthread.php?t=39907)
The darkness of space? (http://www.bautforum.com/showthread.php?t=42170)
About Olbers Paradox (http://www.bautforum.com/showthread.php?t=10494)
Olbers' Paradox (http://www.bautforum.com/showthread.php?t=442)

trinitree88
2006-Nov-05, 03:51 PM
You raise an interesting point in regard to Olber's paradox because not every object in the universe is a star and so star light would be blocked by these non-transparent/non-radiating entities - but I don't know if these non-transparent/non-radiating objects would be numerous enough to block that many stars.

An infinite line of sight would have an infinite number of stars that emit an infinite number of photons and an infinite number of neutrinos....and while they are not transparent to photons....they're pretty transparent to neutrinos, so you'd have mostly them....from every square degree of sky.:shifty:

Mister Earl
2006-Nov-05, 05:34 PM
Ah, but you're not taking into effect the gravitational effect on light. Maybe there's enough dust and nebulae out there to sop up the "excess" light. Or perhaps if the universal expansion somehow halts, the sky will brighten as stars farther and farther out become visable to us.

PhantomWolf
2006-Nov-06, 12:23 AM
The other thing is distance, the further a star is the less of its photons get into our eyes. Hubble has shown that there are vast areas of what we think of as black and empty that in fact have billions of stars and thousands of galaxies in them.

luvkit
2006-Nov-06, 01:53 AM
The night sky is REALLY, REALLY dark! Imagine how many black holes you would have to have to absorb the light from an infinitely bright and old universe! You'd basically have to blanket the whole celestial sphere with them and leave no voids. That would be a very dangerous space to be in. I wouldn't give Earth much time in a universe like that before we were sucked into one of these black holes.

Jens
2006-Nov-06, 08:46 AM
Maybe there's enough dust and nebulae out there to sop up the "excess" light.

This doesn't work because the light (and heat, which is actually also a problem) would be re-emitted somehow. So it doesn't save you from the paradox.

The only ways I'm aware of to solve it are, in addition to finiteness, (1) fractality and (2) the black hole issue. But if black holes are insufficient, then fractality would be the only possible solution AFAIK.

johnspannenburg
2007-Jan-25, 03:46 AM
Really I would have thought there is no paradox and that the 'redshift' argument mentioned in the wikipedia in fact solves the entire problem. Whether the universe is finite OR infinite so long as it is expanding you will have the situation that light eminating from stars far enough away will have their light (red)shifted out of the visible range for our eyes.. This does create the effect of living in an optically (for our eyes) finite universe even if it is not finite. beyond the range or our eyes the light from those stars is still there detectable by instruments . There will be a point at which the light is at the bounds of taking forever to reach us (ie the expansion from us of that point is very close to the speed of light) and that light will be infinitely shifted and probably be (effectively) beyond detection. Further away than this point and you are beyond our 'horizon' and this part of the universe is totally undetectable in any direct way. So really I believe, given an expanding universe, this paradox is totally solved.

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