41–50 of 55 posts
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What about time?
One cannot even assume time is infinite- there are theories postulating infinite time and finite time, as well as theories postulating that time may not really exist at all.
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An infinitely large observable universe is not possible, however an infinitely large and infinitely old universe is still possible with dark sky at night.
Howso? If the universe is infinitely large and old, and light works as well believe it does, then light should come from all directions. That's the entire point of this paradox. Light as we know it moves without limit. If anything is blocked by it, the blocking object would heat up until it glowed just as brightly.
So basically, we don't exactly know why the night sky is mostly dark? (At least, that's what I got out of this)
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Well redshift alone explains the paradox. You don't even need to accept the big bang theory. You can just say "stars that are further away are more redshifted" and that alone explains this. Which we know is true. That's not a hypothesis, redshift can be observed directly. And that fact alone explains the apparent paradox. The most distant stars are redshifted away. To quote the above article >The redshift hypothesise…
Saying "stars that are further away are more redshifted" is Hubble's law and leads almost directly to the big bang. It alone, however, does not explain the paradox. For example even with red shifting, you could have a bright night sky if there are infinitely many stars and the speed of light is instantaneous.
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The paradox itself is that if the universe is both infinite and eternal then we shouldn't have a dark sky. This is 'trivially' solved by demonstrating that either of those conditions aren't true. The article opts to use the explanation given by Edgar Allan Poe to demonstrate this, which is that the universe has a finite age and the speed of light is finite so there's only a finite amount of observable universe, which…
>The paradox itself is that if the universe is both infinite and eternal then we shouldn't have a dark sky I've never really felt like I understood the paradox, since the way people explain it, it sounds to me like they're just denying the idea that an infinite sum can have a finite value. Like, why couldn't the brightness of the sky in an infinite universe be any value at all, depending on the density? The argument…
> To show this, we divide the universe into a series of concentric shells, 1 light year thick. A certain number of stars will be in the shell 1,000,000,000 to 1,000,000,001 light years away. If the universe is homogeneous at a large scale, then there would be four times as many stars in a second shell, which is between 2,000,000,000 and 2,000,000,001 light years away. However, the second shell is twice as far away, so each star in it would appear one quarter as bright as the stars in the first shell. Thus the total light received from the second shell is the same as the total light received from the first shell.
The argument that the universe would collapse in on itself is made using similar math (gravity decreasing with the square of the distance is by no accident the same as brightness) so if you buy one you sorta have to buy the other. Of course, the universe probably is infinite and isn't collapsing in on itself, but that's because of dark energy (OK yes, there are all sorts of universes that obey relativity, and some of them are infinite and not collapsing, but if we live in one of those no one's found the solution that fits our observations. The dominant thinking was that the universe would eventually collapse until we discovered it's actually expanding).
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Howso? If the universe is infinitely large and old, and light works as well believe it does, then light should come from all directions. That's the entire point of this paradox. Light as we know it moves without limit. If anything is blocked by it, the blocking object would heat up until it glowed just as brightly.
> Light as we know it moves without limit. Black holes say no.
Is there a good explanation as to why this paradox isn't explained by universal expansion? From wikipedia: "To any observer in the universe, it appears that all of space is expanding, and that all but the nearest galaxies (which are bound by gravity) recede at speeds that are proportional to their distance from the observer."; Wouldn't this imply that, there was probably a time in the distant past when the night sky…
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Howso? If the universe is infinitely large and old, and light works as well believe it does, then light should come from all directions. That's the entire point of this paradox. Light as we know it moves without limit. If anything is blocked by it, the blocking object would heat up until it glowed just as brightly.
'Infinitely large' isn't a prerequisite to the paradox. Rather, it's an infinite number of stars. Or, more precisely, an infinite number of stars spread out rather uniformly.