The ancient "infinite universe = white sky" thread.

[sayonara]

Ages and ages ago there was an extremely long thread along the lines of "if the universe were infinite, space would be white / no it wouldn't that's stupid / yes it would you twat".

Anyone got it in an archive?

Google and Way Back When are being unhelpful

[W]

I remember that thread.

And space would in fact be as hot and glowing as the surface of a star.

[sayonara]

Don't suppose you have the past 3 years cached?

[ChubbyChecker]

What? White space? Super hot space?

You people are stupid

[Dante Hicks]

vB should have the option to easily export threads, like you can do with Private Messages. That would make systematic archiving a lot easier.

[Superpig #1]

No they are not you twat!
its the same old thread all over again

[Tactitus]

Originally Posted by Dante Hicks

vB should have the option to easily export threads, like you can do with Private Messages. That would make systematic archiving a lot easier.

The admins should stop deleting old threads. This stuff is gold, I tell you. Gold!

[Ragnarak]

Originally Posted by Dante Hicks

vB should have the option to easily export threads, like you can do with Private Messages. That would make systematic archiving a lot easier.

Is VB not run via a MySQL or similar database?

"Archiving" threads would just be a matter of a few SQL queries and a bit of php or whatever.

Have a 'Archives' forum and create a field that can be turned on/off depending on the thread rating, all highly rated threads then have their Forum ID changed from whatever forum they're in to the Archive forum after a certain time.

[acropolis]

Originally Posted by W

I remember that thread.

And space would in fact be as hot and glowing as the surface of a star.

couldn't space be infinite without matter being distributed out to infinity?

Or couldn't we be in the midst of an inifinite distribution of stars, and the universe is simply not old enough to have been completely heated up yet?

Or couldn't the universe be infinite, but the density of stars tails off exponentially out to infinity, but never getting to 0 (a 3d gaussian matter distribution)?

[W]

Originally Posted by acropolis

couldn't space be infinite without matter being distributed out to infinity?

Or couldn't we be in the midst of an inifinite distribution of stars, and the universe is simply not old enough to have been completely heated up yet?

Or couldn't the universe be infinite, but the density of stars tails off exponentially out to infinity, but never getting to 0 (a 3d gaussian matter distribution)?

Yes it could. The old argument assumes a homogeneous distribution

[Leshy]

Originally Posted by acropolis

Or couldn't we be in the midst of an inifinite distribution of stars

If something is infinite, how can it have a 'midst'?

and the universe is simply not old enough

In an universe of infinite age, age is not a factor altogether. As it has always existed.

Or couldn't the universe be infinite, but the density of stars tails off exponentially out to infinity, but never getting to 0 (a 3d gaussian matter distribution)?

I personally believe in an infinitely large void, with a finite amount of matter inside.

[Jennifer]

It's called Olbers' Paradox.

It assumes a universe that is infinite in time and space, and is homogeneous, isotropic, static, and it also neglects absorption. It also assumes a flat universe.

For a star of luminosity L at a diastance r, the flux arriving at the earth is f=L/(4*pi*r^2)

Intergrate this over all space for n stars per unit volume:

int {L/(4*pi*r^2)*n*4*pi*r^2, dr} = Ln int{1 ,dr} from 0 to infinity gives infinity.

Of course, this assumes stupid things that aren't true.

For example, it neglects the fact that objects such as stars have finite lifetimes.

Also, if the strong every condition rho*c^2 + 3p >0 holds (where rho is the matter density, p is the pressure and c is the speed of light, which we observe that it does, within the limits of our experience) then a, the scale factor of the universe, is always decelerating. This means that at some point in the past, a shorter time ago than H^-1, a was zero, and there was an initial singularity ie a horrendous space kablooie (aka big bang). So if the universe isn't infinite in time, then Olbers' paradox can't tell us anything about the universe being spatially infinite or not. I am of the opinion that on large scales (galaxy cluster size scales) the universe is homogeneous, which is why galaxies move apart as the metric expands and we/the earth/the solar system/the galaxy don't, hence I don't like the idea of an infinite universe with finite matter, tho obviously if you have non-zero curvature this is all reseolved nicely as you get something conceptually like a 3 sphere - a volume with no edge that is still finite in size (like the surface of the earth).

[Phang]

thanks Jen


by the way, how COULD there be infinite matter? doesnt this kinda go against pretty much everything physics is based on? and that's assuming we disregard any theory connected to the big bang or what have you. [/scraping a B in GCSE physics]

[sayonara]

Jennifer++

Now all she has to do is use that fancy maths of hers to find the old thread

[MrL_JaKiri]

I don't see why there shouldn't be infinite matter, as (in an infinite space) there'd be infinite matter in all directions and thus the forces should approximately cancel out.

[Thorn]

Could the infinite matter be used to make toilets for warfrigs?

[Baron Morte]

I remember this thread where people would discuss about ships being invisible and people being able to see people craping in their ships

[Jennifer]

I'm afraid you'd have to speak to a higher authority than me if you want to know about infinite matter in the universe.

Infinity is a funny thing. It has the strangest properties. You could make it by adding all the number from 1 to infinity, and get an infinity that way. Then you could say, well, I'm going to make a smaller infinity by adding up numbers from one to inifinity, but only including every other number: 2 + 4 + 6 + 8 etc. And oh, you'd be very clever to make an infinity smaller than infinity like that, except that you haven't. Because you see, you've actually done exactly the same thing as you did the first time, only you doubled all the numbers first, and then added them, So your second infinity is actually twice as big as the first...

Back to the topic in hand. I do not think you could get a gaussian distribution of matter, because of what we observe relating to the expansion of the universe. The galaxies are not flying away from each other at velocities ever increasing with distance - the space between them is expanding, though of course for all practical purposes, this amounts to the same thing. But are *we* getting bigger? Are people getting bigger? Is our metre stick we've got sitting in the physics lab getting longer? No, of course not. If it were, we wouldn't be able to detect the redshift, because we'd measure the longer wavelength with a bigger ruler and conclude that it is the same as when it was emitted and that there is no redshift. This is because we aren't stapled to our positions in the metric. The distance between atoms is our bodies and in our metre sticks are governed by chemical bond strengths. On the scale of the solar system, it's the force of gravity between the sun and planets that determines the size of our orbit, so the solar system doesn't expand with the metric either. This is all fine so far, it's what we observe. What about on galactic cluster scales? When you've got forces coming from all directions, and the metric is moving apart, matter throughout the universe is tugging and being tugged on by matter from all around it, so it all moves apart with the metric. Picture it like this: You've got a balloon, with little blobs on it, that are attached to the surface but are free to move over the surface if a force makes them do so. Now imagine all of these blobs are attached to their nearest neighbours with elastic bands, so that you have an entire net of elastic bands covering the balloon. What happens when you expand the balloon? Intuitively, the blobs all move apart, and the elastic bands stretch. Suppose the blobs were only situated on top of the balloon, in a gaussian density distribution, if you like. Now what happens when you expand the balloon? The blobs just sit on the top, the same distance apart as before, while the balloon gets bigger underneath them. By this argument I would suggest that the expansion of the metric is only observed in the motion of matter on the scale that the universe is homogeneous.

PS Don't take this analogy too much to heart - obviously elastic bands exert a greater force when they are stretched, while the gravitational force on bodies get weaker as they move apart. Also, it's hard to imagine an infinite sheet of rubber and infinite blobs, but I think that such a thought experiment would give the same result as the balloon one.

[Hostile]

I remember the star wars versus star trek thread

that was funny as hell

[LHC]

Guardian vs Everyone :coolio: