Important Math Question

deccan · #1 November 2nd, 2003, 03:44 AM

This sounds like a good time to bring up the:

Cosmology FAQ

One argument against an infinite universe is that the universe seems to be cooling, i.e. the cosmic background radiation is growing weaker over time. If the universe is truly infinite, with an infinite number of stars, it seems that the universe will only get hotter over time.

deccan · #2 November 2nd, 2003, 03:48 AM

Quote:

Originally posted by Phoenix-D:
The photon energy is lost, or absorbed. Some fraction is sent on, which then hits something else and repeats the process. Infinite number of photons..infinite number of barriers. And at any given time, only a finite number of those photons are actually arriving at any given point.

As Jack pointed out, the energy cannot be destroyed. Given enough time, anything that blocks and absorbs those photons will eventually re-radiate it out again.

DavidG · #3 November 2nd, 2003, 04:26 AM

Quote:

Originally posted by narf poit chez BOOM:
if the universe is infinite in size, the distance between us and any galaxy will still not be infinite.

If the distance between us and any galaxy is not infinite then clearly the universe is not infinite in size.

Phoenix-D · #4 November 2nd, 2003, 04:43 AM

Quote:

Originally posted by DavidG:

quote:
Originally posted by narf poit chez BOOM:
if the universe is infinite in size, the distance between us and any galaxy will still not be infinite.

If the distance between us and any galaxy is not infinite then clearly the universe is not infinite in size.

Err, not exactly. A universe being infinite in size doesn't preclude two things from being next to each other.

re: photon energy: true. The background actualy -cooling- probably precludes an infinite universe; it'd have to be either constant or increasing (unless all the non-visible stars are pulsing at the same time, but that is er, not likely).

Fyron · #5 November 2nd, 2003, 04:51 AM

I think he meant "if the distance between us and any one other galaxy is not infinite", meaning unless there is at least one galaxy that is an infinite distance away.

Cyrien · #6 November 2nd, 2003, 05:40 AM

Once again I am going to step in and say that we are making very big statements about EVERYTHING THAT EXISTS when we personally have observed about... less than .00001% of .000001% of .000001% (I am being generous tonight!(also assuming that it is finite and can have a percent value for it)) of everything in the Universe and then stating that we know that ALL OF THE UNIVERSE is cooling so it can't be infinite.

Let's say the Universe is infinite. Then couldn't it quite possible have very small sections of it, oh say 10^999 square light year sections, that are in fact cooling due to their rapid expansion while others are absorbing tons of this radiation and heating up until *BOOM* they make their own big bang in a far far far distant not corner (infinite doesn't have corners) of the universe.

If you can neither create nor destroy matter and energy (and I'm not saying that is correct either but you have to have something to base stuff on) then in an infinite universe you have an infinite amount of energy and matter spread out over an infinite amount of space. But nothing says it has to be evenly spread. Some parts can be heating absorbing the energy until they reach a critical point then they release it while others are cooling off, then they switch off.

Infinity is not inherently linear it isn't nice and orderly. There is an infinity of numbers between any two numbers that can be named.

Quite simply the possibilities stagger the mind and we have no way and probably never will of knowing. So it makes for great arguments in forums all across the infinte space.

Oh... and just because something is infinite doesn't mean it has to include all sets and possibilites. The set of all real rational whole numbers is infinite but excludes things such as Pi, or fractions, etc. Yet it is still an infinite set. You can even make an infinite set with a beginning but no end.

Just because the universe is infinite does not mean that all possibilites are inherently capable of existing within it.

[ November 02, 2003, 04:00: Message edited by: Cyrien ]

Graeme Dice · #7 November 2nd, 2003, 09:58 AM

Quote:

Originally posted by Grandpa Kim:
[QB] Can't agree with you Phoenix-D. You are still underestimating infinity. In an infinite universe, there will be a star in every direction you care to point, in fact, an infinite number of them. Therefore, you are being bombarded by an infinite number of photons. True, each photon puts out an immeasurable amount of heat but that tiny amount is still there.

You need to seriously rethink your entire argument. Even if there is an infinite amount of energy in the universe, it still propagates at a finite speed. It will take an infinitely long time to travel from a source that is an infinite distance away, so we will never see that energy.