Important Math Question

[Cyrien]

Originally posted by deccan:

quote:

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Originally posted by Cyrien:
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.

I don't disagree with logic of your statement, but I do disagree with the sentiment behind your statement. Certainly, all of our theories on the subject of cosmology (and much else besides) should always come attached with the caveat "so far as we can tell". But just because we cannot know for certain is no excuse for saying that we can never know and that we shouldn't speculate, build theories and try our best to extend our knowledge, imperfect as our methods are.

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I never said we shouldn't speculate. I enjoy the speculation. The problem comes when, as I have often seen happen in other forums discussing this and other topics, people start pressing things across as facts to prove themselves when it is all just theory and speculation. IE: the number of atoms in the Universe, how old the universe is, background microwave radiation proves this or that... quite simply we don't know enough to be making any statements on these things based on what we can and can't know. All of this needs to be taken with a grain of salt when you start talking about infinite v finite universe.

Sorry if you took what I was saying the wrong way but I was simply trying to nip that in the bud, since normally as soon as people start posting cosmological data it rapidly approaches that path.

The basic problem is one you can see in every field of science. Older theories have prominence because they are the ones the scientists grew up with and their body of work is based on. If you say it might be wrong then you say that your whole body of work that you have worked on your whole life might be wrong. Most people just won't do this. You can see it historically with great resistance to new ideas and ways until overwhelming proof shows it to be truer and the old false and it can't be ignored anymore.

I wonder how much further along we could be if we as a species could simply admit to ourselves and others when something that we have worked on our whole lives might be wrong. Add up the decades of resistance you get to each new idea before it is accepted and I bet it is quite a alot.

[Cyrien]

And Dark Matter theory is the perfect example of theories growing larger than maybe they should. It is the most largely accepted theory currently. But there are several other theories just as valid and accurate in the predictions for the actions of the universe that we can observe. They differ in what causes that and in their predictions for what we can't observe.

Yet Dark matter and energy is almost always what gets brought up. I know that we normally preface it as "this is just a theory" and quite correctly but the fact that we don't even bring up the others is itself a disturbing trend. If we don't even look at the alternatives will we notice when it starts being more accurate than the mainstream?

[Suicide Junkie]

I wonder how much further along we could be if we as a species could simply admit to ourselves and others when something that we have worked on our whole lives might be wrong. Add up the decades of resistance you get to each new idea before it is accepted and I bet it is quite a alot.

Of course, the flip side of that would be like societal ADD.
Everything in moderation...

[deccan]

Originally posted by XenoTheMorph:
Therefore even in an infinite universe you only get to see a finite volume of space. So only the Photons from objects in this volume can reach you, so no superheating problem! This also means that the cooling of space does not mean energy is being 'lost' only that the density of the energy is decreasing, same amount of energy larger volume.

Good points, and certainly true for a universe which is expanding at an accelerating rate, as our universe currently seems to be. Of course, in such a universe, the volume that we can interact with in any way is certainly very finite, so you throw away much of the appeal of having an infinite universe.

[Ran-Taro]

Originally posted by Phoenix-D:

quote:

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Originally posted by Grandpa Kim:
If the universe is infinite, then there are an infinite number of earth-like worlds, and infinite number of alien civilizations, and the sky would be not be blue but the color, brightness and intensity of your average sun 24/7. Half of infinity is still infinity!

Frankly, we could not survive an infinite universe. Of necessity the temperature would be far beyond what our bodies could stand. I mean, we are talking thermonuclear temperatures.

Since this is not true, the universe is not infinite.

Yep, centillion is huge, but it's pretty miniscule next to infinity.

Not true at all. Look at Hubble's Deep Field photographs sometime- you see entire galaxies that aren't even visible to the naked eye. Infititely sized means infinitely far away, as well. And heat? Do you feel any heat from the stars at night? Didn't think so, and those are the closest ones. Heat does trail off the further you get from an object.

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Plus an infinitely large universe does not mean infinite numbers of everything in it. You could have an infinite amount of space, with a finite amount of planets and suns, for example.

[edit] Oops - I responded to something on the first page thinking it was the whole conversation. Now I see the converstion has covered this ground. Ignore me.

[ November 04, 2003, 10:31: Message edited by: Ran-Taro ]

[geoschmo]

Let me preface this by saying I don't believe the universe is infinite. But the arguments given here against an infinite universe don't hold up. This is somewhat restating what others have already said, but maybe it will help to think of it this way.

If the universe is infinite, there are an infinite number of photons, but each photon is still a finite particle. It can only be in one point in the universe at any particular time. And you are finite as well. You only exsist in one point in space. Being hit with an infinite number of photons all at once would be bad. But for that to be possible one of these has to be true:

1. The infinite number of photons in the universe have to all be in the same place; just where you happen to be standing. Besides being an incredible piece of bad luck, this would be quite difficult to time. And if you managed it somehow, you'd be left with an infinite sized universe empty of photons, except where you are.

2. Every one of the infinite number of photons would have to exsist in every point in space simultaneously. Impossible since they are finite particles.

3. You would have to exsist in every point in space simultaneously.

The point is that over time, an infinite amount of time actually, you would be hit by an infinite number of photons. But at any particular point in time you are being hit by a very small, and very finite fraction of the total number of photons. Your perceived temperature is not dependant on the total number of photons to ever hit you, but on the total number of Photons hitting you at any particular point in time.

Geoschmo

[ November 04, 2003, 13:22: Message edited by: geoschmo ]

[geoschmo]

Hmmmm, I seem to have hit a problem here. My previous post started out as a statement showing why Phoenix-D was right, that an infinite universe would not be infinitly hot.

However, in my post I stated that any particular point in in infinite universe would contain not an infinite number of photons, but very small and finite fraction of the total number of photons in the universe. However, according to those that are supposed to know about this stuff, any fraction of infinity is still infinity. Of course mathematics also tells us that any number divided by itself is 1. Therefore infinity divided by infinity is simultaneously equal to infinity, and 1. (By the way, if noone has thought of that before I am going to name it the Geoschmo paradox. )

So I guess Phoenix-D and Grandpa Kim are both right. Glad we cleared that up.

[ November 04, 2003, 13:51: Message edited by: geoschmo ]