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Topic: How was the real universe created? (Read 23164 times)
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Culture20
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Thraddash Flower Child
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But The_Ultimate_Evil, the limit of science is the observable; you can't just say there might be an infinite number of galaxies and then base your scientific theories on that assumption.
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Death 999
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We did. You did. Yes we can. No.
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But The_Ultimate_Evil, the limit of science is the observable; you can't just say there might be an infinite number of galaxies and then base your scientific theories on that assumption.
Well, one of the nice things about General Relativity is that we can pretty much say "Gee, space looks pretty flat around here." and work within that. Namely, if there IS any curvature to the universe as a whole, it's awfully small, so for our calculations we might as well say it's zero. That simplification suggests an infinite universe.
However, we could have a really big closed, finite universe. If this is so, our calculations, except for those concerning the exact matter in question - namely, the shape of the universe, are unaffected and still apply, with a tiny correction term.
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Death 999
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We did. You did. Yes we can. No.
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Well, if the universe is finite and it wraps around like a torus or sphere, and it is small enough that light has had a chance to get more than half way around it -- well, then we could see the same exact galaxy in opposite directions, and then we'd know that the universe was finite, because clearly the light had wrapped around.
We have not seen this (though there are people looking for it). SO, we could prove it if it were true in a particular way. As time goes on, the number of ways of it being true that we can detect gradually increases. However, we can never exhaust them all. Proving an infinite universe will be spectacularly difficult.
edit: 666th post!
<voice ="evil winnie-the-pooh">
Ooh! Time for my daily satan worshipping.
Satan! Satan!
Thank you for death and despair, and plagues, and all the bad stuff that happens to people!
</voice>
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« Last Edit: May 31, 2003, 01:01:26 am by Death_999 »
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Shinryuu
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You cannot escape... THE MUFFIN.
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erk. I suppose what i was trying to say way back on fourth page wasn't that other sentient life wasn't likely, it is that nobody can say how likely it is <as we haven't got a reasonable ratio of any-sorta-lifebearing planets to non>.
This is just a quick observation from skimming over the posts.
The problem with infinity is that it isn't a number or a quantity. Thus, operations like expansion, contraction, addition, subtraction that apply to numbers and quantities and variables and the like can't be applied to infinity. Infinity is like religion. It's a concept. Infinity can't expand, contract, add, subtract, multiply, slide, increase, decrease, skateboard, sail, comment on politics or even wear a bathrobe.
Therefore, it is actually quite silly to say that something that is infinite is expanding. Especially if that something is the universe. Lemme put it this way:
Infinity + 1=Infinity.
Infinity=Infinity.
By subtracting infinity from either side of the equation via basic 7th grade algebra, we obtain that 1=0. In other words, it tells us that we're trying to do something dumb. Because 1 doesn't equal 0.
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Politics is for morons who haven't developed --- OBFUSCATION!!!
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Death 999
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We did. You did. Yes we can. No.
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Ahem. Read my FREAKING post. The unverse isn't expanding in the sense of the region spanned by it expanding; it is expanding in the sense that all of the bits of matter in it are uniformly getting further away from each other.
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Death 999
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We did. You did. Yes we can. No.
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Consider the integers. They are evenly spaced, 1 apart.
Now, multiply each integer by 1.0001.
Look! They're all a little further apart!
As for the infinite matter -- See any cosmology text -- here.
http://map.gsfc.nasa.gov/m_uni/uni_101shape.html
Note that paragraph 2 refers to a 'critical density', and postulate that the critical density is some normal-number value (i.e. not 0 or dV). Since they are also postulating a flat, nonrepeating universe, this implies infinite volume.
Infinite volume times some normal value for density = infinite matter.
QED that the basic cosmology 101 view is infinite matter
Incidentally, the big bang was a lot more compressed than 'the volume of a small moon' -- we can place NO LOWER BOUND on how tightly packed all the matter that we can now see was. There is no reason to suspect that all of the matter in our sphere of visibility was not compressed into the volume of a single atom, or a single atomic nucleus.
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« Last Edit: May 31, 2003, 08:01:10 am by Death_999 »
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Death 999
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We did. You did. Yes we can. No.
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AH, yes, good point. This reminds me -- when I was giving my balloon example, I did not mean that the universe was INSIDE the balloon. I was making an analog, in which there was a universe on the SURFACE of the balloon. This universe on the surface of the balloon has no boundary - it loops back in on itself.
The example also works if you don't make the balloon a sphere but just stretch it in place as a plane (which is what I was getting at when I had the balloon blown up to infinity).
I am not claiming that there is such a dimension -- it was merely another illustration of how an infinite space can seem to grow.
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Crowley
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Considering the finite vs. infinite debate, I once read a rather simple way of proving that the universe is not infinite:
Why is the night sky dark?
There are stars in the sky. The brightness of an object is divided by four when the distance to it is doubled. However, when the radius of a sphere is doubled, its surface area is quadrupled. Imagine the surface of the sphere is the night sky, and the radius is infinity. Therefore, if we have an infinite universe with an infinite number of light-emitting stellar bodies, the brightness if the night sky should be constant and even.
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Stanz
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I love YaBB 1G - SP1!
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This topic is pointless, its like 'is there other alien lifeforms out there', everone has their theorys but noone knows yet.
So I surgest you stop trying to prove things from your 'theorys' because it hasnt been proven, so it is up to you to believe what you want to... so its best if you dont try to prove other people wrong.
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Death 999
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We did. You did. Yes we can. No.
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Considering the finite vs. infinite debate, I once read a rather simple way of proving that the universe is not infinite:
Why is the night sky dark?
When the universe was young, it was SO HOT that everything was plasma. Atoms could not form. Furthermore, light couldn't go far before it hit a charged particle in open space. So all the light was bouncing around like mad.
Then, as space expanded, things cooled down via adiabatic cooling. This includes the light itself -- as space expanded, the wavelengths of the light were expanded as well. This lowered the frequency and thus the energy of the light (the energy that this sapped out ended up in the gravitational field energy).
When things cooled down enough that the average temperature was low enough that hydrogen atoms could form, they did. In the process, they emitted a very stable spectrum of light -- the emission spectrum for Hydrogen. This event is called the "decoupling". It happened everywhere at just about the same time.
One thing about hydrogen is that it's really close to transparent. Light of almost every frequency below its ionization energy will pass through it unaffected.
SO, as time went on, the light of the decoupling was gradually stretched and stretched and stretched, made cooler by the adiabatic cooling of the expansion of the universe. It was still everywhere the background, but it was getting less and less energetic.
Now, this light, which started out ultraviolet, is microwave-frequency. It is the cosmic microwave background.
So, if we could see in the microwave region, the sky would be quite bright.
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