Since I'm terrible at explaining things, I found a good resource.

Quote:The fate of the universe is determined by a struggle between the momentum of expansion and the pull of gravity. The rate of expansion is expressed by the Hubble Constant, Ho, while the strength of gravity depends on the density and pressure of the matter in the universe. If the pressure of the matter is low, as is the case with most forms of matter of which we know, then the fate of the universe is governed by the density. If the density of the universe is less than the "critical density", which is proportional to the square of the Hubble constant, then the universe will expand forever. If the density of the universe is greater than the "critical density", then gravity will eventually win and the universe will collapse back on itself, the so called "Big Crunch". However, the results of the WMAP mission and observations of distant supernova have suggested that the expansion of the universe is actually accelerating, which implies the existence of a form of matter with a strong negative pressure, such as the cosmological constant. This strange form of matter is also sometimes referred to as "dark energy". If dark energy in fact plays a significant role in the evolution of the universe, then in all likelihood the universe will continue to expand forever.

http://map.gsfc.nasa.gov/universe/uni_shape.html

Quote:Recent measurements (c. 2001) by a number of ground-based and balloon-based experiments, including MAT/TOCO, Boomerang, Maxima, and DASI, have shown that the brightest spots are about 1 degree across. Thus the universe was known to be flat to within about 15% accuracy prior to the WMAP results. WMAP has confirmed this result with very high accuracy and precision. We now know (as of 2013) that the universe is flat with only a 0.4% margin of error. This suggests that the Universe is infinite in extent; however, since the Universe has a finite age, we can only observe a finite volume of the Universe. All we can truly conclude is that the Universe is much larger than the volume we can directly observe.

I was always under the impression that the universe was infinite and constantly expanding, as well. From the books I've read, anyway.

So I've been summoned into this thread via PM to comment on infinities. Whilst I don't claim to be an expert, I think Neil deGresse Tyson explains the concept quite nicely in this 1:25 minute video:

http://www.youtube.com/watch?v=nzQ4-gEesRg

Effectively:

The edge of the observable universe is simply the furthest point away from us (Earth) that light has been able to reach us from. This distance is about 13.7 billion light years away. Note that due to limitations on light speed (i.e. that the speed of light is not infinite) it is impossible to know whether there is any space beyond that edge, though it is quite likely that there is...we just can't see it.

The reason it's quite likely is that we already know there are galaxies that are moving away from us at speeds faster than the speed of light. If that sounds impossible ("nothing can move faster than the speed of light"), then you've hit upon the problem when talking about universal expansion compared to...well, any other kind of expansion.

I've seen analogies of universe expansion that liken it to a balloon gradually being filled with air. The material of the balloon remains the same mass, but the points that make up the balloon are all stretched and the distances between them become greater. Universal expansion is when space itself expands. That is to say, technically speaking, the galaxies themselves are pretty stationary (i.e. they don't move through space that much), but the space between galaxies is expanding. The problem with the balloon analogy is that the balloon is situated within space, and so it expands into other space. This is not true of the universe, because the universe is space. So in order to make the analogy correct, you have to imagine the balloon is the only thing that exists. It doesn't expand "into" anything, because it is the only thing that exists.

In this sense, the universe itself is infinite, the distances between certain points of space in the universe are being "stretched" at speeds which are getting faster the further apart the two points are (though the speed limit of objects within space itself remains a constant), and the observable universe (because it is limited by the speed of light) is expanding at the speed of light, and is most definitely finite.

That last paragraph can serve as a TL;DR btw. :-)

(March 7, 2014 at 6:21 pm)rsb Wrote: I am not sure gravitational lensing is exactly the same as a gravity wave, if it was then observations in the early part of the last century would have resolved it.

I never said it was...
Gravitational lensing is a piece of evidence for general relativity.
Nothing in general relativity states that there is such a thing as a gravitational wave, as far as I'm aware...

(March 7, 2014 at 6:21 pm)rsb Wrote: So sorry I don't believe you and think it is important to hunt for gravity waves.

What's with you and these gravitational waves?...

(March 7, 2014 at 6:21 pm)rsb Wrote: But as I understand it there are many, many closely equivalent theories which would be consistent with what we have observed.

Care to share them?

(March 7, 2014 at 6:21 pm)rsb Wrote: The elegance or beauty of a model is not evidence for it's reality. Until we observe it, we don't have direct evidence. There is no reason to treat science differently than other questions and every reason to hunt for proton decay and gravity waves and keep an open mind.

Exotic stuff tends not to get much funding...
If, during standard funded experiments, there is something that hints towards those exotic phenomena, then funding appears... until then, they remain scribblings with little value and no one to accept them as science.

(March 7, 2014 at 6:21 pm)rsb Wrote: No the visitors center at the grand canyon DOES NOT support Noah

Whew! For a moment, you had me worried.

(March 7, 2014 at 6:21 pm)rsb Wrote: , have you been there?

No, It's a bit out of my way... as I'd need to cross an ocean to get there.
For what? a fissure in the ground? I've seen it on tv.... does that count?

(March 7, 2014 at 6:21 pm)rsb Wrote: There are discussions of radioactive dating of the strata

You know how the YECs argue with this?... "how do you know radioactive decay worked according to your exponential decay law, millions of years ago?"
"Things worked way way faster in the past... that's how you arrive at very old ages, when they should be, at most, 6000 years"

(March 7, 2014 at 6:21 pm)rsb Wrote: and observed erosion rates. It is glaringly obvious that there are hundreds of thousands of years of history there and a flood is not consistent with any of it. Also observe the behavior of tar under even slight water pressure. It would NOT have sealed any cracks in the doomed box that the alleged god, Creator of the universe and all powerful, needed a man to make for him. So no, Noah is obviously BS to anyone with even a slightly functioning brain.

Noah?
Oh, you mean Gilgamesh, or was it Atrahasis?... yes, I agree...

(March 7, 2014 at 6:21 pm)rsb Wrote: As for theory and definitions like that, there are shades of grey and uncertainty in science. It does not help to pretend there are not. Nor does a theory being supported by evidence mean that all theories are equally true. You really have to talk about specifics. We don't need the first few seconds of the big bang to prove or disprove any theology, they are not necessary for support of atheism, they are often obscuring more important things, like the simple science present at the visitors center of the grand canyon.

Indeed, science is not necessary to support anyone's atheism.
But it helps to answer some of the burning questions that the theists like to claim that their god-did-it.

If you supply an alternative explanation, the requirement for a god shrinks in scope.

(March 7, 2014 at 6:21 pm)rsb Wrote: OR the fact that you knew about magnetic monopoles and I didn't could prove you are really the voice of athiesmo, great sky god of atheists.

Oh, thank you for your recognition.
I dub thee, knight of the atheismistic graal!

(March 8, 2014 at 11:10 am)Bittersmart Wrote: Since I'm terrible at explaining things, I found a good resource.

Quote:The fate of the universe is determined by a struggle between the momentum of expansion and the pull of gravity. The rate of expansion is expressed by the Hubble Constant, Ho, while the strength of gravity depends on the density and pressure of the matter in the universe. If the pressure of the matter is low, as is the case with most forms of matter of which we know, then the fate of the universe is governed by the density. If the density of the universe is less than the "critical density", which is proportional to the square of the Hubble constant, then the universe will expand forever. If the density of the universe is greater than the "critical density", then gravity will eventually win and the universe will collapse back on itself, the so called "Big Crunch". However, the results of the WMAP mission and observations of distant supernova have suggested that the expansion of the universe is actually accelerating, which implies the existence of a form of matter with a strong negative pressure, such as the cosmological constant. This strange form of matter is also sometimes referred to as "dark energy". If dark energy in fact plays a significant role in the evolution of the universe, then in all likelihood the universe will continue to expand forever.

http://map.gsfc.nasa.gov/universe/uni_shape.html

Quote:Recent measurements (c. 2001) by a number of ground-based and balloon-based experiments, including MAT/TOCO, Boomerang, Maxima, and DASI, have shown that the brightest spots are about 1 degree across. Thus the universe was known to be flat to within about 15% accuracy prior to the WMAP results. WMAP has confirmed this result with very high accuracy and precision. We now know (as of 2013) that the universe is flat with only a 0.4% margin of error. This suggests that the Universe is infinite in extent; however, since the Universe has a finite age, we can only observe a finite volume of the Universe. All we can truly conclude is that the Universe is much larger than the volume we can directly observe.

I was always under the impression that the universe was infinite and constantly expanding, as well. From the books I've read, anyway.

Omg that nasa page is wrong! Flat geometry does not imply noncompact topology(ie infinite spatial extent)! I'll write them, maybe they'll answer then I post it

---

(March 8, 2014 at 11:18 am)pocaracas Wrote:

(March 7, 2014 at 6:21 pm)rsb Wrote: I am not sure gravitational lensing is exactly the same as a gravity wave, if it was then observations in the early part of the last century would have resolved it.

I never said it was...
Gravitational lensing is a piece of evidence for general relativity.
Nothing in general relativity states that there is such a thing as a gravitational wave, as far as I'm aware...

It does, look up tests of GR and the HT Pulsar

Alex K Wrote:Omg that nasa page is wrong! Flat geometry does not imply noncompact topology(ie infinite spatial extent)! I'll write them, maybe they'll answer then I post it

Really? Damn.

In layman's terms, could you explain it a little? I'm interested in science, but I don't have the extensive learning background, so I usually just go with what the pHD's say.

(March 8, 2014 at 2:19 pm)Bittersmart Wrote:

Alex K Wrote:Omg that nasa page is wrong! Flat geometry does not imply noncompact topology(ie infinite spatial extent)! I'll write them, maybe they'll answer then I post it

Really? Damn.

In layman's terms, could you explain it a little? I'm interested in science, but I don't have the extensive learning background, so I usually just go with what the pHD's say.

So, intuitively one thinks that flat means it cant fold back onto itself, because as the word implies, space would have to be bent like a piece of paper to close on itself. However, this intuition is not correct: the curvature which is relevant in general relativity, the ricci curvature, vanishes e.g. for the torus. This is easiest to see if you understand that a torus is basically a flat square with opposing borders identified as being truly the same. You end up with a space which has finite volume, but no curvature and no boundary anymore - a twodimensional torus. There are like a dozen or so mathematical spaces in 3D with this property, and in nature one of them could be realized as the global geometry of our universe.

(March 8, 2014 at 2:19 pm)Bittersmart Wrote: Really? Damn.

In layman's terms, could you explain it a little? I'm interested in science, but I don't have the extensive learning background, so I usually just go with what the pHD's say.

Apparently NASA is saying that if the geometry of space-time is flat the universe must be infinite.

What Alex is saying is that if the geometry of space is flat, that doesn't necessarily mean the universe is infinite.

A flat geometry would be like a sheet of paper with or without edges. Curved saddle shaped spacetime would be like that old asteroids arcade game were if you went off the edge of the screen you appear on the opposite side.

JL1 still here then...?

He tried. I supposed.

(March 8, 2014 at 8:12 pm)Mr. Moncrieff Wrote: JL1 still here then...?

He tried. I supposed.

He's reading.... give him time...

(March 8, 2014 at 7:15 am)fr0d0 Wrote: Is an equal problem to beginnings > what's at the edge of the universe? It can't be infinite. If it goes to nothing, is nothing an area to measure? If it's something, is that a solid default state? If it folds back onto itself and is also the opposite end of the universe, are we in a bubble like rupture?

Our main problem is that we think that we are at the center of the universe. People look out and say that the edge is 13.7 billion light years from us. So that puts us at an imaginary center. It should be obvious that from diameter edge to diameter edge the distance is really 27.4 billion light years. Now if someone on the edge looks in the opposite direction he might see another 27.4 billion light years, which would make him in the center, and so forth for infinity.

If Nothing creates strings which evolve into quantum foam and forth to hydrogen and stars and galaxies the size of the universe could be 1 trillion gazillion light years in size and still growing. Right now we are where people were before the 1920s. We think that what we can see is all there is. We just need better eyes.