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timothy leary
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Posted: November 25 2013 at 17:48 |
It would define the shape of the universe. Geez don't get mad about it unless you feel like it.
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Equality 7-2521
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Posted: November 25 2013 at 21:52 |
You're not saying anything. You're putting two antonyms next to each other. Infinitely finite is not a shape.
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"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
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timothy leary
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Posted: November 26 2013 at 10:10 |
horn shaped?
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Equality 7-2521
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Posted: November 26 2013 at 10:14 |
EDIT: Oh you must be referring to the Picard horn. I was being a bit obtuse. For the future infinitely finite doesn't mean anything and doesn't describe what you're talking about. It's a possible model. It wouldn't be one that I rank high in probability though.
Further Edit: You can give a few good reasons that, although we can't rule out the Picard model and it would certainly explain some things, it's probably not the most likely manifold to consider. The big thing which we would have to throw out is the cosmological principle Of course you can argue it's not a principle at all merely a fancy term for our realization of our own ignorance, but it's an honored principle since Copernicus' work so it should make you uneasy unless the evidence really compels you to discard it.
Hopefully final edit so I can get back to this research proposal: To cut off anybody: Yes I'm aware that there was some rather profound cosmological discovery this year which seems to call the cosmological principle into question. I have not read much about it so I can't really comment.
Edited by Equality 7-2521 - November 26 2013 at 10:28
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"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
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Dean
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Posted: November 26 2013 at 10:15 |
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What?
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timothy leary
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Posted: November 26 2013 at 10:29 |
Equality 7-2521 wrote:
EDIT: Oh you must be referring to the Picard horn. I was being a bit obtuse. For the future infinitely finite doesn't mean anything and doesn't describe what you're talking about. It's a possible model. It wouldn't be one that I rank high in probability though.
Further Edit: You can give a few good reasons that, although we can't rule out the Picard model and it would certainly explain some things, it's probably not the most likely manifold to consider. The big thing which we would have to throw out is the cosmological principle Of course you can argue it's not a principle at all merely a fancy term for our realization of our own ignorance, but it's an honored principle since Copernicus' work so it should make you uneasy unless the evidence really compels you to discard it.
Hopefully final edit so I can get back to this research proposal: To cut off anybody: Yes I'm aware that there was some rather profound cosmological discovery this year which seems to call the cosmological principle into question. I have not read much about it so I can't really comment.
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Thanks for the explanation.
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Gerinski
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Posted: November 27 2013 at 00:28 |
Equality 7-2521 wrote:
timothy leary wrote:
so are you saying the universe could not be infinitely finite?
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I'm saying that you need to define what the hell that means.
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Perhaps he was meaning 'finite but without boundaries'? (like the surface of the Earth). There's also the distinction 'infinite in size' (at a particular time, for example thinking that the universe is infinite 'now') or 'infinite in time' (it has always existed, the Big Bang did not 'create time' but only our current eon, there were other eons prior to ours, extending into 'the past' without limit. Or, time started indeed at the Big Bang but the universe will continue expanding forever and is therefore infinite in time towards the future, at least so long as the word 'time' will retain any meaning). The mainstream thought is that the universe is certainly finite in size, at least at any moment from the Big Bang until the present, and that time started at the BB so it is also finite in time towards our past. Towards the future it might well continue expanding infinitely so it could be infinite in time towards the future.
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Equality 7-2521
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Posted: November 27 2013 at 07:34 |
I deciphered what he meant above.
EDIT: The consensus says it's finite. But the consensus isn't all that strong in this case, is relatively new, and is in a field which develops very rapidly so I'd be careful.
Edited by Equality 7-2521 - November 27 2013 at 07:44
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"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
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dr wu23
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Posted: November 27 2013 at 09:16 |
Dean wrote:
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Love that digging a hole emoticon......where is it linked to?
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One does nothing yet nothing is left undone. Haquin
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Dean
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Posted: November 27 2013 at 09:31 |
dr wu23 wrote:
Dean wrote:
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Love that digging a hole emoticon......where is it linked to?
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China (or wherever the antipode is to your current location)?
It was made before Pat's edit, it's now irrelevant but I couldn't be bothered to change it.
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What?
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Equality 7-2521
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Posted: November 27 2013 at 11:05 |
Equality 7-2521 wrote:
I deciphered what he meant above.
EDIT: The consensus says it's finite. But the consensus isn't all that strong in this case, is relatively new, and is in a field which develops very rapidly so I'd be careful.
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A friend from across the quad in the physics department disagrees. He says consensus is for an infinite and flat universe. He's not in cosmology, but he certainly knows more than me so there.
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"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
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DreamReaper
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Posted: December 15 2013 at 08:46 |
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Equality 7-2521
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Posted: December 15 2013 at 11:37 |
I don't think that makes the idea of consensus misleading or inaccurate though.
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"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
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DreamReaper
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Posted: December 15 2013 at 13:25 |
Equality 7-2521 wrote:
I don't think that makes the idea of consensus misleading or inaccurate though.
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You're rigth, I should have chosen the words more carefully  What I meant is that the consensus in this case is not as strong as other, more firmly established consensuses regarding more "stable" (well, at least inside the scientific community...  ) subjects such as evolution or climate change
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Equality 7-2521
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Posted: December 16 2013 at 09:19 |
Agreed.
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"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
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Gerinski
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Location: Barcelona Spain
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Points: 5154
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Posted: December 16 2013 at 15:29 |
DreamReaper wrote:
Equality 7-2521 wrote:
Equality 7-2521 wrote:
I deciphered what he meant above.
EDIT: The consensus says it's finite. But the consensus isn't all that strong in this case, is relatively new, and is in a field which develops very rapidly so I'd be careful.
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A friend from across the quad in the physics department disagrees. He says consensus is for an infinite and flat universe. He's not in cosmology, but he certainly knows more than me so there.
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That is correct, even though the word "consensus" is somewhat misleading in this case. Although current data and observations seem to corroborate the idea of a flat and infinite universe, they do not rule out the possibility of a finite universe. Nonetheless, given the rate at which our knowledge of the cosmos is advancing, it wouldn't be surprising if this "consensus" changed drastically in the next few years... The truth is that we've just barely begun to understand the physics of the universe, so there are still lots of questions and very few certainties 
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Again, we are playing with dangerous words here. When we say that 'the universe is infinite', most people understand that we are saying that it is infinite in size, 'now' (let's keep it simple and not start discussing the meaning of cosmic time). That 'right now it is infinitely big'. This is certainly not the case. Consensus is that it has been expanding since the Big Bang, and that the BB happened a finite time ago. Consequently it can not be infinite in size, there has only been time for it to expand to some certain size. Unless I'm very wrong, the latest consensus is also that it is not flat, it is slightly open (lambda is slightly positive) and therefore it should continue expanding with an accelerated expansion rate forever, so it tends to infinite size towards the infinite future. A completely different thing is that even if 'now' it is still clearly finite, for all purposes it is as if it was infinite, since its size greatly exceeds the horizon of our observable universe. There's no way we could ever 'reach its end' (which would mean finding ourselves where we started) since it expands faster than light from our point of view. So for all practical purposes it may be considered infinite, but it is not infinite.
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Equality 7-2521
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Posted: December 16 2013 at 20:09 |
Gerinski wrote:
Again, we are playing with dangerous words here. When we say that 'the universe is infinite', most people understand that we are saying that it is infinite in size, 'now' (let's keep it simple and not start discussing the meaning of cosmic time). That 'right now it is infinitely big'. This is certainly not the case. Consensus is that it has been expanding since the Big Bang, and that the BB happened a finite time ago. Consequently it can not be infinite in size, there has only been time for it to expand to some certain size. |
I'm sorry but this is simply not true. You seem to be assuming that the Big Bang occurred at a point. That's an over simplification of the phenomenon, and this is not the case. The observable universe originated in a "point", but it is not necessarily true that the Big Bang occured at a "point".
Unless I'm very wrong, the latest consensus is also that it is not flat, it is slightly open (lambda is slightly positive) and therefore it should continue expanding with an accelerated expansion rate forever, so it tends to infinite size towards the infinite future. A completely different thing is that even if 'now' it is still clearly finite, for all purposes it is as if it was infinite, since its size greatly exceeds the horizon of our observable universe. There's no way we could ever 'reach its end' (which would mean finding ourselves where we started) since it expands faster than light from our point of view. So for all practical purposes it may be considered infinite, but it is not infinite. |
Yes. As I said the consensus seems to be finite, which would imply a global curvature.
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"One had to be a Newton to notice that the moon is falling, when everyone sees that it doesn't fall. "
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timothy leary
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Posted: December 16 2013 at 20:13 |
I did not realize infinity was dependent on time??
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Gerinski
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Posted: December 17 2013 at 01:40 |
timothy leary wrote:
I did not realize infinity was dependent on time??
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For something that grows (increases size over time), if we talk about size it is obvious that time must be somehow involved. The size of something that grows can only be defined with reference to some moment in its time. There is consensus that the universe grows (expands as time goes forward). Admittedly there are infinities of different sizes, as Cantor showed long time ago.
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Dean
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Posted: December 17 2013 at 02:07 |
Infinity can be measured in any dimension, distance is just one of them.
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What?
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