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BaalChatzaf
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17 Jun 2016, 7:45 pm

Deltaville wrote:
We can only exactly measure the real radius of the whole universe if we assume k=1 for the FLRW metric. We cannot tell whether a flat universe is finite or infinite.

@Baal, You do realize that this is only a measurement for the observable universe?

If the universe is unbounded and finite, our universe could potentially be smaller then the observable.

I can calculate the exact radius of a closed universe, if you guys wish. It is pretty easy.


The surest bet is to rely on what can be observed. Anything beyond that is hypothesis and speculation.


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DentArthurDent
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18 Jun 2016, 4:13 am

Fnord wrote:
Just because a thing may be "possible" does not mean that it "must" be real.

There is an infinitesimal possibility that the Earth will spontaneously compress itself into a black hole. This does not mean that the event will actually occur.

People need to learn the difference between probability and reality.

...

Now, for those who "know" that the universe is not infinite, please cite valid data that defines the size of the universe. Thank you.


Yes, but surely if something is possible then in an infinite universe does that not mean it is infinitely probable and in fact there will be infinite occurrences of that thing no matter how "improbable" we deem it to be?


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b9
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18 Jun 2016, 7:04 am

...



Last edited by b9 on 18 Jun 2016, 7:06 am, edited 1 time in total.

b9
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18 Jun 2016, 7:06 am

DentArthurDent wrote:
Fnord wrote:
Just because a thing may be "possible" does not mean that it "must" be real.

There is an infinitesimal possibility that the Earth will spontaneously compress itself into a black hole. This does not mean that the event will actually occur.

People need to learn the difference between probability and reality.

...

Now, for those who "know" that the universe is not infinite, please cite valid data that defines the size of the universe. Thank you.


Yes, but surely if something is possible then in an infinite universe does that not mean it is infinitely probable and in fact there will be infinite occurrences of that thing no matter how "improbable" we deem it to be?


infinity is unable to be conceived of in any respect.
there is infinity within infinitesimal-ity.
in the smallest conceivable volume of space (sub-sub atomic particular packets of energy) there is an infinite number of points.
so if there are an infinite number of points in 1 cubic centimeter, then how many points are there in 1 cubic light year?
it is not thinkable about.

the fact that something is not impossible is akin to saying that "zero" does not exist, and can not be a quantity ascribed to the likelyhood of any possibility.
but a probability of either 1(which really means infinitely large) or zero are the only states of existence of any possibility.
either it is happening or it is not (at this time in this space in this dimension).
the idea of partial probability is only a crude yardstick that human brains use to chart what they can not foretell with clairvoyance. nothing is only partially possible or probable. it's probability is either 1 or zero.
but it is all in the "either" isn't it. what is the probability of the probability being zero? derrr, .0143276?.

so in the idea that is "nothing is impossible" where one assumes that everything is therefore possible, and to goes on to conclude that "given an infinite chances to occur, even the most unlikely thing will happen an infinite times", the notion of infinity is being used as a variable or an argument in a fallacious equation as in infinity*x=infinity.

so just hypothesising that a circumstance exists that has a 50% chance of occurring, and it will remain having a 50% chance of occurring "FOREVER", then it will never occur because it's chances of occurring will never be 100%, so it therefore has 0% chance of happening. only these 2 states actually are real, and any kind of combination of the 2 are impossible to all but fallacious types of conjecture.



naturalplastic
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18 Jun 2016, 7:31 am

The Universe is not thought to be "infinite" anyway.

But if brane theory and notions of parallel universes are right than we live in a multiverse which might be infinite.

But if the latter the laws of physics in the next "universe" over might be different. Even the laws of mathematics might be different. In the neighboring universe the value of pi might be exactly 3.0 instead of being the irrational number that starts with 3.14 that it is in this universe.

So if there are multiple universes then "anything" might exist. My little pony creatures could be living animals a dozen universes over on some planet.



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18 Jun 2016, 9:39 am

DentArthurDent wrote:
Fnord wrote:
Just because a thing may be "possible" does not mean that it "must" be real. There is an infinitesimal possibility that the Earth will spontaneously compress itself into a black hole. This does not mean that the event will actually occur. People need to learn the difference between probability and reality.

Now, for those who "know" that the universe is not infinite, please cite valid data that defines the size of the universe. Thank you.
Yes, but surely if something is possible then in an infinite universe does that not mean it is infinitely probable and in fact there will be infinite occurrences of that thing no matter how "improbable" we deem it to be?
I asked for valid data, sir, and not more convoluted arguments.


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b9
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18 Jun 2016, 10:09 am

Fnord wrote:
DentArthurDent wrote:
Fnord wrote:
Just because a thing may be "possible" does not mean that it "must" be real. There is an infinitesimal possibility that the Earth will spontaneously compress itself into a black hole. This does not mean that the event will actually occur. People need to learn the difference between probability and reality.

Now, for those who "know" that the universe is not infinite, please cite valid data that defines the size of the universe. Thank you.
Yes, but surely if something is possible then in an infinite universe does that not mean it is infinitely probable and in fact there will be infinite occurrences of that thing no matter how "improbable" we deem it to be?
I asked for valid data, sir, and not more convoluted arguments.

what can you do with valid data fnord but simply cease to protest that the data is not valid? it does not seem to me that you think about things yourself in a way that is inspired from within your own notions that bravely assert themselves.



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18 Jun 2016, 1:43 pm

b9 wrote:
Fnord wrote:
DentArthurDent wrote:
Fnord wrote:
Just because a thing may be "possible" does not mean that it "must" be real. There is an infinitesimal possibility that the Earth will spontaneously compress itself into a black hole. This does not mean that the event will actually occur. People need to learn the difference between probability and reality. Now, for those who "know" that the universe is not infinite, please cite valid data that defines the size of the universe. Thank you.
Yes, but surely if something is possible then in an infinite universe does that not mean it is infinitely probable and in fact there will be infinite occurrences of that thing no matter how "improbable" we deem it to be?
I asked for valid data, sir, and not more convoluted arguments.
what can you do with valid data fnord but simply cease to protest that the data is not valid? it does not seem to me that you think about things yourself in a way that is inspired from within your own notions that bravely assert themselves.
Well, I suppose that a link to a peer-reviewed scientific paper on the subject would make for a good read, and I may actually learn something new.

But as it stands, the discussion in this thread seems suspiciously similar to The Tale of The Six Blind Men and The Elephant, with the six blind men being various members of this website, and the state of the universe being the elephant.

We're all blind on this matter, which is why I framed my cosmological opinions as "[speculation]" and not fact.


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slave
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19 Jun 2016, 12:38 am

Deltaville wrote:


I can calculate the exact radius of a closed universe, if you guys wish. It is pretty easy.


Please do, and thank you. :)



eric76
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19 Jun 2016, 1:48 am

Have we definitely determined that the universe has positive curvature? Has enough matter been found to close the universe?

If not, I'd be careful about claiming that it is finite.



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19 Jun 2016, 5:19 am

As I understand it the evidence strongly supports a flat expanding universe which will eventually succumb to heat death. But then that is only for the "known universe" who knows what lies beyond our grasp. It would be foolish for anyone to suggest they know anything absolute about the universe.

Fnord I was not trying to offer convoluted arguments rather just checking my understanding of what an infinite universe would mean for highly improbable events. Intuitively I do not like the concept of infinity, but then when has the universe and the natural laws within it ever given any consideration for human or any other form of intuition.


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19 Jun 2016, 12:46 pm

KagamineLen wrote:
Only two things are infinite. The universe and human stupidity. And I am not so sure about the universe. - Einstein


Too bad he couldn't accept quantum mechanics...""God (he meant "god" with a small "g") does not play dice with the universe.", but he could never prove this.

So sad he died from lack of a surgical repair commonly done every day now. :( :( :(



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19 Jun 2016, 1:02 pm

ZenDen wrote:
OOPS! I meant 32,615,642,195.20 light year radius. Hope I didn't throw off anyone's navigation. :oops:


Astronomers seem to give a 13.8 billion light year radius....a factor of 2+ difference.

Say there BaalChatzaf, do you feel your estimate of "about 20 gigaparsecs across" was correct?



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20 Jun 2016, 2:49 pm

13.8 billion light years is the estimated radius of the observable universe, not the entire universe.



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21 Jun 2016, 8:15 am

BaalChatzaf wrote:
NewTime wrote:
Does that mean anything we can imagine must exist somewhere?


Not necessarily. We can imagine things that are not physically possible.

Under the many-worlds hypothesis any possible quantum state will be realized.


We probably miss to imagine things that actually exist.


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22 Jun 2016, 3:53 am

DentArthurDent wrote:
Yes, but surely if something is possible then in an infinite universe does that not mean it is infinitely probable and in fact there will be infinite occurrences of that thing no matter how "improbable" we deem it to be?


It is possible that an intelligent being could make a pair of fair dice (i.e. no preference at all to any one side) and roll them a billion times in a row and they come up sixes every time.

While it is possible, I would bet that it would never even happen once.