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eric76
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20 May 2014, 10:26 am

naturalplastic wrote:
MrOddBall wrote:
So basically the universe has already ended but we're catching up to it ?


No.

The universe is expanding faster than the speed of light.

Which means we are all moving faster than light. And according to Einstein when you move faster than light you are going backward in time.


So for the last 14 billion years the whole universe has been ageing backwards.

The big bang was actually the end of the universe. And we are all now moving backward in time to the universe's unknown beginning.


In essence: all of the galaxies in the universe are solid matter being flushed down a comode by God. But since time is moving backwards it APPEARS that all matter is being expelled from the vortex rather than being sucked into the vortex.


I hope this is humor.



naturalplastic
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20 May 2014, 12:33 pm

It IS tongue-in-cheek.



DashboardLogic
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26 May 2014, 2:15 am

My guess is that universe has an end and yet it doesn't have an end. I have thought before that it must just kind of stop somewhere and past that edge would be... nothing at all. Not even the blackness of space itself. Yeah, I think my head just about exploded again trying to image nothing, when our idea of such typically brings us to imagine outer space itself, and I've now just eliminated even the near blackness between galaxies.

On the other hand though, since its expanding faster and faster, lets say we coudl fly at the speed or light or faster even. We'd find ourselves basically chasing that edge forever as it expands faster and faster in front of us. So... endless universe.

Oh dear... yeah I feel so tiny now on this little planet Earth, lol.



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04 Jun 2014, 5:09 pm

I used to wonder about this. If the universe ends somewhere then what's beyond it. I've already solved this problem, though. I'm sticking to Earth. Maybe the entire solar system, and a few fictional planets here and there. As for whether the universe ends or not. It might, it might not. What I do know is that Earth does, beyond the atmosphere. I'll stick to what's within that atmosphere.


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Adamantium
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05 Jun 2014, 11:54 am

This is the sort of conversation that calls for a bit of Max Tegmark: http://arxiv.org/pdf/0905.1283.pdf

There is more than one way that the universe may be infinite, or may contained in a structure with a number of infinite dimensions.



Differentialform
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05 Jun 2014, 3:10 pm

Regarding Tegmark's multiverse ideas, you might want to read this book review and this blog post by Peter Woit:

http://online.wsj.com/news/article_emai ... NjEwNDYyWj

http://www.math.columbia.edu/~woit/wordpress/?p=6551



ruveyn
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05 Jun 2014, 7:43 pm

Space can go on "forever" by being topologically unbounded, that is having no boundary points. For example the surface of a sphere in the topology of the surface is unbounded. Not a single boundary point. One can draw a line in one direction on the surface of a sphere and never hit an edge.



foodeater
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05 Jun 2014, 7:55 pm

mezzanotte wrote:
Humans evolved to comprehend matters of the Earth, because our survival depends on it. Equipped with only five senses and incredibly limited brains, we're not supposed to make sense of everything in the Universe. Just as an earthworm has not the slightest understanding of atomic bombs, we have almost no understanding of the Universe. Attempting to discuss the Universe in simplistic written languages is a joke, to be honest.
i dunno considering we are the only ones on the planet to both attempt to reason and have senses of humor it makes a lot of sense to me. :lol:



Adamantium
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06 Jun 2014, 10:38 am

Differentialform wrote:
Regarding Tegmark's multiverse ideas, you might want to read this book review and this blog post by Peter Woit:

http://online.wsj.com/news/article_emai ... NjEwNDYyWj

http://www.math.columbia.edu/~woit/wordpress/?p=6551


Tosh. Woit is attacking his own pet peeves and trying to make Tegmark fit the target. Tegmark does not claim that all these ideas are true, but that they are worth exploring.

As for experiment vs. math. This is the most quixotic false dichotomy of all. We live after Dirac. The LHC found the Higgs, just as the math predicted. We need the experiment to prove the math, but saying the experiment must come first is retreating to the 18th Century.

Infinities are hard to imagine and think through. Tegmark is pretty good at this.



Differentialform
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06 Jun 2014, 11:19 am

Adamantium wrote:
As for experiment vs. math. This is the most quixotic false dichotomy of all. We live after Dirac. The LHC found the Higgs, just as the math predicted. We need the experiment to prove the math, but saying the experiment must come first is retreating to the 18th Century.


Woit is not saying that the experiment must come first. The problem is:

If a theory doesn't make predictions that can in principle be checked, if a theory is not falsifiable, then this theory is not scientific.

The standard model of particle physics is a successful scientific theory because it makes sound predictions (e.g., the Higgs). The same goes for quantum mechanics, special and general relativity, classical mechanics, and so on.

Experiments need theories and theories need experiments.

From a philosophical point of view, I find Tegmark's ideas and the multiverse in general quite fascinating and worth thinking about.



Prof_Pretorius
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06 Jun 2014, 7:12 pm

It's not.
When you near the edge, there are signs saying "You have reached the edge of the universe, please turn around and go back."


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AdamAutistic
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06 Jun 2014, 8:07 pm

it boggles the mind


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naturalplastic
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07 Jun 2014, 9:46 am

The universe could be infinite in the sense that the earth's surface is infinite: it could be curved onto itsself.

But if the universe is not curved then its no harder to imagine it being infinite than to imagine it stopping at a brick wall somewhere.



Adamantium
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07 Jun 2014, 8:23 pm

Differentialform wrote:
Adamantium wrote:
As for experiment vs. math. This is the most quixotic false dichotomy of all. We live after Dirac. The LHC found the Higgs, just as the math predicted. We need the experiment to prove the math, but saying the experiment must come first is retreating to the 18th Century.


Woit is not saying that the experiment must come first. The problem is:

If a theory doesn't make predictions that can in principle be checked, if a theory is not falsifiable, then this theory is not scientific.

The standard model of particle physics is a successful scientific theory because it makes sound predictions (e.g., the Higgs). The same goes for quantum mechanics, special and general relativity, classical mechanics, and so on.

Experiments need theories and theories need experiments.

From a philosophical point of view, I find Tegmark's ideas and the multiverse in general quite fascinating and worth thinking about.


Tegmark also defend the scientific method and the need for tests... he just doesn't preclude thought experiments with no obvious available test. And when engaging in wilder speculations, as Woit acknowledges, "It's worth remarking that not taking itself too seriously is one of the book's virtues."

Woit ends his dismissive review with "But the great power of the scientific worldview has always come from its insistence that one should accept ideas based on experimental evidence, not on metaphysical reasoning or the truth-claims of authority figures. " --points Tegmark is entirely in agreement with.
Tegmark's exploration of these ideas borders on the metaphysical, perhaps crosses that border in a few places, but he doesn't demand that people accept those speculations as truth or do anything more with them than look for ways in which they may inform real, testable investigation of the observable. He is not trying to start a religion or overturn the standard model and it is dishonest to suggest that he is.

Woit resorts to sleazy ad hominems in his "Not Even Wrong" blog making irrelevant comments about Tegmark's name and relationship to his father. He ends up going so far in mischaracterizing Tegmark's arguments that he qualifies his own belittling remarks with the phrase "this may be unfair." Well said!



Differentialform
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08 Jun 2014, 5:36 am

Adamantium wrote:
Woit resorts to sleazy ad hominems in his "Not Even Wrong" blog making irrelevant comments about Tegmark's name and relationship to his father. He ends up going so far in mischaracterizing Tegmark's arguments that he qualifies his own belittling remarks with the phrase "this may be unfair." Well said!


Tegmark himself discusses his name change in his book:
"Anticipating my publishing debut, I even went ahead and changed my surname to something more unique, from my dad's name Shapiro to my mom's name Tegmark."

Woit's comment "this may be unfair" was in the context of Woit unfairly commenting on an expensive conference. But I agree that those kinds of comments are irrelevant with regard to the scientific discussion and are not worth to be discussed further.

The essay "Theories of Anything" by Paul Steinhardt describes the main points I am concerned about: http://edge.org/response-detail/25405

Getting back to the original topic: I think it is experimentally impossible to directly prove that the universe is infinite. We can only make measurements with regard to the observable universe, which is finite. If a very convincing cosmological theory would crucially depend on the infinity of the universe, then this would be strong indirect evidence for the infinity of the universe. The same applies to the multiverse.

There is an interesting essay by Tegmark questioning the concept of infinity:
http://edge.org/response-detail/25344