Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: Shivan Hunter on October 01, 2010, 07:10:32 pm
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(This article was linked by QuantumDelta on IRC)
http://www.physorg.com/news205133042.html (http://www.physorg.com/news205133042.html)
As far as astrophysicists can tell, the universe is expanding at an accelerating rate, and will likely continue to do so indefinitely. But now some physicists are saying that this theory, called eternal inflation, and its implication that time is endless pose a problem for scientists calculating the probability of any event occurring. In a recent paper, they calculate that time is likely to end within the next 5 billion years due to some type of catastrophe that no one alive at the time will witness.
Basically, they seem to be saying (and I admit I have never before heard of "eternal inflation's implications in probability"), that because you can't compare probabilities using relative frequency across infinite time frames (you'd end up with infinity divided by infinity), time has to end somehow, involving this thermalization barrier thingie which sounds kind of like reaching heat death asymptotically, at least from what the article said.
Um, I thought that the only way to measure probability- regardless of an infinite universe- was by relative probabilities during a finite time period.
They don't claim that their conclusion that time will end is correct, only that it follows logically from a set of assumptions. So perhaps one of the three assumptions underlying the conclusion is incorrect instead.
The first assumption is that the universe is eternally inflating, which is a consequence of general relativity and well supported by the experimental evidence so far observed. The second assumption is that the definition of probability is based on the relative frequency of an event, or what the scientists call the assumption of typicality. The third assumption is that, if spacetime is indeed infinite, then the only way to determine the probability of an event is to restrict one's attention to a finite subset of the infinite multiverse. Some other physicists have already looked into alternatives to this third assumption.
The first assumption is the leading theory about the universe IIRC, and the second seems pretty self-evident to anyone who knows what probability is. But the second assumption basically leads to the third, that we have to measure probability based on a finite time period, and it doesn't seem to follow that the universe itself must be somehow finite.
If I make an infinite number of FS campaigns, and 1/3 of them aren't crap, that is very definitely a probability of 1/3 that any given campaign is not crap, even given the infinity divided by infinity, because at a sufficiently large local subset of campaigns the ratio of crap-to-not-crap will approach 2:1.
Thoughts?
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I haven't even read it but I'm gonna guess that the spontaneous universe ending has something to do with false vacuum decay?
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I just hope I get to eat at Milliways before I go...
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wut
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Where does heat death fit in?
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it seemed like the "thermalization barrier thingie" they were talking about was something similar, but after reading again it seems more like what the Big Rip theory describes. I dunno. How they came up with this particular theory is beyond me, since the initial "the universe must end sometime lololol" doesn't seem very apparent anyway.
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it seemed like the "thermalization barrier thingie" they were talking about was something similar, but after reading again it seems more like what the Big Rip theory describes. I dunno. How they came up with this particular theory is beyond me, since the initial "the universe must end sometime lololol" doesn't seem very apparent anyway.
Neither heat death or the Big Rip are similar to this. It sounds much more like false vacuum decay, which would fit in perfectly with this theory's 'infinite improbability = probability 1' notion, but they never actually SAY false vacuum decay so I'm not sure.
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I don't believe the universe will end anyway, I believe we live in a simulation after all.
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and no one will ever trip over the power cord?
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and no one will ever trip over the power cord?
Hopefully they have good battery backup!
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Hmm. http://arxiv.org/PS_cache/arxiv/pdf/1009/1009.4698v1.pdf (http://arxiv.org/PS_cache/arxiv/pdf/1009/1009.4698v1.pdf)
I find nothing more than logic arguments (I admit most went over my head, the rest seem a bit sketchy) to support this thing. I'm especially disappointed that it makes this enormous claim at the very beginning that "According to the most successful measure proposals, our galaxy is likely to encounter the cuto ff within the next 5 billion years.", and yet it never even discusses how they come to that conclusion.
Also, the fact that this proposed end of time would never be observable/verifiable, makes me wonder what the point of the theory even is. Then again, I couldn't really grasp a lot of the arguments they make, so maybe I just don't adequately understand what it is discussing.
The article didn't really help me out, but maybe someone else here can help put this into simpler terms.
I don't believe the universe will end anyway, I believe we live in a simulation after all.
Wouldn't our existing in a simulation not preclude the possibility of said simulation ending?
Aside: Is the "preview post" button not working anymore?
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Um, I thought that the only way to measure probability- regardless of an infinite universe- was by relative probabilities during a finite time period.
Finite time, too.
Actually if you look at stuff like wave functions in quantum mechanics, they provide you a probability of particle's location within a constrained space.
Integrating the wave function from negative infinity to infinity will result a probability value of 1, which means that the probability of a particle being located somewhere in an infinite space is exactly 1 (which makes perfect sense if you think about it).
To get sensible results out of the function, you need to constrain the space, in very small dimensions when we're talking about quantum mechanics (the probabilistic nature of the physics will only start to emerge at ds ≈ λdB (space constraint close to deBroglie wavelength of the particle).
To mess up with things more, there are formulations of quantum mechanics that are essentially timeless (http://www.colorado.edu/philosophy/vstenger/void.html).
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Sometimes one can't help wondering about the difference between the modern day arguments of the composition of the Universe from the arguments of Theology back in 1500s... Was it really Christ's blood that you were drinking in the church?
Though I would be interested to see the macroscopic tunneling effect, say the size of a car, so if anyone catches that on video, you know whom to send it.
On serious note, how common are the tunneling effects on the molecular size and does it match to theory?
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Sounds to of like they're applying mathematical abstractions about reality a tad too directly to the real world.
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Sounds to of like they're applying mathematical abstractions about reality a tad too directly to the real world.
Yeah its a non sequitur.
The fact that you can model reality quite accurately through statistical mathematics doesn't automatically mean that nature does that itself.
The biggest question actually is whether universe uses natural numbers or real numbers in its inner workings. Quantum mechanics would seem to suggest that most if not everything in universe is quanticized, so that would suggest that world is fundamentally integer-based.
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so that would suggest that world is fundamentally integer-based.
lol PI
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so that would suggest that world is fundamentally integer-based.
lol PI
Mathematics is a formal science. It contains all sorts of abstract ideas, such as pi, which is the ratio of a perfect circle's circumference and diameter.
Perfect circle might not in fact exist at all. As Kronecker said, "God created the natural numbers; all the rest is the work of man."
If that is true, maybe "real numbers" don't actually have any equivalents in reality.
If you calculate the precision of pi long enough, you'll eventually get into lengths where quantum mechanics dominates, and you can get a situation where actually measuring the diameter and circumference with arbitrary precision is simply impossible, and you end up with upper and lower limit for the physically defineable "pi".
As an abstract construct, pi is of course transcendental number (much like Neper's number or Phi), but their real world counterparts might have a finite depth...