Astrophysicists propose new twist on Big Bang • Hacker News Board

Re: Astrophysicists propose new twist on Big Bang

#11

Post by jfoutz » Fri, Aug 15, 2014, 7:25 PM UTC

collyw wrote: post #4

trhway wrote: post #2

>The researchers emphasize that this idea, though it may sound absurd, is grounded firmly in the mathematics describing space and time. Specifically they’ve used the tools of holography to “turn the big bang into a cosmic mirage.” embedding into higher dimension spaces (or in general - into more "richer" structures) is a convenient mathematical tool and it works nice ... in mathematics. To work in physics that higher…

Ignorant question here, but is it not the case that the normal laws of physics don't apply at big bang time? Do we expect the laws of mathematics to still apply? Does anyone really have any clue about this stuff?

Math is independent. If physics works different, it may not support humans, so there's no one around to think those thoughts, but if you accept the axioms of math everything else follows.

Granted, in some bizzaro physics 2+2 may actually equal 3, (along these lines http://lesswrong.com/lw/jr/how_to_convince_me_that_2_2_3/) but you should still be able to construct a successor function and mechanically evaluate 2+2 = 4 according to our rules, even though the answers would seem weird.

We may indeed be assuming stuff we don't know we're assuming. Still the other people would see, oh they're assuming X which is wrong. but the other people take X to be true, it all works out.

Re: Astrophysicists propose new twist on Big Bang

#12

Post by Zarathust » Fri, Aug 15, 2014, 7:26 PM UTC

pawn wrote: post #7

collyw wrote: post #4

Earlier quoted context omitted.

Ignorant question here, but is it not the case that the normal laws of physics don't apply at big bang time? Do we expect the laws of mathematics to still apply? Does anyone really have any clue about this stuff?

It's always been my understanding that the normal laws of physics don't work at big bang time as well. One thing I've wondered about is how people are so adamantly confident in the theory of the Big Bang in light of this. Is it simply because they don't like the alternatives, because they've never been heard an alternative, or is there a better reason?

It depends on what you mean by "big bang time". Standard physics started a few microseconds after the big bang, followed by what appears to be a rapid expansion of the early universe.

The Big Bang is widely adopted in light of this. Preceding the expansion there has to be a state of greater compression, but there is no explanation on how this state could be possible.

Re: Astrophysicists propose new twist on Big Bang

#13

Post by noobermin » Fri, Aug 15, 2014, 8:14 PM UTC

trhway wrote: post #2

>The researchers emphasize that this idea, though it may sound absurd, is grounded firmly in the mathematics describing space and time. Specifically they’ve used the tools of holography to “turn the big bang into a cosmic mirage.” embedding into higher dimension spaces (or in general - into more "richer" structures) is a convenient mathematical tool and it works nice ... in mathematics. To work in physics that higher…

You apparently were flagged by a theoretical physicist.

A lot of "physicists" nowadays forget that we're supposed to be scientists, not dreamers. Dreams are nice, but experiment and observations valid theory.

I agree. Unless this has some modifications to the current model of the big bang which leads to _observable_effects_ , I don't know if this theory could even be validated as...well theory.

Re: Astrophysicists propose new twist on Big Bang

#14

Post by sp332 » Fri, Aug 15, 2014, 8:15 PM UTC

adinb wrote: post #9

Zarathust wrote: post #3

Earlier quoted context omitted.

The next phrase mentions that this theory is testable >Along the way, their model appears to address long-standing cosmological puzzles, and – crucially – produce testable predictions. I'm very curious to know how.

From the fine paper[1]: Finally, let us comment on potential testability of this model. As we pointed out, the simple model of cosmological perturbations, developed in Sec. 4 is already ruled out by cosmo- logical observations at > 5σ level, as it does not predict any deviations from scale-invariance. However, it is easy to imagine small corrections that could lead to a ∼ 4% deviation from scale-invariance, especiall…

So, if we look at parts of space further away from us (so the light reaching us tells us about older times), we should see fewer kinds of gravitons than we see around us now?

Re: Astrophysicists propose new twist on Big Bang

#15

Post by dhimes » Fri, Aug 15, 2014, 8:19 PM UTC

adinb wrote: post #9

Zarathust wrote: post #3

Earlier quoted context omitted.

The next phrase mentions that this theory is testable >Along the way, their model appears to address long-standing cosmological puzzles, and – crucially – produce testable predictions. I'm very curious to know how.

From the fine paper[1]: Finally, let us comment on potential testability of this model. As we pointed out, the simple model of cosmological perturbations, developed in Sec. 4 is already ruled out by cosmo- logical observations at > 5σ level, as it does not predict any deviations from scale-invariance. However, it is easy to imagine small corrections that could lead to a ∼ 4% deviation from scale-invariance, especiall…

So all we have to do is detect, over time, more polarization states of the 5-D graviton. Seems simple enough.

Re: Astrophysicists propose new twist on Big Bang

#16

Post by Ono-Sendai » Fri, Aug 15, 2014, 8:28 PM UTC

pawn wrote: post #7

collyw wrote: post #4

Earlier quoted context omitted.

Ignorant question here, but is it not the case that the normal laws of physics don't apply at big bang time? Do we expect the laws of mathematics to still apply? Does anyone really have any clue about this stuff?

It's always been my understanding that the normal laws of physics don't work at big bang time as well. One thing I've wondered about is how people are so adamantly confident in the theory of the Big Bang in light of this. Is it simply because they don't like the alternatives, because they've never been heard an alternative, or is there a better reason?

The big bang theory explains a lot of stuff, like the cosmic microwave background, and the redshift of far-away galaxies.

Re: Astrophysicists propose new twist on Big Bang

#17

Post by Iftheshoefits » Fri, Aug 15, 2014, 8:46 PM UTC

noobermin wrote: post #13

trhway wrote: post #2

>The researchers emphasize that this idea, though it may sound absurd, is grounded firmly in the mathematics describing space and time. Specifically they’ve used the tools of holography to “turn the big bang into a cosmic mirage.” embedding into higher dimension spaces (or in general - into more "richer" structures) is a convenient mathematical tool and it works nice ... in mathematics. To work in physics that higher…

You apparently were flagged by a theoretical physicist. A lot of "physicists" nowadays forget that we're supposed to be scientists, not dreamers. Dreams are nice, but experiment and observations valid theory. I agree. Unless this has some modifications to the current model of the big bang which leads to _observable_effects_ , I don't know if this theory could even be validated as...well theory.

There are still theoretical physicists who rely on empirical validation of the hypotheses we create. That's rather the whole point, and I'd venture (hope?) that only a small fraction of theoretical physicist think otherwise.

Re: Astrophysicists propose new twist on Big Bang

#18

Post by Zarathust » Fri, Aug 15, 2014, 8:55 PM UTC

adinb wrote: post #9

Zarathust wrote: post #3

Earlier quoted context omitted.

The next phrase mentions that this theory is testable >Along the way, their model appears to address long-standing cosmological puzzles, and – crucially – produce testable predictions. I'm very curious to know how.

From the fine paper[1]: Finally, let us comment on potential testability of this model. As we pointed out, the simple model of cosmological perturbations, developed in Sec. 4 is already ruled out by cosmo- logical observations at > 5σ level, as it does not predict any deviations from scale-invariance. However, it is easy to imagine small corrections that could lead to a ∼ 4% deviation from scale-invariance, especiall…

I'm not sure of what a graviton is, but wikipedia tells me that it is not detectable by any current mean. I'd be tempted to say in light of this that their theory is not testable either.

http://en.wikipedia.org/wiki/Graviton

Re: Astrophysicists propose new twist on Big Bang

#19

Post by Retric » Fri, Aug 15, 2014, 9:02 PM UTC

ars wrote: post #10

collyw wrote: post #4

Earlier quoted context omitted.

Ignorant question here, but is it not the case that the normal laws of physics don't apply at big bang time? Do we expect the laws of mathematics to still apply? Does anyone really have any clue about this stuff?

Yes, we expect the laws of mathematics to still apply. The laws of physics also apply, but we don't know all of them. For example Newtonian physical vs. relativity. Both are correct, but one only comes into play at high velocity or energy. Same with the big bang, there may be a more complete description of what happens that only comes into play at high energy. This doesn't mean the current laws don't apply, but rathe…

A much better mental model of this stuff is Newtonian mechanics is always wrong at every scale. At human masses, velocity's and time scales you can't detect the error but it's still there.

As such the physical laws are unchanged at the big bang, but the simpler aproximations in current use may be noticeably off at these scales. If they are, then they would also be wrong at all other timescales and energy levels etc. The trick is looking for edge cases we can detect that seperate our aproximations from the actual laws running reality.

Given all that; simpler aproximations continue to be useful as long as the errors are hard to detect.

Re: Astrophysicists propose new twist on Big Bang

#20

Post by Sharlin » Fri, Aug 15, 2014, 9:22 PM UTC

pawn wrote: post #7

collyw wrote: post #4

Earlier quoted context omitted.

Ignorant question here, but is it not the case that the normal laws of physics don't apply at big bang time? Do we expect the laws of mathematics to still apply? Does anyone really have any clue about this stuff?

It's always been my understanding that the normal laws of physics don't work at big bang time as well. One thing I've wondered about is how people are so adamantly confident in the theory of the Big Bang in light of this. Is it simply because they don't like the alternatives, because they've never been heard an alternative, or is there a better reason?

NASA uses Newtonian mechanics to send spacecraft to the outer planets and beyond. Everybody knows that Newtonian mechanics stop being accurate in certain conditions, but that does not prevent it being an incredibly useful model outside those conditions.

The best experimentally-verified cosmological models we have point to the fact that the Universe was in a hot and dense state a few microseconds after a specific point of time about 13.7 billion years ago. Extrapolating those few microseconds back in time we get an unphysical result from our current models, but that simply means those models are inaccurate if applied to the beginning of time.

Contrary to the popular belief, The Big Bang model simply does not concern itself with what happened at the exact moment of Big Bang; what it does is describe the evolution of the Universe after that, and does it well.