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  #61  
Old 05-24-2011, 02:51 PM
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Originally Posted by system7 View Post
You may remember that the great question of Einstein's Special Relativity was the "Twin Paradox", where one brother travelled to the nearby Alpha Centauri star at near light speed, and the other stayed at home. When the travelling twin returned home, he found his brother was 50 years older, while he was only 10 years older. This led to the deeper understanding of the relation between space and time, and overturned our ideas of distance.

You perhaps don't know that Stephen Hawking and Leonard Susskind found a similar paradox in our understanding of what a Black Hole does when you fall in one. Hawking said that Entropy was destroyed, Susskind said that it couldn't be or Quantum Mechanics would fall!

Here is a Black Hole like the one at the heart of our galaxy, which is estimated to have an event horizon 13 Million Kilometres across. This one is viewed in empty space against a background of the Magellanic Cloud, the one at the core is probably a bit more cluttered with stars and gas:



Leonard won the argument, and produced a working interpretation of what happens in terms of the holographic principle. This takes 50 minutes to watch, but is some of the most important physics of the last 100 years, so worth your time:

http://fora.tv/2008/07/23/Leonard_Su...Black_Hole_War

If you want to know more, Leonard discusses the very strange new view of our little corner of the multiverse that is emerging:
http://edge.org/3rd_culture/susskind...ind_index.html

I'll stop there for now.
The information paradox produced a very fun debate, though Hawking never claimed that the information must be destroyed, just that it would not be contained the in the thermal radiation he expected to originate from the horizon of the black hole. Of course, all of this still doesn't answer the question of the "size" of the black hole. (I'm just messing with you.)

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Originally Posted by rich wargo View Post
all pervading Higgs field? Sounds like that aether that Michaelson and Morley disproved. Or was it Statler and Waldorf? All those old wrinkly farts look the same.
Yeah, not really. The aether was proposed as a medium through which photons would travel, a byproduct of the belief that light was purely a wave and therefore must have something physical through which to transmit its energy (this was well before the concept of the wave-particle duality came about in the early 1900s). The Higgs field is not a medium for something to travel through, but rather a description of the interactions between particles through the exchange of bosons similar to the way interaction between charged particles and their electric fields is an exchange of virtual photons.
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  #62  
Old 05-25-2011, 04:00 AM
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I'd suspect if the Standard Model needs a particle like the Higgs Boson, it will find one. These models tend to be consistent, but I suspect 25th century string scientists will talk about a dual black hole on a bent brane or something to do the math.

In fact they already do:



This is not something from the Star Trek Warp Core manual, but from a Brookhaven particle accelerator result which postulates creation of short-lived Black Holes (or something... ) to explain a 175.76 MeV energy resonance.

Small Black holes are really quite surprising. They are tiny, massive and hot, and evaporate rapidly. A black hole weighing a tonne would outshine the sun in energy terms, although it would be hard gamma radiation. It would also be a trillionth the size of an atom and last about a millisecond! Whether they exist in the wild is debatable, because Cosmic ones made from collapsing stars will have a mass above 3 solar masses at least and are altogether gentler sort of gravity monsters.

Some fun calculations here, including the physics of the black hole in Larry Niven's novel "The Hole Man": http://library.thinkquest.org/C00757...ance/core7.htm
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  #63  
Old 05-25-2011, 09:43 AM
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While production of tiny black holes is certainly possible, it's not likely. A few quick, back-of-an-envelope type calculations show that the probability of actually producing a black hole, even at the energies and luminosities provided by a collider like the LHC (14 times the energy and 200,000 times the luminosity, currently), are so miniscule that you'd have to run the collider for slightly longer than the current age of the universe to ensure that you'd create a single black hole. This is likely a reasonably accurate calculation since the RHIC fireball is the only signal we've ever seen that even approaches what we might expect from the evaporation of a black hole. Even considering the result at RHIC, there are many more interpretations that correctly predict the hadronic component of the signal; more than I believe these AdS-CFT gravity dual interpretations have produced. I will say, however, that the AdS-CFT correspondence is an interesting and potentially very useful tool for solving some problems that have been giving us trouble.
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Old 05-25-2011, 12:41 PM
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This stuff is fascinating and makes my head hurt at the same time.
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Old 05-25-2011, 07:32 PM
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If your head hurts, you are worrying too much about the details. Everybody can instinctively do physics, otherwise we'd never be able to catch a ball.

AdS-CFT (Anti de Sitter-Conformal Field Theory) is a statement of the holographic principle, which says you can map 4D Standard Model Quantum Field Physics without gravity into 5D String Theory with gravity at low energies. Thus you can now see in the diagram here that Horatiu Nastase is doing this model with simple geometric 5D string theory.



Anti de Sitter space has negative curvature, and would be associated with a universe that has a natural tendency to fall back together after the Big Bang. It is hyperbolic, where the sum of angles in large objects is smaller than in flat Euclidian Space, as in this M.C.Escher drawing of a conformal mapping of it:



A good mathematician is always looking for a mapping or space that makes the maths easy and symmetrical. BTW, because surface curvature is the product of two axes here, the cylinder comes out at zero.



Not many people know about the Pseudosphere, which interestingly has the same surface area as a sphere, but half the volume and the opposite curvature. And the Breather Pseudosphere is quite astonishing IMO, because it has this amateur String Theorist's favourite doughnut in it.
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  #66  
Old 05-26-2011, 05:50 AM
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Quote:
Originally Posted by system7 View Post
You may remember that the great question of Einstein's Special Relativity was the "Twin Paradox", where one brother travelled to the nearby Alpha Centauri star at near light speed, and the other stayed at home. When the travelling twin returned home, he found his brother was 50 years older, while he was only 10 years older. This led to the deeper understanding of the relation between space and time, and overturned our ideas of distance.

You perhaps don't know that Stephen Hawking and Leonard Susskind found a similar paradox in our understanding of what a Black Hole does when you fall in one. Hawking said that Entropy was destroyed, Susskind said that it couldn't be or Quantum Mechanics would fall!

Here is a Black Hole like the one at the heart of our galaxy, which is estimated to have an event horizon 13 Million Kilometres across. This one is viewed in empty space against a background of the Magellanic Cloud, the one at the core is probably a bit more cluttered with stars and gas:



Leonard won the argument, and produced a working interpretation of what happens in terms of the holographic principle. This takes 50 minutes to watch, but is some of the most important physics of the last 100 years, so worth your time:

http://fora.tv/2008/07/23/Leonard_Su...Black_Hole_War

If you want to know more, Leonard discusses the very strange new view of our little corner of the multiverse that is emerging:
http://edge.org/3rd_culture/susskind...ind_index.html

I'll stop there for now.
Weren't some beers exchanged over that argument?
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  #67  
Old 05-26-2011, 09:26 AM
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Originally Posted by rambaldi View Post
Weren't some beers exchanged over that argument?
Beer is a difficult issue in this context. While it is easy to prove that the optimum quantity of sugar lumps or biscuits for those who like them is 2 based on the intelligently designed size of them, beer is usually consumed by friends together and this may be why it comes in 4 packs.

Susskind and Gerard van T'Hooft simply and immediately realised that if Hawking was right about entropy in Black Holes, then the 2nd Law of Thermodynamics and Unitarity in quantum scattering falls. It took 13 years for Susskind to come up with the explanation, but everybody remained friends. In the end, the physics wins.

Since 4 sentences is the optimum size for posts without photos IMO, I shall stop there.
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  #68  
Old 05-26-2011, 09:56 AM
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Four packs? Gawd, you Brits sure are sissies. Here, it comes in six packs, if not in 24 bottle cases. Of course, most tend to go straight for the keg.

What I want to know, all this blathering on by these welfare-supported theorists is fine and all; keeps 'em off street corners and what not, but what's it all good for? Is it gonna give us FTL capability before I die? 'Cause I'd sure hate for my remains to remain on this mudball. I wanna be buried anywhere else. Even Uranus would be preferable.
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  #69  
Old 05-26-2011, 10:34 AM
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Trust the footballers to overrun this thread with a discussion of of beer!

I'd suspect that British 500 ml cans of real brown beer are bigger than your 333 ml cans of pale watery stuff, thus explaining the discrepancy in pack size of 4 and 6. Personally, I drink to the natural limit of the cupboard being empty or that I have fallen over.

Back on-topic:

Quote:
Originally Posted by Leonard Susskind
What we've discovered in the last several years is that string theory has an incredible diversity—a tremendous number of solutions—and allows different kinds of environments. A lot of the practitioners of this kind of mathematical theory have been in a state of denial about it. They didn't want to recognize it. They want to believe the universe is an elegant universe—and it's not so elegant. It's different over here. It's that over here. It's a Rube Goldberg machine over here. And this has created a sort of sense of denial about the facts about the theory. The theory is going to win, and physicists who are trying to deny what's going on are going to lose.
Lenny reckons us Brits TOTALLY get String Theory, while crackpot creationists and people who want a definite fixed answer (aka intensified bores) in the US are less open to it. Well, THEY can keep their creaking Standard Model till it falls apart. I've jumped ship and so should you!
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  #70  
Old 05-26-2011, 10:59 AM
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Now HERE'S the big statement I have a problem with. If you go with the point of view that Susskind proposes, which is that the universe is NOT the same everywhere, you're advocating against the cosmological principle and suddenly every observation you make or experiment you do is completely useless since it only applies to the tiny region of space we currently occupy. If you believe this, then you believe that true science is impossible; you can't possibly construct any sort of universal model if the rules change from place to place. I've brought this point up to a few of Susskind's most devout followers that I know and they all tend to get a little fidgety and suddenly want to change the subject. I have yet to get a satisfactory answer as to how Susskind's point of view doesn't violate the cosmological principle or, if it does violate it but somehow doesn't matter, why it doesn't matter.
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