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  #51  
Old 05-17-2011, 09:15 PM
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I've gotta agree that String Theory is at an early stage. I don't know if it's right. But it is impressive in the way it unites the photon of light in the tiny atom with the graviton in the huge Black Hole. It is making the World think about geometry again. No other theory comes close.
String Theory is 50 years old; that's not exactly the "early stages". As for uniting things with the huge black hole, I should point out that black holes have no physical size, unless you maybe count the circumference or diameter of the singularity in something like a Kerr black hole, and even then, you can make black holes down to the Planck mass that have horizons on the order of the Planck length. Speaking of horizons, the horizon itself (or "horizons themselves" if we're talking about something fun like a charged black hole) are simply coordinate singularities and not real physical constructs, which is why we shouldn't use them to denote the "size" of a black hole.
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Old 05-17-2011, 10:15 PM
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@system7

This is great stuff... I wish I could add to it...
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  #53  
Old 05-18-2011, 02:18 PM
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Brother Michigan, please stop sniping the subject under discussion. If you can't see that a Black Hole with a mass of several stars is huger than an electron, I am talking to a goat! In fact you can construct an 11D M-Theory entirely using charged Black Holes as a D0-Brane, if you want to look at it that way.

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This idea was made more precise by Leonard Susskind, who had also been developing holography, largely independently. Susskind argued that the oscillation of the horizon of a black hole is a complete description of both the infalling and outgoing matter, because the world-sheet theory of string theory was just such a holographic description. While short strings have zero entropy, he could identify long highly excited string states with ordinary black holes. This was a deep advance because it revealed that strings have a classical interpretation in terms of black holes.
http://en.wikipedia.org/wiki/Holographic_principle

Now back on-topic. What is a closed string? It's the boundary of a hole in space isn't it? Einstein's rubber sheet Space-Time geometry turns out to have little holes in it.



And a string attached at both ends to a D-Brane which we identify as a photon. Well it's a little wormhole isn't it? It can connect two distant points in space.

So we have a very simple palette of particles to choose from, and the subtlety (and the holdup currently) lies in the excitations and the 10D geometry which give the detail. There are people who hate string theory because it is not currently predicting the spectrum of particles exactly, but I think it is going places.
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  #54  
Old 05-18-2011, 02:27 PM
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Brother Michigan, please stop sniping the subject under discussion. If you can't see that a Black Hole with a mass of several stars is huger than an electron, I am talking to a goat.
I believe I did keep to the topic at hand, that topic being string theory, which is 50 years old and still hasn't produced any results. Again, it's elegant, but ultimately useless at this time. The rest of the post may be taken as an aside. As for me being a "goat", please feel free to contact me outside of this thread and tell me exactly how an electron is smaller than the Planck length. I'd be happy to hear the rationalization.

Last edited by Brother Michigan; 05-18-2011 at 02:29 PM.
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  #55  
Old 05-20-2011, 10:29 AM
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Default OK, we'll talk about Black Holes....

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.
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  #56  
Old 05-24-2011, 04:33 AM
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Default Let's do something speculative...

Most of our knowledge of particles comes from smashing electrons and protons together in accelerators, which has given us the rather arbitrary Standard Model:



Neutrinos are not something in our everyday experience, but seem to have a rather bizarre property called oscillation whereby they actually flip between each other in identity, thus an electron neutrino can be a Mu or Tao neutrino a few hundred metres away!

This brings us onto a speculative observation about lepton (ie electron-like) masses embodied in the Koide Formula at the top. This has been extended to Neutrinos by Carl Brannen in the lower formula.



The formula closely resembles 3 types of particles moving in the same direction in a classical gas. What is interesting about the 25 year old Koide Formula is the wonderful 45 and 120 degree symettry of the result for the electron, and bigger muon and tauon, and the Koide formula actually predicts the value of the Tau electron mass from the other two to any current accuracy. I am looking forward to playing with Brannen's formula, since the Koide one was so elegant.
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  #57  
Old 05-24-2011, 07:11 AM
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...This takes 50 minutes to watch, but is some of the most important physics of the last 100 years, so worth your time:...
************ you work! I'll watch it when I get home
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  #58  
Old 05-24-2011, 08:43 AM
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Since nobody did it so far, Imma tell you a mathematical joke.

Q: How does a mathematician imagine a ten dimension space?
A: He first imagines an n dimension space, then he substitutes n with 10.

Thank you, what a splendid audience!

I'll watch some of the videos later, but I am unfortunately too dumb in this area of science to participate.
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Old 05-24-2011, 09:22 AM
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Actually, I do hope we aren't getting too deep here. So far it's all relatively non-mathematical I think and everyone can enjoy his sort of thing.

Did anyone spot the rather lovely conformal mapping around the NASA artwork of a Black Hole? I have drawn in the (Red) Einstein Ring of the gravitational lens here, and star A and A* are actually the same object transformed around that ring, as are galaxies B and B*. The Black Hole creates another little mapping of its own at the very centre. You don't normally see the Einstein Ring because the usual sort of star like our sun making it looks bigger and blocks it out.



Related to the mirror-ball effect at the Orrery Cafe in Ryde High Street.



Not often you see a conformal mapping in the wild!
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Last edited by system7; 05-24-2011 at 09:31 AM.
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  #60  
Old 05-24-2011, 12:07 PM
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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.
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