Brian Greene's "The Elegant Universe" about string theory.

I'm re-reading now. Fascinating book. One to read slowly, so you can put it down from time to time and straighten things out in your head.

Anyone more up on string theory have any comments on this book? Any other readers of it have any thoughts?

For people involved with physics and string theory, Is it holding up well? Holes being punched in it? Or does that strongly depend on who you ask?

You may be able to get it in the library.

"The Fabric of the Cosmos".

http://www.amazon.com/exec/obidos/ASIN/0375412883/103-5258379-3553411

As an experimental physicist, my big problem with string theory is the lack of experimental evidence. Theorist can get pretty wild without us experimentalist keeping them "reality based".

Is it a matter of the energy levels required, or some kind of quantum uncertainty thing? Or is there some other reason experiments have lagged behind theory?

are so high that's it's considered untestable. As a result, some scentists believe string theory does not qualify as a scientific theory.

Personally, I think there will be ways found to test it. At some point, it has to generate different predictions from the conventional Standard Model.

...as presented by Prof. Greene on his NOVA show, but I want to know, when they smash atoms, do they have microscopes that can actually SEE (visually) Protons, Neutrons and Electrons, and/or even Quarks?

One more Question: approximately how many atoms would it take to make up the average Adult Human Brain?:hangover:

type of microscope would be way out of the visual range. People have been able to isolate a single atom and make it visible though.



Here's a picture of a single Barium ion (the little blue dot in the center) trapped by researchers at the university of washington

Physicist Peter Woit has more at his blog "Not Even Wrong" from a couple weeks back: http://www.math.columbia.edu/~woit/blog/archives/000151.html

Michael Douglas gave a colloquium at City College this afternoon, with the title "Are there testable predictions of string theory?" I went up there to the talk, figuring that I knew more or less what he would say, but he really surprised me.

...

Given this, in the conclusion of his talk, I was expecting him to answer the "Are there testable predictions" question in the negative. Instead, he did something very strange. He announced that string theory does make predictions, lots of them, adopting the Lubos Motl definition of a "prediction" of string theory as being anything consistent with string theory. Examples he gave included Polchinski's cosmic string networks, where one could tell from the behavior of the network whether the strings were fundamental or not, and short distance modifications to GR. Of course these are not in any sense real predictions; all sorts of different modifications of GR at short distances are compatible with string theory, as are either no visible fundamental cosmic strings, or visible ones with a huge variety of possible different properties.

...

In the question section, some obnoxious guy who has a weblog asked him whether it was really true that the best prediction string theory could come up with was the no variation of the fine structure constant one that was really an effective field theory prediction, and didn't that mean there was no hope of string theory ever really predicting anything. For some reason this made him rather defensive, and he began by saying it depended on the meaning of the word "prediction". After having it explained to him what most physicists consider a prediction to be, he launched into a sequence of analogies designed to explain why you can't get real predictions out of string theory.

...

Feynman's line that: "string theorists don't make predictions, they make excuses" has been changed from a criticism into a new motto about how to do science.

I suppose it's obvious that Woit isn't exactly a fan of string theory.

--Peter

That sounds like the feeling I got from Greene's book (but I'm not a physicist, so my opinion isn't worth much). But I thought Greene's coverage of special and general relativity are terrific, the clearest explanation I've seen. So, to anyone who regards relativity as a bit of a mystery, I recommend this book: it'll make you say "oh, so that's how it works!". The description of string theory is less satisfactory, but that's not Greene's fault: it's obvious from the book that you can't really grasp string theory without the mathematics, and Greene probably does as good a job as anyone could at explaining it to the layman.

I'm no physicist, but I love reading books that bring science to the layman. As I understand it, there is just no way to observe what goes on in the sub-atomic world beyond the Planck length which seems to be a barrier to experimental testing of the theory. Someone more well-versed could correct me or explain it more precisely. It has been a few years since I read the book, but I seem to remember it going something like that. I remember doing further research on the internet and it was put like this: The energy required to do experiments to test the validity of string theory would create either a rip in the fabric of space time, possibly creating a new universe in the process. In other words, if I understood correctly, even if we could harness the energy required, we would blow up our universe in the process by causing a new "big bang" that would replace our Universe with another. Of course, I could be completely mis-informed--hence my earlier disclaimer: "I'M NO PHYSICIST!!!"

I don't know if string theory is the answer toward a theory of everything, but it is fairly clear that it is the best theory put forward so far in bridging the gap between the physics of the very large and of the very small.

P.S.: I'm reading "Fabric of the Cosmos" now.

:-)

I would also recommend anything by Dr. Richard Feynman. Excellent stuff...

that were his Cal Tech Freshmen Physics class -

and now they seem to be gone forever.

I do not recall reading anyone that was clearer on what he was talking about.

I miss those Red monsters! :-)

but I would hate to try and teach freshman physics out of them. I used them to review for my Ph.D. qualifying exam.

:-)

but once you get past kinematics and dynamics, it certainly is helpful in reading them if you know the material already. Not a great learning aid, but a wonderful referance...

.... all these other replies are just silly - probably from people with epsilonishly small mathematical ability. Everybody knows that the FLP are the best physics texts ever written.

LOL - next people'll be talking about how much the Knuth books suck..... sheesh - America is soooooooo anti-education, it isn't even funny any more...

EDIT: typo

His technical stuff are dry to me, but I love his stories from life. They make me go back and try to get further in the technical stuff.

... GEB is about the only thing I can think of that's better, within the general genre. Of course GEB isn't *just* a popularization - it contains non-trivial technical material, but whatever.

The Yahoo article about escaping gravity I posted earlier today on this forum relates to string theory, and says that the escaping gravity notion can be tested.

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=228x3838

From what I recall, Greene suggested that there might be indirect ways of testing string theory, and maybe this may be one of those cases.