Top ten unsolved probblems in physics
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This is from the the funniest book review I've read in a long, long time, on Amazon.com by Peter W. Shor for The Trouble With Physics (original here: http://www.amazon.com/review/R2H7GVX4BUQQ68/ref=cm_cr_rdp_pe...):
The string theorists were scammed!, September 25, 2006
By Peter W. Shor (Wellesley, MA USA)
The part of the book I found most interesting was the part which tells how the string theorists were scammed by Nature (or Mathematics). Of course, Smolin doesn't put it exactly like this, but imagine the following conversation.
String theorists: We've got the Standard Model, and it works great, but it doesn't include gravity, and it doesn't explain lots of other stuff, like why all the elementary particles have the masses they do. We need a new, broader theory.
Nature: Here's a great new theory I can sell you. It combines quantum field theory and gravity, and there's only one adjustable parameter in it, so all you have to do is find the right value of that parameter, and the Standard Model will pop right out.
String theorists: We'll take it.
String theorists (some time later): Wait a minute, Nature, our new theory won't fit into our driveway. String theory has ten dimensions, and our driveway only has four.
Nature: I can sell you a Calabi-Yau manifold. These are really neat gadgets, and they'll fold up string theory into four dimensions, no problem.
String theorists: We'll take one of those as well, please.
Nature: Happy to help.
String theorists (some time later): Wait a minute, Nature, there's too many different ways to fold our Calabi-Yao manifold up. And it keeps trying to come unfolded. And string theory is only compatible with a negative cosmological constant, and we own a positive one.
Nature: No problem. Just let me tie this Calabi-Yao manifold up with some strings and branes, and maybe a little duct tape, and you'll be all set.
String theorists: But our beautiful new theory is so ugly now!
Nature: Ah! But the Anthropic Principle says that all the best theories are ugly.
String theorists: It does?
Nature: It does. And once you make it the fashion to be ugly, you'll ensure that other theories will never beat you in beauty contests.
String theorists: Hooray! Hooray! Look at our beautiful new theory.
Okay, I've taken a few liberties here. But according to Smolin's book, string theory did start out looking like a very promising theory. And, like a scam, as it looks less and less promising, it's hard to resist the temptation to throw good money (or research) after bad in the hope of getting something back for your return. One of the questions Smolin addresses in the rest of the book is why the theoretical physics community has kept with string theory and largely abandoned all the other approaches to quantum gravity. The short answer is that it's hard to admit that you've been scammed. The long answer is much more complicated. Another thing Smolin addresses in the book is other approaches to quantum gravity....