Tuesday, October 03, 2006

Greetings from Pasadena

I'm at Caltech for a couple of days, giving a talk at the Institute of Quantum Information (slides are here). The weather is beautiful, and, judging by the screaming on campus last night, the tradition of frosh initiation is alive and well.

The Nobel prize in physics was awarded to Mather and Smoot for COBE (measurement of temperature fluctuations in the microwave background, confirming the big bang model of cosmology). When I was a grad student I had an office across the hall from Smoot's group at LBNL. They were moved at some point and some HET postdocs (including Raman Sundrum) inherited the nice view of the bay. Smoot used to drop by all the time to look out the windows and lament his loss. He told me that, contrary to rumor, he was not the Smoot used as a unit of length by MIT students to measure the Harvard bridge. (If you don't know what I'm talking about there is always Google.)

Finally, via Dave Bacon, a hilarious history of string theory by Peter Shor (of quantum factoring fame), which appeared as a review of Smolin's book on Amazon. Now string theorists can complain about how Shor is not smart enough to have an opinion on the subject, or understand what they are doing. (See further down the same page for Lubos' review.) Oh, and as pointed out elsewhere by Wolfgang, it was not Nature scamming the string theorists, but rather Mathematics masquerading as Nature ;-)

The string theorists were scammed!, September 25, 2006
Reviewer: Peter W. Shor (Wellesley, MA USA) - See all my reviews

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. And as could be predicted, he gives lots of space to his own approach and too little space to others, especially Alain Connes' non-commutative geometry. But overall, I found it very worthwhile and entertaining, and a good explanation as to how theoretical physics came to be in the state it is today.


Anonymous said...

Here is yet another example of the useless baggage I carry around in my head: If you go to Ruddock House, Alley 4, the room across from the bathroom, and look behind the mirror in that room, you will find Peter Shor has signed his name there!

Anonymous said...

While the implications may far outlast humanity -- the end of the universe may be coming in a few more billion years -- Smoot has been clear on the need for the work.

"It is extremely important for human beings to know their origins and their place in the world," Smoot said in a statement.

Krauss said the prize supports his own arguments -- made to NASA and the U.S. Congress -- that funding should go to similar experiments.

President Bush has urged NASA to concentrate on getting people to the moon and Mars.

"New experiments on the cosmic microwave background, new experiments to probe dark energy, to look for habitable planets -- all these have been delayed and/or canceled because we are sending people back to the moon," Krauss said.


Steve Hsu said...


You are a nut! And, while reading your message, I thought for about 5 seconds about whether I should go look at the signature, before deciding it would freak out the occupants of the room :-)

Carson C. Chow said...

Hey Steve,

Cute talk. I didn't know about the Everett argument before but I like it. Afterall, the Central Limit Theorem is practicallly the foundation of everything I do.


Anonymous said...

I once told an entire summer school class about the signature. I wonder if any of them ever went and took a look. They probably weren't as excited about this signature as I was. Yep, a nut!

Steve Hsu said...


Preskill told me that both Feynman and Gell-Mann claimed to have independently invented many worlds, before becoming aware of Everett's work!

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