Thursday, February 15, 2007
The Hidden Matter of the Dwarf Spheroidal
I spent about an hour yesterday explaining what I knew of the state of contemporary physics to a rock 'n' roll publicist who clearly felt his job wasn't quite enough to fill his eager mind. He is right to be interested. Now, it seems, we have discovered dwarf spheroidals, galaxies composed almost entirely of dark matter. The universe is made, I learn from reading the superb Lee Smolin, of more than 90 per cent dark energy and matter of which we know nothing. Hamlet was on to this - 'There are more things in heaven and earth, Horatio,/Than are dreamt of in your philosophy.' - but he probably had no idea how much more. Smolin also thinks that most of the physics of the last thirty years has been barking up the wrong quantum-cosmological tree. I have suspected as much myself and previously posted on this suspicion. Modern physics is the theology of our time and, like theology, is never quite clear about its subject matter - or, more exactly, about its subject, matter.
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A blog about, among other things, imaginary ideas - What ifs? and Imagine thats. What if photographs looked nothing like what we see with our eyes? Imagine that the Berlin Wall had never come down. What if we were the punchline of an interminable joke? All contributions welcome.
Just before I missed an absolute sitter, I told my opponent that snooker is pure physics. Was I right, then? Or does it matter when your highest break is only 18 (blue, pink and black)? Perhaps I shouldn't have attempted a touch of left-hand side?
ReplyDeleteJust wanted to clarify that dwarf spheroidals are actually distant relations of pixie onlinius.
ReplyDeleteAs you were soldier.
Have you read Smolin's book 'The Trouble with Physics'? It really is superb. In 2002 Smolin had to write a review paper which assessed the various approaches to quantum gravity, including string theory. String theorists have always claimed that string theory is a finite theory, hence Smolin sought a citation for this:
ReplyDelete"Looking at different sources, I found referenced only the original paper by Mandelstam - the one that, I had been told by mathematicians, was incomplete. I found a few other papers on the problem, none of them claimimg a final result. I then began asking string theorists I knew, in person and by e-mail, about the status of finiteness and where I could find the paper containing the proof. I asked a dozen or so string theorists, young and old. Almost all who answered told me that the result was true. Most didn't have the citation for the proof, and those who did gave me the paper by Mandelstam. In frustration, I consulted review papers...Of more than fifteen review articles I consulted, most either said or implied that the theory was finite. For citations, I found only earlier review papers or the paper of Mandelstam...I finally found that D'Hoker and Phong had, just in 2001, succeeded in proving the finiteness to the second order of approximation. Until then, over the seventeen years since 1984, no substantial progress had been made...Thus, the fact was that only the first three out of an infinite number of terms in the approximation were known to be finite. Beyond that, whether the theory is finite or infinite was (and is) simply not known.
"When I described this situation in my review paper, it was greeted with disbelief. I got several e-mails, not all of them polite, claiming that I was mistaken, that the theory was finite, and that Mandelstam had proved it...But their shock was as nothing compared with that of those physicists and mathematicians I talked to who were not string theorists, and who had believed that string theory was finite because they had been told that it was." (p279-281).
Reading it now, Gordon. Superb indeed.
ReplyDeleteI'm heartened by the thought that one's lack of snooker prowess is not related to actual skill - more a proper appreciation of dark matter. I've never believed before but now I have a reason - it makes a big difference!
ReplyDelete