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Showing posts from March, 2005

We don't need no stinkin dark energy II

David Wiltshire has opened a new front in the dark energy wars with gr-qc/0503099. He has an allegedly simple and exact model using the Kolb,
Matarrese, Notari and Riotto (KMNR) idea of super-Hubble density variations to explain apparent cosmic acceleration without dark energy.

I have been trying to understand his "spirit of Mach's principle" assumption. My current guess goes like this: At the end of inflation, the universe was nearly flat and uniform in density, so that FRW "comoving" coordinates closely approximated the actual geodesics. As the density variations amplified with time, these coordinates increasingly deviate from geodesics. Here is what I consider the money quote: "...an observer who would measures
no dipole anisotopy even in the observable universe, must
be referred to the time, t..." I think that means he is assuming that the observers measuring no dipole anisotropy are the ones moving along those (non-geodesic) FRW t coordinates. …

We don't need no stinkin dark energy

Edward Kolb and collaborators have posted a new Paper hep-th/0503117 which suggests that maybe we don't really need dark energy to explain the accelerating universe. About 10 years ago, you may recall, evidence started accumulating that the rate of expansion of the Universe was increasing.

We've known for 70 years or so that the Universe is expanding, that distant galaxies are rushing away from us, and each other, and that the more distant they are, the faster they are rushing away. As it turns out, this was predicted by Einstein's General Relativity, though the prediction was quite a nasty shock to Al when it was first noticed. This story, and everything else I will say except about the new paper, is told very well in Brian Greene's book The Fabric of the Cosmos.

In the General Relativistic picture, the long term fate of the Universe depends very critically on a parameter called Omega. If this parameter is greater than 1, the Universal expansion slows down, halts, a…

Frankly, My Dear, I don't give a damn.

Robert H. Frank, a Professor at Cornell's Johnson School of Management, has a lament for America's shamefully low savings rate in today's NYT. Unfortunately, it's not an especially honest or enlightening lament, though he does get in a few good points, like his finale.

It is clear, in any event, that the failure to save entails risks of its own to freedom. America's rapidly rising debt to foreigners now threatens the economic prosperity on which so many of our cherished liberties depend.
So what's wrong with his article?

Money invested at 7 percent interest, for example, will double every 10 years, which means that $1,000 deposited at that rate by Benjamin Franklin in the late 1700's would be worth more than $3 trillion today. The same $1,000 invested in 1945 would be worth more than $64,000.

Of course you can't get anything like that interest rate unless you are a mafia loan shark or a credit card company (my apologies for the redundancy). My savings acc…

The Persecution and Execution of Larry Summers as Performed by the Inmates of Harvard

The Faculty of Arts and Sciences at Harvard have today voted a motion of no confidence in President Lawrence Summers. His crime: speaking an unpopular truth by suggesting that science should be preferred to PC dogma. I think this will be a permanent black mark on Harvard's reputation. It does seem a shame that the reputations of its many brilliant thinkers and scholars will be tarnished by the actions of a willful majority.

This should serves as an object lesson to, say, Caltech and MIT, on the hazards of loading up your faculty with practitioners of fashionable psuedo-scholarship. It's alread too late for the Ivies.

Abortion: Is Compromise Possible?

Every survey appears to show that about one third of Americans believe that abortion should always be legal, one third that it should never be legal, and one third that it should sometimes be legal. Most of Europe and the rest of western civilization has adopted some version of the compromise position, with abortion legal but restricted.

The de facto situation in the US is that abortion is always legal. This is a bit strange because the Supreme Court's Roe vs. Wade clearly opened the door to some regulation of abortion, but the courts have consistently thrown out laws criminalizing any abortions.

Naturally enough, abortion rights supporters want to maintain this situation, while abortion foes want to overthrow it. The survey statistics mentioned above give each some aid and comfort, since abortions rights people can claim that a large majority supports legal abortions and abortion opponents can claim that a large majority favor some prohibition of abortion. The natural way of r…

Mozart was a Space Alien!

There are a few humans whose accomplishments seem so many standard deviations from the rest of us that it seems like they can hardly have been made of the same stuff. Archimedes, Leonardo, Newton, Shakespeare, and Mozart must have been made of some special metal, or so it would seem. I greatly admire the music of Haydn, Beethoven, and Wagner, but somehow Mozart is at another level. Similarly for the others on my list.

Evidently there is something in human nature that makes us pick out special heroes and promote them beyond ordinary mortality. The ancients promoted dead heroes and live emperors to demi-god status. You don't really need to be an all-time genius to get demi-god points, though. Michael Jordan and Tiger Woods made it too.

My own guess is that there is some evolutionary hardware installed in humans that makes us tend to exaggerate the virtues of our heroes. On a few occasions I have found myself in the capacity of leader in a potentially perilous situation. Never …

The Blue Academy

This obscure editorial found that the ratio of Democrats to Republicans at Stanford and Berkeley was almost ten to one. Apparently other studies have found similar ratios at other top schools. I sort of suspect that Bob Jones U and some similar institutions were not included in any of the surveys, but what should we make of this? Shocking evidence of discrimination or something less sinister? I don't know the answer, and in fact have never attended either of the institutions mentioned (though I've bought books at their bookstores and a sweatshirt at Stanford).

I can imagine some fairly overt discrimination, especially in the humanities and social sciences where ideology is tightly bound up with scholarly approach and worldview, but I think there are some other things in operation too. The cornerstones of the Republican party's program, at least in the last election, were Christianity, opposition to abortion, opposition to homosexual rights and especially homosexual marria…