Archive for March, 2007

A must-see for modern humanists. One of my fave short speeches, a very sharp snatching at religion’s balls, if I may put it that way.

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Uh, about that UFO…

Phil Plait at Bad Astronomy has a nice post explaining exactly what were those ‘mysterious’ Phoenix lights (military flares), that we’ve known what they were for ages, and wondering why the hell CNN essentially propagated the UFO nonsense in an uncritical piece and why the ex-governor, who really, really, really should know better, somehow felt the need to confess his belief in aliens based on this sighting.

Personally, I think the governments plants these things in the sky to see how stupid some people are. If Symington had gotten into federal politics he would then never have been privy to confidential information relating to national security issues (one hopes) as he’s undeniably too silly to use it responsibly.

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One good thing about the PS3: it’s damn good for research. It’s currently contributing the majority of processing power to Folding@Home.

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Update to my previous post: Kayll points out that the equation of motion for the stars probably leads to orbits that are unstable. Also, the three authors of the paper have between them two publications. If that means something. I still want to know how they make the field theory description for the stars work.

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This week I will be giving a talk on a new paper that showed up on astro-ph positing that flat galactic rotation curves can be explained by string theory (!). Galactic rotation curves – that is, graphs of the speed at which stars and gas rotate about the centre of the galaxy – are found to remain flat or even rise far outside where the visible galaxy ends, and we can’t account for that using only Newtonian dynamics assuming the visible matter is the only matter there; they should eventually fall off gradually rather than maintaining very high speeds. So astronomers postulate the existence of dark matter to add extra acceleration to the matter orbiting the galaxy centre, to make up for the apparent difference. We’ve never directly detected the components of dark matter.* Other theories exist to explain this, such as an ad hoc modification of the Newtonian force law (modified Newtonian dynamics, or MOND) that is not theoretically motivated.

The very intriguing string theory argument, meanwhile, seems to be that in the Nappi-Witten model of IIB string theory, where the string theory equations can be solved exactly in the case of a plane polarized gravitational field background, it can be shown that the gauge potential couples to the worldsheet of the strings via the gravimagnetic field (a gravimagnetic field is a field produced by a moving mass in general relativity, in the same way that a moving electric charge produces a magnetic field in electromagnetism). Therefore strings interacting under this field will follow Landau orbits, much like a charged particle moving in a magnetic field.

So this means (and here is the great logical leap of the paper) that stars themselves will follow the same trajectories (they don’t provide a description for how this happens) – and this adds a term linear in the circular speed to the force equation which compensates for the drop in speed far from the galaxy centre! C’est un miracle! And it looks like it sort of works in real galaxies, too. Except sometimes. Probably when the galaxy doesn’t benefit from string background rotation, since it needs a componenet of the gravimagnetic field perpendicular to the galactic plane to act. But maybe there is somethnig to this idea.

Well, it’s fun to speculate…

*We have never directly detected the components of dark matter experimentally but there are a couple of results that corroborate it: first, we know that the dynamics of satellite galaxies suggest a density drop off of r^(-3) far from the centre, which is predicted by cosmological simulations of structure formation. Second, the ‘Bullet Cluster‘ result, in which dark matter was detected in a colliding galaxy cluster, is the first direct detection of a dark matter halo.

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Hat tip Ilya Somin (via Eugene Volokh): The first openly atheist member of Congress is Pete Stark, D-CA. From the link:

There is only one member of Congress who is on record as not holding a god-belief.

Rep. Pete Stark (D-Calif.), a member of Congress since 1973, acknowledged his nontheism in response to an inquiry by the Secular Coalition for America. Rep. Stark is a senior member of the powerful House Ways and Means Committee and is Chair of the Health Subcommittee.

Although the Constitution prohibits religious tests for public office, the Coalition’s research reveals that Rep. Stark is the first open nontheist in the history of the Congress. Recent polls show that Americans without a god-belief are, as a group, more distrusted than any other minority in America. Surveys show that the majority of Americans would not vote for an atheist for president even if he or she were the most qualified for the office.

Herb Silverman, president of the Secular Coalition for America, attributes these attitudes to the demonization of people who don’t believe in God. “The truth is,” says Silverman, “the vast majority of us follow the Golden Rule and are as likely to be good citizens, just like Rep. Stark with over 30 years of exemplary public service. The only way to counter the prejudice against nontheists is for more people to publicly identify as nontheists. Rep. Stark shows remarkable courage in being the first member of Congress to do so.”

Thank God!

(er… sorry, bad joke)

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This website (and all of wordpress, I believe) is blocked in China, according to http://www.greatfirewallofchina.org/test/.

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