## Monday, November 26, 2007

### Paul Davies does not know what science is

Paul Davies, best known for exploiting anthropic arguments in the service of religious apologetica and presenting the results to the unsuspecting public as popular "science" books, is at it again: a November 24th Op-Ed piece in the NYT that trots out the old canard that science is based on faith in the same way religion is.

When I was a student, the laws of physics were regarded as completely off limits. The job of the scientist, we were told, is to discover the laws and apply them, not inquire into their provenance. The laws were treated as “given” — imprinted on the universe like a maker’s mark at the moment of cosmic birth — and fixed forevermore. Therefore, to be a scientist, you had to have faith that the universe is governed by dependable, immutable, absolute, universal, mathematical laws of an unspecified origin. You’ve got to believe that these laws won’t fail, that we won’t wake up tomorrow to find heat flowing from cold to hot, or the speed of light changing by the hour.
Of course, almost none of this is true, as almost any scientist at any type will quickly tell you.

First of all, the "laws of science" are observed regularities of the way the Universe works, convenient descriptions for human consumption. Indeed, if there were no such regularities then everything we know, including life, could not exist. But that does not mean that a Universe that works differently could not exist.

That nature is ordered such that laws can be ascertained is not an untested assumption (or "faith" as Davies misleadingly but deliberately words it), but a hypothesis that is effectively tested. Even quantum mechanics, with predictions and behaviour that are extremely unusual by everyday standards, is rational and intelligible. Davies statement that "you have to believe that those laws won't fail" is an extremely unusual thing to say - physicists I known don't go around reciting "f=ma" for fear that Newton's Laws will stop working. Imagine if physics on the scale of everyday objects (houses, planets, etc) were not ordered and the so-called laws did fail - you'd work out that was happening pretty quickly.

Why would Davies even make such poorly reasoned claims, why use the word faith for something that is nothing like religious faith (belief without evidence)? Nor is this the only attempt to tie science to religion, specifically Christianity, in the article. The wikipedia article on Paul Davies (as seen at the time of writing on Nov 26th 2007 at 5:30pm EST) is blunt in one (quite probable) interpretation:

Davies recently made his commitment to deism clear in his New York Times Op-Ed, Science on Faith, 24 November, 2007 going so far as to write:

Clearly, then, both religion and science are founded on faith — namely, on belief in the existence of something outside the universe, like an unexplained God or an unexplained set of physical laws, maybe even a huge ensemble of unseen universes, too. For that reason, both monotheistic religion and orthodox science fail to provide a complete account of physical existence.

While coyly refusing to name or identify a particular candidate monotheistic religion, equating faith in the supernatural with a faith that the universe is itself real, testable and knowable is essentially a reductio ad absurdum where science can be faulted for not knowing anything if it can't explain absolutely everything. The only motive for making such an absurd argument is to open a crack where the wedge of deism can be inserted into scientific reason, to divide and dominate it. It is essentially a political, not scientific argument, one that advocates deism in exactly the same way as the "intelligent design" religious movement.

Sadly it is unlikely that the hordes of NYT readers who made this article one of the top emailed articles in the last 48 hours will learn just how wrong Davies is.

## Monday, November 12, 2007

### The Biggest Eyes in the Sky

NASA's "Great Observatories": Hubble, Chandra, Spitzer and Compton, cost on average $1-2 billion each to build, launch and operate, in a program that has well taken over twenty years to develop. By way of comparison, NASA spends approximately$1.3 billion per year on astrophysics (excluding Solar and Solar system related research), or about $5 billion per year on science in total, out of a total budget of$18 billion per year. This useful PDF describes the Great Observatories program, its aims, and NASA's budget.

Together they covered much of electromagnetic spectrum inaccessible to ground based observatories due to atmospheric absorption: Hubble probed ultraviolet as well as optical wavelengths, Spitzer probed lower energy infra-red radiation, while Chandra and Compton were sensitive to X-ray and Gamma ray radiation respectively. In many ways they are the most advanced telescopes ever created by mankind, for those specific wavelengths.

However, for the optical, near-IR and radio wavebands there is no doubt that much better telescopes have been launched into space, and built at greater cost to the public. The difference is that they're not pointed outward but instead inwards, down at the Earth. They are, of course, spy satellites. Quite apart from the vital intelligence-gathering work they do, they're fascinating and impressive technical accomplishments.

The NYT has a fascinating article by Philip Taubman about spy satellites, more specifically about the financial woes affecting latest generation of US spy satellites. Well worth a read when you're having a break from work.

[Edited at Mon Nov 12 11:09 to fix formatting and note article is mainly about the financial aspects of the spy satellite program]

## Thursday, November 08, 2007

### Comets, X-rays, and Pumpkins

I've been rather busy lately writing a NSF grant proposal, so I haven't written any posts for a while. Despite the time-crunch, I feel like taking a few minutes to briefly mention Comet Holmes which I managed to see with the naked eye (even from light-polluted Baltimore suburbia) last week and the week before.

As everyone is probably now aware, Comet 17P/Holmes is currently visible to the naked eye (to find it check out this S&T article, or the easier-to-use directions from SPACE.com), after undergoing a dramatic and unexpected increase in luminosity believed to be associated with some form of explosive out-gassing. Note is only through binoculars or a telescope that the truly diffuse nature of the comet is apparent, but even with small binoculars it was pretty impressive. Far more impressive to my mind than Halley was in 1986, so if you haven't seen it yet please go look for it.

Indeed, this one of rare astronomical phenomena that is more impressive to see yourself than when viewed as a picture taken with a big telescope (Astronomy Picture of the Day has a whole series of Comet Holmes images: 1, 2, 3, 4, 5).

I have a soft spot for comets, I worked very briefly (for a few hours) on trying to explain the X-ray emission from comets. The material evaporating off a comet is very cold (only about T~50 K), so it was a great surprise when X-ray emission was discovered coming from Comet Hyakatuke in 1996 using the ROSAT X-ray telescope (see e.g. Glanz, 1996, Science, 272, 194). Many explanations were advanced at the time, the vast majority of which did not work out. As the Solar wind has a velocity of several hundred km/s, one hypothesis was that a shock wave caused by the interaction of the Solar wind with the cometary halo caused X-ray emission by thermal bremsstrahlung. Ian Stevens, my thesis advisor at the time, performed hydrodynamical simulations of this, and my job was to take the simulations and calculate the expected X-ray luminosity. Which turned out to be orders of magnitude less than the observed emission, hence disproving the hypothesis. We didn't even bother considering to publish the results.

The real explanation for the cometary X-ray emission turned out to be charge exchange with the Solar wind. The material in the Solar wind is highly ionized, while the material out-gassed from the comet is largely neutral. A highly ionized ion interacts with a neutral atom, basically stealing one or more electron from the neutral atom. The formerly neutral atom is now ionized, and is left in an excited state. This excited state decays to a ground state by the emission of one or more photons. Dennis Bodewits PhD thesis "Cometary X-rays : solar wind charge exchange in cometary atmospheres" (2007, The University of Groningen) deals with many aspects of X-ray emission from comets, and is available chapter by chapter in PDF form.

Ironically solar wind charge exchange (SWCX) has now been recognized as a process than almost all X-ray astronomers must worry about (see Snowden et al 2004, ApJ, 610, 1182), even those like me who study distant galaxies. SWCX is now recognized as a major contributor to the soft X-ray background that affects all X-ray observations, and which makes observing faint diffuse X-ray emission difficult. Worse still, the SWCX can be time variable, further complicating background estimation and removal.

In acknowledgement of this link my Halloween pumpkin this year was a comet, which looked quite good until our local deer ate it.