May 20, 2007 8:00

Totally Cool Optical Illusions

Like me, you probably thought that they'd all been invented already and stuck into psychology textbooks (maybe Magic Eye illusions haven't made it yet), but thanks to a blog called Mixing Memory, I've learned how wrong we all were. Experts in perception are coming up with new ones all the time. And it turns out they even have an annual contest. For this year's winners, go here.

Your eyes will deceive you, I promise.

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May 15, 2007 1:00

Dark Matter Revealed

Dark matter in the core of, and in a ring surrounding, the galaxy cluster Cl 0024+1 / NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)

Last summer, astronomers used a really clever observing strategy to present the best evidence to date that dark matter, once dismissed as a hare-brained idea, really does make up most of the mass of the universe. The image above does it again, in a slightly different way.

What you're looking at is a giant cluster of galaxies that underwent a collision with another cluster just behind it (we just happen to be on the line of sight that includes both clusters). As the two passed through each other a billion or two years ago, their combined gravity sucked the dark matter in and around the visible galaxies toward the center of the cluster. In the collision's aftermath, the dark matter rebounded, but then slowed and piled up in the bluish ring you can see in the photo.

The ring, and the clump of dark matter you can see in the core of the cluster, aren't really blue. They aren't really visible at all (there's a reason they call it "dark matter.") They're simulations, based on the the fact that gravity distorts the passage of light: the very strong gravity of the dark matter has warped the images of more distant galaxies, and by measuring the amount and type of warping with great precision--something that would have been impossible without the Hubble Space Telescope--the astronomers can infer where and how much dark matter there is.

This simulation shows not only that it's there, but also, because it's clumped in ways the ordinary matter is not, that it's not made of some dark version ordinary matter--confirming what theorists have been saying for years.

The phenomenon that makes this all possible, by the way, known as gravitational lensing, was discussed by Einstein in a celebrated paper back in the 1930s. His conclusion, after explaining how it would work: we'll probably never actually observe this. The first gravitational lens was discovered in 1979, and lensing has since become one of the most powerful tools for probing the universe. For once, Einstein just didn't think imaginatively enough.

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May 14, 2007 1:34

Intelligent Design—Bad Career Move?

The always alert Discovery Institute has let us know that Guillermo Gonzales has been denied tenure at Iowa State University. The DI is shocked--shocked!--at such a decision. Gonzales has done all sorts of serious work in astronomy, his field of expertise; obviously, this travesty is a result of Dr. Gonzales' extracurricular work on Intelligent Design.

For those who don't recall, ID is the idea that certain aspects of the natural world can't be explained without invoking a Really Smart Being having tinkered with the works. (The RSB isn't necessarily God, insist ID proponents, even though every last one of them seems to believe it actually is God--which is why detractors suspect the whole thing was cooked up to get around the Supreme Court's decision back in the '80s that you can't teach religion in a public science classroom).

Most ID people focus on evolution, and how you need a Go...I mean, a RSB, to explain the complexities of the biological world. But Gonzales is more interested in how the RSB is required to explain our planet's amazingly benign environment that has nurtured life.

The Discovery Institute is screaming foul. How can an institution like Iowa State claim to protect academic freedom if it rejects Gonzales' tenure just because he believes in ID? Well, for one thing, that may not be the only, or even the major reason. Yes, he's done good work in astronomy. But as the blogger Pharyngula puts it beautifully:

"Complaining that one met all the requirements is like proposing marriage, getting turned down, and then protesting that one has a good job, a nice apartment, and excellent personal hygiene. That may be true, but it's irrelevant. The university does not want a long-term, committed relationship with you—nothing personal, you can still be friends." (The full entry is here.)

It wouldn't be a huge surprise, though, if ID were one of the factors, and that's not inappropriate at all. Because Gonzales was up for a science professorship—and despite the most strenuous efforts of the Discovery Institute to spin it otherwise, ID ain't science. It's magic. It says, as ID's most celebrated proponent, Michael Behe, admitted in the Dover, PA court case on ID, that the definition of science is too narrow, and should be widened to include the supernatural. And unless Iowa State wants to merge with Hogwarts, it can certainly take into account the fact that Gonzales has a distorted view of what science actually is (again, I don't know the basis of their decision--I'm speculating, just like the Discovery Institute. Except from a point of reason, not spin-doctoring).

If Iowa State tried to fire Gonzales or anyone else after giving them tenure, I should add, for any reason other than extreme incompetence or commission of a serious felony, I would of course be opposed.

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May 9, 2007 1:00

Exoplanetary Weather Report

When astronomers found the first planet orbiting a sun-like star back in 1995, they assumed they'd have to wait a couple of decades for a telescope powerful enough to learn much about such distant worlds.

What they didn't count on was human cleverness. That first discovery and the two that followed lured dozens of scientists into an area of astronomy that had until then been viewed as a hopeless backwater. The resulting onslaught of ingenuity has moved the timetable up, and now two very cool discoveries (and by cool I mean scorchingly hot), made with the Spitzer Space Telescope, have just been announced in Nature.

Temperature map of HD 189733b/NASA/JPL-Caltech/Harvard-Smithsonian CfA

The first, above, is a rough map of the surface temperature of a planet known as HD 189733b, about 60 light-years away. The planet, comparable in size to Jupiter, races around its star in just 2.2 days, keeping one face toward it at all times. But while you'd expect the starward side to be much hotter than the dark side, it's only 500 degrees hotter--1700F vs. 1200F. Beyond that, the hottest spot isn't directly below the star, but off to one side. Both suggests that there are winds blowing the atmosphere around on this mostly gaseous planet at an almost unimaginable 6,000 m.p.h., distorting the pattern you'd expect and evening things out.

Artists' conception of HD 149026b /NASA/JPL-Caltech

The second is an overall temperature (no map here, just an artists' rendering) for a planet called HD 149026b, 279 light-years away, which at 3700 F is the hottest planet known (it's about four times hotter than Venus).To be so hot, it must absorb most of the light that falls on it, which makes it likely also to be the blackest. What could such a world be made of? Nobody knows, but it's far denser than most Jupiter-like planets, which is in itself a mystery.

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May 3, 2007 8:39

Hey, This Isn't Pluto! But Pluto Would Fit Inside

Jupiter's Little Red Spot, as imaged by New Horizons/NASA/JHUAPL/SWRI

The New Horizons space probe is on its way to Pluto (which was still a planet when the probe was launched last year), but to get there in any reasonable time it needed a gravity boost from Jupiter. So while it was in the neighborhood, why not take a few practice shots with its cameras? This is just one of them (you can see more here), but I have to admit this is my favorite. It's the Little Red Spot, which blossomed into existence just about two years ago to join the Great Red Spot first seen by Cassini (the astronomer, not the spacecraft). It's basically a gigantic hurricane, so large that not just Pluto, but Earth itself would fit inside. And it's still puny compared with the Great Red Spot, which is twice as big. But the Little Spot is still growing. Stay tuned.

Stay tuned as well for images from Pluto, which should be here in 2015.

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