Monday Science

This week's science:

• First, over at Not Exactly Rocket Science, Ed talks about how pterosaurs landed: Several million years ago, at a time when dinosaurs walked the earth, a flying reptile - a pterosaur - came in for a landing. As it approached, it used its powerful wings to slow itself down and hit the ground feet first. It took a short hopping step before landing a second time. On solid ground, it leant forward, put its arms down and walked away on all fours. The landing made quite an impression on the underlying limestone mud and in the following millennia, the creature's tracks became fossilised. Now, they have been unearthed by Jean-Michel Mazin from the University of Lyon at a site near Crayssac in southwestern France.


• At Pharyngula, PZ surveys pre-Darwin geology, or how people already knew the earth was really old before the Theory of Evolution: I actually spend a fair amount of lecture time on the early history of geology in my introductory biology course. One reason is that, if you talk to most people, you will discover this fallacious belief that evolution leapt fully-formed from the brain of Charles Darwin, and there's an anachronistic idea that ideas about the age of the earth, which are built on independent evidence from geology and astronomy, are somehow rooted in biology. It's not so! Darwin's antecedents had already laid the foundations in working out that the earth was old, that life had undergone many transitions, and that maybe species were mutable. Evolution was an inevitable conclusion of the evidence; Darwin and Wallace were just the clever fellows who managed to pull the whole story together. I find it very useful to give students a quick overview of 18th and 19th century geology before we talk about Darwin, since the creationists in the classroom usually have this image of Darwin as Satan who foisted a false belief on the world because he hated god (hey, sounds like Terry Mortenson!). It's very useful to be able to show how views of the world evolved, not by ideology, but by the growth of a body of evidence.


• At Starts With A Bang, Ethan shows us how we know the Big Bang really happened: Recently, a discussion started in one of my comment threads about whether the Big Bang was necessarily valid or not, and whether there were any reasonable alternatives. The answer is that not only is the Big Bang the best theory to explain the start and evolution of the Universe, it's the only one that doesn't make incorrect predictions. Let's see this in action.


• At Bad Astronomy Phil hosts a movie from Christopher Go (follow the link back once you're there) showing Io passing over Ganymede: All this together means that when we look at Jupiter, the moons appear to orbit the giant planet on a line, too. They swing back and forth, moving "left to right" and "right to left" over time. In fact, if you watch Jupiter for long enough you’ll certainly see a moon pass directly over the planet’s face, and sometimes you can see the moon’s shadow as well. It’s very cool. It’s much less common to catch the shadow of one moon falling on another; the moons are small and it’s a rare thing to see such an event. But amateur astronomer Christopher Go caught exactly that on August 16, 2009: the shadow of the moon Io going right over the moon Ganymede. That. Is. So. Cool. You can see the shadow of Io (which is roughly the size of our own Moon) pass over Ganymede (as big as Mercury!), then Io itself pass directly between us and the giant moon.


• At Mike Brown's Planets, Mike shows us the solar system in scale: With the third-year anniversary of the demotion of Pluto having just occurred, I’ve been thinking a lot about planets again (or perhaps I should just say “still”). But rather than worrying about planet classification anymore, which I think is on pretty solid ground these days, I’ve been wondering about the people who simply can’t give up on the concept that Pluto simply has to be a planet. Why are they so attached to the 18th largest object in the solar system when they probably can’t even name all of the 17 larger things? (try this at home: can you without looking it up?) Lilah’s placemat drove home a likely part of the problem. Most people have absolutely no idea what the solar system actually looks like. They see pictures of planets of placemats, on lunch boxes, on walls at school, but none get the scale of the solar system even remotely correct. Why? First: it’s boring. The solar system is mostly empty space. How much empty space? If you were to draw a top-down view of the solar system from the center out to the edge of the Kuiper belt, it would be 99.999999% (that’s 8 nines, if you’re counting) empty. And 99% of that non-empty fraction is taken by the sun. Making a placemat with that much empty space is pretty dull (though presumably you would save on printing costs). I would show you here what it would look like, except that you would need to view it on a monitor with 12,000 pixels across (about 10 times your typical laptop screen). The sun would occupy only one pixel in the center. You’d see nothing else. If you had grown up with a picture of the real solar system on your placemat, you would be forgiven for thinking the number of planets was precisely zero.

Enjoy!