Bad Astronomy

Braking news for creationism

Creationists who bang the pulpit about the Universe being young tend to use old, outdated, and long-debunked arguments.

The astronomy ones just crack me up. Sometimes they are based on faulty data, sometimes on twisting or misinterpreting the results, sometimes on outright lies. They are most pernicious, perhaps, when there is a kernel of truth in what they say… though generally they leave out a HUGE amount of information that shows they are wrong.

One argument has to do with angular momentum. This is a tendency for a rotating object to stay spinning unless acted upon by a force of some kind (that “acted upon” part is important later). Mathematically, it depends on how big an object is and how fast it spins.

What does this have to do with creationism? Well, astronomers think that the solar system – the Sun, the planets, the moons, and all that – formed from a collapsing cloud of gas and dust. The cloud became a disk, and the center got big as junk fell in, and got compressed, and got hot, and got fusion. That became the Sun. Eddies and whorls in the outer part of the disk became the planets and moons.

But there’s a problem. Since angular momentum depends on mass, you’d expect, upon doing the math, that the Sun would have most of the angmom (as we scientist-types call it when we’re lazy) in the solar system, since it has something like 98% of the total mass. But that’s not the case: Jupiter has more! That’s because even though Jupiter has only about 1% of the mass of the Sun, it is way out in the solar system, 400 millions out from the Sun. This gives it a huge advantage over the Sun, angular momentum-wise (which may be the first time that term was ever used).

So why doesn’t the Sun have all the angular momentum? The creationists would say, “Aha! It’s because the solar system did not form that way, astronomers are stellar evilutionists, and are lying to you!” (They say this here, and here, and here and many other places too; that last one in particular says “There is no know [sic] mechanical process which could accomplinsh [sic] this transfer of momentum from the sun to the planets”, which is an out-and-out lie).

Imagine how I feel about that. Wait! You don’t have to imagine. I’ll tell you. It’s wrong.

It’s been theorized for a long time that when a star is born, it spins rapidly, and has strong magnetic fields. These fields spin through the disk of material around the star, and accelerate the disk. At the same time, it slows the star’s spin (like in the image above). Imagine you have a trash bag open in your hands, and you try to spin around. The bag will act like a parachute, accelerating the air, but slowing you down. So it is with the young star. Eventually, the star slows quite a bit, and the disk material spins up and gets flung off.

This was theoretical… until now. It’s been observed.

My friend Luisa Rebull published a paper showing exactly this effect. They looked at 900 stars in a nearby star-forming region, and they found that stars that rotated slowly are far more likely to have disks than those that rotated rapidly. This makes a clear connection between rotation speed and disks– a star that rotates quickly and has no disk will stay rotating quickly, and one that does have a disk tends to spin more slowly. This is precisely what the magnetic braking theory predicts.

While this is not proof that the stars magnetically brake themselves with the disk and slow their spin, it’s pretty darn good evidence of it. And it’s certainly a “known” way for stars to slow themselves.

As Bender my namesake, Philip J. Frye from Futurama (kindof) said: Creationism:0 , regular theories: a billion!

By the way, you can see an animation of all this on the Spitzer Space telescope website.