Braking News for Creationism
2 Jul, 2007 04:51 pm
Creationists who bang the pulpit about the Universe being young tend to use old, outdated, and long-debunked arguments.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.
But thereís a problem. Since angular momentum depends on mass, youíd expect, upon doing the math, that the Sun would have most of the angmom (as we scientist-types call it when weíre lazy) in the solar system, since it has something like 98% of the total mass. But thatís not the case: Jupiter has more! Thatís 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 doesnít the Sun have all the angular momentum? The creationists would say, "Aha! Itís 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 donít have to imagine. Iíll tell you. Itís wrong.
This was theoreticalÖ until now. Itís 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 disksĖ 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, itís pretty darn good evidence of it. And itís certainly a "known" way for stars to slow themselves.
By the way, you can see an animation of all this on the Spitzer Space telescope website.
Originally published on Bad Astronomy