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Topic: Would the universe rotate plane polarized light?  (Read 4086 times)

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Offline spirochete

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Would the universe rotate plane polarized light?
« on: February 02, 2008, 10:10:04 PM »
I recently learned something about chemical reactions: A reaction between two achiral molecules will always yield either a symmetrical product or a racemic mixture/s. A reaction involving chiral molecules may yield any possible product. Thus symmetry is always preserved, but asymmetry may yield symmetry.

Given billions of years of chemical reactions, regardless of what molecules we started with it would seem that we are proceding toward symmetry. Does this mean that the universe must be composed entirely, or virtually entirely, of some combination of achiral molecules and racemic mixtures?

Offline optimusprime

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Re: Would the universe rotate plane polarized light?
« Reply #1 on: February 03, 2008, 04:24:01 AM »
Interesting question.  I think it's correct to say that the universe would NOT rotate light, simply because there's no energetic or entropic reason why it should.  If you start with a simple prochiral molecule, it will give you 50:50 racemic mixture.

Basically, you know that if you start with achiral materials, you get racemic or achiral products.  The only way we know to make chiral molecules is to a) start with a chiral material or b) make a racemic mixture and separate the enantiomer you want.

Since the primordial ooze didn't contain a bunch of chiral organic molecules, I think it's best to say that it's a racemic universe.

(Of course, if we make a bunch of L-amino acids and metabolize the leftovers to carbon dioxide, humans might have some enantiomeric excess. :-) )

Offline sjb

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Re: Would the universe rotate plane polarized light?
« Reply #2 on: February 03, 2008, 03:32:16 PM »
There's a famous experiment (though I can't remember full details) whereby some nuclei spin a certain way rather than another in an electric field (not NMR related, if I recall correctly). Perhaps this is the origin of chirality..?

Offline adam

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