Tuesday, November 18, 2014

Dark Matters: Using GPS to Find the Unfindable

Astrophysicists have a major problem. They’ve calculated the mass of the universe. They know how much stuff is supposed to be out there. But they can only find about 5% of it. The rest of the universe is composed of something that they call “Dark Matter” and “Dark Energy.” They know its out there because they can see how it bends the light coming to earth from distant stars. But they can’t directly detect it. It’s invisible to our sensors. If we look right at it, it disappears. So how can they find the dark matter that they know is there?

In a way, their problem is similar to one that an elderly woman I know has. Her vision isn’t what it used to be. She can no longer see black, blue, or red cars when she’s driving. “It’s pretty lucky that everyone drives white and silver cars these days,” she reminds me.  Both of my cars are maroon. She can’t see us, but she’ll find out we exist when she crashes into us.

Two scientists have come up with a creative new way to crash into dark matter so that we can ‘see’ it. They’re going to analyze data from the existing GPS satellite system. 

Every GPS satellite is equipped with an atomic clock. Atomic clocks tell time based on how frequently an element absorbs microwave radiation. Theoretically, every clock should be in sync, but the satellite clocks do fall out of sync as the circle the earth. Scientists know how  big these discrepancies should be. If they find a clock that’s fallen further out of sync than it should have, they’ll know that the GPS satellite has encountered dark matter.

The scientists tracking dark matter have an alternate theory about what it might be. Currently, most scientists think that dark matter is composed of actual particles. However, these particles don’t react to electromagnetic radiation like light, x-rays, or radio waves, so we can’t see them.  The scientists analyzing GPS data think that dark matter may not actually be ‘matter’ at all, but lumps, tears, and other imperfections in the very fabric of the space time continuum.  Sounds more like Star Trek than science class, doesn’t it?  It’s pretty cool.

So, what does this have to do with what you’re learning in class? Well GPS functions using basic properties of circles. Without coordinate geometry, there would be no GPS, and therefore no dark-matter detector. Plus, atomic clocks work based on microwaves, which we model using sine and cosine functions.   Math. You can’t escape it. But if you learn it, you might get to do really cool things some day.

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