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Science, WIMPs and Dark Matter

BY Jonathan Strickland / POSTED June 5, 2013
Hammerbrook - City can this really be true?
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Courtesy of NASA, ESA, M. Postman (STScI), and the CLASH Team This image of galaxy cluster MACS J1206.2-0847 shows light being warped by what is believed to be the gravitational force of dark matter. | Courtesy of NASA, ESA, M. Postman (STScI), and the CLASH Team

I am consistently and constantly amazed at how phenomenal the universe is. It’s clear that we only know the tiniest fraction of a percent of all there is to know, and that’s exciting. Due to the limitations of the human brain, we may never be able to know all that we otherwise could if our grey matter were just wired a little bit differently. This is about as philosophical as I get.

Science is the methodology we rely upon to try to learn more about the universe. It’s not necessarily perfect but it has a specific set of rules that make it the most reliable method we have available to us. A really simplified definition of science would be a method in which we test ideas to see if they are valid using rigorous approaches that are replicable and reliable.

Scientists understand that their hypotheses are falsifiable — that means that given the right data and circumstances, those ideas can be shown to be incorrect. For example, gravity is falsifiable because if you were to let go of an apple and it flew up into the sky it would defy what we thought of as a confirmed phenomenon. On the other hand, if you claim there is an invisible, undetectable gnome who always walks three feet behind and to the left of you, there’s no way to prove that statement is false. It’s not science.

I say all that because of this post I read on LiveScience. It’s a great story: The Fermi Gamma Ray Space Telescope detected some light from the center of the Milky Way galaxy. There’s a chance that this light wasn’t actually present — that the detection was actually the result of an instrument error or other problem. But if this gamma radiation is actually there, it may indicate the presence of something that has been hypothesized but never directly observed: dark matter.

Dark matter is really a placeholder. Scientists can see light bending in space as if affected by a gravitational force. Stars zoom around at a different speed than they theoretically should based upon our knowledge of how gravity works and the amount of matter we’re able to observe. Dark matter, then, is something that has mass and can affect gravity but has remained undetectable by any other means so far. We can even map out where it is based upon the way light behaves in space, but we still can’t see it.

So what makes up this invisible stuff? We aren’t sure, but one possibility is a type of hypothetical particle called a weakly interacting massive particle (WIMP). These WIMPs could create gamma radiation as they bang into one another, annihilating themselves. We wouldn’t be able to see the WIMPs but we’d be able to detect the radiation their collisions would generate.

So is that what the Fermi telescope saw? Maybe. Or it might be that it’s just an error or a meaningless blip. That’s why we would need to direct the telescope to look toward the center of our galaxy — where these interactions between WIMPs are more likely to occur — and see if we can suss out if there’s some wimpy collision going on.

Why is that important? It would help us confirm that dark matter is really made up of WIMPs — only one of several candidates for what dark matter might actually be. And it would give us more information about this phenomenal universe we’re in.

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