Monday, October 15, 2012

What is Dark Matter?

One of the more ominous sounding names in astronomy is dark matter. Today we're going to be shining some light on it.

Dark matter is an astronomical term for the theoretical matter that, together with dark energy, makes up ~95% of the universe. That might seem like a typo - it is not. The matter we can see makes up only 5% of the universe. The rest is invisible matter or related energy that is not in any way directly detectable.

Now, this doesn't mean that there is some unknown creature standing behind you like The Silence from Doctor Who - dark matter is a strictly astronomical phenomenon. Jan Oort was the first to provide evidence for the existence of dark matter. In 1932 Oort found that the movement of stars inside the milky way could not be correctly defined by the mass that could be seen.

Physics describes the movement of...stuff. We can throw a ball and calculate where it will land. Physics does not accurately describe all of the motion in the universe. There must be some mass affecting the movements of those stars, but there is nothing we can see that would have that effect. The following video does a good job of describing dark matter.

There are many possible explanations for what dark matter is, and some of those explanations are pretty weird. And, since I just mentioned something about a weird scientific theory it must be time to show Michio Kaku doing what he does best: being weird.

<rant>I think Michio Kaku is very unscientific, especially in his interactions with the media. He tends to propose the least probable, most sensational possibilities. Then he assumes that those possibilities are reality and makes another, even more sensational proposition based off his new reality and presents that to the media without any context. The video above is no different. He starts with the assumption that there are layered universes (He's pulling this, I assume, from an interpretation of quantum mechanics that is not widely accepted and he further distorts to fit his odd fantasies). Then, he makes the leap from there that dark matter is our universe interacting with that other universe.

The second problem I have with this video is that he says "of course, there are other theories to explain dark matter" and then gives another "out there" explanation. Sure, those two explanations are possible, and are based in legitimate theoretical physics. But why not mention a more down to earth possibility? Dark matter could simply be standard model particles that have yet to be discovered. Here's why I think he didn't mention that hypothesis - it's just not sensational enough for Michio Kaku.</rant>

I wasn't going to include that Michio Kaku video, mostly because I knew I couldn't avoid going into a Michio Kaku rant. Maybe that's an idea for another post: The Michio Kaku Rant (believe me, I have enough material). Michio Kaku may be right, dark matter could be an alternate universe interacting with ours. Until I have reason to believe that, though, I won't be betting on it.

What do you think? Is Michio Kaku right and I'm just closed minded? Head over to the Facebook page and leave a comment for this post.