Tuesday, January 16, 2007

1/16/2007 - Dark matter, as the crow flies

Not too long ago, I passed through a town called "Crow Agency." If you said "Native Americans," you were right. Crow agency is actually the capital of "Crow Nation," indigenously known as Apsáalooke. Crow is an attempt at translation, but it's more likely that the eponymous bird is extinct.

I must say, I have never fully digested the nation within a nation status of the reservations. Crow Nation has a 3-branch government, much as our states and Federal government does. Are there any crimes which must be extradited to state of federal government? Surely the nation gets to take advantage of social benefits. How does taxation work?

One can imagine that, as I passed through Crow Agency, I found the answers to these and many other questions. In reality, I had a little time to browse through an article on Wikipedia and that will have to do.

On the home-front

While I have been having some difficulty counting my steps since I switched pedometers, I have had little trouble counting my eldest's steps on many recent days. Zero. Like others with his condition, he is prone to bleeding in his joints and muscles. Bleeding and swelling in his right thigh took him off line.

For the first day or two, he logged no steps and was okay with that, preferring to sit quietly on a couch. More recently, he has gone stir crazy. At first, he would crawl across the room when nobody was looking. As he has healed, he has taken to hobbling around, looking for all the world like he is looking for his cane.

He will be back in school soon and will suffer no long-term effects of the past week. Not all of his friends are so lucky. I count my blessings.

The Universe

On to a lighter topic -- dark matter. Dark matter is a perennially fun topic for hacks such as myself. It's just fun to say. It sounds like the intersection between Star Wars and Harry Potter. I heard an excellent discussion of dark matter on Astrocast (but more about that in a minute). The two things you have to know to enjoy the upcoming observation are [1] that dark matter is something we can only detect indirectly, through its effect of non-dark matter and [2] that dark matter is just a euphamism for "stuff we don't know about."

To the first point, dark matter is called dark matter because we can't see it. It emits no particles that we can interact with in the way we interact with those particles emitted by, say, Barack Obama. You can imagine astoronomers as a little like a driver with 20/20 vision who just can't see stop signs (and you know who you are). As the astronomer drives down the road, he notices an oddity, that cars seem to pause at certain intersections, and infers the existance of stop signs. Similarly, the astronomer looks at the sky and notices stars rotating too slowly, or whatever, and infers the presence of matter that he cannot detect.

To the second point, you have to think of the universe as a grand tally. We more or less know how much mass the universe has, but we can only 4% of it. We call the rest dark matter. Or weirder yet, dark energy. As we discover things we didn't know about (e.g. that neutrinos have mass) we move some of the chits from the "dark matter" category into the "stuff we know about" category.

Now here's the observation, which really concretizes the whole notion of dark matter for me: Nepute was once dark matter. Oh, Neptune is pretty much the same Neptune it ever was, but there was a time when we couldn't find it, but we inferred its existance from the odd wobbles that Uranus took. Then our telescopes (and math) got better and we found Neptune. And then Pluto. And then the ice ball formerly planetized as Pluto. I'm still bitter. But at least I admit that I'm wrong.

Anyhoo. So dark matter: Lots of little Neptunes or a disturbance in the force? You be the judge.


So one of my favorite podcasts used to be Slacker Astronomy. I say used to be, because the team split up and formed the nucleii of two new podcasts: Slackerpedia Galactica and Astronomy Cast. Left with no choice, I started listening to both. And I enjoy both.

SG is, in many ways, an expanded version of SA. They still do some scripted skits, they walk through recent news and they now have an increased staff, including a tenured professor, to expand the range of anlaysis that they are able to provide. As an added bonus, Aaron has come out from behind the scenes, which I think improves the chemistry. Aaron, who lives too close to comfort, would probably hunt me down and shoot me if I didn't mention their awesome Slackerpedia which is based on the Wiki and provides excellent articles about all things Astonomical.

Astronomy Cast is a to Slackerpedia what the New York Times magazine is to the New York Times. It is a 30 minute discussion of something that SG might have discussed in 7 minutes. On their self-proclaimed "fact based journey through the cosmos" they hit such topics as planamos and dark matter (so far). Additionally, you might consider giving AstroCast a listen for the sole purpose of hearing one of the loveliest voices in the podosphere (Pamela's). It's a nice touch that Travis from SG supplied the music for AstroCast.

9,700 pitiful steps today. Cheers,


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