Annoyance at Inconvenient Facts
Yesterday, I gave a lecture on Galactic dark matter to my undergraduate class. Galactic Dark Matter is what we call whatever it is that's responsible for the observations of "flat rotation curves" of galaxies --- that is, the fact that once you get to the edge of the optical light of the disk, you can still measure how quickly gas clouds are moving from their emission lines, even well out beyond where the stars are all gone -- not just in our own galaxy, but in other galaxies out there, too.

If you've studied the planets, you know this is a problem, because the velocities of the planets *decrease* as you get further and further away from the sun, due to weakening gravity. If you want to keep the velocity constant, that means you have to keep adding mass at greater and greater distances -- well beyond where the stars end, and with no change in how this mass is distributed. The total mass implied is enormous, too, usually 10x that which we can see in optical star-light.

What was interersting about this lecture is that some of the students had barely concealed disgust at having to learn about something which was not well understood. I might guess that their response is simply "These Bozos. If they don't understand it, why do they teach it? Why don't they just spend the time, and figure it out?"
- posted by Unknown @ 3/23/2004 08:16:00 AM