On 25/04/2011 1:42 PM, Chris L Peterson wrote:
On Mon, 25 Apr 2011 11:17:14 -0400, Yousuf Khan
wrote:

Actually, Sam, this study is debunking the density wave theory.

I think "debunk" is the wrong word. The analysis doesn't strongly
argue against the density wave theory (which itself has some direct
observational support), but rather, demonstrates a simulation that is
able to produce arm structure via a different mechansism.

All very interesting and useful. And I think it is far too early to
say with any confidence that either theory is entirely right or wrong,
or that galactic arms aren't the product of multiple causes.

Well, actually, the density wave theory wasn't conclusively proved yet
to call it debunkable, true. But somehow the density wave theory had
become the favoured theory. We won't know for sure until we set up a 1
million year observational survey to see how stars move with the arms.
Perhaps we might get sensitive enough observations in 100,000 years to
make the call, but I don't know.

Yousuf Khan