There was an article about physics blogs a little while back in Physics World, that didn’t mention me by name, but did link to the Steelypips site. It mostly talks up the informal information exchange side of things.
In that spirit, here are some things I found via physics blog (mostly through Mixed States (after the cut):
If you were wondering when to expect your pony, Steinn Sigurdsson at Dynamics of Cats has an exhaustive analysis of the budget requests of various science agencies (start with that link, and work your way up through the more recent posts). Verdict: no pony for you!
Former Quantum Diarist Gordon Watts comments on George Deutsch, and provides a new bit that I hadn’t seen before: a link to a collection of excerpts of Deutsch’s student writing. They’re about what you’d expect.
In Actual Science News, there’s been a bit of excitement in astrophysical circes regarding some measurements that purport to determine the temperature of dark matter. P.P. Cook is your one-stop shopping spot for links to the original sources.
Unfortunately, those original sources are all stories in the mass media, not scientific journals, or even scientific preprints, so take it with a grain of salt. If the observation holds up, though, expect this to be very big news, because the temperature they report is several orders of magnitude higher than previously expected. Most theories I’ve heard (including a terrific colloquium talk last week by Kristine Spekkens) emphasize that dark matter is cold– a few Kelvin or less. The new observations claim a temperature of about 10,000 K, or a bit hotter than the surface of the Sun. Explaining that, if it holds up, will take some work.
(This is not my area of research, but this year’s coloquium coordinator is an astonomer working on dark matter, so I’ve heard a lot of talks about dark matter in galaxies…)
The link to Deutsch’s articles also had the word ‘scienciness’, which aptly describes the Bush admininstrations’ approach to science, just as ‘truthiness’ serves the purpose in other situations.
Clueless.
Regarding the temperature of Dark Matter… how (in current theory) is dark matter described phenomenologically? I got the feeling that fundamentally it was very plasma-like, or fluid-like. To me (I am not a physicist!), this type of dynamic has at least the possibility of having really high temperatures.
Of course, I’m completely talking out of my realm… anyone care to smack me around a bit?
Jeebus-
Dark matter is usually treated like a non-interacting gas. The usual fluid dynamics applies.
I would have to see a scientific journal article on this, because the news articles seem potentially misleading. Take the following statement from the BBC article:
Theories predict that dark matter is “very” cold (order of CMB temp of 3K) before gravitational collapse (that few mm/s seems way too low), but any gravitational collapse actually heats the dark matter. For WIMP type dark matter (particles of masses around 1-100 GeV), the most commonly assumed (and simplistic) model of a galaxy halo is a simple isothermal sphere with a velocity dispersion about the same as the rotation velocity of the galaxy. For the Milky Way, that is about 300 km/s; do the math on that and we are talking about large temperatures. 9 km/s and 10,000 K are not actually very large numbers.
The numbers given in the article do not seem all that unexpected for the dwarf galaxies they seem to be looking at, except for the mass scale they are talking about. That is a potentially interesting result.
I should point out another potential source of confusion. The use of “cold” and “hot” with regards to dark matter are meant to imply non-relativistic and relativistic speeds, respectively, and not the hot and cold we are accustomed to weather wise. 10,000 K and even 1,000,000 K for a 60 GeV particle are non-relativistic and, hence, “cold”.
Do I understand correctly then that the newspaper article is confused in calling 10,000K “hot”? Does that mean that the quoted researchers found dark matter not to be hot in the sense of relativistic, but that they were using “hot” to mean simply faster than a few mm/s?
Strictly speaking, the articles don’t call the dark matter temperature they measure “hot.” They describe it as “tepid,” which is what passes for wit in the physical sciences.
This ‘science by press release’ is a rather suspect tactic. It’s very hard to judge the merits of the work this way, as opposed to if they had gone the traditional route of publishing in a scientific journal at the same time they release their findings to the press.
Any idea why this team chose this approach for what they claim is such a significant finding?
Any idea why this team chose this approach for what they claim is such a significant finding?
Scrambling for funding?
Would one expect any radiation from dark matter of this energy or higher?
You wouldn’t expect to see any radiation from dark matter except if they can annihilate with each other (which is expected to be a rare occurance).