Dark matter teases scientists

If you’re interested in the reports about “dark matter” being found, this Daily Kos diary provides some useful context. The short version is that the vast majority of the universe doesn’t seem to be made of the conventional matter we can observe. About four percent is the stuff we can see, 25 percent is “dark matter”, and the rest is “dark energy”, a different kettle of fish again. But, at this point, we’ve never directly detected dark matter, which, I’m sure you’ll be surprised to learn, represents a waving red cape to expeirmental physicists! So they’ve built strange gadgets down various mine shafts which try and detect the echoes that occur when, once in a blue moon, a piece of dark matter crashes into a piece of regular matter. The trick is then to weed out the “signal” of dark matter crashes from the “background noise” from collisions caused by radioactivity in the rock surrounding the devices.

I’m no physicist, but from what I’ve been able to glean from the media reports, the experimental results being reported would have been the kind of thing that really irritated me – strong enough to convince you’re fundamentally on the right track, but not strong enough to be definitive, as this announcement from the experimental team itself explains:

In this new data set we indeed see two events with characteristics consistent with those expectedfrom WIMPs. However, there is also a chance that both events could be due to background particles. Scientists have a strict set of criteria for determining whether a new discovery has been made. The ratio of signal to background events must be large enough that there is no reasonable doubt. Typically there must be fewer than one chance in a thousand of the signal being due to background. In this case, a signal of about five events would have met those criteria. We estimate that there is about a one in four chance to have seen two backgrounds events, so we can make no claim to have discovered WIMPs.

In this situation, scientists generally have two choices – collect more data using their existing experimental design, or come up with a more powerful and accurate experiment. Fortunately for the patience of everyone concerned, it seems like two powerful dark matter detectors – an enhanced experiment from the same team, and an another independent experiment in Italy – are going to come online soon.

Isn’t science fun?