Web edition: October 22, 2010
Print edition: November 6, 2010; Vol.178 #10 (p. 31)
Underground particle hunts
The dark matter experiments described in “Mining for missing matter” (SN: 8/28/10, p. 22) sound almost identical to those looking for neutrinos. Both are placed deep underground to help screen out background radiation, especially neutrons. How do particle hunters differentiate between neutrino hits and those by the putative dark matter particles? Also, the article makes it sound like investigators think there is only one type of [exotic] dark matter particle. Why is that when there is an entire zoo of normal matter particles and forces?
James Smith, San Jose, Calif.
Neutrinos, for the most part, would deposit much more energy than that expected for dark matter particles, though a few rare types of neutrino interactions could produce signals similar to those of dark matter particles. The sizes of the detectors have been very different, though, with dark matter detectors in the 10 to 100 kilogram range and neutrino detectors upwards of 100,000 kilograms. If much larger detectors have to be built to detect dark matter, then neutrino interactions may well prove to be a limiting background, says Dan Bauer of Fermilab. He adds that, in fact, “most theories do allow for an entire zoo of exotic particles. However, most of these particles will be either charged or decay into other exotic particles. The particle that makes up dark matter has to be neutral and stable to have survived for the entire history of the universe. Typically, this is taken to be the exotic particle with the lowest mass, into which all other exotic particles eventually decay.” —Ron Cowen
Seeking truth with science
Wow! Harold Kroto is a scientist (“Treat science right and it could help save the world,” SN: 8/28/10, p. 32) who can explain in lay terms what science is and what we need to do to help young people, who will soon be the ones dealing with the catastrophe our planet has become. Thank you. Spoken from a stance of firm, but insightful argument.
Nanci Watkins, Frederick, Colo.
Mr. Kroto’s comments highlight a serious problem in today’s culture. The loss of civility in our society has made it popular to advance our particular beliefs by attacking the failure of others rather than to focus on how we can cooperate with the larger community to accomplish our goals. We have developed many disciplines to help order our lives. Science is only a recent development. I think it is way too early for science to claim the mantle of The One and Only Ultimate Truth.
L.R. Davis, Margaretville, N.Y.