Sometimes coming up with nothing in science can advance human knowledge, as long as your experiment works well enough to actually rule something out. A good historical example is the Michelson-Morley experiment, which ruled out the existence of “ether” – a substance that was supposed to provide an absolute frame of motion and rest. Special relativity rests on the idea that there is no absolute state of rest, and therefore no ether.
A number of science writers last week took on the challenge of explaining why it mattered that an early run of the world’s most advanced dark matter detector did not find certain types of particles that theorists had proposed as candidates. Eventually these experiments should narrow down the field of possibilities.
One failing in all these stories was the lack of explanation for why scientists are so convinced dark matter exists in an exotic form. Yes, many people explained that we see the effects of its gravitational tug on stars and galaxies, but nobody saw the need to answer a crucial logical question that many intelligent lay readers would be asking: Why do they think it’s some never-before-observed form of matter and not just dust or stray planets or rocks or something?
The answer is fascinating and not that hard to explain in a couple of sentences. It has to do with the detail with which cosmologists have come to understand the big bang, including just how many bits of garden variety matter (baryons) were produced.
Despite that shortcoming, there were some nice stories out there on the importance of finding nothing:
Here’s Adam Mann at Wired.com
“Basically, we saw nothing. But we saw nothing better than anyone else so far,” said particle physicist Daniel McKinsey of Yale, a member of the LUX collaboration.
It might appear strange to the rest of us, but a null finding is actually encouraging for physicists, who will use the results to set stringent limits on what kind of dark matter they might expect to find in the future. It also seems to rule out the results of several previous experiments, which had seen hints of what might be dark matter.
“Something that they had thought was in play is being kicked off the field,” said physicist Richard Gaitskell of Brown University, who also works on LUX.
Another excellent story comes from Tom Griffith at the Rapid City Journal, with an emphasis on the local angle and the nature of the experiment. He covered the science with more sophistication than most of the national publications could manage.
But by far the best story of any I read was the one by Dennis Overbye in the New York Times. This piece is a real story, each paragraph propelling readers onward. Here’s how he starts:
The former Homestake Gold Mine in Lead, S.D., has a hallowed place in the history of physics as a spot where nothing happens.
It was there, in the 1970s, that Raymond Davis Jr. attempted to catch neutrinos, spooky subatomic particles emitted by the sun, in a vat of cleaning fluid a mile underground and for a long time came up empty. For revolutionizing the study of those particles, he shared the Nobel Prize in Physics in 2002.
It’s an opening that promises a story rich with background and context, and the story delivers. My one quibble was a statement, attributed to no one, that the theory known as supersymmetry is “much-hyped.” What if it turns out to be backed up by experiment? Seems like then it would be a big deal. Perhaps some people are saying it’s hyped, but Overbye owes us some explanation here.
Other people covered the story as well. Here's AP, Space.com, the Wall Street Journal and Nature.
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