Friday, November 07, 2008

How studying dark matter helps society

One question we astronomers get asked a lot is, "how does your research help society?" It's a fair question, but it is often hard to answer. The connections are often not direct; it's not like my understanding of the life of a white dwarf star is going to cure cancer. But there are indirect connections. Many years ago, I worked on an X-ray astronomy project. The mathematical tools that another astronomer had developed for the project were useful for mathematically similar problems, and that astronomer and some medical researchers found that the same tools were useful at diagnosing a specific kind of dangerous heart arrhythmia.

Anyway, on our daily astronomy preprint server (where research articles are posted before they actually appear in our professional journals), a dark matter researcher named Leo Stodolsky posted an article on the "practical applications of dark matter research."

Dark matter is a mysterious substance that interacts with normal matter (the stuff out of which we are made) primarily by gravity. There are many ideas as to what dark matter could be, some of the favorite models are weakly interacting particles, which means subatomic particles that can interact by gravity and by the weak nuclear force, a force of nature that works only on subatomic scales and is, well, weak.

If dark matter can interact with itself and with normal matter by the weak force, then very sensitive detectors cooled to temperatures near absolute zero (about -460 degrees Fahrenheit) might be able to detect dark matter. The atoms in these really cold detectors have virtually no energy. So, if a dark matter particle passing through the detector interacts with one of these atoms, the dark matter will give the atom some energy. The heat from that tiny amount of energy can be measured (or this is the idea). Several physics groups, including the group in which Dr. Stodolsky works, have built these detectors and are trying to "see" dark matter.

As of yet, no one has definitively seen dark matter. This is because these very sensitive detectors have lots of sources of energy besides dark matter interactions (like radioactive decay from radioactive elements in the detector itself). So, most of the time these teams are tracking down and eliminating this noise, which allows the scientists to get closer and closer to the point at which they think they'll be able to see dark matter.

In his paper, Dr. Stodolsky points out that, as he has been working on his detector, he's discovered some uses for his work besides just dark matter. For instance, an early version of the detector kept getting microscopic cracks in it because the detector was pinched too tight in one spot. When the cracks appeared, they released energy that looked a lot like the seismic energy released during earthquakes. So, it may be possible to understand some aspects of earthquakes in the laboratory, where microscopic "earthquakes" could be produced on demand.

A second story related by Dr. Stodolsky involves a different detector. Again, it was very sensitive at measuring energy. In biology, scientists often want to study the chemical makeup of individual proteins. These detectors are sensitive enough to be able to measure the energy of different protein molecules and tell them apart with much higher precision than earlier biological instruments. Using a contraption containing one of these detectors, the physicists and biologists were able to build a commercial detector that can help diagnose certain types of liver diseases.

Both of these inventions came out of studies of dark matter, and were completely unexpected and unanticipated byproducts of research!

I could give other examples (but I won't) of astronomy research that ends up having practical applications. We don't usually expect these applications at the beginning of a project, and they are rare. But it does allow us to claim that astronomy is good for more than just understanding the Universe in an abstract sense -- it can, and sometimes does, lead to useful applications back home on Earth.

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