Reading the headline at Science News earlier, I was pretty sure this bit of research would be about how DNA might be used as a calculation tool in the dark matter hunt. Because that’s a thing: DNA computers. But, no, the proposal offered at the yearly New Horizons in Science meeting by University of Michigan theoretical physicist Katherine Freese is to use DNA strands as the key components of an actual detector, kinda like the water vapor that filled the early cloud chambers used to chart cosmic rays. The idea is to get dark matter particles, or one theorized form of it, to leave a trail through a forest of DNA strands like big game tromping through underbrush. But instead of random vegetation, you have tightly ordered molecules.A quick refresher: dark matter is the stuff that makes up about 23 percent of everything in the universe. We don’t know what it is exactly because dark matter is very difficult to observe directly — so far, we only have indirect observations made by measuring its gravitational influences on nearby cosmic stuff. Scientists in a number of places around the planet are currently hunting for dark matter particles in labs deep underground, shielded from interfering “normal” matter sailing through the atmosphere. (Though, it bears repeating that normal matter is actually the smallest category of stuff in the universe and is, thus, abnormal.) Most of these experiments are designed around waiting for collisions between dark matter and normal matter and looking for post-collision particle scraps moving through liquid xenon.Freese’s idea is a bit different, taking advantage of what we think we know about the direction dark matter particles should be heading when they arrive on Earth. Researchers believe our galaxy is surrounded by a halo of dark matter in the form of WIMPs, or weakly interacting massive particles. As the Sun orbits the center of the galaxy and Earth orbits the sun, there should be a variable “wind” of particles arriving as a result of Earth’s changing position in relation to the WIMP halo.From Science News:Freese and her colleagues’ proposed detector, which would be sensitive to these fluctuations, consists of a stack of thin gold sheets with single-stranded pieces of DNA hanging from them. When a WIMP smacked into the nucleus of a gold atom, the nucleus would whiz off, cutting through the DNA at specific locations in the strands.
Scientists would then collect and sequence the DNA to reconstruct the path traveled by the nucleus, and by extrapolation, that of the WIMP. If the detector spotted the daily fluctuation and the particles’ paths proved consistent with the WIMP wind’s direction, it would be compelling evidence that the signals came from dark matter.The advantage is that DNA has a much higher resolution than current detectors and, thus, DNA-based detectors could be much, much smaller. The idea also hasn’t been tested out yet, and maybe by the time it comes to fruition, some other researcher working deep in an abandoned mine somewhere will have already nailed the stuff to the wall. But the idea that this evolution-supplied material could be the best thing for the job is pretty neat nonetheless.Reach this writer at michaelb@motherboard.tv.
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