A map of possible dark matter distribution in a cluster of galaxies

If you still worry about the millirems of radiation you get at the dentist’s office, you might soon have yet another reason to gobble down an Ambien at bedtime. A paper just posted to the arXiv physics preprint server outlines the amount of dark matter that all of us are exposed to on a regular basis.

Dark matter—the missing mass in the universe, estimated to make up 80 percent of the known there there—may collide with a “70 kg lump of meat made largely of oxygen, hydrogen, carbon and nitrogen,” as a post at Technology Review’s Physics arXiv blog put it—30 times a year for one plausible candidate for a dark matter particle and nearly once a minute for a more lightweight version.

The researchers don’t make any estimate of the health impact, which is contingent on the energy and motion of an oxygen or hydrogen nucleus—the most likely targets—after being broadsided by a shot of the dark. “It must surely represent a tiny risk per human but what are the implications for the population as a whole? That would be an interesting next step for a biological physicist with a little spare calculating time,” the blog post notes wryly.

It’s a little early to reach for the pill bottle, actually, as the measurements of the spooky stuff are still a bit on the shaky side, to say the least. The estimates made in the paper by two physicists—Katherine Freese of the University of Michigan and Christopher Savage of Stockholm University—are based on a few experiments that have furnished suggestions of the prevalence of what are endearingly called WIMPs, Weakly Interacting Massive Particles.

But don’t sweat it, more research is needed. These experiments have not even actually found the dark substance, only “intriguing hints” of it. As the researchers themselves acknowledge, WIMPs could be supersymmetric particles, or Kaluza-Klein particles “motivated by theories with extra dimensions.” Not enough for the insurance actuaries to fire up the spreadsheets just yet.

Stay tuned to this channel for periodic health advisories.