Interstate Traffic Jams and Galactic Structure

Last fall I drove up to Williamsburg and Washington with a couple of my kids. It was a pleasant trip, except for the stretch of I-95 between Richmond and Washington. There, on a sunny Sunday afternoon, we encountered a series of sporadic traffic jams. Each time we hit a slowdown, I expected to see an accident by the side of the road, but no such accident ever appeared. Instead, the traffic simply speeded up again a few miles down the road for no apparent reason. So what was the origin of this mysterious roving I-95 traffic jam? I suspect it's the very same thing that produces these beautiful structures in spiral galaxies:

Is Dark Matter Hiding Right Under our Noses?

Consider the lowly neutron. Neutrons make up about half the mass in your body, but they contribute nothing to chemistry. They just lounge quietly inside the atomic nuclei and get carried along for the ride. But this past week, two physicists at the University of California, San Diego, suggested that the neutron might be the key to unlocking the mystery of dark matter in the universe.