![60-Second Space show](https://d3dthqtvwic6y7.cloudfront.net/podcast-covers/000/030/805/small/60-second-space.jpg)
Summary: Dark matter doesn't usually collide much with itself or with ordinary matter, but it appears to be uncharacteristically clumping in the galaxy cluster A520. John Matson reports
Summary: Dark matter doesn't usually collide much with itself or with ordinary matter, but it appears to be uncharacteristically clumping in the galaxy cluster A520. John Matson reports