The bouncing gas
When two clouds of gas meet, they normally pass right through each other. But now, MIT physicists have created clouds of ultracold gases that bounce off each other like bowling balls, even though they are a million times thinner than air. This marks the first time that such impenetrable gases have been observed.While this experiment involved clouds of lithium atoms cooled to near absolute zero, the findings could also help explain the behavior of other strongly interacting systems such as neutron stars, high-temperature superconductors and quark-gluon plasma: the hot soup of elementary particles that formed immediately after the Big Bang. A paper describing the work appears in the April 14 issue of Nature. Two gas clouds (one red and one blue), each a million times thinner than air, are seen to completely repel each other under the influence of strong, quantum-mechanical interactions. Such gas clouds can model matter under extreme...