High energy collisions between fast- moving atomic nuclei create Little Bangs—small regions of extremely high temperature. We calculate that in such regions the “ether” or “condensate” of quark-antiquark pairs that normally fills space vaporizes. As the fireballs expand and cool the ether heals, releasing energy. It is an interesting challenge to find traces of those dramatic happenings in the complicated debris. (Courtesy of Brookhaven National Laboratory)

Suppose some species of deepwater fish, that never break the surface, evolved to become more intelligent, and started to do theoretical physics. At first they might formulate the laws of motion for the world they live in, and presumably would take for granted, namely the laws of motion for bodies moving through water. Now we humans know that the laws of motion for bodies moving through water are complicated, and they are not the most basic laws. The laws of motion for bodies moving through empty space are the most basic laws, and you can deduce the more complicated laws for bodies in water by applying those more basic laws to water molecules (deriving hydrodynamics) as well as the bodies moving through them. Eventually the fish-physicists would realize that they could get a nicer version of mechanics by assuming that they lived in a medium—call it water—complicates the appearance of things. In this way, they’d realize that what they hitherto regarded as “nothingness,” their ever-present environment, is actually a material medium. And then they might be inspired to do experiments to try to make ripples in the medium, to find its atoms, and so forth.

Well, we’re like those fish. Human-physicists have discovered that we can get nicer, simpler accounts of how particles behave by assuming that we’re embedded in a medium, whose presence complicates the appearance of things.

continued on page 65 High energy collisions between fast- moving atomic nuclei create Little Bangs—small regions of extremely high temperature. We calculate that in such regions the “ether” or “condensate” of quark-antiquark pairs that normally fills space vaporizes. As the fireballs expand and cool the ether heals, releasing energy. It is an interesting challenge to find traces of those dramatic happenings in the complicated debris. (Courtesy of Brookhaven National Laboratory)

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