Inside his lab in Israel, Jeff Steinhauer crafts microscopic black holes. These objects are but humble specks, lacking the spaghettifying suction strength of an actual dead star. But Steinhauer, a physicist at the research university Technion, assures me that he’s constructed them mathematically to scale. Zoom in far enough, and you’ll see a miniature event horizon restaging the drama of a true black hole.
Each of these tiny blobs consists of 8,000 rubidium atoms that Steinhauer has cooled to near absolute zero and then swished around with a laser. Collectively, the atoms weigh about a thousandth of a single bacterium.
At a real black hole, gravity is so strong that once you cross its event horizon, not even light can escape. Steinhauer’s replica, technically called a Bose-Einstein condensate, has the same property but for sound waves. Past a boundary in the blob, no sonic vibrations can escape.
This work is an example of a new type of scientific experiment called a quantum simulator. Quantum simulators are small-scale replicas of complicated natural phenomena whose behavior obeys the rules of quantum mechanics. It’s the quantum equivalent of building a model airplane to predict how a real jet would fly, says physicist Ignacio Cirac of the Max Planck Institute for Quantum Optics.
Steinhauer, for example, learned from his quantum replica that it emitted sonic waves analogous to the light waves that real black holes are supposed to produce, known as Hawking radiation. Because real black holes are so difficult to study, and Hawking radiation is so dim, researchers had never observed the radiation in outer space. But the sound waves in Steinhauer’s simulation offered some support to that idea.
In another experiment involving cold atom blobs, physicists at the University of Chicago simulated a different extreme environment—what it would be like for a person to accelerate to billions of g’s. Theory predicts that a person accelerating this fast should be able to see objects emitting light, called Unruh radiation.
It’s impossible to accelerate a person that much in the lab; for one, they’d crash into the walls almost instantly. So the researchers made the treadmill version of the scenario—everything stays in place, but they manufacture the illusion of the lab accelerating past their atom blob. “It’s like we put ourselves in a flight simulator,” says physicist Cheng Chin of the University of Chicago. “You think you’re driving a jet, but you’re really just in the laboratory.”