At this cold, low-energy state, the atoms collectively behave as a single quantum object. ![]() A BEC is a quantum state of matter where atoms in a cloud all condense to their lowest-energy state (see Core Concept: How Bose–Einstein condensates keep revealing weird physics). In 2016, Jeff Steinhauer, a physicist at the Technion Israel Institute of Technology in Haifa, finally succeeded, using a BEC as an analogue of space–time ( 2). So, following Unruh’s idea, physicists began looking for Hawking radiation around a system that was much more accessible-an artificial black hole. This radiation is impossible to observe in a real black hole out in space. Just outside of the region of a black hole where light can no longer escape, when a particle and its anti-particle spontaneously pop into existence, sometimes one falls into the black hole and its partner escapes and radiates outward. One classic case in point: Hawking radiation. In regions where the curvature of space–time, and hence the gravity, becomes extreme-near a black hole, for instance-the intersection of general relativity and quantum field theory causes weird things to happen to these fields. Light, for example, is an excitation of the electromagnetic field. Quantum field theory describes everything else embedded in this space–time, all of which are excitations of different fields. The geometry or curvature of space–time is actually gravity. Position a marble on this deformed sheet and it will roll down toward the bowling ball, emulating something like gravity’s pull. Any massive object will warp the fabric, much like a bowling ball placed on a taut rubber sheet. General relativity says that space–time is a deformable fabric that can be stretched and squeezed. ![]() Our modern understanding of the universe consists of two disparate theories: general relativity and quantum field theory. “We finally have something where we can get our hands dirty and…test our theories,” says Silke Weinfurtner, a physicist at the University of Nottingham in England. Thanks to a quantum fluid of atoms called a Bose-Einstein Condensate (BEC), scientists are simulating everything from black hole physics to the origin of the universe in the lab. Yet even he was doubtful that a lab-made “analogue black hole” would ever yield useful insights into the actual phenomena out in space.īut now, 50 years after Unruh’s riverine musings, analogue experiments are being used to study the interplay between gravity and quantum fields such as light. He suggested that this analogy could help physicists study the theory of black holes. Unruh argued that the fish’s screams are trapped by the river’s flow in much the same way that light is trapped by the gravity near a black hole ( 1). Image credit: Image credit: NASA, ESA, CSA, and STScI. This recently released James Webb Space Telescope image shows the galaxy cluster SMACS 0723 as it appeared some 4.6 billion years ago. Experiments using Bose-Einstein Condensates could help physicists better understand cosmological phenomena, including what happened to our universe in the first moments after the Big Bang.
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