A new warp-velocity experiment may finally offer an indirect test of famed physicist Stephen Hawking’s most famous prediction about black holes.
The new proposal suggests that by nudging atom to become invisible, scientists could glimpse into the ethereal quantum Glow that envelops objects moving at nearly the speed of light.
The glow effect, called the Unruh (or Fulling Davies Unruh) effect, causes the space around rapidly accelerating objects to appear to be filled with a swarm of virtual particles, bathing these objects in a warm glow. Because the effect is closely related to the Hawking effect — in which virtual particles known as Hawking radiation spontaneously appear at the edges of black holes — scientists have long sought to discover one as a clue to the existence of the other .
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However, it is incredibly difficult to discern either effect. Hawking radiation only occurs around the horrid chasm of a black hole, and achieving the acceleration required for the Unruh effect would likely require warp drive. Now a groundbreaking new proposal, published in a study April 26 in the journal Physical Verification Letters, could change that. Its authors say they discovered a mechanism to dramatically increase the strength of the unruh effect through a technique that can effectively rotate matter invisible.
“Now at least we know that there’s a chance in our lifetime to actually see this effect,” says co-author Vivishek Sudhir, an assistant professor of mechanical engineering at MIT and designer of the new experiment. said in a statement. “It’s a tough experiment and there’s no guarantee we would succeed, but this idea is our best hope.”
First proposed by scientists in the 1970s, the Unruh effect is one of many predictions emerging from quantum field theory. According to this theory, there is no such thing as an empty vacuum. In fact, every pocket of space is crammed with endless quantum-scale oscillations that, given sufficient energy, can spontaneously break out into particle-antiparticle pairs that annihilate each other almost instantly. And every particle – be it matter or light – is simply a localized excitation of this quantum field.
In 1974 Stephen Hawking predicted that the extreme gravitational force felt at the edges of black holes – their event horizons – would also produce virtual particles.
Gravity, according to Einstein’s Theory of the General relativitydistorted leisureso that quantum fields become more distorted the closer they get to the immense gravitational pull of a black hole singularity. Due to the uncertainty and weirdness of quantum mechanics, this distorts the quantum field, creating uneven pockets of differentially moving time and subsequent spikes in energy across the field. It is these energy mismatches that create virtual particles from seemingly nothing at the edges of black holes.
“Black holes are believed not to be entirely black,” said lead author Barbara Šoda, a PhD student in physics at the University of Waterloo in Canada. said in a statement. “Instead, as Stephen Hawking found, black holes should emit radiation.”
Similar to the Hawking effect, the Unruh effect also creates virtual particles through the strange merging of quantum mechanics and the relativistic effects predicted by Einstein. But this time, they’re not coming from black holes and general relativity-induced distortions, but from near-light speeds and special relativity, which dictates that time runs slower the closer an object gets to the speed of light.
According to quantum theory, a stationary atom can increase its energy only by waiting for a real photon to excite one of its own electrons. However, for an accelerating atom, fluctuations in the quantum field can add up and look like real photons. From the perspective of an accelerating atom, it’s moving through a mass of warm particles of light, all of which are heating it up. That heat would be a telltale sign of the Unruh effect.
But the accelerations required to produce the effect far exceed the power of an existing particle accelerator. An atom would have to be accelerated to the speed of light in less than a millionth of a second – while being subjected to a force of one quadrillion square meters per square second – to produce a glow hot enough for current detectors to see.
“To see that effect in a short amount of time, you would have to have incredible acceleration,” Sudhir said. “If you had reasonable acceleration instead, you would have to wait a gargantuan amount of time – longer than the age of the universe — to see a measurable effect.”
In order to make the effect feasible, the researchers proposed an ingenious alternative. Quantum fluctuations are made denser by photons, meaning that an atom made to move through a vacuum while being hit by light from a high-intensity laser could theoretically produce the Unruh effect, even at fairly small accelerations. The problem, however, is that the atom could also interact with and absorb the laser light to increase the atom’s energy level and generate heat that would drown out the heat generated by the Unruh effect.
But the researchers found another workaround: a technique they call acceleration-induced transparency. When the atom is forced to follow a very specific path through a field of photons, the atom cannot “see” the photons of a specific frequency, making them essentially invisible to the atom. By chaining all of these workarounds together, the team would then be able to test the Unruh effect at that specific frequency of light.
Making this plan a reality will be a difficult task. The scientists plan to build a laboratory-scale particle accelerator that will accelerate an electron to the speed of light while hitting it with a beam of microwaves. If they can demonstrate the effect, they want to conduct experiments with it, particularly those that will allow them to explore the possible connections between Einstein’s theory of relativity and quantum mechanics.
“The general theory of relativity and the theory of quantum mechanics are still a bit apart at the moment, but there must be a unified theory that describes how things work in the universe,” says co-author Achim Kempf, Professor of Applied Mathematics at the Professorship University of Waterloo said in a statement. “We have been looking for a way to unify these two major theories, and this work helps bring us closer together by opening up opportunities to test new theories against experiment.”
Originally published on Live Science.
https://www.livescience.com/unruh-effect-could-probe-quantum-gravity Warp drive experiment to turn atoms invisible could finally test Stephen Hawking’s most famous prediction