In 1974, Stephen Hawking hypothesized that the darkest gravitational pull in the universe, black holes, was not the dark black star astronomers imagine, but that it automatically emitted light – a phenomenon now called Hawking radiation.
The problem is that no astronomer ever observed the mysterious Hawking radiation, and because it was expected to be very faint, they may never do so. And that is why scientists today are making their own black holes.
This is exactly what researchers at the Technion Israeli Institute of Technology have done. They made an analogue of a black hole out of a few thousand Atoms. They were trying to confirm two of Hawking’s most important predictions, that Hawking radiation originates from nothing and that it does not change in intensity over time, which means that it is constant.
“The black hole is supposed to radiate like a black body, and it is basically a warm, steady emitting object InfraredStudy co-author Geoff Steinhower, Associate Professor of Physics at the Technion-Israel Institute of Technology, He said in a statement. “Hawking suggested that black holes are just like regular stars, which emit a certain type of radiation all the time, constantly. This is what we wanted to confirm in our study, and we did.”
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The gravity A black hole is so powerful that even light cannot escape from its grasp, once the photon or light particle passes the point of no return, which is called Event horizon. To escape these limits, a particle has to violate the laws of physics and travel faster than the speed of light.
Hawking showed that although nothing can escape the event horizon, black holes can still emit light automatically from boundaries, thanks to quantum mechanics and something called “virtual particles.”
As explained by Heisenberg The uncertainty principle, Even the entire emptiness of space is teeming with pairs of “virtual” particles that appear and disappear from existence. Usually these passing particles with opposite energies destroy each other almost instantly. But due to the intense gravitational pull at the event horizon, Hawking suggested that pairs of photons could be separated, so that a black hole would absorb one particle and the other escape into space. The absorbed photon has negative energy and gives off energy in the form of mass from the black hole, while the escaping photon becomes Hawking radiation. From this alone, given enough time (much longer than the life of the universe), a black hole could completely evaporate.
Hawking’s theory was revolutionary because he combined the physics of quantum field theory in general RelativityEinstein’s theory describing how matter is deformed Spare timeSteinhauer told Live Science. “It still helps people search for new laws of physics by studying the combination of these two theories in a physical example. People want to verify this quantum radiation, but it is very difficult to have a real black hole because the Hawking radiation is so weak compared to the background radiation of space.” .
This problem inspired Steinhower and his colleagues to create their own black hole – which is much safer and smaller than real holes.
DIY black hole
The researchers’ laboratory black hole was formed from a flowing gas of about 8,000 Rubidium The atoms were cooled to nearly absolute zero and held in place by a laser beam. They have created a mysterious condition for matter, known as Bose-Einstein capacitor (BEC), which allows thousands of atoms to work together in unison as if they were one corn.
Using a second laser beam, the team created a ramp from Potential energy, Causing the gas to flow like a rush of water down a waterfall, thus creating an event horizon where half of the gas was flowing faster than The speed of sound, The other half is slower. In this experiment, the team was looking for pairs of phonons, or quantum sound waves, rather than pairs of photons, that spontaneously form in the gas.
Steinhower explained that the phonon in the slower half can move against the gas flow away from the escarpment, while the phonon in the faster half becomes trapped at the speed of the supersonic flowing gas. “It’s like trying to swim against a stream faster than you can swim. [That’s] Just like being in a black hole, once you enter, it is impossible to reach the horizon. “
Once these phonon pairs were found, the researchers had to confirm whether they were interconnected and whether the Hawking radiation remained constant over time (if it were). This process was difficult because every time they capture an image of a black hole, it is destroyed by the heat generated by the process. So the team repeated their experiment 97,000 times, and it took more than 124 days of continuous measurements to find the correlations. Ultimately, their patience paid off.
“We showed that Hawking radiation was constant, which means that it did not change over time, which is exactly what Hawking predicted,” Steinhower said.
Researchers detailed their findings Jan 4 in the journal Nature Physics.
Originally published on Live Science.