They created a black hole, confirmed Hawking's prediction, and observed the inner horizon
Stephen Hawking predicted that Black holes Emit radiation like a black body. This emission, known as the Hawking emission, is constant over time and its temperature is determined by the Gravity certainly. Although Hawking's prediction is 50 years old, the temperature of the radiation has not yet been confirmed by observations. It will likely be extremely low, on the nanokelvin scale or less.
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Researchers at the Physics Department of Israel's Technion Institute of Technology have one acoustic black hole that is an analogue to real black holes. It is a system of which sound waves cannot escape.
In an in Nature physics published work, the researchers rejected the existence of the stationary Hawking radiation such a hole. The hole with a diameter of 0,1 mm was formed from 8000 rubidium atoms. Every measurement destroyed it, so the scientists - in order to observe the evolution of their black hole - had to recreate it, measure it and recreate it. They repeated the experiment 97.000 times, which corresponded to 124 days of observations and measurements. During this time, they managed to record 6 moments of spontaneous radiation and confirmed that their temperature and strength were constant. Professor Jeff Steinhauer, who led the research team, says the emission of the sonic black hole consists of sound waves, not light waves. Rubidium atoms move faster than the speed of sound, so the sound cannot reach the event horizon and escape the hole. But beyond that Event horizon the atoms move slowly, so that sound can also move freely.
Imagine that you are swimming against the current. If the current is moving faster than you, you will not be able to move forward, but will be pushed back. That happens in a black hole, explains the scientist.
Hawking believed that the radiation from black holes is spontaneous. Steinhauer and his team had already confirmed this in previous studies. Now they wanted to check whether this radiation is also constant, i.e. whether it does not change over time. Hawking radiation consists of one Pair of photons. One of them falls into the black hole, the other escapes it. So Steinhauer and his colleagues looked for similar pairs of sound waves. After finding them, they still had to determine whether there was a connection between them. In search of this, they carried out the aforementioned 97.000 repetitions of the experiment. The results achieved by the Israelis are in line with the Hawking predictions. Everything indicates that the radiation is stationary. Of course, it's a laboratory-generated sonic black hole, but the scientists believe that further theoretical work will lead to the conclusion that these results are applicable to black holes as well. Important questions arise from our study because we observed the entire life cycle of the corresponding black hole, i.e. saw how the Hawking radiation was created. In the future, someone might compare our results with what theories are about what is going on in Black holes say. Does the Hawking radiation really come from nowhere?