INA - SOURCES
Now, in a black hole analog made of – ironically – light, a team of physicists led by Lorenzo Procopio of Paderborn University in Germany has observed an analog of Hawking radiation backreaction.
Their findings have been published in the journal Nature.
Black holes are the strangest, most extreme objects in the Universe. They're so incredibly dense that, once you get close enough, there's no escaping their gravitational pull.
Hawking radiation, first proposed by physicist Stephen Hawking in 1974, is black-body radiation predicted to arise from quantum effects near a black hole's event horizon. However, while Hawking radiation is a robust and widely accepted prediction of quantum field theory in curved spacetime, exactly how the energy is transferred from the black hole to the radiation has remained an open question.
The big problem is the same one we always have with black holes: Direct observation of Hawking radiation is currently impossible. In fact, the signal is expected to be so faint that we may never disentangle it from the background radiation that permeates the Universe.
This is where physicists get creative. Instead of studying black holes directly, they build laboratory systems that obey the same underlying physics. Some are surprisingly simple, such as water swirling down a drain to mimic the flow of spacetime around a black hole. Others use ultracold Bose-Einstein condensates or atomic chains to recreate the physics of an event horizon.
Previous experiments using this setup recreated Hawking radiation itself. This time, the researchers were looking for something subtler – the tiny backreaction that reveals how energy is transferred from the analog black hole into the radiation it emits. To understand backreaction, it might help to think about Newton for a second.
Previously, physicists thought the Hawking radiation seen in black hole analogs emerged through a complex cascade of optical interactions. Instead, the new results point to a single, direct process that naturally explains both the radiation and the backreaction.
"Our experiment and the underlying theory show that Hawking radiation is the result of a direct process, if the interaction between the radiation and the equivalent of the gravitational field is biquadratic," the researchers write in their paper. "Maybe astrophysical black holes radiate by a process as simple and direct as ours. The resulting backreaction would describe in microscopic detail how black holes evaporate."