One of the theories Stephen Hawking developed is that, despite sucking in even light, black holes do actually emit a type of radiation. Christened “Hawking radiation”, physicists have been hunting for it ever since.
Here’s how it works: A vacuum, according to quantum physics, is not actually empty. It’s got pairs of particles, and their anti-matter equivalents, popping into existence. In Hawking’s theory, a pair of protons pops up at a black hole’s event horizon, and while one gets sucked in the other escapes. Hence, a faint glow.
Yes, like Thunderdome.
The problem is that we haven’t been able to get close enough to a black hole to test this one out. Not that this is stopping scientists from trying… with, of course, lasers. And it also might make a laser itself, with some truly bizarre properties.
Needless to say, making black holes in a lab is impossible. If it weren’t, it would then be both stupid and expensive, and scientists, being neither morons nor possessed of limitless grant money, have instead been simulating the effects of a black hole’s event horizon.
In this case, it was a laser pulse being fired through a piece of glass to create an event horizon, which we’ll remind you is a point where events cannot affect an outside observer. I’ll let New Scientist explain the physics:
The pulse temporarily increased the glass’s refractive index as it traveled, creating a gradient in its wake that would slow a second pulse of light trailing it to a greater extent the closer the two got. Crucially, the second pulse would never be able to cross the first, turning the first into an event horizon from the point of view of the second.
And it generated more photons, meaning Hawking’s theory might be correct.
The laser shenanigans get even wackier when you drag simulated white holes into the mix. A “white hole”, which has never actually been seen in nature, wouldn’t allow photons inside of it. So, in the lab, if you put a simulated white hole next to (or inside) a simulated black hole, you get an incredibly weird laser. Since the light bounces between the two holes, it would theoretically be amplified… and also cycle through all the different wavelengths since it’s constantly being stretched and squished.
This doesn’t definitely prove Hawking’s theory… but on the other hand, science is inventing a laser powered by a black hole and a simulation of its reverse which may be too unstable to even exist in reality. This is why we love physics.