- If spacetime (and gravity) is powered by energy alone, could you energize a black hole?
- Unfortunately, due to two major features of quantum cosmology, you could not.
- Electromagnetic fields and colliding photons each create new particles and shed energy.
In new preprint research, scientists work through a counterintuitive but compelling idea: could you focus enough light in a specific way to create a black hole? These researchers have walked through the possible scenarios, and they’ve concluded that it, sadly, isn’t possible. But until the research is peer reviewed and repeated, we can still hope someone will take this “impossible” as a challenge. (The answer is still no, though.)
The authors introduce their idea by explaining something important about the universe. Since energy is what defines space and time, gravity—something that contributes to space and time—should be able to exist without the universal requirement of mass. Scientists are exploring the ways it may be possible to have massless fields that, nonetheless, cohere via gravity, the authors explain. These are called geons.
So, how does this tie back to black holes? Well, if black holes are defined by their incredible gravity, and gravity could exist as a result of energy alone, you might be able to form a “massless” or virtually massless black hole using only electromagnetic radiation. This theoretical object is called a kugelblitz—the German word for ball lightning. And while ball lightning in real life is considered unverified and unexplained so far, kugelblitze are hotly debated on a more basic level.
If a kugelblitz were to exist, there’s a catch-22 built into the idea. Even at their very lowest possible energy levels, they would spray out particles and lose that energy, essentially removing themselves from existence just as they got started. One way this happens, the researchers explain, is via the Schwinger effect—a quantum phenomenon where an electric field causes the creation of particles called electron-positron pairs (electrons and positrons have the same mass, but opposite electrical charges).
The other quantum phenomenon at play is called the Breit-Wheeler process—when two photons strike each other and an electron-positron pair is created. Both of these processes explain ways in which pure electromagnetic radiation can appear to lose energy over time and distance. In reality, these newly created particles are believed to be subtracting that energy one electron and positron at a time (thanks, e=mc2).
In the paper, the researchers work through the math in detail. That includes calculations on black holes existing on the tiniest nano-scales all the way up to one so large it would take a bright quasar 10 thousand years to generate it.
For those who love a little wiggle room outside a definitive “impossible” label, that’s where you’ll find it—a black hole smaller or larger than this enormous range. The authors don’t claim to know for sure that a black hole created by electromagnetic radiation is impossible across all possible parameters.
But that’s an exceptionally extreme and tiny category—not really enough room to wiggle in at all. “[E]ven if one only trusts the estimations of the model to some extent, the predicted orders of magnitude are so vastly unrealistic as to make this study a very compelling argument against the viability of kugelblitze, both artificially or as a naturally occurring phenomenon,” the researchers conclude.
Looks like we’ll just need to keep looking for the next wild cosmic phenomenon.
Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all.
