Black Holes from Light?! – Impossibility Pushing Quantum Limits

Black holes cannot be created from pure light, as quantum physics would prevent their formation under any likely circumstances, according to a recent study. Typically, the formation of black holes involves matter, often resulting from the implosion of a star’s core at the end of its life cycle. However, matter is not strictly necessary for the formation of a black hole. Einstein’s general theory of relativity posits that black holes could theoretically be formed from concentrated energy alone.

A black hole formed purely from electromagnetic energy, or light, is termed a kugelblitz. This concept has intrigued physicists for decades. Nonetheless, generating a kugelblitz appears to be impossible, as theoretical physicist Eduardo Martín-Martínez and his team explain in a paper accepted by Physical Review Letters. They conclude that no known source in the current universe, whether artificial or natural, could produce such a phenomenon.

Despite its impracticality, the idea of a kugelblitz has captured the imagination of science fiction writers. For example, viewers of the Netflix series Umbrella Academy may recognize the term, which translates to “ball lightning” in German. In the show’s third season, a kugelblitz annihilates vast portions of existence.

In general relativity, gravity arises from the curvature of spacetime caused by matter. When a sufficient amount of mass is concentrated in one area, the spacetime can curve so intensely that it creates a region from which escape is impossible — a black hole. According to general relativity, energy and mass are interchangeable, meaning that energy can curve spacetime just as matter does. This concept suggests the intriguing possibility that black holes could form entirely without matter.

This idea has fascinated scientists, including theoretical physicist Juan García-Bellido of Universidad Autónoma de Madrid. He finds the notion particularly compelling when considering the potential for laboratory experiments. Researchers have speculated whether advanced lasers might one day create black holes in a controlled setting, and even proposed using a kugelblitz — a black hole formed from light — as a potential energy source for spacecraft.

However, calculations indicate that efforts to create a kugelblitz would be futile. Theoretical physicist Eduardo Martín-Martínez points out that such attempts would fall significantly short of success. Not only would they fail to create a black hole, but they wouldn’t even generate an object with the gravitational pull of Earth.

This limitation arises due to a quantum effect that comes into play when electromagnetic energy is extremely concentrated. According to quantum electrodynamics, a well-established theory, when light reaches high intensities, it results in the formation of particle-antiparticle pairs. These pairs, consisting of electrons and positrons (electrons’ antimatter counterparts), would escape the region, carrying energy with them. This escape of energy prevents the concentration needed to create a black hole from being achieved.

Creating a kugelblitz in a laboratory setting would necessitate light intensities that are over 10⁵⁰ times greater than the most advanced laser pulses currently available, according to calculations by the research team. This factor, which is a 1 followed by 50 zeroes, represents an almost unimaginably large value. Even in nature, the brightest quasars, which are the extremely luminous centers of active galaxies, are far too dim to achieve this feat.

The impossibility of forming kugelblitzes applies across a vast range of scales. It rules out the formation of extremely tiny kugelblitzes with radii as small as one hundredth of a quintillionth of a nanometer, up to those with radii of 100 million meters. Even beyond this range, Martín-Martínez argues, the likelihood of creating a kugelblitz remains exceedingly low.

However, Juan García-Bellido suggests a potential exception. He proposes that the early universe might have provided conditions conducive to the formation of such phenomena. Just after the Big Bang, the universe is believed to have undergone a rapid expansion, known as inflation. This inflation could have induced fluctuations in the curvature of spacetime, potentially causing light to collapse into primordial black holes. Although light alone cannot form black holes under its own gravity, the preexisting curvature of spacetime during the early universe might have enabled the creation of something similar to a kugelblitz.

1. ^{ONLINE NEWS} Conover, E. (2024, June 24). A black hole made from pure light is impossible, thanks to quantum physics. Science News. [Science News]
2. ^JOURNAL Álvarez-Domínguez, Á., et al. (2024). No black holes from light. Physical Review Letters. (in press) [Physical Review Letters]
3. ^JOURNAL Crane, L., & Westmoreland, S. (2009). Are black hole starships possible. arXiv (Cornell University). [arXiv.org]