Chinese scientists have proposed a new theory that combines two phenomena predicted by Albert Einstein: gravitational waves and forced radiation. The scientists suggest that these phenomena can sometimes merge to form rare and exotic “gravitational lasers,” opening up the potential for a new way to detect dark matter, one of the most elusive substances in the universe. The study outlining this theory can be found here.
Dark matter, a mysterious and invisible substance that is estimated to make up 85% of matter in the universe, is represented in the scientists’ model as axion particles. These hypothetical ultra-light particles possess significant quantum properties due to their small mass, behaving as both waves and particles. The wave nature of axions allows them to be captured by black holes, forming structures akin to atoms, with axions existing around black holes in a similar way to electrons around the atomic nucleus.
These “black hole atoms” are expected to be common throughout the universe. Additionally, black holes emit gravitational waves, which are fluctuations in the fabric of spacetime. If the wavelengths of these gravitational waves are suitable, they can excite the axions surrounding the black hole, resulting in a coordinated movement that leads to the emission of even more gravitational waves.
This process can create a cascading amplification similar to the functioning of a laser that emits focused gravitational waves in a specific direction. The researchers have named this theoretical phenomenon a “gravitational laser,” noting that it would be a new type of gravitational wave signal that is unlike any others previously studied.
Despite their potential power, gravitational lasers would be exceptionally rare, as specific conditions must align for the amplification to occur. Furthermore, most of these lasers would not be directed towards Earth, as they are emitted from black holes in random directions. However, the next generation of observatories designed to observe gravitational waves may be able to detect gravitational lasers. If this occurs, it would provide strong evidence for the existence of dark matter in the form of axions and confirm the astonishing nature of our universe, which permits the existence of gravitational lasers.