Should a person venture into a specific type of black hole, it may be able to provide them with infinite possible futures, according to a study published Jan. 17.
The study focused on the “fate of Cauchy horizons” — whether or not someone who approaches these horizons would survive based on the exchange of energy within and beyond the black hole. Peter Hintz, a UC Berkeley postdoctoral fellow in mathematics who contributed to the study, used a theoretical, highly charged black hole.
“Normally, when physics works as it is supposed to, if you know your position and velocity, and those of anything that might influence you, you can compute, at least in principle, what will happen,” said study contributor Aron Jansen in an email. “This is what breaks down at a Cauchy horizon; we simply don’t know what will happen (and) in that sense it can be anything.”
It is possible to travel beyond the event horizon of a highly charged black hole and enter the Cauchy horizon, according to Hintz. The Cauchy horizon is a point within a black hole beyond which one’s past does not uniquely predict one’s future.
Whether or not the Cauchy horizon is traversable has long been contested in the astronomical community, Hintz said. Crossing the horizon was recently thought to be impossible because of the horizon’s curvature strength, according to Jansen.
But within black holes of higher charge, this may not be the case — the expansion of the universe also decreases the strength of the disturbance causing the curvature, leading to an increase in the stability of the Cauchy horizon, Jansen said. He added that once someone passes the Cauchy horizon, researchers “cannot predict what happens.”
This loss of predictability within the Cauchy horizon was likened to the act of dropping a coin by another contributor to the study, Vitor Cardoso. In our universe, a coin dropped would always fall, but in a universe where the outcome of dropping this coin depends on when you drop it, it could fall in one second, one minute or never.
“This is what it means to (lose) predictability: it’s the end of science really!” Cardoso said in an email.
Albert Einstein’s general theory of relativity accounts for regions of space-time that cannot be fully predicted, such as the regions beyond Cauchy horizons, but the physical application of this study has yet to be explored, said campus physics professor Yasunori Nomura.
Another group has published a study in response to Hintz’s study that explores similar concepts relating to Cauchy horizons, but within spinning black holes instead of the theorized charged black holes used in Hintz’s study.
“We are at such an exciting moment that we need to keep an open mind and expect – and look for – the unexpected,” Cardoso said in an email.