We raised cyclic causal loops and traveling back in time as examples of ideas which are motivated by science fiction.
Research of gravity seems to have different standards from other branches of science. If someone working in biology would claim that a certain animal can create an infinite force and travel back in time, people would be highly sceptical.
But a gravity researcher can claim that if we make a small mass to rotate, and compress it to a small space, then the mass can exert an infinite force at the horizon, and one can travel back in time inside it. The mass might even open a road to another universe through a white hole.
There is no empirical evidence whatsoever that infinite forces can exist, or that there are white holes. Traveling back in time seems to be logically contradictory, or would require incredible fine-tuning, so that there would be a loop in a complex sequence of events.
The physics that we know does not allow infinite forces, it does not allow traveling back in time, and matter cannot disappear from a closed box.
In gravity research there also exist motives that could be called religious. Hawking radiation is the prime example. People do not like the idea that objects can fall into a black hole and stay there forever. They hope that there is a "rebirth". Matter magically rises up from the black hole, and is free to fly again.
The derivation of Hawking radiation in Hawking's original 1975 paper is extremely speculative. It is based on a claim that the horizon of a black hole is almost infinitely strong, and can in a mysterious way create radiation from nothing. No one has been able to come up with a derivation which would be convincing.
If someone would present an idea like Hawking radiation in electromagnetism, few people would take it seriously. But many gravity researchers and string "theorists" firmly believe that such radiation exists. It exists even though it creates the black hole information paradox and seems to break unitarity. They rather break physics than give up on the idea of a rebirth.
Creation of new universes from black holes is another idea which sounds religious. It would be nice if a new universe were created. It is a rebirth of another kind.
Photo by George Hodan
We currently cannot make empirical measurements of the event horizon. We cannot measure if the horizon radiates. We cannot empirically study what is inside a black hole.
When there are no empirical tests, "hype" may flourish inside a branch of physics. Researchers debate how many angels can dance on the head of a pin, to quote a 17th century joke about medieval scholasticism.
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