Can black holes send information back in time?

Extremely curved spacetime can warp cause and effect, creating channels for backward communication

If something is allowed by the laws of physics, then scientists can assume that it probably exists. Under that reasoning, certain exotic structures of spacetime called closed timelike curves may be real—and they may allow a message to travel from the future to the past .

A new study has calculated how much information can be sent backward through time via closed timelike curves . Albert Einstein’s general theory of relativity predicts that these spacetime pathways can form under intensely bending, rotating space—such as around a spinning black hole. “Spacetime can curve around so much that you can be innocently going forward in time and then you meet yourself in the past,” says study co-author Seth Lloyd, a quantum information scientist at the Massachusetts Institute of Technology.

According to general relativity, in a rotating black hole, the singularity—the theoretical point of infinite density at the center—is really a one-dimensional ring, with closed timelike curves arcing around it. No one knows if these spacetime structures actually exist in our universe, but they are plausible. We do know, however, that black holes are plentiful in space and that most of them spin. “So they might very well exist,” Lloyd says.

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Inspiration for the study came in part from a movie. “In early 2025 I watched the film Interstellar , ” says Kaiyuan Ji, a graduate student at Cornell University who, with his advisor Mark Wilde, collaborated with Lloyd on the new research. The findings were published recently in Physical Review Letters .

In the movie, an astronaut played by Matthew McConaughey travels up close to a black hole and sends a message to his daughter in the past. Ji realized the plot was mathematically equivalent to a question he and his colleagues had posed in previous research.

The group decided to investigate how best to use closed timelike curves to transmit information between the future and the past. “The strategy has a different structure than communicating forward in time,” Ji says. “The key difference is that the sender in the future has memory of what happened in the past, and that causes a causal loop. You now have the ability to bend the probability of success.”