A wrinkle in time: Computers may give answers now, solve problems later

The capacity for time travel may still be light years away, but one physicist is already planning for a day when computers can send information backward in time. Todd Brun, a theoretical physicist at the Institute for Advanced Study, conceived of a computer that sends the results of its computations back to itself through a wormhole.

"This computer could solve a very difficult set of problems very quickly," Brun said.

Popularized in the television show "Star Trek: Deep Space Nine," a wormhole is a shortcut in spacetime that connects two points. This tunnel may create a closed timelike curve, a path that curves back on itself without exceeding the speed of light. According to Brun's theory, a computer could send the result of a calculation back to its own past by way of a closed timelike curve.

"The computer would get the answer before it actually solves it," he said.

In Brun's computer program, the result of a computation is displayed if it has been sent from the future. If no result has come through, Brun said the machine will use "brute force calculation to obtain an answer and send it into the past." However, the latter situation is contradictory because if the computer sends the result to itself in the past, it must have already received the message.

"If the laws of physics require consistency, only the first situation is possible," Brun said. Thus, according to Brun's algorithm, the computer must obtain a calculated result that it has sent from its future via the wormhole.

"You get something for nothing, which makes you think it's impossible," he added.

Early descriptions of wormholes are found in the writings of 19th century mathematician George Riemann, who conceived of a connection between spaces with zero length known as a Riemann cut. Based on Einstein's 1916 Theory of General Relativity, logician Kurt Gödel conjectured that time travel is possible if space-time were bent in a loop — the closed timelike curve.

In the 1930s Einstein himself, along with colleague Nathan Rosen, suggested that tunnels in black holes — Einstein-Rosen bridges — connect universes that mirror each other.

A potentially viable model of traversable wormholes was not suggested until 1985, when Carl Sagan asked Kip Thorne of the California Institute of Technology to envision a hypothetical space-time tunnel for his novel, "Contact." Thorne not only gave Sagan a physics lesson for his bestseller, but revolutionized the study of time travel through rifts in space-time.

Thorne's model of wormholes, which is the basis for Brun's computing theory, makes use of exotic matter, a material with negative gravitational force that can be converted to negative energy which prevents the wormhole from collapsing.

However, the notion of negative energy violates the principles of general relativity, leading some theorists to contend that wormholes do not exist.

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The legendary Stephen Hawking has conjectured that the universe forbids closed timelike curves because they create paradoxes in chronology. Brun joked, quoting Hawking, "It keeps the universe safe for historians."

Quantum mechanics, on the other hand, can support Brun's thinking. At the quantum level, on a scale of 10-35 meters, wormholes may exist in space-time distortions.

"It's possible that wormholes occur naturally but disappear too quickly," he said.

While Brun has detailed how his hypothetical computer could solve a calculation that would take longer to solve than the lifespan of the wormhole — or the universe — he does not expect to see a desktop model any time soon.

"[The computations] would require enormous energies, energies equivalent to masses of many suns." Brun said. "Maybe it would be possible for an advanced civilization.

"Maybe it's science fiction rather than science."