Time Travel Is Possible, But We'll Need Lots Of Negative Energy, Says Astrophysicist

Patricia Grannum

Humans have been fascinated with the elusive idea of time travel for generations, but there's an astrophysicist who now says that it can actually happen. In a blog for Forbes called "Starts with a Bang," Ethan Siegel of Lewis & Clark College says by using the laws of theoretical physics, we could technically construct "elaborate wormholes" that could deliver humans back to the past.

As Spiegel notes, the spacetime fabric is constantly undergoing positive and negative fluctuations. Theoretically, a strong positive fluctuation and a powerful negative fluctuation could connect to form a quantum wormhole. The wormhole can then become a passageway that can transport particles from one point in spacetime to another. But this only works if the wormhole can hold up long enough for that time travel to happen.

But creating a big enough wormhole to take a human from the present to the past will not be an easy task, Spiegel says. The search for the negative energy particles has been unsuccessful thus far.

"While every known particle in our Universe has positive energy and either positive or zero mass, it's eminently possible to have negative mass/energy particles in the framework of General Relativity," the astrophysicist writes. "Sure, we haven't discovered any yet, but according to all the rules of theoretical physics, there's nothing forbidding it."

When you travel at speeds close to the speed of light, a phenomenon called time dilation occurs, Spiegel says. This means that as you increase your motion through space, your motion through time will decrease.

For example, if you traveled to a star that was 40 light-years away at speeds close to the speed of light, you may get there in a year and take a year to return. But, according to Spiegel, when you got back to Earth, 82 years would have passed.

"This is the standard way time travel physically works: it takes you into the future, with the amount of travel forward in time dependent only on your motion through space," he writes.

But his quantum wormhole theory changes that and avoids the "grandfather paradox" i.e. the notion that you can change the course of your life through time travel by going back in time and killing your grandfather.

"Even if the wormhole were created before your parents were conceived, there's no way for you to exist at the other end of the wormhole early enough to go back and find your grandfather prior to that critical moment," Spiegel says.

Astronomer Frank Tipler came up with a device, often called the Tipler cylinder, where you roll matter into a long, dense cylinder. Tipler theorized that when you spin the matter a few billion revolutions per minute, a spaceship orbiting the cylinder could lock itself into a "closed, time-like curve" that would facilitate time travel.

But there are some downsides to this theory that make it seem impossible as well. The cylinder must be infinitely long and the matter that you start with must be 10 times the sun's mass.

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