There Are Scars in Our Universe That Could Unlock Time Travel, Physicists Say

Einstein’s theories support the science behind this time-travel loophole. But could it actually work?

In the moments before the Big Bang, our universe was a hot, dense, and extremely high-energy place. That all changed when the universe exploded 13.8 billion years ago. Rapid inflation divided a single “super” force into the four fundamental forces we know today: gravity, electromagnetic force, weak nuclear interaction (responsible for radioactive decay), and strong nuclear interaction (which holds atomic nuclei together). Elementary particles were created. And, eventually, the cosmic flash dance left behind scars in the fabric of space-time. Physicists call them cosmic strings.

Like stretch marks left on skin that expanded too quickly or cracks embedded in freezing ice, cosmic strings are artifacts of what the universe looked like in the moments before it rapidly changed from a high-energy to low-energy environment, scientists believe. These strings are roughly as thick as a proton, extremely dense, and light-years long.

Scientists believe cosmic strings are passively floating through the universe, minding their own business. But actively studying them could unlock the mysteries of our early universe and may even be key to a form of time travel, some physicists suggest. Traveling back in time through relics of the early universe might sound like pseudoscience, but it’s an idea supported by cosmic string theory. At least, theoretically.

Ken Olum, Ph.D., a research professor of physics and astronomy at Tufts University, says that two infinite, parallel cosmic strings passing each other would create a time machine by warping space-time. As a result, if you traveled in a path around these strings, you would return to your starting point at an earlier time than you left it.

But while the math explaining this cosmic string-enabled time travel checks out, Olum says not to get too excited. In addition to practical concerns regarding a cosmic string-powered time machine, there’s also the small issue that scientists have never actually observed cosmic strings yet.

In 1991, Princeton physicist J. Richard Gott proposed the most popular idea for cosmic-string time travel. In his model, Gott explores how two infinite, parallel cosmic strings passing each other—much like two cars driving along an endless two-lane highway—could warp space-time to create a path in time called a closed time-like curve. Essentially, this is a loop in time that returns a time traveler to their point of origin before the moment they left it.

What is particularly intriguing about Gott’s theory is that this kind of time loop is an accepted solution to Einstein’s theories of general relativity. In a nutshell, these theories tell us that massive objects can distort space-time, which allows for the possibility that one could take a shortcut through time by condensing space. Closed time-like curves also explain how wormholes theoretically work.

The math behind a theoretical cosmic-string superhighway is sound, but that doesn’t necessarily mean we’re any closer to realizing this model of time travel. For one thing, the near-light-speed travel required to pull it off is incredibly difficult (and maybe even impossible). According to Einstein’s relativity, the faster an object goes, the more energy it requires to continue accelerating. Simply put, there’s no method yet that can produce the massive amounts of energy necessary to propel a spacecraft to such incredible speeds.

But that’s not the only issue, Olum says. Assuming that scientists of the future would plan to build a time machine based on this idea—rather than wrangling existing cosmic strings—the infinite nature of Gott’s strings is a non-starter. “Nobody can make this situation because nobody can make something which is infinitely long,” he says. “So this exact idea is not useful.”

However, compared to other theoretical modes of time travel, like wormholes, Henry Tye, Ph.D., an emeritus professor of physics at Cornell University, says he is more convinced by the possibilities of cosmic strings. In fact, Tye and a student have explored their own model using cosmic strings, as well.

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