Could time travel become a reality? Cosmic strings may hold the answer

So far, time travel has only become reality in the realm of science fiction, yet modern physics is posing ever bolder questions about the nature of space-time. According to some theories, cosmic “scars” left behind from the earliest moments of the universe — known as strings — may not only tell the story of the birth of the cosmos, but could also hint at the possibility of travelling back into the past.

The idea of time travel has fascinated humanity for centuries. While most people regard it as mere fantasy, some physicists argue that the universe may contain structures which, at least in theory, could allow a return to the past. These peculiar phenomena are known as cosmic strings and are described as “scars” dating back to the universe’s earliest moments.

Cosmic strings and the Big Bang

At the dawn of time, the universe existed in an extremely hot, dense, and high-energy state. When the Big Bang occurred some 13.8 billion years ago, the released energy split into four fundamental interactions: gravity, electromagnetism, and the weak and strong nuclear forces.

As Popular Mechanics notes, this transformation is believed not to have occurred without leaving a trace, as permanent imprints were formed in the very fabric of space-time.

These are the so-called cosmic strings, whose behaviour is difficult to imagine at first glance, but which may resemble stretch marks on human skin or cracks that form in ice during freezing. Some physicists believe that these structures may still exist in the universe today, seemingly passive, yet studying them could prove crucial to understanding how the early universe functioned — and, according to certain theories, even to the realisation of time travel.

Time loops and Einstein’s theory of relativity

According to Ken Olum, research professor at Tufts University, two cosmic strings moving parallel to one another could together bend space-time in such a way that a closed timelike curve is created. This concept essentially describes a time loop: if someone were to pass through it, they would return to their point of departure — but at an earlier moment in time. In this sense, cosmic strings could theoretically function as a kind of natural time machine.

This form of time travel is particularly intriguing because it is consistent with Einstein’s general theory of relativity, which states that massive objects can distort space-time and, under certain conditions, even allow the usual rules of time to be overridden. Cosmic strings belong to this same conceptual framework and provide a theoretical foundation for other ideas related to time travel.

So, is time travel possible?

All of this, however, does not mean that time travel is anywhere close to becoming feasible in practice. One of the greatest obstacles is the extraordinary speed required: for the model to work, motion close to the speed of light would be necessary, demanding an astonishing amount of energy — something we have discussed in a previous article as well.

According to Einstein’s theory of relativity, the faster an object moves, the more energy is required to accelerate it further. At present, no technology exists that could achieve this. Nevertheless, not all physicists completely dismiss the idea of time travel.

Research continues

At present, the key question is whether cosmic strings actually exist at all. A breakthrough may come from the NANOGrav research collaboration, which detects low-frequency gravitational waves by analysing signals from pulsars. This method makes it possible to identify almost imperceptible changes affecting space-time. In 2020, the group identified a signal that did not match patterns produced by black holes and may be consistent with the theory of cosmic superstrings.

The hypothesis of cosmic superstrings originates from string theory, which proposes that the universe consists of more dimensions than we can perceive. In this model, elementary particles are replaced by tiny vibrating strings, with different vibrational modes corresponding to different particles. If these strings were stretched to extreme lengths in the early universe, they could have become cosmic superstrings which, although rarer, are theoretically easier to detect.

New data expected in the coming years, along with the space-based LISA detector planned for launch in 2034, may help determine whether these signals truly originate from cosmic strings. If confirmed, this would not only cast the theoretical possibility of time travel in a new light, but would fundamentally transform our understanding of physics. Until then, time travel remains one of the universe’s most fascinating — and most mysterious — questions.