Physicists: Travel to the Future Is Theoretically Possible, Going Back to the Past Is Not Established
According to Albert Einstein's theory of relativity, travel into the future is physically grounded, while travel to the past lacks both evidence and a complete theory. Scientists stress that visiting the past remains in the realm of science fiction for now.
Can people travel through time? According to physicists' explanations based on leading modern theories, travelling into the future is theoretically possible, while going back to the past remains an unsolved question. The answer rests on Albert Einstein's theory of relativity, which describes the structure of space and time, and on quantum physics, which studies the behaviour of particles and energy at the smallest scales.
Time does not pass equally for everyone
Relativity predicts that time is not absolute. Its pace depends on both speed of motion and gravity. The faster a person moves, the slower time passes for them compared with someone who stayed on Earth. A pronounced difference would appear only at speeds approaching the speed of light.
The twin paradox illustrates this: if one brother stayed on Earth while the other flew through space at near light speed, the traveller would have aged less upon returning. He would have experienced less time while more years passed on Earth, so he would effectively have arrived in Earth's future. However, humanity currently has no technology that would allow flying at such a speed.
Gravity works in a similar way: the stronger the gravitational field, the slower time runs. On Earth the difference is tiny, with time passing slightly faster at head height than at the feet. These effects are taken into account in satellite navigation systems such as GPS, whose accuracy requires correcting the readings of clocks on satellites.
The past remains unknown
Some theoretical models allow closed timelike curves, trajectories that would return to their starting point, as well as wormholes, hypothetical tunnels between distant points in space and time. But there is no evidence that wormholes exist or that they could be used to move people. Cosmic strings, which might warp spacetime, have likewise not received experimental confirmation.
In quantum physics, some scientists discuss retrocausality, the idea that cause and effect in the quantum world may be more complex than usually assumed. That does not mean one could send a letter to the past or change history, as these ideas concern very specific systems.
Physicists note that there is no theory combining relativity with quantum mechanics that would allow firm conclusions about travel to the past. There is no evidence that a person could meet a version of themselves from the future.
