Time travel to the past: Yes in fiction, but science?

For a long time, time travel has existed in popular imagination. From science fiction classics like The Time Machine and Back to the Future to recent films like Interstellar, the concept of sliding through time has been explored – whether to see and even participate in the past or to glimpse the future.

However, the concept poses fundamental problems regarding physics, causality, and the nature of reality itself. Is time travel possible? And if so, under what circumstances?

Time travel is an idea that predates modern physics. H.G. Wells' The Time Machine (1895) presented it as a literary technique, but science would not begin to seriously consider feasibility until the twentieth century.

Albert Einstein's theory of relativity demonstrated that time is not absolute nor constant, but can stretch and compress based on the speed at which you travel and gravity.

Kurt Gödel, a close collaborator of Einstein, postulated in 1949 that under certain unusual situations, such as a rotating universe, it may be feasible to construct a path through spacetime that loops back into the past, Indian Express reported.

Einstein was allegedly disturbed by the consequences. Although his equations did not directly exclude time travel, they implied a universe far stranger than he was comfortable with.

Moving forward is easy, but backwards?

In fact, we are all-time travellers, going forward at a consistent rate of one second each second. However, general relativity allows for more dramatic impacts. Clocks aboard high-speed spacecraft or near enormous objects such as black holes tick slower than those on Earth, as proved by studies with atomic clocks on aeroplanes and satellites.

This explains why astronauts on the International Space Station age slightly slower than the rest of us. However, travelling back in time presents even more difficult obstacles. Backward travel may be possible via theoretical entities such as wormholes, which are shortcuts across spacetime, or closed timelike curves.

Paradoxes of time travel

Even if time machines could be developed, they would present troubling logical paradoxes. The most famous is the grandfather paradox, which asks what happens if you travel back in time and prevent your grandparents from meeting. If you were never born, how did you get back here?

One proposed answer is the Novikov self-consistency principle, which states that any previous events induced by a time traveller must be compatible with the history that gave origin to the traveller.

Alternatively, some quantum mechanics theories propose the existence of branching universes, in which each change creates a new, alternative timeline, avoiding contradiction. Stephen Hawking, a well-known sceptic, once organised a "party for time travellers" but did not send out invitations until after the event. No one came.

Currently, there is no experimental proof that travelling back in time is possible. The majority of physicists believe that factors such as quantum mechanics, energy limitations, or the fundamental structure of spacetime itself would ultimately make it unfeasible.

Some scientists also suggest that time travel might violate the second law of thermodynamics, which states that entropy—or disorder—must always increase, giving time its “arrow.”

Despite these challenges, time travel continues to be a subject of serious scientific inquiry. It pushes the limits of our understanding of causality and spacetime, while also probing the unresolved tension between general relativity and quantum mechanics — two foundational yet incompatible theories in physics.

Why, then, are we so drawn to the idea of time travel? Perhaps because it offers the ultimate form of control: the ability to relive moments, fix past errors, or witness origins. Yet, for now, time appears to move only forward.

Still, as scientific knowledge and technology evolve, the possibility — however faint — remains open. Until that day comes, time travel will likely continue to flourish most vividly in fiction, where imagination still outpaces the reach of science.