Written by Eric Olson
6 min read
Ask the Experts: Is It Possible to Time Travel by Going Faster Than the Speed of Light?
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Try for freeCan we break the cosmic speed limit to journey through time? We asked four physics and astrophysics experts to evaluate this popular sci-fi concept. From university professors to research scientists, these specialists examine whether faster-than-light travel could enable time travel as depicted in countless movies and books. Their evidence-based perspectives cut through speculation to reveal what modern physics actually tells us about the relationship between speed, light, and time.
Antonija Grubisic-Cabo has answered Extremely Unlikely
An expert from Monash University in Physics, Materials Science
It is not possible for matter to travel faster than the speed of light (speed of light is speed limit of the universe).
Regarding the time reversal, the arrow of time on macroscopic level is considered to be asymmetric, meaning it only goes in one direction, from past to future and cannot be reversed.
Sean Matt has answered Extremely Unlikely
An expert from University of Exeter in Astronomy, Astrophysics
As far as we know, nothing can go faster than light. However, if one travels close to the speed of light, time behaves differently than we are used to, and in this way, one can move forward in time faster than those left behind. So it is theoretically possible to travel to the future, but one could not return. I have answered this question negatively, since time travel usually implies being able to go backwards in time, which is not possible.
Chris Woodruff has answered Extremely Unlikely
An expert from Walter+Eliza Hall Institute of Medical Research in Bioinformatics, Optics
Not according to current understanding in physics – though there have been recent claims to teh contrary but these have yet to be adequately tested by physicists. The essence of relativity theory is that energy/matter/information cannot be transferred at faster than the in vacuo speed of light.
Eric Tittley has answered Extremely Unlikely
An expert from Edinburgh University in Astrophysics, Astronomy, Computer Science
No. That is the simple answer to a complicated question.
If something (matter or information) were to travel faster than the speed of light in a vacuum, then how it would perceive the direction of time and how we as outside observers would perceive its behaviour in our time and space reference is not clear to me, so I cannot give an authoritative answer to that.
However, it is clear that no object or information can travel faster than the speed of light. It is not a question of not having enough energy to push it that fast. From an external perspective, any extra energy added to a body to get it to and past the speed of light just asymptotically accelerates it to the speed of light, with the extra energy just increasing the mass (which is energy) of the object.
Note a few of caveats to this “nothing can travel faster than the speed of light”. First, it refers to light in a vacuum. Light is slower when it moves through media like water or air. Particles travelling near the speed of light, when they encounter these media, move through them faster than the local light speed and encounter no strange effects other than giving off a special light called Cerenkov radiation. Cerenkov radiation can be thought of as a sonic boom of light waves.
Light travels at the speed of … well … light. But a packet of light, like a short pulse or the packet acting as the waveform of a photon, is comprised of a multitude of waves that continually interfere with each other to form a pulse. The individual waves can travel forward in the pulse, so their wave crests actually travel faster than the speed of the pulse. The pulse travels at the speed of light, so the waves travel faster. These different speeds are referred to as the group and phase velocities. The light pulse travels with the group velocity. It is the pulse that carries information so it can never exceed the speed of light.
The expansion of the Universe can lead to distant objects appearing to move away from us faster than the speed of light. Indeed, it is perfectly acceptable to talk about distant galaxies moving at many times the speed of light because they are not moving through anything at those speeds. Locally, way out in the distant universe, the galaxies are moving very much sub light speed. The light we see from them has been redshifted during its long voyage to us by the expansion of the universe.
But to answer your question, No, it is not an urban myth that in the 1978 Superman film, Superman reverses time by flying counter-rotationally around Earth faster than the speed of light. It is indeed the rather disappointing climax of an otherwise superb film.
Verdict: Physics Says No, With Good Reason
The experts unanimously agree: time travel through faster-than-light speed is not possible according to our current understanding of physics. Einstein’s theories of relativity establish light speed as a fundamental cosmic limit that cannot be exceeded by matter or information. While time dilation does occur at very high speeds—allowing travelers moving near light speed to experience time more slowly than stationary observers (effectively “traveling” into the future)—this is fundamentally different from the backward time travel depicted in science fiction. What many find fascinating is that the prohibition against faster-than-light travel appears to protect causality itself, preventing the paradoxes that would arise if we could travel to the past. Despite occasional speculative claims, the evidence overwhelmingly suggests that Superman’s time-reversing flight remains firmly in the realm of fiction rather than physics.
Find more research on relativity theory and the physics of time on Consensus, or explore the related questions below to dive deeper into this fascinating topic!
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