Time travel has long been a popular theme in science fiction, but can it…
2023
Time travel has long been a popular theme in science fiction, but can it actually exist? The Daily Mail reported that Professor Brian Cox says it can. He goes on to say that it can only take you into the future, though, and once you’re there, you can’t come back.
The theory is based on Einstein’s Theory of Special Relativity that is based on two principles. One is that the laws of physics don’t change, even when objects move at constant speeds to each other. The other is that the speed of light is the same for everyone, no matter how they move in relation to the light source.
If two objects are both moving through space and want to compare what they see, the only way to do that is to compare how fast the objects are moving relative to each other. The Special Theory specifically includes that the objects’ movement must be in a straight or uniform line, and at a constant speed. In order to travel through time, an object must approach the speed of light. As an object nears the speed of light, the clock slows down, but only for the object in motion. Everything else is still moving through time at the same rate.
This brings us to Russian Cosmonaut Sergei Krikalev, who has spent more time in orbit than anyone else in the world-803 days, 9 hours, and 39 minutes. If you add up all the accumulated speed from the time he has spent in orbit, Krikalev has actually moved ahead into his own future by about 0.02 seconds, according to Universe Today.
On what theory/law is time travel based on?
- A.
Hubble's Law of Cosmic Expansion
- B.
Einstein’s Theory of Special Relativity
- C.
Kepler's Laws of Planetary Motion
- D.
Newton's Laws of Motion
Show answer & explanation
Correct answer: B
Special relativity rests on two postulates: physical laws are identical in every inertial (constant-velocity) frame, and the speed of light in vacuum is the same for all observers regardless of their own motion. A direct consequence of these two postulates is time dilation — a clock moving relative to an observer runs measurably slower than a clock at rest with that observer, with the effect growing as speed approaches that of light.
The passage states this explicitly: time travel is based on Einstein's Theory of Special Relativity, built on exactly those two principles — that the laws of physics don't change for objects moving at constant speed relative to each other, and that light's speed is constant for every observer. Applying time dilation to Sergei Krikalev, who spent 803 days, 9 hours, and 39 minutes in orbit at high orbital speed, his onboard clock accumulated slightly less time than a clock on Earth — about 0.02 seconds less — so relative to Earth he has effectively moved a fraction of a second into his own future.
Hubble's Law of Cosmic Expansion describes recession velocity versus distance for galaxies — a cosmological-scale relationship, not a statement about a moving clock's rate.
Kepler's Laws of Planetary Motion describe orbital shapes and periods under gravity — they say nothing about how time is measured by a moving observer.
Newton's Laws of Motion treat time as an absolute background common to all observers, the opposite of the frame-dependent time the passage describes.
Therefore, the theory underlying the passage's account of time travel is Einstein's Theory of Special Relativity.