Is time travel possible

Answer 1

Various opinions, then the problems... There are several applications of theoretical physics that allow travel from one point in space-time to another. Some address the issue of travel into the past or the "future" but the concept of time as a "one-way arrow" makes future travel simply suspended time followed by a return to the present as the past.

Some calculations include theoretical rotating black holes and their effects on time dilation (a generally accepted concept related to speed in a separate reference frame). But the principle of causation would create problems with interacting with or altering the past, which created the world from which the time traveler departs.

At the current time (no pun intended) we can't prove the idea of time travel, seeing how we can not time travel right now. But we also can't just discard the idea seeing how physics doesn't disprove it.

Memory may be considered time travel, a one way image of the past. If you can revisit the past through memory, that really is a ''time machine".

It is theoretically possible to travel back in time. When an object is going extremely fast, such as the space shuttles, Time slows down just a little. The astronauts come back 2-3 seconds younger than they should be. This is called time dilation.

Now if we talk about, hypothetically, if an object with mass traveling the speed of light, theoretically time would seem to "halt". And if you go faster than the speed of light, time would begin to go again, except backwards. In some mathematical theories, this is possible. But the only problem with proving this theory right is the Mass Factor. As you get closer to light speed, your mass increases. When you are traveling at light speed, you have infinite mass, which would make it impossible to go faster. Keep in mind, this only works to travel back in time, theoretically.

One Way to the Future (time dilation)

If you were to travel into outer space and then return to Earth at light speeds, you could actually "travel" thousands of years into the Earth's future! This is because traveling at close to the speed of light actually alters the passage of time: an object traveling at extremely high speeds will not age in the same way as an object which is static. So, if you were to stay on Earth, and your friend was to travel into space and travel distances at the speed of light and then return to Earth, your friend would return to Earth much younger than you, even though you were the same age before they left!

Einstein explained motion in time with his theory of relativity: the stars bend time in space: it is time in space which dictates how the planets move, and at what regularity. Time in space is not absolute, i.e. it is not fixed, because it is relative to the speed at which you are moving. So really, time travel already occurs!

But there are MAJOR Problems here...

It seems that all the answers here are talking about the physical and fantastical possibility of time travel rather than a common sense approach to its possibility, with a pragmatic understanding of the limitations of physics and quantum mechanics. There are several problems with the arguments.

To move backwards in time one would have to travel fasterthan light, in the same way as hypothetical particles called "tachyons", which would, if observed, disappear before they appeared (if you could believe that). However, Einstein showed that for a mass to travel at the speed of light it would require an infinite amount of energy as the mass of the object increases to infinity as well as time slowing down, so that an infinite amount of force would be needed to accelerate that infinite mass, and an infinite amount of energy needed to do so. Therefore matter cannot travel at light speed, let alone faster than light. Therefore, by Einstein's reckoning alone, time travel would not be possible.

Secondly, as regards the principle of cause-and-effect, time travel would cause great paradoxical problems.

The old chestnut of the grandfather paradox is a prime example. Suppose you travelled back in time, and met your grandfather and shot him dead, which may be perfectly possible. Your grandfather, being dead, would not have sired your father and therefore you would not exist - yet you must have existed to go back in time in the first place. Such a paradox sounds silly, but is perfectly possible if time travel existed. Therefore, anyone going backwards (or forwards) in time cannot have any effect on the surroundings (both in time and space)of where he or she ends up.

Yet, the mere fact that they are there alters history. By the Chaos Theory, even a minor event can create a major difference in the nature of a place. Therefore just by being 'in history' could eventually change that history so much that our "history" would become different. But as it isn't different as texts, documentation and sources tell us, not even minor events could have been changed. In other words, no one must have been able to reach the past to cause that change.

Thirdly, time travel is impractical even if you don't consider the almost infinite energy required. It's because you also need to consider the acceleration necessary to reach that speed. To reach the speed of light (or near it) with an acceleration of 1g (which would feel to the astronauts that they were back on the earth although 'weightless' in space) would take over 54 years of CONSTANT acceleration. Even at a constant 5g - the maximum experienced by astronauts in the space shuttle, and then only for very short periods because of the dangers, the time taken would be 13 years of constant 5g acceleration (meaning a 150 pound man would weigh 750 pounds for 13 years - enough to break his bones unless it was for a very brief period, let alone 13 years!). Even at 12g - the point at which the human body experiences brown outs, loss of peripheral vision blackouts, brain damage and death, even after short exposure, the time needed would be over four and a half years constant acceleration at this rate. Therefore, any attempt to even get close to time dilation speed is absolutely futile.

Finally, if time travel will one day exist in the future, how is it that we have never seen travellers from the future visit us? UFO sightings are sometimes claimed to be 'time travellers' from the future, but the evidence is very scarce for this - and even more scarce for UFOs in the first place. It seems then that using simple common sense, time travel is an impossibility.

So, I am sorry to disappoint everyone, but possibly Time Travel should be confined to H.G. Wells and Dr. Who, for Science Fiction is where it belongs. Einstein Would Say Yes

First of all, to travel through time (forward) is what humans always do.

However, to travel back in time.... well, Einstein would say it's possible. But the necessary technology currently does not exist.

Time-travel as we consider it, will never be possible. Time is a concept, but not a physical dimension or place, nor is it something we can physically touch or measure. Time in reality is only motion. The motion is only forward. No matter what we do, we are unable to make this motion reverse and go backwards. At our best, if we managed to go faster than light, we could only observe the effects of what has happened, not reverse any of the processes of the universe itself.

Einstein proved that time is relative. The faster the relative motion of a traveling object, the slower the progression of time observed in its reference frame. In effect, the aging of traveling cosmonauts will slow down. Because motion is relative, a cosmonaut who returns after traveling for 10 years at near the speed of light may find that the Earth has aged 100 years or more.

This is not time travel. It is just a consequence of relative motion on a subatomic level near the speed of light. The cosmonauts may experience the effect as that they have traveled into the future. But in reality, they have only slowed down their atoms' motion, hence gaining the effect of slower/relative aging.

Wormholes may still exist (or be created) for traveling to different places in the cosmos in a manner faster than light, but in no way will this allow for actual time-travel. Not forward in time - the perceived travel forward in time is a consequence of relative motion due to high speed. Not backwards in time - we cannot make universe go backwards.

The motion in the cosmos cannot be undone, hence we can not travel back, only calculate motion backwards at best. By calculations, we can simulate how objects move and behave backwards and forwards in our concept of time. But to actually shift the universe so that we can end up at a fixed "stored" physical image of the cosmos itself...forget it.

Answer 2

Yes, time travel both into the past and into the future is possible. As it is possible to change the future, it is also possible to change the past, though we on Earth don't know how to do it yet.

Answer 3

Currently, time travel as commonly depicted in science fiction is not considered possible according to our current understanding of physics. While theories like wormholes and time dilation suggest ways in which time travel could occur, they remain theoretical and have many unresolved scientific and philosophical challenges.