Do we need the ability to travel back in time?

You may not realize it, and even surprised, but, by the time you finish reading this text, you will get about 2-3 minutes into the future. The truth is that from a theoretical point of view to travel into the future is actually much easier than to travel back in time. Why? Partly because we now literally move forward in time.

The Idea of the possibility of time travel originates from the special theory of relativity of albert Einstein, which, if to speak a simple language, describes the relationship of space and time. The difference in the speed of the clock or movement time can be attributed to two factors: gravity and the relativistic effect. The last is that in a moving body, all physical processes are slower than they should be for a stationary body at the time the fixed (laboratory) frame of reference. That is, for different observers located in different places and conditions, time can flow differently.

Interestingly, the theory of time travel is partly confirmed (rather strange) fact: the clock mounted on the spacecraft (be it the internal GPS clock and the atomic clock, brought into space for experimental purposes) are slower than reference clocks on Earth. In this respect, the cosmonauts and astronauts on extended missions can be considered to be time travelers, because they are located in space time moves faster than for those who are at this moment on Earth. On average, the difference is about $ 38700 NS/day.

"Time on the moon you will move faster than the Earth and more slowly than it moves on Jupiter", — says the famous popularizer of science Michio Kaku from City College of new York.

"in Other words, if you decide to go to the moon or Jupiter, you can go back or forward in time. Now the difference in this respect would form only a tiny fraction of a second".

From a practical point of view, more attractive is the relativistic effect of time dilation. What is the use?

"If you reach 99% the speed of light and move with such speed in the course of the year, say around the Solar system, then returned to Earth you will find that the planet has gone to 100-200 years in the future," — comments Dr. Ulvi Yurtsever, co-author of the original article on time travel.

So, in theory, the presence of propulsive systems that will allow us to move at a speed close to the speed of light, we can "skip" for centuries. But with the help of this method we will not be able to travel back in time.

Some scientists believe that traveling back in time is also possible. However, we will need the involvement of black holes and "custom wormhole" and very, very, very much energy.

"Bring the equations and find solutions for them possible. Most likely, using these equations we can figure out two things: how to bend space and time and what is the amount of matter and energy we will need. Assume that for each such curvature of space/time, which is perceived by us as a method of time travel will require so much of energy and matter, but does not exist in the Universe. If you want, that is the answer explains the lack of enthusiasm in this direction," — says Professor of theoretical physics Clifford Johnson of the University of southern California.

Actually, the technical complexity is not the only aspect, «prevent» create a time machine that will allow us to move not only in future but also the past. A special role in this issue is a moral choice. A move in the past will be accompanied by high risk of creating a time paradox, the scientists say. There is a theoretical probability of a situation when a guest from the future will do something, he visits the past, that change is a journey from the future, for example, making it impossible (as the displacement itself, and the present). In General, if you develop a time machine, only with the ability to travel in the future.
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