As some of the respondents noted, we are continually traveling through time — just forward, and all at the same pace. But seriously, time travel is more than just fiction, as Gary T. Horowitz, Professor of Physics at the University of California at Santa Barbara, said:
“Maybe unexpectedly, this turns out to be a nuanced question. Clearly, it is not ruled out by our current laws of nature. Recent inquiries into this issue have provided some indications that the answer is no, but it has not yet been proved to be impossible.”
Is it possible to travel through time?
To address this question, we need to be a bit more precise about what we mean by traveling through time. Discounting the normal advancement of time, the question can be split into two parts; is it possible, within a limited period (less than a human life span), to travel into a distant future? And is it possible to travel into the past?
Our current understanding of fundamental physics informs us that the answer to the first question is a definite yes, and to the second one, perhaps.
The explanation for traveling into the far future is to use the time-dilation effect of Special Relativity, which suggests that a traveling clock tends to be ticking more gradually as it reaches the speed of light. This phenomenon, which has been largely confirmed by scientific studies, applies to all forms of clocks, including biological aging.
If one were to leave the Planet in a spacecraft that could accelerate continuously at a steady one g; (an acceleration that would create a force equal to the gravity on the surface of the Earth); one would begin to exceed the speed of light relative to the Earth within about a year.
When the ship began to accelerate, it would be ever closer to the speed of light, and its clocks would appear to be operating at an increasingly slower pace compared to the planet. In these conditions, a round trip to the center of our galaxy and back to Earth; — a journey of some 60,000 light-years — could be completed in just over 40 years of ship time.
Upon returning back to Earth, the astronaut would only be 40 years older, while 60,000 years would have passed on Earth. (Note that there is no ‘twin paradox,’ because it is unmistakable that the space traveler has been experiencing constant acceleration for 40 years; while the hypothetical twin left behind on a spaceship that surrounds the earth has not.)
Building a time machine
Time travel to the past, which is what people generally mean by time travel, is a much more elusive proposition. There are several solutions to Einstein’s equations of General Relativity that allow a person to follow a timeframe that would lead in him / her meeting themselves-or their grandparent-at an earlier time.
The question is whether these solutions reflect conditions that could exist in the real world; or whether they are pure mathematical oddities inconsistent with existing physics.
No experiment or observation has ever indicated that time travel is taking place in our universe. But a lot of work has been done by theoretical physicists over the last decade to try to determine whether a time machine can be built in a universe that is initially without time travel.
In other words, whether it is feasible to manipulate matter and space-time geometry in such a form as to create new paths that loop back in time.
How do you create a time machine? The easiest method currently under consideration is to take a wormhole; (a tunnel linking space-time space-separated regions) and assign one mouth of a wormhole a large velocity relative to the other. Passing through the wormhole would then make it possible to travel to the past.
“Maybe the greatest surprise of past decade’s work is that it isn’t clear that laws of physics preclude time travel. It is increasingly apparent that the problem will not be resolved until scientists establish an appropriate theory of quantum gravity.”
Reference: https://www.scientificamerican.com/article/according-to-current-phys/
Photo de abdullah . provenant de Pexels
