The desire to hug a departed loved one again or stopping murders are among the compelling causes that keep the idea of time travel alive in the minds of many. Whereas this notion makes for great fiction, according some scientists traveling to the past is impossible. Here are the few reason why it is impossible:
The fourth dimension
In physics, time is defined as a dimension much like the other three, length, width, and height. When you travel from your residence to the grocery store, you’re traveling through a direction in space, making movement in all the spatial dimensions, which are length, width and height. But you’re also traveling forward in fourth dimension i.e time. According to Charles Liu, an astrophysicist at the City University of New York, and also co-author of the book, One Universe: At Home In The Cosmos, “Space and time are tangled together in a sort of a four-dimensional fabric called space-time.”
Space-time, as Liu explains, can be considered as a piece of spandex with four dimensions. When something that has some mass, you, I, an object, an asteroid, or any star, lies in that piece of four-dimensional spandex, it causes it to create a dimple. That dimple created by the object is a manifestation of space-time bending to accommodate its mass. The bending of space-time makes objects to move on a warped path and that curvature of space is what we called as gravity. Mathematically one can go backwards or even forwards in the three spatial dimensions easily. But time doesn’t hold this multi-directional freedom. In four-dimensional space-time, you’re can only move forward in time.
Tunneling to the past
A handful of suggestions exist for time travel. The most advanced of these suggestions involves a wormhole, a hypothetical tunnel linking two different areas of space-time. The areas linked could be two entirely different universes or two parts of one universe. Matter can travel from either opening of the wormhole to reach a destination on the other side. Michio Kaku, author of “Hyperspace” and “Parallel Worlds” and also a physicist at the City University of New York, says “Wormholes are the future, wormholes are the past. But we have to be very careful. The gasoline necessary to energize a time machine is far beyond anything that we can assemble with today’s technology.”
To create a hole into the fabric of space-time, Kaku clarified, would involve the energy of a star or negative energy, an unusual entity with an energy of less than nothing. Which is impossible for now.
Another widespread theory for possible time travelers includes something called cosmic strings, narrow tubes of energy stretched across the whole length of the ever-expanding universe. These thin regions, leftover from the early universe, are anticipated to comprise huge amounts of mass and so they could twist the space-time around them.
According to J. Richard Gott, author of “Time Travel in Einstein's Universe” and an astrophysicist at Princeton University, cosmic strings are either infinite or they’re in rings, with no ends at all. So you can say that they are either like spaghetti or SpaghettiO’s.
The approach of two cosmic strings parallel to each other, will twist space-time so strongly and in such a particular alignment that might make time travel possible, theoraticaly.
Gott told LiveScience “This is a project that a super civilization might attempt. It’s far beyond what we can do. We’re a civilization that’s not even controlling the energy resources of our planet.”
Some physicists think that traveling to the past is, in fact, theoretically imaginable, however impractical. Perhaps if there were a theory of everything, one might solve all of Einstein’s equations through a wormhole, and see whether time travel is actually possible. But that would involve equipment far more advanced than anything we can muster. So don’t expect any young inventor to reveal tomorrow in a press release that he or she has created a time machine in their basement.