Throughout history, physicists have been discussing the plausibility of time travel. The theory of relativity allows for time travel into the future, going at high speeds returning to earth only aging slightly compared to your peers. Einstein's theory is a theory of space and time; it should be no surprise that black holes offer, in concept, a way to travel through space and time as well. Since it possible in concept only, it does not mean that it has been achieved as of yet. Black holes are the product of a collapse of a massive star that has such an extreme gravitational force that it keeps light particles from leaving its surface, making the star practically invisible.
Black holes act like a one way street, only allowing objects to fall into the black hole but nothing can escape from its gravitational pull. In the 1960's a mathematician from New Zealand, Roy Kerr said, that if a black hole is rotating a singularity forms in the shape of a ring. In principle, it would be possible to dive into such a space and through the ring, to emerge in another place and time. The "Kerr Solution" was the first mathematical example of a time machine. Nobody took Kerr's idea seriously until the 1970's when astronomers discovered what seemed to be real black holes in our galaxy and the hearts of other galaxies. There is an interior tunnel in the exact Kerr solution of the Einstein Field of Equations, but it is unstable.
The slightest disturbance inside would seal it off and turn the tunnel into a physical singularity, which would allow nothing to pass through it. White holes are like black holes in the way they are formed. The difference is that, in white holes, objects are pushed away from the center, unlike black holes, which engulf objects not allowing them to escape their gravitational force. Therefore, black holes and white holes must be connected in some way, theorists believe they are connected by wormholes.
If thi were true, the way that this system would work is that the object would be pulled in through the black hole and shot through the wormhole at a speed close to that of light. Then at the end the object would be pushed out through the white hole in another area in space. Antigravity is a force that is opposite to gravity, instead of attracting all objects it repels them. This works kind of like when two protons come in contact with each other. Wormholes are theoretical objects in space.
Wormholes are tunnels that connect two areas of space. Theoretically black holes and white holes are connected by wormholes. The traveling through the wormhole will cause you to emerge into another universe. The problem with emerging in this new world is finding a way to get back.
The only way to get back to where you came from is by finding another black hole that will cause you to emerge in the same place which you left. Otherwise there will be difficulty in returning to your home. What is needed for time travel is an object that is massive enough to create distortion of space-time. Today's great physicist Stephen Hawking has already discredited the possibility of creating time machines. Although Stephen Hawking is a great physicist, an Israeli researcher, Amos Ori, has discredited his thoughts of time travel being impossible. Ori found a flaw in the argument put forward by Hawking, claiming to rule out any possibility of time travel.
Physicists look more deeply into general relativity for details concerning time travel. In these areas of astrophysics and cosmology, the existence of black holes and wormholes is the only place to look for a mathematical or any type of equation to the existence of these celestial bodies. Cosmology is the study of large-scale structures, the composition and evolution of the universe. Astrophysics is an older type of astronomy that uses the theory of relativity, along with other attributes to help explain certain occurrences in the universe. The main purpose of Einstein's theory of special relativity was to establish the similarities of the reproduction of light and the validity of the physical laws in all frames. Galileo felt that time was constant at all times throughout the universe and Lorentz felt that when an object is moving it makes time move at a slower rate than that of the stationary clock.
Einstein proved that time can seem to travel at different speeds, the speed at which the time seems to travel all depends upon the state of motion of the observer. Einstein said, that a clock in a moving laboratory would seem to tick slower than a set of clocks in a reference laboratory. When discovering how wormholes are created, it was practically common sense. Gravity pushes matter together, creating singularities to close the wormhole. But the wormhole would be able to stay open, if a form of matter gives off a negative pressure which had antigravity associated with it.
As Newton's third law of motion states, any object that comes in contact with a force an equal and opposite force will be distributed. This third law proves that if a wormhole would exist in the universe, that it would not be closed shut because of the equal and opposite force given against it. Since wormholes are the connectors of black holes and white holes, there is equality being created at each of the two ends. The amount of force that the black hole is forcing onto the wormhole the white hole absorbs and distorts into another area in the universe.
Therefore this existing system works in a complete equilibrium. One of the problems with time travel in the past is called the "grandparent" paradox. Suppose that you are back in time and kill your grandparents before they have any children. By doing this do you eliminate your own existence Doing something of that sort is forbidden, and in a sense you would have no free will since you are not "allowed" to kill your grandparent then. Paradoxes limit the free will of people since they are not allowed to kill their grandparent due to the laws of causality.
Causality refers to the power, by which one event causes another. It has been believed that some kind of connection is necessary between the cause and the effect of events. The study of causality has centered, in part, on trying to discover and define this connection. It is easy to see how one can make a time machine if one will consider the "twin paradox" in special relativity. If there are two people, one is in a fixed position and the other is moving at a high speed relative to the person at the fixed position. Each of the people have a watch in their hands, the person moving at a high velocity's clock will seem to be moving relatively slower compared to the person just standing there.
This occurs because of the time dilation in special relativity. We are all time travelers in one sense, or another, simply by the process of aging. We are all moving towards our future, according to decisions we make in the present and made in the past. As for today's world time travels might be allowed theoretically, but literal time travelers are still science fiction.