Time Travel

Time travel: science fact or science fiction Priyanka kasturia Department of Physics, Kalindi College, University of Delhi.

Abstract Basically we define time travel as the departure from a certain place in certain time followed by arrival at the certain place at a different time whether in future or in past. In this paper, the possibilities and certainty to travel time, and if it is possible then how we can travel into future or past is explored and explained. Thus, in this paper we will study about the time travel in physics and also explore some related theories. We will also explore how general and special theory of relativity and the concept of wormholes account for the time travel. Also the concept of the time machine is also discussed.

Introduction Time travel is the moving between different points in different time, i.e., to move from one moment in one time to another moment in another different time, typically using a hypothetical device known as a time machine. It is uncertain that if time travel to the past is physically possible while the time travel to the future is an observed phenomenon and understood within the framework of special and general relativity. Not all scientists believe that time travel is possible. Some even say that an attempt would be fatal to any human who chooses to undertake it.

While most of people think of time as a constant, according to Newton. But Einstein showed that time is relative — it can vary for different observers depending on your speed through space. Einstein's theory of special relativity says that time slows down or speeds up depending on how fast you move relative to something else. Approaching the speed of light, a person inside a spaceship would age much slower than his twin at home. Einstein’s special and general theory of relativity, suggest that suitable geometries of space-time or specific types of motion in space might allow time travel into the

Past and geometries possible.

future if these or motions were

Special and relativity

General

There are two types of time travel: time travel to the future and time travel to the past. Time travel to the future is definitely possible. Einstein’s special theory of relativity, developed in 1905, shows that time passes at different rates for people who are moving relative to one another although the effect only becomes large when you get close to the speed of light. Here, the special relativity of theory plays the role. If you travel in space and travel near the speed of light, and when you came back to the earth, your clock will be ticking off the time more slowly. So when you reach the Earth, it is going the future on Earth. Time travel to the past is something where the argument happens. It is theoretically possible according to general relativity where the space and time bends to form space-time curved geometries that allow travelling faster than speed of light. But Einstein’s equation showed that the nothing is faster than the speed of light as the object which attained the speed of light would have infinite mass And zero length which seems to

Be physically impossible, although Some scientists have extended his equations and said it might be done. It allows for the possibility of the concept of wormholes– a kind of tunnel through space-time connects very distant parts of the universe through which we can travel to past or future.

Time travel Wormhole

through

A wormhole (or Einstein–Rosen bridge) is a speculative structure linking disparate points in spacetime which can be visualized as a tunnel with two ends, each at different locations or different points of time. It was realized that if you manipulate the openings of the wormhole, i.e., put one near a black hole or take one a high speed journey, then time of two openings of this wormhole tunnel will not tick off at the same rate so that you will not longer just go from one location in space to

Another, but from one time to another different time. In this way a wormhole leads to travel in past or future by covering a huge time in some small distance at a speed faster than light. Science fiction is filled with tales of traveling through wormholes. But the reality of such travel is more complicated, and not just because we've yet to spot one. The first problem is size. Primordial wormholes are predicted to exist on microscopic levels, about 10–33 centimeters. However, as the universe expands, it is possible that some may have been stretched to larger sizes. Another problem comes from stability. The predicted Einstein-Rosen wormholes would be useless for travel because they collapse quickly. A recent research study found that a wormhole contains "exotic" matter that could stay open and unchanging for longer periods of time. Exotic matter contains negative energy density and a large negative pressure. Such matter has only been seen in the behavior of certain vacuum states as part of quantum field theory. If a wormhole contained sufficient exotic matter, whether naturally occurring or artificially added, it could theoretically be used as a

Method of sending information or travelers through space. Unfortunately, human journeys through the space tunnels may be challenging. Today's technology is insufficient to enlarge or stabilize wormholes, even if they could be found. However, scientists continue to explore the concept as a method of space travel with the hope that technology will eventually be able to utilize them.

The concept of time machine Time travel requires a device called time machine to take us to another time. This term is often used in fiction movies and stories, but it was popularized by the novel ‘the Time machine’ by H.G. Wells.

Research often involves bending of space and time so that the lines form a loop known as ‘Closed time like curve’. Research studies also thought of the need of an

exotic matter having negative density as present in wormhole.

3. http://www.physics.org/ar ticle-questions.asp?id=131

But the exotic matter only exists theoretically. Even if it really does, then it might be present in limited quantity which would be too small for the construction of a time machine.

4. https://www.livescience.co m/19582-time-travel.html

Conclusion Time travel to the future is somehow is considered as an easier task for the scientists while time travel in past does not appear to be possible for the present time, but maybe it will be possible if the wormhole or time machine could exists in future. With the physics that we use today, the field is constantly changing. Advances in quantum theories could perhaps provide some understanding of how to overcome time travel paradoxes. One possibility, although it would not necessarily lead to time travel, is solving the mystery of how certain particles can communicate instantaneously with each other faster than the speed of light.

Bibliography 1. https://www.space.com/21 675-time-travel.html 2. https://en.wikipedia.org/w iki/Time_travel

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