Have you ever wondered how it would be like to go to the past and get a look at the dinosaurs in the stone age? or about visiting your grandchildren in the future? If the answer is Yes, you’re not the first person to do so. Human have imagined of time travel since the origin of human civilization. Travelling backward of forward in time, commonly known as time travel, is a topic explained by modern physics. The concept of time travel is more less frequently seen in popular sci-fi movies around the world. 

Time travel is the concept of movement between certain points in time, analogous to movement between different points in space by an object or a person, typically using a hypothetical device known as a time machine. Time travel is a widely recognized concept in philosophy and fiction. The idea of a time machine was first popularized by H.G. Wells’ 1895 novel, “The Time machine”.

In Physics, time travel can be described by a special effect called ‘time dilation’ and one day the same effect might make the significant time travel to the future commonplace. Time dilation is the relativistic showing of time (by a clock) that moves with respect to a stationary observer.

To see why moving faster through space affects passage of time, Let’s take an example here. Let’s say that ‘A’ and ‘B’ are wearing identical watches which they synchronize right before ‘A’ blasts off to space around the earth while ‘B’ stays on Earth. In the space shuttle, ‘A’ is travelling at roughly at 28,000 km/hr. relative to the Earth. If ‘A’ makes a few orbits round the Earth before he returns. After returning to the Earth, they compare the watches, it’ll be seen that less time has passed in the clock of ‘A’ as compared to ‘B’ (a very small amount of time nevertheless). Yes, the exact same effect is called as Time Dilation and is based on ‘The Theory of Special Relativity’ given by the great Albert Einstein.
The concept can be further explained by another example which goes as:
Let us consider that an Astronaut is travelling to a planet that is at a distance of 10 light years from the Earth at a speed of 90% of the light’s speed (approx. 2.7*10^7). By calculation, the time required to reach there would be around 11 years, right? This is actually not the case!! To a stationary observer it would indeed seem to take 11 years but to the astronauts inside the space shuttle, the time would reduce and the astronaut would get there at about 4.4 years. If they would return Earth at the same speed, they would be almost 9 years older than they were when they left Earth. But everyone on Earth would have aged 22 years more. In that sense, they’ve travelled 13 years into the future relative to the time on Earth.

If you could travel really close to the speed of light, say 99.99% (although it is practically impossible to gain such high speed due to the large amount of energy required and also our body would break up into atoms) and return to earth after travelling in space for 10 years. After returning you’d find that you had returned to Earth around 9000 A.D.

So, from the above examples it is clear that travelling into the future is totally possible!! We do it all the time! We do it all the time. Even when I’m writing this, I’m travelling to the future at the rate of 1 second per second. No machine required. However, if you want to travel to the future faster, you’ll have to travel faster. The ‘Theory of Special Relativity’ tells us that as you go faster, for an external observer at rest, time for you slows down as per the given expression:

Δt = the observer time, or two-position time (s)
Δt0 = the proper time, or one-position time (s)
v = velocity (m/s)
c = speed of light (3.0 x 108 m/s)

How about travelling to the past though? Physics doesn’t allow that because there is absolutely nothing to suggest that time is moving in any other direction other than forward. And also because of the famous Grandfather paradox which goes like- if you were to travel to the past and kill your grandfather before your father was conceived, there will be no father and hence no you in the first place. So, how could you have travelled to the past if you didn’t exist? So, to me, time travel to the past isn’t possible, however technologically advanced we may be?
   
Thinking about the conventional ‘Time Machine’?
Come on. It happens only in movies.