Relativity Theory and Time-Travelling

When we see the word 'relativity' somewhere, we cannot avoid reminding the great Physicist, Albert Einstein (1879 – 1955). Einstein introduced his 'special theory of relativity' in 1905 and developed into his 'general theory of relativity' which was published in 1915.

According to the theory of relativity; the mass of matter is given by

m = m₀ / (1 - v²/c²)^1/2

where m₀ is the rest mass and c is the velocity of light. The inequality v < c must be satisfied to have a rest mass to the matter. (i. e. m₀ has a real value). When v -> c, rest mass m₀ -> 0 and it reveals that the electromagnetic waves has no rest mass as they travel at the velocity of the light.

Time dilation is a concept which has been derived by the theory of relativity. Before this concept was introduced; time was not considered to be relative with respect to the frame we consider. But throughout the theory of relativity, the non-relative measurement is only the velocity of the light.

Consider a person on the Earth observing a rocket.

(dt) = (dt') / (1 - v²/c²)^1/2

where (dt') represents the time difference in the rocket , (dt) represents the time difference on the Earth and v represents the velocity of the rocket.

In smaller velocities (such as speed of a vehicle), it ts obvious that dt' is almost similar to dt, as (v/c)² value is negligible. But when v becomes larger; (say about 0.7c) there is a considerable time difference between the frames. And when v -> c ; (dt) -> 0 and this leads to the famous postulation; "If a person can travel at the velocity of the light, he never becomes old."

Let us assume that a person can travel at the velocity of 1.1 c. If we consider a time of a second, the person has traveled a distance of 0.1 light seconds more than the light. Have the glance at the following diagram.

Diagram 1:

When the light source and the man, both at rest; the light emitted when t=T is seen by the man by t=(T+1).

Diagram 2:

Consider a beam of light and the person travels by his maximum velocity. In the instance the person reaches line 'A', he can observe the light emitted in the same time (i. e. t=T), unlike in the previous sequence.

Diagram 3:

Consider the continuation of the motion in the above sequence. In the instance when the man reaches 'B', the light emitted in t=T is a light second away from 'B', in other words, the person sees the light which was emitted in t=(T-1). The man has started his motion when t=T and this means that he sees the past, hence this is the concept of 'time traveling'.

In the concept of 'time traveling', we had an assumption that the specified person's velocity is greater than c. But when the velocity of matter equals to c, it totally converts to energy as in E = mc² ; as the rest mass of the matter becomes zero. It implies that only the energy can achieve the ultimate goal of 'time traveling', but not the matter.