### Is Photon a Time Traveler ?

Time Travel is the biggest imagination and dream to the astrophysicists. Many great scientists like Albert Einstein, Nikola Tesla, Stephen Hawking, believed that time travel in possible by human being. Albert Einstein, in his Theory of Relativity, proposed some breakthrough techniques or processes of travel through time. But those techniques can’t be executed in practical using real life objects. So the whole concept of time travel remained in the Philosophy and fiction.

The Time Machine is a hypothetical device or a vehicle which makes time travel possible. The idea of a time machine was popularized by the writer H.G.Wells in his novel “The Time Machine” on 1895. And who travel through time he is the time traveler. The time traveler can be a person or an object or a particle.

### The Theory of Relativity

Albert Einstein, in his Theory of Relativity, explained how we or an object or a particle can travel through time. It means how a particle can go to the past light cone and the future light cone of its present state.
According to the Theory of Relativity, there are two basic techniques those provides us a concept of time travel. The techniques are,

(i)                  If a particle or an object or a person can travel almost in speed of light (3 x 108
m/s) then his or its respective time will be very less respect to the time in real natural world.

(ii)                If a particle or an object or a person can travel in a very massive area, then his or its respective time will be very less compared to the time of natural world.

Here, we will discuss about the first assumption of the theory of relativity.

According to the First assumption, if a particle or an object or a person can travel almost in speed of light, then according to him or it, the time will be very less respect to the time in real natural world. It means, if we can create a machine or a vehicle that can reach almost (approx 90% of) the speed of light, and if we can travel with the vehicle our respective time will be very less compared to the real world time. It means by executing this process we can go to the future (future light cone) of ours real time.

Now, here the problem to execute the whole process is, when the speed of the vehicle reaches the speed of light or almost the speed of light, then the mass of the vehicle increases to infinite. It means that to run the vehicle we have to provide huge amount of energy to it. But we don’t have that much of energy or fuel to run a vehicle in almost speeds of light. As we know that, speed of light is the maximum in vacuum and nothing can travel faster than light in vacuum. So we can imagine that how big is the speed of light. And to reach the speed of light, a vehicle needs a very very huge amount of fuel or energy. But in practical we can’t provide that much of fuel or energy.

And that is the main reason that we can’t use the process in reality.

But, if we think in a different perspective, we can get a thing that can travel in the speed of light. And that is light itself. As we know that, from the viewpoint of Quantum physics, light has a particle nature. Means, light is made of many particles, called Photon. Photon is a basic element of light. Like a cell is the smallest structure and functional unit of any living body, so cells do the same job that is done by the living body. In case of a non-living body (object), the structural unit element is the atom, so the job of a single atom is similar to the job of the whole body or object. Like all these, photon, being the structural unit element of light, the job of a single photon is completely similar to the job of light.

It means the speed of light is same as the speed of a single photon. So from this statement, we can understand that the particle photon is the only particle that has a speed of light. And also we know that the photon is mass less, means the mass of a photon is 0 (zero). So in case of travelling in a speed of light, the mass of photon can’t increase. So we don’t have to bother about the energy of the photon.

So can we say the photon a traveler?

As a photon can travel in speed of light, I think the photon can travel through time, according to the Theory of Relativity. And if photon can travel through time, of course photon is a time traveler.
But photon being a very mysterious particle it shows very mysterious behaviors. So we can’t think about a real time machine using a photon. Hope we can use a photon or the principle of a photon to make a time machine in future.