Can we travel in past or in future?

We can travel in the past as well as in the future too but for this, we require a metal who can travel more than the speed of light, Albert Einstein's theory of special relativity says that time slows down or speeds up depending on how fast you move relative to something else. Tychon is an element that travels at the speed of light but not more than it. It's why we can not travel through time machines, other metals can not travel at the speed of light. 

    Albert einstein shows time is an illusion, it is relative, it can vary for different observers depending on your speed through space. To Einstein, time is the "fourth dimension." Space is described as a three-dimensional arena, which provides a traveler with coordinates such as length, width, and height —showing location. Time provides another coordinate which direction although conventionally, only moves forward. 

    

We have to travel around our solar system greater than the speed of light then we will come in the future but there is no way to travel in the past by the theory of Albert Einstein.

2. We can also travel in time with black and white holes. With the help of black holes, we can travel in the past, and with the help of white holes, we can travel in the future. 

Where black hole exist?

There is no reflection/refraction of light in a black hole that why we call it a black hole.  

Another possibility would be to move a ship rapidly around a black hole or to artificially create that condition with a huge, rotating structure.

"Around and around they'd go, experiencing just half the time of everyone far away from the black hole. The ship and its crew would be traveling through time," physicist Stephen Hawking wrote in the Daily Mail in 2010.

"Imagine they circled the black hole for five of their years. Ten years would pass elsewhere. When they got home, everyone on Earth would have aged five years more than they had."

However, he added, the crew would need to travel around the speed of light for this to work. Physicist Amos Iron at the Technion-Israel Institute of Technology in Haifa, Israel pointed out another limitation if one used a machine: it might fall apart before being able to rotate that quickly.

Father Paradox:

Here is a hypothetical theory states by paradox. Besides of physics problem, If it's possible to time travel in the past or future.

 If a traveler travels time through the past and kills his father then what is the existence of a time traveler? or he killed himself in past then really time traveler exist? or it will destroy automatically? If that were to happen, some physicists say, you would be not be born in one parallel universe but still born in another. 

    Some scientists disagree with the options mentioned above and say time travel is impossible no matter what your method. The faster-than-light one, in particular, drew derision from American Museum of Natural History astrophysicist Charles Lu.