Have you ever wondered how superman changes things to previous by rotating the earth in the opposite direction or how a man would go back and forth in a time machine in a sci-fi movie? Can we really travel in time? Do we need a time machine as shown in movies? Let’s see how time travel could be possible?
To begin with we need to know that space and time are mixed and time is relative but not absolute. Time slows down if you are at high gravity source and it speeds up if you are at low gravity source. Also, a fast-moving clock will tick slowly and slow-moving clock will tick faster as per Einstein’s theory of relativity.
Time travel can be done in two ways and are completely different:
- Time travel to the Future
- Time travel to the Past
With Einstein’s theory of relativity, he showed us that Time travel to the future is much easy if you can travel with the speed of light at 299792458 m/s. The law says that at this speed your clock will stop relative to earth’s time and when you step off the machine you will find yourself in the future earth.
To understand in a better way, let’s say you have a twin. You alone took the machine and traveled at the speed of light and returned back to the earth. You will be the same age and your twin would have aged older than you as your time has stopped relative to earth.
Time travel to the future can also be done if you can stick to a high gravity source like a neutron star or a black hole just like in Interstellar movie. Due to high gravity your time will slow down relative to earth’s time and when you return back to earth you will be in future earth.
We also have a theory proposed by Einstein which says warm holes connect different locations of the space time. To better understand, it is like a tunnel that connects different locations in space.
But if you can manipulate the openings of the warm hole in such a way that one is at high gravity and one is at high speed journey by which the time does not tick at the same rate at two entrances. By this you can not only go from one location to another but also can go from one moment to another moment in time.
We don’t know if warm holes are real or if we can manipulate their entrances and also a major challenge would be to keep the entrances open for too long as the gravity may close them. To keep them open we may need exotic matter which has negative mass. Though we have several uncertainties, these theories are not ruled out and we are constantly putting efforts to achieve time travel.
Want to know how Einstein’s Theory of Relativity helps in working of GPS, click here