If you have a time machine, where would you like to go? You’d like to see your future maybe. We are always more interested in the future than in the past for obvious reasons. If you are someone who spends a lot of time thinking about the universe, then you may like to go to the time of BIGBANG i.e. considered as the starting of this expanding universe. Perhaps you even travel to the end of the universe. But how’s it possible? For this, we need to see the TIME in terms of physics.
TIME in terms of physics
As a 4th dimension. We all are familiar with three dimensions. A car moving on a straight path, take turns to left or right, up and down on a hilly road are the examples of motion of a car in one, two, and three dimensions respectively. All of us exist in the 3rd dimension.
Everything has a length, width and height. But there is another kind of length.A length in time. A human may survive for 80-90 years. The stones and mountains last for thousands of years. And the solar system last for billions of years. This is the length of time and travelling in time means travelling through this 4th dimension.
We are grown watching the science fiction movies in which scientists create a machine or tunnel to the past or future. A person whom we call time traveller steps into a machine and find a door that leads him to some other universe. Maybe the reality will be very different from this but the idea itself is not so crazy.
Scientists always wonder if the portal to the past and future could ever be possible with laws of nature. And it was believed that this is true and they give this a name. WORMHOLES: the tiny gaps and voids. Wormholes are all around us. But they are too small to see. These voids are also present in the 4th dimension and the concept is the same. They are smaller than a molecule or even an atom and come under the quantum foam.
These tiny tunnels through space and time constantly form, disappear and reform within this quantum world. They link two separate places and two different worlds. This was considered as a basis of time travelling. Unfortunately, these time-travelling tunnels are a billion trillionths of a centimeter i.e. too small for a human to pass through.
It may be possible to construct a giant wormhole by using power and technology but still, it may not be possible to travel to the past because of issue of causality and that brings us to a paradox. The science related to the time travel back to the past is quite complex. If, however, the Novikov self-consistency principle is correct then there is still a chance of time travelling to the past.
Time in Outer Space
Time is like a river. It flows with different speeds in different places and that is the key to travelling in the future. The idea was proposed by Albert Einstein. He realized that there is a place where time slows down and another where it speeds up. He was correct and the proof is right above our head i.e. in space. The Global Positioning System or GPS.
A network of satellites that revolve around the earth. Satellite makes satellite navigation possible. And these satellites reveal that time runs faster in space than on earth. Inside each spacecraft, there is a very precise clock. Despite being so accurate, they all become as fast as a billionth of a second every day.
These clocks are corrected every day from the earth. If it is not fixed daily, then the entire system will shatter causing every GPS device on earth to go up by 10 kilometers every day and you can imagine what difference it can create in just a day. The problem doesn’t lie in clocks. They run fast because time itself runs fast in space.
The reason for this extraordinary fact is the mass of the earth. Einstein realized that the mass drags on time. The heavier the object, the more it drags on time and this is what that open the door of the possibility of time travel to the future. Time is dependent on gravitation.
The higher the gravity, the slower the speed of time. This means that time is travelling with different speeds on different planets of our solar system because of different gravities of different planets. But this difference of time on the planets of the solar system is very minor.
If we want to see the difference of time than we need to find a celestial body whose gravitation is million times more than the Sun. One such body is BLACKHOLE that was considered a natural time machine. But using a black hole as a time machine is pretty dangerous.
Building a Time Machine
And the last but the best hope for building a real-time machine is to make a machine or anything like that which allow us to travel very fast. And let me give you any fact about the universe. There is cosmic speed i.e. 299,792 km/sec (speed of light). Nothing can exceed that speed.
This sounds strange but this is one of the most important principles of science. Travelling nearly with the speed of light will transport us to the future. To attain the speed of light means circling the earth very fast. 7 times a second. Travelling exactly with a speed of light is impossible as it violates the law of physics. But to travel to the future we need to travel with 99% of the speed of light.
With this speed, a trip to the edge of the galaxy will take just 80 years. This gets a bit tricky when we talk about travelling to the edge of the universe since the universe is not only expanding but also accelerating. The space that exists between the galaxies is continuously expanding which drives the edge of the universe further and further from us every single second.
Unfortunately, the universe is technically expanding faster than the speed of light (due to the expansion of space between matter) and currently it is theoretically impossible to reach to the edge of universe but who knows where science and technology will take us.