Thinking With Stephen Hawking: Time Travel
What do you think can we travel through time?? Can we go back to the past or look into the future?? Well, it may sound impossible but the famous cosmologist Stephen Hawking gave three theoretical realistic ideas about traveling through time, out of which one is even practical.
Hawking says that time is a dimension, just like length, breadth and height. To explain it, he gave the example of a moving car. You go forward, that’s the first dimension. Then you turn left or right, that’s the second dimension. Then when you move up the hill, that’s the third dimension. Just like all the above three dimensions, time is a dimension, the fourth dimension.
Hawking says “the time machine is visualized in time travel movies. It provides the way or path to reach the fourth dimension, time. A brave and crazy guy travels through the time. The concept may be far-fetched, and the reality may be very different from this, but the idea itself is not so crazy”.
Hawking says that wormholes can act as the gateway to the time travel. He says that wormholes are present everywhere around us but they are too small to see. Physics has a principle that nothing is totally flat or smooth. Everything, right from the smoothest pool ball to anything else has some irregularities, holes and wrinkles. This principle is applicable to time also. The wormholes are present in these irregularities at the quantum foam which is considered even smaller than an atom. These small wormholes are constantly being created, then destroyed and then again are recreated. The two ends of a wormhole connect two different places at different times (suppose one end at earth and other at some distant planet). But if both the ends are placed at the same place, then it could work as a time machine. It can pass a man or spaceship to that place only from where he entered but at different time. In that case the two ends of the wormhole will be separated by time instead of distance. But unfortunately these wormholes are just billion-trillion-trillionths of a centimeter making them too small to see so it is obviously not possible for a human or a spaceship to travel through it. But physicist says that it may be possible to catch a wormhole and to enlarge enough so that a man or spaceship could enter it. So in this way we will only be able to travel to the future and not to the past. Reason being the nature may make it impossible to travel to the past so as the relationship between the cause and effect is maintained. For example, if you succeed to enlarge the wormhole and went only a few minutes back in past and kill yourself or went back in the past and prevent yourself from being born then there will be no chance to come back in the present time. You will no longer exist in the future to travel back in time.
Now, the question is will we be able to create such a large wormhole?? The answer is maybe scientist could expand a wormhole large enough to travel through but the wormhole will not survive. It will collapse due to the radiation feedback. When the natural radiations created by them (wormholes) will enter the wormhole continuously it will destroy it. This you can understand by taking the example of the sound of ‘peeeeeeeeee’ that you must have heard in some concerts or any function where mics have been used. These sounds from the mic are very sharp and irritating to our ears. These are produced due to continuous entering of our sound into the mic. As a result loops of radiations are formed which produces this kind of sound. If this kind of sound is not prevented then the system will be destroyed. The same thing will happen in the wormholes.
Hence, it will not be possible to travel through time using the wormholes.
No matter if the first experiment failed. There is another way to travel time. This method is based on the fact that just like a river, time flows with different speed at different places. This idea was given by Albert Einstein some about 100 years ago. “He was absolutely right”, Hawking says. And the proof of this gives the GPS (global positioning system) satellite network. The GPS system reveals the fact that time runs at a faster speed at space. All the aircraft are consist of a very precise clock. But then also the clocks present in the aircraft gains around a third of a billionth of a second every day. The system has to be corrected everyday otherwise that tiny difference would upset the whole system, causing every GPS device on Earth to go out by about six miles a day. This happens because of the Earth’s pull.
Einstein realized that matter drags on time and slows it down like the slow part of a river. The heavier the object, the more it drags on time. For example, a black hole present 26,000 light year away (40 lakh times the weight of sun). Hawking says that black holes can act as the natural time machine. It slows down the time far more than anything else in the galaxy. However, its gravitational pull is so strong that nothing can escape entering it but still if with the correct speed and direction/angle an object is projected towards the black hole, it will be possible that the object would simply revolve around the black hole. Suppose, if we succeed to make a spaceship revolve around it, from Earth it will look like the ship is making one revolution in 16 minutes but for the ones near the black hole (in the spaceship), the time will slow down. For 16 minutes, they will only experience 8 minutes. So, if they continuously revolve for 5 years, 10 years would have passed on earth. So after 5 years when they will return to Earth they will be actually entering the future and would be 5 years younger than the ones of their age. Hawking says that this is a better method than the wormholes but still impractical as it would be very difficult for an aircraft to revolve around the black hole sucessfully.
The practical way to travel through time is to move with a very high speed. Hawking says that the cosmic speed limit is 186,000 miles per second or the speed of light. Nothing can move with a speed of more than that and if you move with the speed of light, it will take you to the future. Just imagine that a super fast train is moving on a track that goes around the Earth. After some time the train speeds up and circles the Earth again and again with a speed of light. So with that much speed the train will take 7 revolutions around the Earth in one second. But it will not be possible for a train to move with that much of speed as the laws of physics doesn’t allows that. So let’s say it gets close to the speed of light. There will be an extraordinary event. The time will be flowing with a slower speed inside the train as compared to outside. Hawking says this happens to protect the cosmic speed limit. If a child is running inside that train then her speed will be added up with the speed of the train. In that way she will be running faster than the train (more than the cosmic speed limit). In this way she will be breaking the speed limit. But actually this do not happens. The nature will prevent her from doing this by slowing down the speed of time. With that much of speed, suppose the train starts on January 1, 2050 and continuously moves for 100 years and return on January 1, 2150. But the people inside the train will only experience one week inside the train because of the slowed down speed of time. They will travel 100 years in just one week. And it would be a totally different world from the one they’d left. In this way we can travel the future.
Today, the fastest motion going on the Earth is in CERN, Geneva. Pi-mesons are accelerated from 0 to 60,000 mps in a circular tunnel. They are accelerated till it starts taking circles 11,000 times a second in the circular tunnel which is almost the speed of light (99.99%). Because of pi-mesons we came to know that we can travel to future by moving with a high speed. The life span of pi mesons is just 25 billionths of a second but when they are accelerated with the speed of light their life span increases for about 30 times.
The fastest speed with which humans have traveled is 25,000 mps in Apollo 10. We need to move with a speed 2000 times than this (in Apollo 10) to travel in time and a spaceship large enough to carry that much of fuel that would be required by the ship to reach almost the speed of light. Hawking says it would take 6 years for the spaceship to reach nearly the speed of light.