Introduction to Time Travel
Time travel is one of the most interesting and controversial topics in the world of science. The majority of people think that time travel is not a real concept and is only science fiction. But in the world of science, while science fiction is bound to exist, some things are based on real experiments and are said to be scientifically proven. However, some things are not proven by real experiments but are theoretically proven by mathematics, and thus they are considered theoretically proven. Time travel is one such concept that has not been proven practically but has been proven theoretically by mathematics.
Theories and Scientific Basis
The theories of Einstein and many other scientists actually allow for the possibility of time travel. This is why time travel has become a controversial topic. As mentioned earlier, the idea that time travel has not been practically proven is both right and wrong at the same time. On a small scale, time travel has actually been proven. In an experiment, time travel was achieved, but only for a few nanoseconds. This is not a long duration, but it does demonstrate that time travel is possible.
The Hafele-Keating Experiment
This experiment was conducted in October 1971 and is known as the Hafele-Keating experiment. Astronomer Richard Keating took four atomic clocks, boarded an airplane, and flew twice around the world. When he returned to the Naval Observatory in the United States, he compared the time on the clocks. The amazing discovery was that the clock in the observatory was a few nanoseconds faster than the clocks on the plane.
Understanding the Results
To understand this with an example, if the initial time on both clocks was 4 hours, 10 minutes, and 10 crore 10 lakh nanoseconds, then after 4 hours, when they returned, the time on both clocks should have been 8 hours, 10 minutes, and 10 crore 10 lakh nanoseconds. However, the time on the clock on the plane was 10 lakh nanoseconds behind the time on the clock at the observatory, meaning the time was 8 hours, 10 minutes, and 10 crore nanoseconds. Some might argue that this difference is just a few nanoseconds and doesn't make much difference, or that the clock might have been damaged. But it's important to note that the experiment did not use just any general clock or even an advanced electronic clock; it used an atomic clock. The atomic clock is the most accurate clock in the world, capable of recording even the trillionth fraction of a second.
Implications of the Experiment
This experiment scientifically proved that the clock kept in a fixed place on Earth was faster than the clock kept on the plane. So what does this mean? Did the clock on Earth move faster, or did the clock on the plane slow down? In fact, the clock on the plane slowed down, which means that the faster an object moves, the slower time will pass for that object. This was the only proven experiment in history that demonstrates time travel. It was an official experiment, with no mysterious time machines involved. The clock on Earth remained stationary, while the clock on the plane traveled at a speed of 900 km per hour. This indicates that for any moving object, time passes more slowly compared to an object that remains stationary.
Everyday Time Travel
This means that if we examine it closely, we can notice that whenever we travel by bus or car, time passes more slowly for us compared to when we are simply sitting in our house. Yes, this may sound strange at first, but it's true—there is definitely a difference of a fraction of a nanosecond. So if we want to achieve time travel in the future, this method could be used. But what can we accomplish by traveling into the future by just milliseconds, right? If you wish to go five years into the future, you would have to travel really fast at a great speed. This is exactly what the great scientist Stephen Hawking said. Many sources on time travel state that if you travel at the speed of light, you can achieve time travel, but they often don't explain the logic behind it, which was discussed earlier. That's why it's said that if you travel at the speed of light, you can time travel.
Time Travel at the Speed of Light
What happens is that when you travel at the speed of light, time will pass very slowly for you compared to someone on Earth. If you travel close to the speed of light or at the speed of light in a spaceship, you will be experiencing time travel. If you travel in such a spaceship for three years and then return to Earth, you will find that 900 years have passed on Earth. This is because time passed slowly for you, but not for the rest of the world, so the amount of time that passed was less for you, but for everyone else in the world, time passed normally. Now, most people will ask how you can casually say that if you travel for three years, then 900 years will pass. There must be some exact ratio.
Mathematical Explanation
Yes, there is an equation and a ratio, and you can read about it on the official Wikipedia page. As mentioned earlier, time in the spaceship will be slower, and in comparison, time will pass much faster on Earth, but not for you. You will be traveling comfortably in your spaceship, and when you return, many years will have already passed. In this way, you can travel into the future. But one limitation is that you won’t be able to come back from that future. If you travel into the future using this method, you will have to stay there forever.
Practicality of Time Travel to the Future
So this is the science behind traveling into the future. But why is this method not practical and just theoretical? It's obvious that building a train that travels at the speed of light isn’t practical at all. Even if we manage to create such a machine, we won’t be able to provide any power source to operate it. So we can say that time travel into the future is not impossible, but it is not practical.
Time Travel to the Past
Since we’ve discussed time travel into the future, let’s now look at time travel into the past. We cannot go into the past by using something that travels at the speed of light. This makes traveling into the past even more controversial because of a paradox called the ‘grandfather paradox.’ This famous paradox states that if you somehow manage to travel into the past and kill your grandfather, how is it possible for you to exist in the present? If you killed your grandfather, then how were you born? You weren’t even born, so who killed him? This does not make any sense. This is a highly confusing problem with no clear answer, which is why many people think that traveling into the past is impossible.
Wormholes and the Grandfather Paradox
However, Stephen Hawking suggested that this is possible, and the method is through a wormhole. Albert Einstein had mentioned this earlier, and another name for a wormhole is the Einstein-Rosen Bridge. So what is a wormhole? It can be explained as a tunnel that connects two places or two time zones in the universe. But this concept is highly non-theoretical. Scientists argue that wormholes exist, but no one has ever seen one. So you can say that the chances of such a wormhole existing are very low, and this remains a mystery. Like every other unexplainable phenomenon, it only has theories. It is just mathematically proven, not practically.
Time Machines: Science Fiction or Reality?
The most interesting method of time travel is through a time machine. However, a time machine may seem like something straight out of science fiction. To operate this, we would need a special type of energy called negative energy. Negative energy is also a theoretical concept, like many other typical mysterious concepts that are only mathematically proven. No one has a specific formula for making a time machine, but we can still hope that in the future, someone might invent one. So we can conclude that time travel into the future is practically possible, even though we cannot yet build something that travels fast enough to achieve it. But time travel to the past is possible only mathematically, not practically.
Conclusion
So just imagine a time machine is made—would you like to travel back into the past to correct a mistake, or would you rather travel into the future instead?