Can we really travel through time? The short answer is yes! That’s right. We all have the ability to move forward in time, even if we don’t realize it. If you want to jump into the future, can you just go to sleep and wake up a few hours later? Of course, that question is deceptive. We want to be able to go back and repeat the stupid mistakes we made many years ago. Who doesn’t want them to go back and talk to their 15-year-old relatives? Tell them not to make the mistakes you made (or they will). Or maybe you want to travel 500 years into the future and see the flying cars that we promised in the 2000s. Fortunately, time travel is theoretically possible.
In fact, there is no law in physics that prevents time travel. That’s right, according to all the laws of physics we know, it is perfectly reasonable to travel at any time. But as the saying goes, with great power comes great responsibility. Time travel is an extremely dangerous endeavor with devastating consequences, and it is also confusing in paradox.
For example, what if I travel on time and prevent World War II? Sounds like a brilliant idea doesn’t it? Countless lives could have been saved, I would have been admired as a hero! Not necessarily. Although I want to save lives, I want to destroy others as well. Do we rely on all the technologies that were developed during the war, such as jet engines and nuclear power? In fact, the map of the world can be completely different. The situation could be worse than we actually kept history.
Another famous time travel paradox is the Grandpa Paradox, which basically says that if we say, for example, I go back to the time before my parents were born and prevent my grandfather from meeting my grandmother. My parents could not meet and thus, I was never born. So how could I go back in time to stop seeing my grandparents in the first place?
So we see that time travel can be a bad idea, but suppose we really want to go back in time, how do we do it? Well first we need to understand how time works.
Time is something we are all very familiar with, we all know what it is, but still we can’t see it, we can’t touch it, we can’t communicate with it in any way, we can only observe it. Isaac Newton thought that time is constant and never deviates, which would certainly make time travel impossible. Even Einstein believed that it was impossible, yet his equations made it possible. Einstein theorized that space and time are inextricably linked, which he referred to as “space-time.” So theoretically, if I were to combine space with something extremely powerful like a black hole, I would spend time too. While this seems to be true and scientists are exploring its possibilities, the real possibility of time travel seems to lie in its other theories; Relativity. In fact time travel using relativity is not just a theory, it has actually been done, several times! Now you probably think I’m crazy but the mystery seems to be going very fast.
According to Einstein’s theory of general relativity, no object with mass can travel faster than the speed of light, which is amazing at 299,792,458 meters per second in a vacuum (it is no air). This is an incredible 1,080 million kilometers per hour! So in terms of general relativity, we can only travel at 99.99% of the speed of light. But let’s say for example that I am sitting in the back of a plane traveling at the speed of light and I am walking from the back to the front of the plane at the rate of 10 kilometers per hour. I’ll skip the equations from this, but that means my speed and the speed of the plane means I’m traveling at a speed of 1,080 million and ten kilometers per hour, which is 10km / h faster than light, isn’t it? Wrong. According to the theory of relativity, time will actually slow down for me to prevent it from traveling faster than light. Sounds weird, doesn’t it.
Of course this scene will never happen in real life, as I said before we cannot travel faster than the speed of light. In fact, traveling faster than your light will require more than an infinite supply of fuel, which is obviously impossible.