Time travel is one of those topics for which I always get goosebumps when someone talks about it and I turn super excited and thrilled. And of course, it is one of my favorite topics. Today we gonna talk about time travel and it’s possibilities. So let’s get started.
What is time travel?
We all travel through time always. During the last year, I’ve moved forward one year ahead and so have you. Another way to say that is that we all travel in time at the rate of 1 hour per hour. But the key question is, can we travel in time faster or slower than “1 hour per hour”? Can we actually travel forward and backward in time, going forward or backward, say 2 hours per hour, or 10 or 100 years per hour?
It is mind-boggling to think about time travel. What if you went back in time and prevented your grandfather and grandmother from the meeting? You would prevent your father as well as yourself from ever having been born! But then if you hadn’t been born, you could not have gone back in time to prevent them from the meeting. This is called Grandfather paradox.
How could it be possible to imagine?
One of the greatest physicist Albert Einstein developed a theory called Special Relativity. This theory says that space and time are really aspects of the same thing, he called it space-time. There’s a speed limit of 300,000 km/sec (speed of light) for anything that travels through space-time. Special Relativity also says that when you move through space-time, especially when your speed relative to other objects is close to the speed of light. Time goes slower for you than for the people you left behind. You won’t notice this effect until you return to those stationary people.
Time travel also occurs for objects in gravitational fields. Einstein had another remarkable theory called General Relativity, which predicts that time passes more slowly for objects in gravitational fields (like on Earth) than for objects far from such fields. So there are all kinds of space and time distortions near black holes, where the gravity can be very intense.
Possible ways to travel through time
There are so many theories exists which claims that time travel is possible, but these theories are only theories and there is no practical way to do that yet. Let’s throw some light on some of the theories.
By increasing the speed
This is the easiest and most practical way to get to the far future i.e. go really fast.
According to Einstein’s theory of special relativity, when you travel at speeds approaching the speed of light, time slows down for you relative to the outside world. This is not a just a thought experiment – it’s been measured. Using twin atomic clocks (one flown in a jet aircraft, the other stationary on Earth) physicists have shown that a flying clock ticks slower, because of its speed.
In the case of the aircraft, the effect is minuscule. But If you were in a spaceship traveling at 90% of the speed of light, you’d experience time passing about 2.6 times slower than it was back on Earth. And the closer you get to the speed of light, the more extreme the time-travel.
The highest speeds achieved through any human technology are probably the protons moving around the Large Hadron Collider at 99.9% of the speed of light. Using special relativity we can calculate one second for the proton is equivalent to about 11 months for us.
With the assistance of Gravity
This method is also inspired by Einstein’s theory. According to his theory of general relativity, the stronger the gravity you feel, the slower time moves. As you get closer to the center of the Earth, the strength of gravity increases. Time runs slower for your feet than your head.
Again, this effect has been measured. In 2010, physicists at the US National Institute of Standards and Technology (NIST) placed two atomic clocks on shelves, one 33 cm above the other, and measured the difference in their rate of ticking. The lower one ticked slower because it feels a slightly stronger gravity.
To travel to the far future, all we need is a region of extremely strong gravity, such as a black hole. The closer you get to the event horizon, the slower time moves – but it’s risky business, cross the boundary and you can never escape.
Assuming you had the technology to travel the vast distances to reach a black hole (the nearest is about 3,000 light years away), the time dilation through traveling would be far greater than any time dilation through orbiting the black hole itself.
Note: The above situation described in the movie Interstellar, where one hour on a planet near a black hole is the equivalent of seven years back on Earth.
The most mind-boggling thing, perhaps, is that GPS systems have to account for time dilation effects (due to both the speed of the satellites and gravity they feel) in order to work. Without these corrections, your phones GPS capability wouldn’t be able to pinpoint your location on Earth to within even a few kilometers.
Through the Wormholes
General relativity theory also allows for the possibility for shortcuts through spacetime, known as wormholes, which might be able to bridge distances of a billion light-years or more or different points in time.
Many physicists, including Stephen Hawking, believe wormholes are constantly popping in and out of existence at the quantum scale, far smaller than atoms. The trick would be to capture one and inflate it to human scales – a feat that would require a huge amount of energy, but which might just be possible, in theory.
Attempts to prove this either way have failed, ultimately because of the incompatibility between general relativity and quantum mechanics.
Through the Black holes
Another possibility would be to move a ship rapidly around a black hole or to artificially create that condition with a huge, rotating structure. “Around and around they’d go, experiencing just half the time of everyone far away from the black hole. The ship and its crew would be traveling through time,” physicist Stephen Hawking wrote in the Daily Mail in 2010.
“Imagine they circled the black hole for five of their years. Ten years would pass elsewhere. When they got home, everyone on Earth would have aged five years more than they had.” However, he added, the crew would need to travel around the speed of light for this to work.
So is the time travel possible?
While time travel does not appear possible – at least, possible in the sense that the humans would survive it – with the physics that we use today, the field is constantly changing. Advances in quantum theories could perhaps provide some understanding of how to overcome time travel paradoxes.
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