**"**

**Is time travel possible?"**- the most perplexing question that annoys every physicist.

Is time travel really possible,huh?

Yeah, of course. According to quantum theory and Einstein's relativity, time travel could be possible! Let me explain how certain physical theories claim that it could be possible, in a nutshell.

**Einstein's Special Relativity:**Einstein's theory of Special Relativity unfolds a bundle of concepts, that were weird and puzzling to his generation. Some of them are the mass-energy equivalence, Lorentz contraction, relativity of simultaneity, invariance of the velocity of light and time-dilation.

In this context, his concepts on "Time-dilation" is going to help us figure out "Time-Travel"

According to Time-dilation, clocks that are moving with respect to an inertial system of observation are measured to be running slower. In other words, for a stationary observer, moving clocks appear to go slower than stationary clocks. This thing can be represented mathematically as

So, if the velocity of a body approaches the speed of light in vacuum(c), then the time interval between two events increases appreciably.

If our velocity(v) equals the speed of light in vacuum(c), then the denominator becomes zero and the measured time becomes infinity. That is, Time stands still!

Thus, this theory explains that it is possible to travel time! We can project ourself to the space and travel at the velocity of light(c) for several centuries and return back. But the problem is that one cannot attain the speed of light in vacuum.

But there has been a group of scientists who say that this "time-travel" concept of Einstein is just a theoretical and hypothetical crap and has no significance in reality. If you are one among them, the you must read this example.

**Proof:**

You might not know, but every second, a bunch of tiny nuclear particles called "cosmic ray muons" passes through your body. They are too small to detect and causes a very little damage to your body cells. Most of the time your body repairs the cells that has encountered this cosmic ray attack. These particles are formed in the atmosphere due to the collision of stable nuclear particles from the sun and stars and the atmospheric molecules. They are unstable and they travel at the speed of light(300,000 km/s). They arise from the atmosphere which is at a distance of 20 km from the surface of the earth. Also, they travel at the speed of light.

So they must take roughly 7 millionth of a second to reach the earth's surface. The problem is they are unstable and live for only 2 millionth of a second. After that time, they vanish. So they should have been vanished in the atmosphere itself. But how do they manage to reach the earth's surface, even after their life-time?

Einstein's special relativity claims that they should have travelled across time and thus they've managed to reach the earth's surface. Their high velocity which is comparable to the speed of light in vacuum enables them to travel across time and reach the earth!

Well, exemplified by this case, Einstein's time-travel concept has been proved to have significance in reality. Cheers!

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