Every so often we stumble across an idea that changes our understanding of the world we live in.
Sometimes this “new understanding” affects the way we live or the way we think. It may enlighten us, entertain us, or even scare us.
Generally speaking, these epiphanies become more and more rare as one gets older. A couple of years ago, I was fortunate enough to experience such a revelation- and it blew me away.
At the time, I was reading about Einstein and studying some of his theories. Though I was familiar with terms like general relativity and quantum mechanics, I couldn’t tell you anything about the concepts they described. Given that it took me over a year to develop a solid grasp of the theories (the strength of one’s grasp being, of course, relative), I won’t waste time in a futile attempt to convey them here.
However, I would like to spend a moment exploring a few of the more mind-blowing ramifications of Einstein’s concepts— the concept of time dilation.
(If you’re not concerned with why the twin paradox is true, you can skip ahead to the next section)
Time dilation is best demonstrated by thinking of trains.
Imagine that Bob is standing in a moving train and Erin is standing on the ground where the train is about to pass by. Bob is bouncing a ball, which travels from his hand to the ground and back up to his hand (a distance of roughly 5 feet, from Bob’s perspective). However, from Erin’s perspective, the ball travels the same 5 feet PLUS the distance the train traveled during that time.
Now, the initial reaction is to say, “Well, the ball really traveled the same distance- since Bob was moving and Erin was standing still, she was correct”. But is Erin standing still?
Isn’t she standing on the Earth and isn’t the Earth moving? Follow this road a bit further and you must eventually concede that the ball traveled different distances depending on who is observing it (destroying the idea of absolute space).
But we’re still left with absolute time- because in this illustration, we are saying that the ball is also traveling at different speeds depending on who is observing it.
What Einstein proved through special relativity is that this is not the case with light.
Light travels the exact same speed no matter who is observing it or where it is observed from.
Bob and Erin, though they are traveling different speeds themselves, both observe the exact same speed for light- 186,000 miles per second. Imagine Bob is now shining a light from a flashlight down to a mirror onto the floor and it is reflected back up to his eyes.
It becomes a simple equation: Speed = Distance / Time.
If a) speed is the same (as is the case for light) and b) distance changes depending on your perspective, then c) time must also change depending on your perspective.
No doubt that all makes perfect sense to you. But just in case it doesn’t, here are a couple of videos explaining it further:
The Twin Paradox
Complicated as the concept is in and of itself, the implications are even more perplexing.
We come now to the thought experiment known as the Twin Paradox.
Time dilation requires that the closer one gets to the speed of light, the more time must “slow down” relative to other observers. Imagine, for instance, Bob and Erin are twins. Bob stays on Earth and Erin gets into a space shuttle that travels out into space and returns to Earth.
Time dilation requires that when Erin returns, she will have aged slightly less (less time will have passed) than Bob. The faster Erin travels, the less she will age relative to Bob.
Think this is sounding more like science fiction?
Consider an experiment first conducted by Joseph Hafele and Richard Keating in 1971. Two atomic clocks are used- one placed in an airplane and another on the ground. The airplane then travels around the Earth and returns to where it began. When the clocks are then compared (and other effects are accounted for), it is found that the moving clock “ran slower” than the stationary one.
Now for the fun part… How big can this effect be?
Can Erin travel fast enough to return and meet Bob’s great great grandson? How far “into the future” can she go?
Surprisingly, the only thing that places a limit on time dilation is technology. In the 1971 experiment, the “moving” clock only lost a fraction of a second relative to the “stationary” one because the airplane was only moving at a very small fraction of the speed of light.
In the future, it is completely conceivable that vessels may be built fast enough that time travel (into the future) can be done on a more significant level.
Could a person “jump” 10 years into the future? 50? 1,000? These are all possibilities given adequate advances in technology.
In conclusion, “time travel” fundamentally occurs every time we move relative to each other, though on an insignificant scale. However, there is nothing but technology to prevent small-scale time travel to one day become large-scale.
It’s really just a matter of time.
*Photo Credit: Xava Du (Creative Commons)