Everyone has their own theories on the existence of time and time travel.
Take, for example, some of the comments from my post Are These Images Proof Of Real Time Travel? Now, granted, that post is entirely tongue-in-cheek. Those images aren’t proof of anything other than our wild imaginations. But some have left comments on that post stating that time doesn’t exist, it’s imaginary, or nothing more than a human construct used as a system of measurement. Something we ourselves invented.
On one hand, time is a form of measurement. Minutes, hours, days, years. We use the rotation of the Earth and its orbit around the Sun to count the passing of days and years. We create clocks and calendars, sun dials and ancient monuments to mark the positions of heavenly bodies. Those are, indeed, systems of measurement.
But time is never that simple, and imaginary it is not.
When I was younger, I also used to think that’s all it was — a form of measurement, something people made up. But then I found out about relativity, and my old ideas on time went flying out the window, very near the speed of light.
Einstein’s Theory Of Relativity
I don’t want to write a dissertation on Einstein’s theories, but I will point you in the right direction if you’re interested in learning more.
Basically, just know this: Einstein changed the way we view the universe. When, before, time was seen as immutable, after Einstein it became relative to the observer.
What’s more, space and time became linked — spacetime. And spacetime could be dilated. Changed.
Oh, and nothing could travel faster than the speed of light.
Scientists later performed experiments to confirm Einstein’s theories, proving not only the constant speed of light, but observing light bending, caused by gravity, and revealing the existence of time dilation, either as a result of velocity or gravitational forces.
One of Einstein’s better-known thought experiments is the twin paradox, in which one twin stays on Earth while the other flies through space in a super-fast rocket. When the spacefaring twin returns to Earth, he finds that he’s aged more slowly due to time dilation.
Everyday Proof Of The Existence Of Time (And Dilation)
The number one piece of evidence that time exists, and can be dilated, may very well be in your possession right now: a GPS.
A Global Positioning System, or GPS, is a satellite navigation system that allows you to locate your current position almost anywhere on Earth, to find routes to your destinations, or track other GPS devices. Maybe you have one in your car. Maybe on your smartphone.
The point is, they’re pretty common, and it’s all because of Einstein’s relativity and our modern understanding of time that we can make proper use of them.
This is because, in order for a GPS to accurately measure positions, the time dilation caused by its relative velocity and gravity compared to those of us on Earth must be calculated. Otherwise, our GPS devices wouldn’t be accurate at all.
Both relative velocity time dilation and gravitational time dilation occur in low-Earth orbit.
“To achieve this level of precision, the clock ticks from the GPS satellites must be known to an accuracy of 20-30 nanoseconds. However, because the satellites are constantly moving relative to observers on the Earth, effects predicted by the Special and General theories of Relativity must be taken into account to achieve the desired 20-30 nanosecond accuracy.” – Real-World Relativity: The GPS Navigation System
Let’s Wrap This Up
So, there you have it. Time is real. It exists. But you know what? Despite the science, people will continue to form their own theories and opinions on the existence of time, and muse about the potential of time travel.
It’s all for fun, after all, and we can take solace in the fact that, regardless of what we think, the universe is what it is.