No, it’s not just how much longer an hour feels while you’re in tutorial
By Daryn Wright and Ben Buckley
If you’ve never heard of time dilation before — or you have but have never thought on it long enough to want to hide under a table — prepare to experience a confusing amount of feelings, ranging from awe to terror to existentialism.
Wikipedia defines time dilation, according to the theory of relativity, as an actual difference of elapsed time between two events as measured by ob- servers either moving relative to each other or differently situated from gravitational masses. If this jargon confuses you, don’t worry, you’re not alone. Essentially, what we hold true on Earth for the relative experience of time differs due to differences in velocity and gravity in outerspace. So the farther away you are from the gravitational pull of the giant mass that is Earth, the more time becomes a relative term.
In order to fully understand what exactly is going on here, we must first separate the effects of velocity and gravity on time. Both of these fall under the category of relativity, with special relativity pertaining to the effects of speed/velocity on time and general relativity referring to the effects of gravity on time.
With special relativity, the effect of a hypothetical astronaut’s velocity (a measure of speed in a particular direction) as s/he approaches the speed of light relative to an observer, is that less time passes for the astronaut than for the observer. Technology limits the effects of velocity on astronauts though, so the difference it creates is minuscule; as their velocity approaches the speed of light, the difference would be higher, but as it stands, the astronaut crew has only aged about 0.007 seconds less than those on earth.
Not that you could travel at the speed of light, though. The speed of light in a vacuum is constant, and stays the same no matter who’s measuring it. Whether you’re the twin on Earth or the twin in space traveling near light speed, no matter how fast you’re going, you will always measure the speed of any light in a vacuum as being exactly 299,792,458 metres per second.
For example, if you’re in a train going 40 meters per second, and you run at five meters per second towards the front of the train, an observer standing still by the tracks will measure your speed as 45 meters per second. But if you shine a flashlight towards the front of the moving train and measure the speed of the light, both you and the observer will measure the light as being exactly the same speed.
General relativity works like this: the further away from Earth this hypothetical astronaut travels, the force of gravity decreases, thus increasing the amount of time that has passed. The effect of being far away from a gravitational force, though, is different. It will appear as if the clock is moving faster than if it were close to the source of the gravitational force, aka on Earth. The experience of time feels the same to both parties (those on Earth and those in space), despite the effects of time dilation, but the person in space has experienced less time than the person on earth. This is also exaggerated as more time elapses.
Think of it this way: an astronaut with a non-astronaut twin spending ten years in space would come back to Earth, where 50 years have passed. These twins are traveling at different speeds (one on Earth, one in the rocket) but they measure the speed of light in a vacuum to be the same. This sounds crazy, but it adds up because time is also passing differently for each of them. That’s why the twin in the rocket has aged more than the twin on Earth.
The part that makes me squeamish is the larger implications of all of this. Time travel isn’t some fictitious tale involving morlocks; it’s not just possible, it’s already happening.
If this doesn’t make you marvel at the wonders of the universe, I don’t know what will. It certainly makes everything seem rather slippery and intangible though, and I feel a tiny bit like a shivering doe in headlights, wondering what it is that’s inside that Cadillac hurtling towards me at 100 mph.
BRB, gotta go curl up in a blanket in a dark room now.
