We’ve all seen a scene in a movie where the world around the hero (or villain) appears to be in “slow motion”. It usually happens when the individual is moving very fast; notable references would be the famous “bullet-time” scene from the movie: The Matrix, or the Quicksilver scenes from the X-men Days of Future Past and X-men Apocalypse movies. The question is; why does this happen? Well, science has an answer!
According to the theory of relativity, time dilation is a difference in the elapsed time measured by two observers. This can be due to a velocity difference in travel speeds relative to one another or being differently situated relative to a gravitational field (think of black holes for example). In the perspective of the movie scenes it’s usually due to the first situation: “a velocity difference in travel speeds relative to one another”.
Essentially the individual who can view the world in “slow motion” is traveling at such a high velocity that everything else around him “appears” slow. The best way to observe this phenomenon is by looking at another object (i.e cars) travel at a fixed velocity while you (the observer) moves at different velocities.
If you’re stationary and a car travels past you at a speed of 40 mph (64 kmph), you’ll observe and assume that the car is moving “relatively” fast. However, if you’re traveling at the speed of 80 mph (128 kmph) the car moving at 40 mph doesn’t appear to be fast anymore; actually, the car moving at 40mph looks “slow”. This is because in your reference frame, you are moving faster than the object you are observing.
For individuals that are in uniform relative motion; that is two observers are remaining stationary or are traveling at the same speeds; time dilation is symmetric. Both of the observer’s clocks will run at the same time. A big factor that affects situation 1 of our time dilation definition is due to the invariance of the speed of light, and here’s where things get really weird.
To see this in effect, let’s assume we board a plane that can move at 95% the speed of light. Then, while we’re inside the plane you decide you really have to use the restroom so you run towards the front of the plane (where the restroom is) at 10% the speed of light. If you add the fact that the plane is already traveling at 95% the speed of light and you’re traveling at 10% the speed of light inside the plane, you’re technically moving at 105% the speed of light, right?
No, and this is where “nature” will stop you from traveling faster than the speed of light. The time inside the plane will get slow enough to where you cannot exceed the extra 5% speed of light. Because for one; nothing is supposed to travel faster than the speed of light, and two the speed of light does not hold any variance in all reference frames. If you traveled faster than the speed of light, then light would need to “catch up” to you which is also impossible. In short, the faster you go the more time slows down because you can’t run faster than the speed of light.
TL;DR: Whenever you think of the word slow motion it’s usually due to the fundamental ideas behind special relatively and time dilation. Super heroes such as The Flash, and Quicksilver view the world around them in “slow motion” because of their high speeds. Essentially if we viewed time from their reference frame while they we’re running extremely fast everything else would appear to be very slow.
This is because the speed of light remains constant in all reference frames; consequently, meaning the faster you move, time slows down because you can’t travel faster than the speed of light nor can light move at any different speeds.
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