So can Flash run faster than the speed of light?
It’s finally out, du Snyder cut Justice League. So what about Flash? This isn’t a spoiler, as Flash does in other situations: it has to travel faster than the speed of light to go back in time to warn the Justice League about something.
Of course many questions about physics need to be answered, so let’s get straight to the point.
What is so special about the speed of light?
It is easy to understand that speed is relative. If you were walking at 1 m / s inside a train moving at 10 m / s, someone standing still would see you moving at a speed of 9 to 11 m / s (depending on the way you walked). But our ideas about relative speeds are based on our experiences with things that move. And here’s the important part: almost every example of a moving object moves slowly. Yes, that supersonic plane is slow. The rocket going to the moon is also slow. Everything is slow, slow compared to the speed of light, with a value of about 3 x 108 anderea. We often represent the speed of light as a constant c.
At a faster speed, things are a little different. It turns out that even if you are in any frame of reference, you will measure the same value as the speed of light. Okay, let me give you an extreme example so I can see how this works.
Suppose you are sitting on the floor with a flashlight. In your frame of reference (let’s call it frame A), the Earth is stationary, and you measure its speed when you turn on the light. c. Sounds reasonable, right? Now there is another person in a spaceship in the middle of the speed of light towards the Earth (0.5c). Let’s call this spacecraft the B frame of reference. It is also stationary from the point of view of frame B, but the Earth moves towards 0.5c.
But what about the speed of light measured from frame B? Since the light came from the Earth and the Earth seems to move at 0.5c, wouldn’t it give the impression that this is moving at 1.5?c? No. It doesn’t work that way. It seems that frame B normally measures the speed of ERE light c. That is the fundamental idea of Einstein’s theory of special relativity.
Dilation of time and speed of light
Do you know what happens when two different people in different reference frames measure the speed of light? Strange things happen with perceptions of time. We call it time dilation. Let me explain with a classic example — a light clock. Imagine you have a watch and the “ticks” are light bounces between two mirrors. If the reference frame of this light clock is in the same frame (speed), then the time to tick 1 will be the distance between the mirrors divided by the speed of the light (c).
Now suppose you see another light clock, but this one is in a spaceship (so you can see inside with the windows). The spacecraft moves very fast, about half the speed of light (0.5c). You can see that the light on the clock is just moving c, as everyone sees the light at that speed. But with each “tick” that light moves back and forth between the mirrors, it has to move forward, because the mirrors are moving along with the spacecraft.