/sci/ - Science & Math

>>10290607
I can explain exactly "why" but it's going to be a bit hard to stay with me.

First you need to know something. Light always goes the same speed for every observer.

Normally if you drive in a car at 50 miles a second and throw a ball straight with 30 miles a second the ball will go 30 miles a second from your perspective and 80 miles an hour from an outside perspective because of the added speed from the car.

THIS IS NOT THE CASE WITH LIGHT. Light emitted from the headlights of the car won't go the speed of light+50 miles an hour. It'll still go the speed of light from both the outside perspective as well as the perspective of the driver.

Okay so now that we have established that light always goes the same speed to all observers we can give you an example of a really cool thing.

Imagine there is a giant glass train that is completely transparent. And someone inside (Observer Green) is dribbling a basketball in it while standing stationary on the same place.

You (Observer Red) are standing outside of the train on a hill looking from the side so that you can see the entire length of the train when it rides past.

Look at my shitty paint drawing. For Observer Red looking from the outside the Basketball is moving in a zig-zag motion because the train is moving through space from left to right and the ball inside it is moving up and down. Meaning the net motion is a zig-zag.

However to Observer Green dribbling the ball it only goes up and down. However you can easily explain this away by just saying that the speed differs from the observer since Observer Green doesn't take into account the motion of the train and you would be correct.

However now instead of a basketball. Imagine a ray of light bouncing between 2 perfect mirrors up and down instead. Light must always move the same speed to all observers.

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