Einstein showed that time is relative. But … why is he?

No, no 20 m/s. The ball moves at a speed of 30 m/s (i.e. 10 + 20). A lot for a good sense. The difference arises from the fact that it measures different “reference frames”, one moves, and the other is fixed.

Everything is good, though; Everyone agrees on the result. If the ball strikes the person, the outstanding pegs and passers -by will count the same time to influence. Yes, the people in the car see the ball moving at a slower speed, but they also see the passers -by moving towards them (from their point of view), so they work in the end.

This is the other main assumption of special relativity: physics is the same for all reference frameworks or to be specific, for all “self-deficiency” frameworks or non-acceleration. Observers can move at different speeds, but these speeds should be fixed.

However, perhaps you can now see why it is actually strange that the speed of light is the same for all observers, regardless of their movement.

Waves in an empty sea

How Einstein got this crazy idea? I will show you two reasons. The first is that light is an electromagnetic wave. Physicists have long knew that light was spent like a wave. But the waves need Medium To the “wave” in. Ocean waves require water; The sound waves require air. Remove the middle and there is no wave.

But then, what is the way that sunlight passes as it travels across space? In the nineteenth century, many physicists believed that there should be a means of space, and they called it the name Luminifour aether Because this is fun to say.

In 1887, Albert Michelson and Edward Morley created a smart experience to reveal this ether. They built a device called the intervention scale, divides a beam of light into two halves and sent the half along two tracks of equal length, bounced mirrors, and merged again into a detector, like this:

Clarification: Rit Allen