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

No, not 20 m/s. For them, the ball is moving at 30 m/s (i.e. 10 + 20). That much for common sense. The difference arises from the fact that we are measuring from different “reference frames.”

But it’s all good. Everyone agrees with the outcome. If the ball hits that person, the villain and bystanders calculate the same time of impact. Yes, people in the car see the ball moving at a slower speed, but they also see it moving towards them from their perspective, so they ultimately work the same way.

This is another major assumption of special theory of relativity. Physics is specifically the same in all reference frames, or in all “inertia” or non-affiliated frames. Observers can move at different speeds, but their speeds must be constant.

Anyway, now we can see why it’s so strange that the speed of light is the same for all observers, regardless of its movement.

Sea waves in the sky

How did Einstein get this crazy idea? I’ll show you two reasons. The first is that light is electromagnetic waves. Physicists have long known that light behaves like waves. But the waves need a Medium Sea waves need water. Sound waves require air. If you remove the medium, there will be no waves.

But what medium does sunlight pass through when you move through space afterwards? In the 1800s, many physicists believed that there must be a medium in the universe, so they did so Lighting equipment ether Because it’s fun to say it.

In 1887, Albert Michaelson and Edward Morley devised a clever experiment to detect this ether. They build a device called an interferometer, splitting the beam of light in half, sending half along two paths of equal length, bouncing the mirror, and fused again with the detector as follows:

Illustration: Rhett Allain