((work in progress} My proposal...

The theory of special relativity was proposed by Albert Einstein in whatever.

This theory claims that time is relative but the speed of light is constant.

In order to understand this we must first understand how we measure time, and how it is related to speed and distance.

Intuitively, in our minds, we measure short term periods of time by "beats" of our heart or of music. But when searching for precision we use "clocks". Time can be measured with a clock using a pendulum repeatedly reaching the same location, or by accumulation of sand grains or water falling through a thin hole.

Time is related to speed. Speed is measured in units of distance per time. For example meters per seconds, or miles per hour. Speed can be measured without regard to time, using a speedometer, or by comparing it to the speed of other moving objects.

So if we know something's speed and the distance it went, we can know how much time passed. Thus we can define time by speed and distance. Since speed is measured in distance per time (e.g. miles per hour), time is defined as distance per speed.

${\displaystyle t=d/s}$

${\displaystyle hours=miles/(miles/hour)}$

Actually all clocks rely on a constant speed. A sandhour clock relies on the speed of sand falling through the hole to be constant. A pendulum clock relies on the relative speed of the pendulum (compared to the distance it goes from the center) to be constant.

Here are some examples:

A regular hand clock's minute-arm moves one full circle every hour, so the time of an hour is when the minute-arm moved a whole circle, and half an hour passed when it moved half a circle.

If a car moves at 30 mph and went 30 miles, then we know that 1 hour passed, and if it went 60 miles, then two hours passed.

If we know that our car is moving at 50 mph, and see another car going the same distance and starting or ending at the same time, then we know its going at the same speed as us. Assuming the cars go at a constant speed we can see what distance the car went, and thus know how much time passed.

But if we look at a car driving in font of us and going at the same speed as we are, the other car seems to be at zero speed. Its not moving away from us at all.