# Einstein Explained to the Layman

People wonder how the theory of relativity arose. Was it sucked out of the air? Does the theory work?

With sound in still air we find that it is propagated at a definite speed and whether we emit sound while we are travelling fast or travelling slowly the speed of the sound relative to the air remains constant. We cannot make the sound go any faster or slower by travellingat different speeds while we are emitting it. If we are travelling almost at the speed of sound and we emit a sound we find that the wavefront travels just a bit faster than us, so we can almost keep up with it.

Now with experiments with light it was found to people’s amazement that light always travels the same speed relative to the person observing the light, not to what we might think the light is travelling through. Unlike sound we can never keep up with emitted light – it always moves away from us (the observer) at the speed of light which is a constant 300000000 metres per second. Whether we are at rest and shine a torch in front of us or are travelling almost at the speed of light and shine a torch in front of us the light wavefront travels away from us at 300000000 metres per second.

Using the evidence showing that light always travels at the same speed relative to the observer of the light, no matter how fast he/she is going, scientists used mathematics and this showed that we need a different concept of time. In fact the mathematics also showed that moving objects contract (become shorter) in the direction they are travelling and moving clocks slow down relative to the stationary observer. The mathematics also showed that moving objects become heavier as they speed up.

Was the mathematics correct? Well the mathematics has been used to design the shape of tunnels in which particles are accelerated to speeds near the speed of light. Using the mathematics consistent with the Theory of Relativity the tunnels do work and scientists can predict the path of particles. If we did not use this mathematics and assumed that the particles have a constant mass, rather than have an increased mass when they speed up, the tunnels would not work and the particle would crash into the tunnel sides. The mathematics consistent with Einstein’s Theory of Relativity has been used successfully so many times that those opposing the theory are considered to be a long way out of the scientific community and belonging to the society of daft cranks.

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