Einstein vs Newton! How time is relative and why it matters

Einstein vs Newton! How time is relative and why it matters

If you’re even remotely into physics or science generally (or you’ve just been alive during the last 100 years) you will have heard about Einstein’s theory of relativity. To properly understand it though, and it’s importance to our understanding of how the universe works, is another matter entirely.

The truth is that, while complicated, it’s also absolutely fascinating!

Another famous scientist (who lived long before Einstein) was British scientist, Isaac Newton. Newton did away with the accepted theory of the time that the natural state of any object anywhere in the universe was stationery. Instead, he proved that all objects are in a constant state of movement and that the movement of each object is relative to the movement of other objects (both men also went on to develop theories about gravity too but that will be the next post).

Interestingly, while Newton touched upon the theory of relativity before Einstein, it was the latter who found a hole in Newton’s research when he realised that the concept of ‘time’ was in fact a relative construct (this is where most people log off but stay with me).

Assuming, as Einstein did, that the speed of light is constant (186,000 miles per second) it doesn’t matter how fast another object is moving – the speed of light is not relative, it remains the same. Always.

Now, if the speed of light is constant, that meant that Newton’s theory that everything moved relative to everything else was flawed (read ‘imperfect’).

For example, if you were to flash a light, two people travelling at different speeds – one walking straight toward the source of the flash and another running in the opposite direction, the person facing the light will observe the flash (what astrophysicists would call an ‘event’) before the second person because time is equal to the distance something has travelled divided by its speed. The speed with which the light rays were travelling were the same for both persons, but as the distance is different their observation of the flash would have occurred at different times.

In other words, the time of the flash is different (or relative) for each of the two individuals observing. That, ladies and gentlemen, is relativity!

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