60 Second Adventures in Astronomy. Number
ten, Special Relativity. Does time fly when you’re having fun? In 1905 Albert Einstein introduced the theory of Special Relativity, which said that – if
the speed of light is constant – then people
must experience time differently. Which may sound impossible – but Richard
Feynman later showed that you can prove it with
just lights and mirrors. If you set up two mirrors, one of which had
a flashbulb and a detector on it, you could build a
clock which ticked every time the flash was reflected back to its original source.
It would keep time perfectly – though would make a slightly annoying alarm clock.
But if you make this ‘clock’ go past you very quickly – the light has further to
travel. And since light always travels at the same speed – the
moving clock runs slower than when it was at
rest. So, though time might not fly when you’re
having fun – a moving clock does tick more slowly
than the observer’s stationary clock. Which may have changed the way we see the
universe – but doesn’t always make for a good