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
excuse.
