ec2-3-145-36-10.us-east-2.compute.amazonaws.com | ToothyWiki | RecentChanges | Login | Webcomic Aren't clocks brilliant?!? In ancient times, no-one really knew what time it was. This made organising things over wide areas extremely difficult (some might say this is a good thing, as for example it makes waging war more difficult), and ocean navigation impossible, and that was terrible.
Therefore quite a lot of human energy has gone into making better clocks. Notable innovators include John Harrison, who had the first clocks that would keep accurate time despite being shook up. These days we have the quartz movement, which is extremely accurate compared to spring wound movements. Fantastic!
The ultimate we have for accuracy is the atomic clock, which uses the decay time of various radioactive isotopes to mark time. Atomic clocks are so accurate that they can be used to perform relativity experiments and stuff in reasonable sized laboratories (like, the entire world, or a reasonably sized mountain range). Brilliant!!!!
It probably also helps that they re-defined the second based on Caesium-60 atoms ;-) --Bobacus
Unfortunately, this means they are more accurate than the Earth itself, which makes them problematic for actually measuring the time of day for people, as opposed to science experiments. The SI unit of time is the second and all others are derived from that, which is pretty much backwards from the actual useful measurements where the base unit is the time it takes the earth to go round the sun. That this can vary by small, but (now) measurable amounts from day to day is something we just have to live with, rather than define away, as most people are less interested in how long it takes light to get from a screen to their eyes than in what time they have to be in the cinema in the first place.
That's what LeapSecond?s are for. I was going to write a blurb about ET, UT, UT0, UT1, UTC, GMT, etc. but wikipedia does a better job already :-) [1] --Bobacus
Clock making is a loverly hobby. You can buy kits and assemble them and it's way better than making airfix models.
Some things these days called clocks do not really measure time. The 'clock' on a processor for example keeps everything synchronised, but is no chronometer (as any fule no, using the clock on a processor to count out a loop to keep time, even carefully calibrated, is no good as the variation in the speed of the clock will send you hours off every week).
Some funky things that measure time aren't really clocks. MoonShadow really likes the bamboo ones that gently fill up with water and then tip - measuring time isn't their purpose, but monks used to use them for that. Google: shishi odoshi
Now, read this again and this time try not to think of the FastShow 'clocks are brillllliant' guy. --Vitenka
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Clocks