Clocks

[undercovers]

What is the most accurate clock in the world, and how do we measure its accuracy (i.e. not the speed at which its counting but the point at which someone started it), is there a "master clock" from which all other should be set and if not why don't we all end up with different "times" around the world... thanks

[amarillis]

The National Physical Laboratory (NLP) has constructed the world's most accurate clock.

Previously, the most accurate way of measuring time, developed in 1967, was to measure the cycles of radiation that corresponded to a caesium atom's transition from one state to another.

By using this method scientists placed the duration of a second at 9,192,631,770 caesium cycles.

However, the a optical frequency method, uses a single strontium ion and is three time more accurate than its competition.

Not sure if there is a 'master clock' in use though.

[Kinetic]

An interesting point about atomic clocks is that due to their immense immense accuracy, they can be relied on to conduct incredibly accurate experiments. An atomic clock was once flown around the world and was found to be a few billionths of a nanosecond out from a stationary atomic clock with which it was previously synchronised - proof of travelling affecting time in some way I don't really understant it, this probably ties in with some space/time theory or another.

[IndieSinger]

You may be interested in this BBC story which appeared just last Friday!

[IndieSinger]

You may be interested in this BBC story which appeared just last Friday!

[IndieSinger]

You may even be interested in it twice, I don't know.

[IndieSinger]

Lovely, I didn't even provide the correct link... http://news.bbc.co.uk/1/hi/sci/tech/4023777.stm

 

[undercovers]

thank you - that is very interesting - i really had no idea that time could be measured like this in any feasibly useful way. some very accurate clocks out there - makes my casio look rubbish. Thanks for all your answers they have really helped my understanding (thanks for your perseverance with that link indie), but does anyone have any info regarding to what these very accurate clocks are synchronised (sorry still obsessing about a Master Clock)

[trilobite]

By master clock from which everything is measured from, do you mean as in time of day? (As in 'it's noon GMT therefore it must be X o'clock in Tokyo and Y o'clock in New York'?)

The requirements by science for measuring periods of time outstripped the accuracy of the 'second as a fraction of a day' definition and led to the second being redefined by cycles of a caesium-133 atom in 1967 as already described above, and the developement of 'atomic clocks'.

These clocks would be far too accurate by themselves to keep 'world time', as the length of a day (24 hour rotation) varies too much, and is actually increasing as the Earth slows down.

World time (Universal Co-ordinated Time or UTC) is still kept with atomic clocks, but uses a system of leap-seconds, (based on astronomical data and observations), which takes account of variances in the period of rotation etc. Leap seconds are added where necessary at the end of the month at 23.59.60 hrs. This ensures that, for example, 12.00pm GMT continues to occur, on avearge,  at noon on the prime meridian.

When you think about it, it's pretty meaningless saying its 12 minutes and 43.57341431.....etc seconds to five when asked the time.

[seal!]

Cheers IndieSinger, u just cheered me up. lol

[Carlos26]

As to where is the master clock, if I remember correctly from a program a few years ago, the good old Brits have it in Greenwich ue to some discovery showing the most accurate clock at that date.  used to be somewhere else apparently, not sure where thoughcould be France.