davegtt

60 I all hear you say? Well not on the 31st of December 2008 there isnt.

2008 gets an extra second - | MSN News UK - news & weather

Very strange.

scoobynutta555

Not so strange. The speed at which the earth rotates differs slightly (due to tides and wind). Also, it's believed that the earth's spin speed is ever so gradually slowing so days are becomming longer. Time on Earth is provided by atomic clocks which are a more accurate reading of time in a day than an earth day (hence the need for adjustment). I'm no boffin, just watched a programme last week about it on tv.

sarasquares

iTrader: (1)

this post makes borats thread make sense now

ex-webby

This is indeed true.

Known as "leap seconds", and is the bain of a WRC timing company's life (or that of anyone using GPS time as an accurate time reference)!

Its currently set at something like 13 seconds.

Can't you tell I'm great fun at parties!

ex-webby

Director of Time!

Now THAT's a business card!

mrtheedge2u2

Simon.... you getting out a bit more nowadays????

ex-webby

LOL.. clearly not!

TopBanana

Aren't relative times more important? Unless it changes during an event of course...

ex-webby

Yeah, absolutely.. the "bain", is that when a GPS device first fires up, it needs to acquire two things - a gps signal, a what's called "almanac".

The almanac contains loads of information like the current position of the satellite constellation, and what the current leap seconds are.

This almanac is broadcast across the GPS network once every 12.5 minutes.

This means that a device that has fired up from cold, or after coming out of an airfreight flight case from another continent, (or worse, one which has a failed internal battery) will run at the wrong time until it has received almanac - potentially 12.5 minutes (or multiples of that, if it misses the bit with leap seconds)

The worse part is that the majority of GPS devices don't tell you whether they have almanac or not.. the time just suddenly changes.

In WRC, we use GPS as the main time reference for all the timing.. and not just the "timing", as in the timing of the rally, but the intricate high resolution timing to control all the data communications for the safety tracking, etc. So its critical that it is controlled exactly.