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Jenny
7757.  Thu Jul 01, 2004 3:34 pm Reply with quote

I've started a thread about this in the Other Place, but I came across a nice little nuggetoid that I thought might be a good basis for a question.

Did you know that the earth is running slow?

Civil time is occasionally adjusted by one second increments (leap seconds) to ensure that the difference between a uniform time scale defined by atomic clocks does not differ from the Earth's rotational time by more than 0.9 seconds. Coordinated Universal Time (UTC), an atomic time, is the basis for civil time. Currently the Earth runs slow at roughly 2 milliseconds per day. After 500 days, the difference between the Earth rotation time and the atomic time would be 1 second. Instead of allowing this to happen, a leap second is inserted to bring the two times closer together.

The Earth is constantly decelerating because of the braking action of the tides, by about 1.4 milliseconds per day per century. This makes Earth's rotational time slow with respect to the atomic clock time.

The length of the mean solar day has thus increased by roughly 2 milliseconds since it was exactly 86,400 seconds of atomic time about 1.79 centuries ago (i.e. the 179 year difference between 1999 and 1820). The length of the mean solar day is at present about 86,400.002 seconds instead of exactly 86,400 seconds. Over the course of one year, the difference accumulates to almost one second, which is corrected by inserting a leap second into atomic time a little less than once per year. This leap second can be either positive or negative depending on the Earth's rotation. Since the first leap second in 1972, all leap seconds have been positive and there were 22 leap seconds in the 27 years to January, 1999. This pattern reflects the general slowing trend of the Earth due to tidal braking.

People get confused by this because they mistake leap seconds for a measure of the rate at which the Earth is slowing and think that the need to insert leap seconds means that the Earth might stop rotating within a few millennia. The 1 second increments are, however, indications of the accumulated difference in time between the atomic clock and the actual rotation of the earth.

The situation is similar to what would happen if a person owned a watch that lost 2 seconds per day. At the end of a month, the watch will be roughly a minute in error and the person would then reset the watch by one minute to have the correct time again.

The difference between that scenario and the leap second is that instead of setting the clock that is running slow, we choose to set the clock that is keeping a uniform, precise time. This is because we can change the time on an atomic clock, but it is not possible to alter the Earth's rotational speed to match the atomic clocks!

Source: http://tycho.usno.navy.mil/leapsec.html

 
IM2L844
12500.  Thu Dec 23, 2004 9:20 pm Reply with quote

Quote:
The difference between that scenario and the leap second is that instead of setting the clock that is running slow, we choose to set the clock that is keeping a uniform, precise time. This is because we can change the time on an atomic clock, but it is not possible to alter the Earth's rotational speed to match the atomic clocks!


Why wouldn't it be possible to re-define the second to x number of vibrations of the atomic clocks workings to match the earths rotation?

 
Flash
12505.  Fri Dec 24, 2004 5:26 am Reply with quote

I suppose because you'd no sooner do so than it'd be out of date because
Quote:
The Earth is constantly decelerating

 
Frances
12511.  Fri Dec 24, 2004 7:01 am Reply with quote

Q; Why is a stopped watch more use than one that loses a second every thousand years?

A; Because the stopped watch is right twice a day.

 
Caradoc
12513.  Fri Dec 24, 2004 7:08 am Reply with quote

So Eccles' bit of paper with 8 O'clock written on it is bettter than an atomic clock.

 
laidbacklazyman
12524.  Fri Dec 24, 2004 11:24 am Reply with quote

No Eccles' bit of paper was a forgery what you need is what Bluebottle's Grandad got when he did retire,that not only tells him when it's eight oclock but it also makes him a cup of tea

 
IM2L844
12526.  Fri Dec 24, 2004 5:31 pm Reply with quote

Quote:
Civil time is occasionally adjusted by one second increments (leap seconds) to ensure that the difference between a uniform time scale defined by atomic clocks does not differ from the Earth's rotational time by more than 0.9 seconds. Coordinated Universal Time (UTC), an atomic time, is the basis for civil time. Currently the Earth runs slow at roughly 2 milliseconds per day. After 500 days, the difference between the Earth rotation time and the atomic time would be 1 second. Instead of allowing this to happen, a leap second is inserted to bring the two times closer together.


This might all change in the not too distant future. The link below connects to a site with some information I find a little disturbing.

http://www.ucolick.org/~sla/leapsecs/dutc.html

 
Flash
12528.  Fri Dec 24, 2004 7:24 pm Reply with quote

That site made my head ache, but I did get as far as this bit:
Quote:
over the past 30 years (coincidentally since the inception of leap seconds) the rotation of the earth's crust has accelerated (my emphasis). This acceleration is apparently due to changes of fluid circulation in the outer core of the earth.

 
Frances
12536.  Sun Dec 26, 2004 7:32 am Reply with quote

So somebody sometime did actually say, 'Stop the world, I want to get off!' and for once God's doing it - but in His/Her/Its/Their own good time. Never mind - it's like the Big Bang, theoretically intriguing but of no practical use. Either that, or it's another conspiracy theory. Somebody Out There doesn't like us...

Don't worry about it - have a Good New Many Years anyway!

 
laidbacklazyman
12595.  Thu Dec 30, 2004 12:46 am Reply with quote

Jenny wrote:
Did you know that the earth is running slow?


as a result of the tsunami in the Indian Ocean it would seem the world has speeded up a little, how sad that the Americans had the technology to prevent the losses but the asians didn't seem to want to use it

from the news thread on davegorman.com wrote:
The north-west tip of Sumatra might have shifted to the south-west by as much as 36 metres, Mr Hudnut said. "That is a lot of slip. That earthquake has changed the map," he said.

However, scientists will have to use handheld GPS devices to establish the exact degree of shift. Some believe the land mass may have moved up or down, not sideways.

Richard Gross, a geophysicist with NASA's Jet Propulsion Laboratory in California, theorised that a shift of mass towards the Earth's centre during the quake caused the planet to spin faster by three microseconds, or three millionths of a second, and to tilt about 2.5 centimetres on its axis.

 
eclipse
12639.  Thu Dec 30, 2004 10:09 pm Reply with quote

laidbacklazyman wrote:


as a result of the tsunami in the Indian Ocean it would seem the world has speeded up a little, how sad that the Americans had the technology to prevent the losses but the asians didn't seem to want to use it

from the news thread on davegorman.com wrote:


I imagine that the Americans were selling it for a dirt cheap $5billion.

p.s Yahy Dave Gorman, defenetly the funniest man ever.

 
laidbacklazyman
12642.  Fri Dec 31, 2004 12:58 am Reply with quote

I think it was more the American Tsunami Research bods that have the gear to early detect, and I think they only need somerwhere to set up their study centre in a reciprocal agreement type thing. My understanding from BBC News was the Tsunami guys in Hawaii had enquired sometime ago about setting up a centre for the Indian Ocean but were met with a brick wall of red tape. Although you understand this is my take on what was said on the news, I am in no way an authority on research so it is quite likely that I have the wrong end of this stick.

On a side note with the world speeding up, does this mean I will put on or lose weight as a rate of the side efect on gravity? not that I'm vain or anything I'm just curious in a male version of the question "does this dress make my bum look big" kind of way

 
Cleverina Clogs
12698.  Sun Jan 02, 2005 1:52 pm Reply with quote

The earth is running slow! Personally I blame the government ;o)

 
eggshaped
13038.  Thu Jan 06, 2005 9:43 am Reply with quote

Something that struck me about the tsunami. Seeing as a butterfly flap can change the weather in ways we cannot predict, could this catastrophic event, which displaced so much water, lead to some massive meteorological changes? I know it's a piffling question in the scheme of things, but it's been bugging me.

 
Flash
13047.  Thu Jan 06, 2005 11:32 am Reply with quote

I think the point of the butterfly hypothesis is about chaos, which is to do with unpredictability. So a major event like this would have pervasive (but unpredictable) consequences.

 

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