For the fifth year in the row, we don't need a leap second to synchronize the Earth's orbit with the atomic clock.
Hm. What happens if, one year, Earth's orbit finishes one second early? Does atomic time lose a second? (What a mess that'd make!)
Re:Yes
ziggy on 2003-12-31T16:11:56
That'll be weird. Enough systems don't account for positive leapseconds, I'm sure even more don't account for negative ones.I wonder what they'll do. Will they keep the one second lag in the hope that everything realigns within a year?
Re:Don't buy it
ziggy on 2003-12-31T16:14:29
You forgot about door #3: that the wobbles a little as it moves and doesn't take a fixed amount of time to orbit the sun.Re:Don't buy it
phillup on 2003-12-31T18:35:48
Why can't the earth's rotational speed increase?
It doesn't need "new" energy... it just has to use the energy it has a bit differently. Or am I way off base there? (It has been a bit of while since physics class...)
If the friction between the core and the mantle changed a little bit... wouldn't that allow for a different amount of the rotational energy to get expended in actually rotating the planet?
And, possibly account for the magnetic drift that we've also been noticing...
Not trying to actually address *why* the friction may have changed... but... it seems to me that since the earth isn't really "solid" then we may have some shifting of contents during shipping that could account for the changing speed.Re:Don't buy it
jdporter on 2004-01-02T15:27:41
Sure.... except we're not talking about the length of a day here, we're talking about the length of a year. How many seconds does it take for the earth to make exactly one revolution around the sun?Re:Don't buy it
phillup on 2004-01-02T18:03:46
I don't think so... the length of a day is the measure... it just takes a year for enough of the errors to accumulate to make a sizeable adjustment.
Here is a quote:
The length of the mean solar day has 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). That is, 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 compensated by the insertion of a leap second into the scale of UTC with a current regularity of a little less than once per year. Other factors also affect the Earth, some in unpredictable ways, so that it is necessary to monitor the Earth's rotation continuously.
In order to keep the cumulative difference in UT1-UTC less than 0.9 seconds, a leap second is added to the atomic time to decrease the difference between the two. 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.
From: http://tycho.usno.navy.mil/leapsec.html
