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Re: How do you plan on spending your leap second?

by jonix (Friar)
on Dec 26, 2005 at 11:07 UTC ( #519111=note: print w/replies, xml ) Need Help??

in reply to How do you plan on spending your leap second?

Our current system of civil time is based on coordinated universal time (UTC), which is based on a system of atomic clocks. Leap seconds are used to guarantee that UTC does not differ from the Earth's rotational time by more than 0.9 seconds. The Earth's rotation is decelerating at a rate of about 1.5 to 2 milliseconds per day per century due to the frictional action of the tides. Currently, the Earth is slower than UTC by about 2 milliseconds per day, so every 450 to 500 days the time difference reaches 0.9 seconds. Leap seconds are added to UTC to keep the two times in agreement.
Interesting questions arise:

How long will it take until...
  • we need a yearly, monthly or daily leap second?
  • we need a leap second per second?
  • we need a leap day per second?
  • Earths rotation will finally stop? Within our Sunīs lifetime?
(Update: Spelling enhancements)
  • Comment on Re: How do you plan on spending your leap second?

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Re^2: How do you plan on spending your leap second?
by Aristotle (Chancellor) on Dec 26, 2005 at 11:37 UTC

    Certainly not within the Sunís lifetime. The rate of deceleration is decreasing. What happens is that the tidal wave that the Moon pulls around the Earth is actually at an angle from the line that connects the gravitational centres of Earth and Moon, and is big enough to tug at the Moon. So the Moon gains momentum at the expense of Earthís torque and inches to an ever higher orbit. (See an illuminating explanation of how the tides really work.)

    In about two billion years (if memory serves) the Moon will be too far away to cause a totality when transiting in front of the Sun during solar eclipses. We live today in the era of the Earth-Moon system where the Moon is just far enough away to cover the Sunís disc exactly in a total eclipse that leaves the corona visible.

    Makeshifts last the longest.

Re^2: How do you plan on spending your leap second?
by kwaping (Priest) on Dec 26, 2005 at 15:45 UTC
    So that's why my clocks are always wrong..!
      If you have one clock, you know the time. Having two, you are not so sure anymore... ;)

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