Earth Slowing Down

From Dr. Richard Sauder, PhD

Hi Jeff,
Did you know that the Earth's rate of rotation is slowing down? Could this be a precursor event to a possible upcoming shift in the Earth's axis? (Or some other major geophysical event?) Consider that when a spinning child's top slows down, it begins to wobble around its axis of rotation. That wobbling of a spinning body is called nutation. Is the Earth (also a spining body) possibly going to nutate? This is not an idle question, as the geologic record unambiguously reveals that the poles have not always been in their present positions.
Go here:
International Earth Rotation Service
Look in the upper left column under "Earth Orientation". Then click on "Leap Second". Read carefully. Note that there have been 21 "leap seconds" added to the clock since 1972. It seems that the day has lengthened by 21 seconds in just 32 years. That's a lot. The Earth is slowing down.
Scroll down the same "Leap Second" page for a graphic depiction of the addition of leap seconds in recent decades.
I wonder if something is getting ready to happen? Remember that if the Earth is slowing down, then all that kinetic energy will go somewhere else --perhaps into crust slippage, magnetic field alteration, physical changing of the axis of orientation? Something else? Like massive vulcanism? Global warming?
This story is not being widely reported by the popular press.
Richard Sauder
From Tony Kimball
The rotation of the Earth is not intimately related to the length of the year. It is related to the length of the day. The period of the Earth's orbit around the Sun determines the length of the year, and it is this value that is being synchronized by the leap second program.
The period of the Earth's orbit around the Sun is subject to variations resulting from interactions with all of the gravitational objects of the universe, but most particularly those nearby -- the other planets of the solar system. Because the orbits of the planets around the Sun are not synchronized, the forces upon the Earth due to those planets is different each year, as their arrangement in their repective orbits continually changes. Intercalary or "leap" days are added to the calendar on a regular basis, because the actual length of the year is not an even number of days. This does not imply that the Earth's rotation has slowed down. If it had, it would become necessary to add Intercalary days more and more often, until eventually every year would be a "leap" year.
Leap seconds are similar. The routine addition of 1 second to the year does not indicate that the Earth's rotation is slowing, but rather that the somewhat complicated devices of the leap year tradition are slightly inaccurate. The goal of the leap second program of the IERS is to insure the close synchrony of the UTC and UT1 time scales, as measured by reference to our most accurate reference clocks, so-called "atomic" clocks. As tiny (presumably) gravitational perturbations occur in the orbit of the Earth around the sun, the amount of deviation between UTC (which is how clocks are set around the world) and UT1 (which tracks the time of Solstice at Grenwich) is also perturbed. Without these variations, leap seconds could be scheduled on a regular basis, like leap days, but because these perturbations are sometimes more, sometimes less, and because the goal of the IERS is to keep UTC and UT1 within 1 second at all times, leap seconds are instead reactively scheduled.
The matter of leap seconds has become increasingly prominent in public attention, especially in technical circles, recently, because the LORAN and GPS satellite navigation systems maintain an absolute time measure, which deviates from UTC increasingly as leap seconds are added. As a result, the compromises which resulted in the current system are being reconsidered at the level of the international standards bodies, and in global academic discourse. As the ways in which people use time measurement systems change, the technical means of measuring time and synchronizing clocks change, and the defects in the older models become increasingly visible, it seems likely that some substantial change will occur in the definition of UTC, at least. What form it will take, I will not guess, being an uninformed outsider to the process.
Finally, I will note that the rate of the Earth's rotation is in fact slowing -- but that this slowing will not result in any additional leap second during our conventinally expected lifetimes.



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