- 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
- http://hpiers.obspm.fr/eop-pc/
-
- 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
-
-
-
- Comment
-
- From Tony Kimball
7-7-3
-
- 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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