Measuring the Earth's Slowdown/Re: Planet X: EARTHQUAKE Increase

josX wrote:

> And a note: the earth is at farthest away at 4 of juli right?

Right, for 2001. In 2002 it's July 6.

> I saw on the web, this means a difference from greenwich local solar
> time of 16 minutes, and on the oposite side of the year a difference
> of 16 minutes to the other side of the average clock. I think this must
> mean we have a shorter-than-average day now, 16.07 seconds shorter,
> however I am measuring (prematurely, I know, but I didn't want to post
> it yet!) now some 14.15 seconds slower than 24-hours, which is 30.22
> seconds slower than should.

You are somewhat off, there. Yes, the eccentricity of the Earth's orbit 
results in the fact that one solar day (from one culmination to the
next) is usually not exactly equal to 24 hours. But this effect only
amounts to the Sun being early or late by +- 7.66 minutes.
There's also the obliquity of the Earth's axis which has a similar
effect: the Sun is early or late _twice_ a year by +- 9.87 minutes.

The two effects added together result in the so-called "equation of
time". The EOT tells you by how much the real sun culminates earlier
or later than a fictitious mean sun (which would culminate every
24 hours). Obviously, if you attempt to measure the time between two
culminations you have to allow for the EOT, otherwise you are simply
measuring the EOT instead of a slowing-down of the Earth.

Currently, the EOT has a minimum of -14m 15s on February 11, is zero
on April 15, has a maximum of 3m 41s on May 14, is zero on June 13,
has a minimum of -6m 30s on July 26, is zero on September 1, has a
maximum of 16m 25s on November 3 and is zero on December 25 (data
taken from J. Meeus). So it seems things are slightly more complicated
than you thought.

If you expect official time to be manipulated at the level of a few
seconds, then you need to compute the EOT for each observation with
an accuracy of at least several seconds, too. I hope you know how to do
that (and be careful if you simply take data from the web. They might
have been manipulated...).

A suggestion: why do you observe the sun? Stars are not subject to the
EOT and culminate at regular intervals (which are not solar days of 24 
hours but sidereal days of 23h 56m 4.091s) so you need much less theory.
Furthermore, you have not only one opportunity of observation per day,
but you can keep an eye on a variety of stars (and you will need several
stars since in the course of a year the culminations of a specific star
will be unobservable for a while and they will happen at uncomfortable
times during other periods).

A question: what happens if your telescope gets displaced? This would 
force you to start a new series of observations. Have you thought of 
observing the moment at which the sun/star disappears behind a distant 
high building or mast or similar object? This defines a specific azimuth
(which need not be due south) and you only need to keep your scope in
the same place, you need not care for an undisturbed orientation of the tube.

Another question: what if your watches start to behave strangely (I think
you already saw something like this, but I skimmed your log only superficially).
Shouldn't you have several watches which control each other and use their
_average_ time for measurements? This would be all the more important since
you can't rely on (possibly manipulated) time signals; your own watches
are all you've got to tell you the time.

And a third question: you are trying to observe the rotation of the Earth
and to compare it to your own (unmanipulated) watches. You can't compare
it with official time signals because 'they' might make sure the time signals
follow each change in the Earth's rotation.
But there are other 'clocks' in the sky which you might use to check the 
time signals. For example, the motion of the Moon with respect to the fixed
stars or the Sun. Nancy has already made a lot of noise about the times
of Full Moon being out of sync with official time. Other correspondents
here have made it sufficiently clear (I hope) that the motion of the Moon
_is_ irregular by its nature and the inept attempts of some Nancyites to
read a speeding-up or slowing-down into the data are only inappropriate 
use of uneducated statistics.
But what about _really_ observing the Moon? The instant of Full Moon cannot
be determined very precisely, but there are other methods. For example, you
could determine the distance of close-by stars from the Moon. This can be
done with a sextant or by analysing photographs. Then you consult your
astronomical software at which instant this distance was expected to occur,
and you compare this time with the time shown by your watch when you did
the measurement (incidentally, this is precisely the method that was used 
for a while to determine official time before there were atomic clocks).

The best opportunity for such a measurement occurs when the Moon actually
occults the star, then you don't have to measure a distance, you just note
the time when the star disappears. If you measure this with 'official time'
and compare with your software, you should see some increasing discrepancy
if official time is indeed manipulated.
These occultations don't occur too often, but occultations of brighter stars
are quite easy to observe. Actually, the folks of the International Occultation
Timing Association http://lunar-occultations.com/iota/iotandx.htm have been
doing this all the time. Gee, I wonder if any of the Nancyites have ever bothered
to ask them whether they see such a discrepancy or not...

OK, that's it for today. We'll wait with discussing UT, UTC, Delta-T and
similar things until the need arises.

Ah yes, the equation of time was -1m 41s for June 20 and -1m 54s for June 21,
so you should currently measure something like 24h 0m 13s between culminations.

And no, I will not point out now how the atomic clocks in the world's timekeeping
institutes are regularly compared with each other, so that the U.S. clocks would
immediately be the odd man out, would they diverge more than some tiny fraction
of a nanosecond (or some such, too lazy to look it up now) from the others.
I will not point out that there must be a lot of atomic clocks at private institutes
which are _not_ regularly and stealthily synchronised to the Master Clock. I will
not talk about astronomers observing pulsars whose regular spinning makes them
some of the most precise clocks known to mankind and which would all together suddenly
make an apparent jump in their phase or frequency if the official time - against
which they are of course measured - were manipulated.

Bye,
Thomas

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Thomas Schmidt e-mail: schmidt@hoki.ibp.fhg.de