Re: Earth Deceleration theory likely a farce

Just for fun I took the Delta-T values listed in the first column
of the second table on the web page:

http://user.online.be/felixverbelen/dt.htm

and fitted a second order polynomial to the values, first converting
the date values to "years ago" starting in year 2000. That is, year
2000 becomes t = 0, and 2000 BC becomes t = 4000.

The polynomial is of the form:

Dt(t) = a0 + a1*t + (1/2)a2*t^2 where t is "years ago"

so that the coefficients are, and can be interpreted as:

a0 = 125.98 sec : initial offset at t = 0 (year 2000)
a1 = -1.322 sec/yr : initial rate of change of offset
a2 = 5.99 msec/yr^2 : acceleration in rate of change of offset

Note that this is a very crude model that doesn't take into account
the fact that the Earth rotation rate, and the change in rotation
rate, and the change in the change of rotation rate,..., actually
fluctuate nonuniformly due to myriad physical processes. However,
that being said, it does actually fit the data values pretty well.

Now, we can differentiate the polynomial to determine the rate of
change of the Delta-T value for given years:

dD(t) = a1 + a2*t

and for 500 BC (or t = 2500 years ago) the expression gives 13.6
sec/yr change in Delta-T, corresponding roughly to a mean day length
about 37.2 msec shorter than 24 hours for that year.


.

Relevant Pages

  • Re: Earth Deceleration theory likely a farce
    ... Just for fun I took the Delta-T values listed in the first column ... and fitted a second order polynomial to the values, ... the fact that the Earth rotation rate, ...
    (sci.astro.amateur)
  • Re: Earth Deceleration theory likely a farce
    ... but the point is that Delta-T alone does not specify the day length, ... milliseconds extrapolated back to 1250 BCE. ... the current rate of deceleration which is nanoseconds per day allegedly, ... celestial reference for daily rotation through 360 degrees. ...
    (sci.astro.amateur)
  • Re: Earth Deceleration theory likely a farce
    ... the fact that the Earth rotation rate, ... sec/yr change in Delta-T, corresponding roughly to a mean day length ... about 37.2 msec shorter than 24 hours for that year. ... So one orbit of the Earth is 365.25 x 24 hrs, and the day length in 1250 BC ...
    (sci.astro.amateur)
  • Re: Earth Deceleration theory likely a farce
    ... the latest research simply indicates the delta-T was invented to ... Seleucid Period references for establishing ERP (earth's rotational ... maintains the rotation within a second of today's rotation. ... as the Delian problem due to a legend that the Delians had consulted PLATO ...
    (sci.astro.amateur)
  • Re: Earth Deceleration theory likely a farce
    ... other lunar times. ... Ultimately, though, only lunar eclipse times would be adjusted with zero ... The delta-T is definitely defective ... Considering that the value you assign for daily rotation through 360 ...
    (sci.astro.amateur)
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