On Jul 9, 1:02*pm, oriel36 wrote:

It is no exaggeration that none of you can state that the Earth is
round and rotating and regardless of what you think of me or my
intentions,that 'flat Earth/sidereal time ' point of departure is the
only way anybody can claim as a certainty.

It certainly is true that the change in local time with longitude is
evidence that the Earth is round.

And this change adds up to 24 hours as you go around the world and
return to your starting point. It doesn't add up to 23 hours and 56
minutes. That is true.

It may not make sense to you when we say this is a geometric fact;
that local time expresses a geometric relation between one's location
on Earth, the center of the Earth, and the Sun (projected on the plane
of the Earth's equator).

But if that does make sense, perhaps you can also see why it is not
tied to the speed of the Earth's rotation as such.

The Earth, after all, orbits the Sun at the same time as it turns on
its axis. So, if you wait a day, the Earth will not be in the same
orientation when the same place again experiences local noon.
Otherwise, the return of a star would take place in 24 hours.

Again, you have every right to ask: what's the big deal about the
return of a star.

This becomes more technical. The argument for taking the "sidereal
day" as the value of the Earth's rotation is that it removes the
qualification of the Equation of Time. The Earth is too big and heavy
to speed up and slow down over the course of a year, and so regarding
the return of a star, which takes place at genuinely uniform intervals
by a mechanical clock, unlike natural noon, as the proper starting
point lends itself to bringing the motions of the Earth to a clear
understanding.

If you don't find our understanding clear, because it depends on a lot
of fancy mathematics, I can't change that for you. But because we
understand that mathematics, and it's clear to us, we know we aren't
doubting you because we're brainwashed.

John Savard