View Single Post
Old October 28th 17, 08:41 AM posted to sci.astro.amateur
external usenet poster
Posts: 7,003
Default The First Known Interstellar Comet

On Friday, October 27, 2017 at 5:56:01 PM UTC-6, palsing wrote:

Gerald, no matter what you say or think, a star returns to 2 sticks every 23 56
04. Just about everyone knows this, and we define this as a Sidereal Day. Even
you can make this measurement for yourself. for it is incontrovertible. What is
your own interpretation of this easily verifiable measurement?

I'm pretty sure this same question has been asked of you several times in the
past, but I don't remember if you've ever answered it... but I doubt it.

Why, he has answered it countless times!

Point 1:
"Stellar circumpolar motion" is all very well, and one can certainly take into
account its periodicity as an "observational convenience" when designing, say,
clock drives for telescopes.

But if you will look at a clock, you will find that its hour hand returns to the
12 every 12 hours - so it does that twice in 24 hours. Not 23 hours, 56 minutes,
and 4 seconds.

So the 24 hour average day, not the "sidereal day", which forms the basis of our
calendar system and all our time measurement, is what is important and
fundamental. he is well aware that 23 hours, 56 minutes, and 4 seconds is the time between stellar transits. His interpretation of that fact is "So what?".

Point 2:
The geocentric astronomers, who followed Ptolemy, were mistaken in thinking that the Sun and the planets all went around the Earth. Copernicus was right; like the other planets, the Earth orbits the Sun. So we need to bring our thinking up-to-date.

An Earth-centered coordinate system is, thus, all very well for the purpose of tracking the movements of cars, boats, and airplanes. But the movements of the planets are properly understood from the viewpoint of a Sun-centered coordinate system.

The Earth being a celestial body, its rotation is a celestial motion, and this rule applies to that.

....and, of course, while the first two paragraphs state the obvious truth, it is
in the third paragraph where he goes off the rails.

Because his idea of a "Sun-centered coordinate system" for the Earth's rotation
isn't the one formed by the Sun and the fixed stars - which would be indeed just
peachy for keeping track of planetary orbits. And in which the Earth's rotation
would indeed have a constant period of 23 hours, 56 minutes, and 4 seconds.

Instead, since clearly (to him) parallax invalidates any attempt to transfer
Sun-centered *directional* co-ordinates to the Earth, the only right and proper
truly Copernican Sun-centered system against which to judge the rotation of the

is the one proposed by Tycho Brahe.


So you _are_ indeed right that if he ever tried to explain himself *in
sufficient detail* as to get down to where he is contradicting himself, he would
have to face the flaw in his way of thinking.

But he refuses to go that far; he is content to rest serenely with the
unquestionable truth of his mass of verbiage on the subject.

John Savard