Rama Set
I am just thinking this through now: would the analemma of the sun at the point of axis rotation be completely dependent on the earth's orbit and not rotation?
Rottingroom
I would think it would be nearly vertical and you'd only see half of it
If you took an analemma photograph
Rama Set
Yeah, I was just reading that at the North Pole it is completely vertical and you only see the top half.
Rottingroom
Anyways if you were standing at the north pole there would no rotational velocity, and you'd just be spinning once in a day but that doesn't mean the sun wouldn't go 360° around you.
Rama Set
Yeah. Is it worth pointing out that the point of zero velocity is one dimensional, so even if you were standing on it you would still be turning?
Rottingroom
Yes you'd still be turning.
I don’t know if he would understand that. Maybe a merry go round example.
Stand in the middle, zero velocity but spinning.
Rama Set
He is right that there are two points that are not spinning. But they would not be measurable and effectively do not exist. Unless there is some way to measure a 1D object?
Rottingroom
How does that matter though?
How does it matter in reference to the suns position in the sky?
Rama Set
His example is not wrong but it is completely metaphysical. If you could observe from the two non-rotating spots, the sun would only move across the sky due to its elliptical orbit. However, this is a physical impossibility so we will always see the sun rotate in the sky from our FOR.
Rottingroom
Actually kudos to him cause this is very interesting
Rama Set
Yeah.
Rottingroom
One could not get directly in that spot though
It is absurdly small
Rama Set
It's one dimensional. Not even a lepton could occupy it.
Rottingroom
Hah
Rama Set
Actually they may be point like. Proton!
Rottingroom
Perhaps you could put a Foucault's pendulum right there and show that it will just sit there while the earth rotates underneath it.
Rama Set
I think it is the impossible. The calibration would be limited by the uncertainty principle.
Rottingroom
Even then though, I can't see how the pendulum could turn but I'm probably underestimating the difficulty in finding the sweet spot.
Rama Set
Yeah. I don't know what kind of tolerance you would get.
Rottingroom
But isn't this the point of swinging the pendulum? To avoid the tolerance. Therefore couldn't we swing it in
the direction of the sun and it would just stay that way?
Rama Set
There was a Foucault set up at Amunsden Scott station. It precesses at 15 degrees per hour.
http://www.southpolestation.com/trivia/00s/southpolefoucault.htmlOh, yes it should do that I think.