Starship Asterisk*

DavidLeodis wrote:

Beyond wrote:It's 3-smilies per post, David. Same as the quotes.

Oops, . I meant post not thread, honestly.

Beyond wrote:It's 3-smilies per post, David. Same as the quotes.

Nitpicker wrote:

DavidLeodis wrote:I am confused about the images of Saturn in the APOD and would appreciate any help. The "images of Saturn" link brings up images of Saturn ( ) that vary in the angle of the rings, but the images in the APOD all show the rings at the same angle. I wonder if they have been arranged like that so as to perhaps make a more picturesque montage? In any event though the images of Saturn are superb.

The "angle" in question is the angle that the ring plane (and Saturn's equator) is inclined to our line of sight. So, the angle does vary in the APOD. From top to bottom, we progressively see less of the South pole and more of the North pole of Saturn.

You could rotate any one of these images of Saturn by any angle, and it would be a natural, "horizontal" representation of how Saturn would have appeared to an observer from some place on Earth, at some time of the night. From most places on Earth, Saturn will appear to rotate through the sky each day (by about 180 degrees) from it rising, through its culmination, to its setting. But the "angle" under discussion in this APOD, varies very slowly, over Saturn's orbital period of ~29.5 years.

JimShea wrote:To Chris Peterson and others:
Whoopppsss! I was wrong. Sorry about that. I should have remembered the old axiom: Better to keep silent and be thought a fool
than to speak and remove all doubt.
Jim shea

DavidLeodis wrote:I am confused about the images of Saturn in the APOD and would appreciate any help. The "images of Saturn" link brings up images of Saturn ( ) that vary in the angle of the rings, but the images in the APOD all show the rings at the same angle. I wonder if they have been arranged like that so as to perhaps make a more picturesque montage? In any event though the images of Saturn are superb.

Chris Peterson wrote:

JimShea wrote:I have a bone to pick with today's discussion of the APOD.
Actually, Earth's axis of rotation is NOT pointed directly at the sun today (or on any day for that matter). A better description would be to say Earth's axis of rotation on the summer solstice is perpendicular to the plane of its revolution around the sun.

On either solstice, the Earth's axis of rotation "tilts directly toward the Sun" in the sense that it lies on the same plane as a line between the Earth and the Sun. The Earth's axis of rotation is never perpendicular to the plane of its revolution around the Sun. The angle between the two is called obliquity, and is about 23°, which doesn't change with the time of year.

APOD Robot wrote:... Since Saturn's grand rings orbit along the planet's equator, these rings appear most prominent -- from the direction of the Sun -- when the Saturn's spin axis points toward the Sun. Conversely, when Saturn's spin axis points to the side, an equinox occurs and the edge-on rings are hard to see. ...

geckzilla wrote:

Chris Peterson wrote:"Tips directly toward the Sun" doesn't mean "points directly toward the Sun" (which is where I presume some people find confusion). I don't think the wording is ambiguous, although it could possibly be clearer.

If the word "directly" were removed, it would remove the ambiguity of "tilt" which is where the ambiguity is.

Chris Peterson wrote:

geckzilla wrote:

Chris Peterson wrote:On either solstice, the Earth's axis of rotation "tilts directly toward the Sun" in the sense that it lies on the same plane as a line between the Earth and the Sun. The Earth's axis of rotation is never perpendicular to the plane of its revolution around the Sun. The angle between the two is called obliquity, and is about 23°, which doesn't change with the time of year.

Someone else on the Facebook page had a gripe about this, too. Personally, I did not find the explanation confusing at all because I am quite familiar with Earth's axial tilt and its relationship to the sun and I know better than to think it means anything but what Chris has elaborated on, here. It was ambiguously worded, but I would give most people the benefit of the doubt and presume that, like myself, they also figured it out.

"Tips directly toward the Sun" doesn't mean "points directly toward the Sun" (which is where I presume some people find confusion). I don't think the wording is ambiguous, although it could possibly be clearer.

geckzilla wrote:

Chris Peterson wrote:On either solstice, the Earth's axis of rotation "tilts directly toward the Sun" in the sense that it lies on the same plane as a line between the Earth and the Sun. The Earth's axis of rotation is never perpendicular to the plane of its revolution around the Sun. The angle between the two is called obliquity, and is about 23°, which doesn't change with the time of year.

Someone else on the Facebook page had a gripe about this, too. Personally, I did not find the explanation confusing at all because I am quite familiar with Earth's axial tilt and its relationship to the sun and I know better than to think it means anything but what Chris has elaborated on, here. It was ambiguously worded, but I would give most people the benefit of the doubt and presume that, like myself, they also figured it out.

Chris Peterson wrote:

JimShea wrote:I have a bone to pick with today's discussion of the APOD.
Actually, Earth's axis of rotation is NOT pointed directly at the sun today (or on any day for that matter). A better description would be to say Earth's axis of rotation on the summer solstice is perpendicular to the plane of its revolution around the sun.

On either solstice, the Earth's axis of rotation "tilts directly toward the Sun" in the sense that it lies on the same plane as a line between the Earth and the Sun. The Earth's axis of rotation is never perpendicular to the plane of its revolution around the Sun. The angle between the two is called obliquity, and is about 23°, which doesn't change with the time of year.

JimShea wrote:I have a bone to pick with today's discussion of the APOD.
Actually, Earth's axis of rotation is NOT pointed directly at the sun today (or on any day for that matter). A better description would be to say Earth's axis of rotation on the summer solstice is perpendicular to the plane of its revolution around the sun.

Chris Peterson wrote:

Craine wrote:Last I heard the concept of a toroidal planet was still, though highly theoretical, not impossible.

What mechanism could produce a toroidal structure in a planet massive enough to in hydrostatic equilibrium? As it spins faster, it simply becomes more oblate, until the outer surface can no longer be maintained by self-gravitation.

Craine wrote:Last I heard the concept of a toroidal planet was still, though highly theoretical, not impossible.

PhilT wrote:Great shot but interesting that no mention is made of the shifting cloud patterns, specifically the large blue one on the Saturn just below centre.......