mincam

Please note that I am not talking about eclipses, any part of a shadow touching (or not,) will do.

I can easily imagine the hula hoop being the Epsilon Ring shown in the image of Uranus and never casting a shadow, IF that ring is "stationary" with regard to the sun. As I understand it, the claim claim Uranus' moons do not cast a shadow on Uranus depends upon their orbital planes being stationary and always facing the sun. In that case the "moon's orbit is not in the plane of the planet's ecliptic " but intersects it. However that intersection is always "off to the side" and never casts a shadow on Uranus. I am pretty sure I can feel my question is answered in a way I can understand if I can be assured that the moon's orbital plane can or cannot stay "stationary" with regard to the sun. Here is what I am now thinking: "If the moon's orbital plane rotates along with the planet, it will always cast a shadow on the planet some time or other; however, if the moon's orbital plane is stationary and does not rotate along with the planet, it is quite possible that the moon will never cast a shadow on the planet. But darned if I know which case is true, although my Earthly experience should make the answer obvious - so I'm goin' with always a shadow. But I'd like to be wrong." So does Uranus get shadowed or not?

I am now guessing that the answer to my question is obvious and that a moon always casts a shadow on its planet sometime during the year, because it cannot have an "orbital plane" that is stationary to the sun. For it if it did have a stationary orbital plane it could/would not travel across the sky in the manner that our moon does. DUH. This seems intuitive to me, but I can't explain why, and I understand that I am probably confused and likely have it wrong. Maybe it's not as obvious as I now think. Maybe Uranus' moons don't cast shadows, although I think they have to. HELP!

Thank you. From the comments about Uranus, I considered that it was meant that its moons' orbits were "stationary," with the orbital plane (if that is what it is called,) always facing the sun. It would seem t me that if the moons of Uranus act as you describe (which I guess is at the core of my original question,) then they do indeed cast a shadow on Uranus., and it would be impossible for the moons of any planet not to cast a shadow on their planet. So is that correct, and the moons of Uranus do indeed cast a shadow? I don't see how they could be an exception, but I will be the first to admit that I do not understand planetary physics.

Thanks for the replies I have some comments. 1. It would seem to me that if the planet never sees the moon's shadow, the moon will also never see the planet's shadow. Correct, or no? 2. I am probably misunderstanding the orbital physics, but from what has been said about the moons of Uranus, please comment on the following observations, based on the doctored image of its orbits that I have uploaded. Case A: If we rotate the orbit around the red axis in the directions of the red arrows, we can go a small distance with the rotation before we will ever cast a shadow on Uranus. Further, the greater the radius of the orbit, the further we will be able to rotate without causing a shadow. Case B: If we rotate the red axis of rotation in the direction of the green arrows, we can go a small distance with the rotation before we will ever cast a shadow on Uranus. Further, the greater the radius of the orbit, the further we will be able to rotate without causing a shadow. If either Case A or Case B, or both, are true, there is an almost infinite number of orbits that will not cast a shadow on the planet. Again, I appreciate the responses, and hope for more.

I am a newbie, and really uninformed (read stupid.) Here is my question: Would it be possible for the Earth (or any planet,) to have a moon whose orbit was such that it never came between the sun and the Earth? In other words, could we have a moon that never cast a shadow on the Earth? Or is it inevitable that sometime during a year a moon must cast at least a partial shadow on its planet?