Strange Phases.


The episode "Nothing Left on Earth Beside Fishes" has a series character stranded on an alien planet.

In one night scene two "moons" are seen close together in the sky. Nothing odd about that in a science fiction episode set on an alien planet. I assume that those two "moons" are both large natural satellites of the planet the character is on, though of course that is not absolutely certain.

Except that one of the moons shows a full or almost full phase and the other moon shows a thin crescent!

That can't happen if both moons are illuminated by the same light source which is in the same direction from both of them.

From what I remember, the crescent moon should have been at least 135 degrees of arc away from the full or almost full moon, and thus they would have been almost at opposite horizons of the sky, not looking close together in a small area of the much larger sky seen in that shot.

It is certainly physically possible for someone on a planet to see two astronomical bodies close together in the sky that seem inconsistent phases of illumination. Perhaps one or both of those bodies are actually illuminated by countless millions and billions and trillions of artificial lights on their surfaces, instead of light from the star(s) in that system, for example.

And I can think of other hypothetical explanations for the conflicting phases of those two "moons".

But I don't think that I the viewer should have to think of theories to explain impossible looking special effects. The job of the special effects persons is to make the special effects look plausible.

So if I ever meet the persons who did the special effects for that episode I would like to ask why they didn't realize how strange it is to see two "moons" close together in the sky with different phases, and ask their explanation of how the "moons" are illuminated to have the phases seen.

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Oh, Neil...

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Hmm, what if there is another moon or planet that obstructs the light reaching that moon?

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That might work as part of an explanation.

But as I wrote in my post:

It is certainly physically possible for someone on a planet to see two astronomical bodies close together in the sky that seem inconsistent phases of illumination. Perhaps one or both of those bodies are actually illuminated by countless millions and billions and trillions of artificial lights on their surfaces, instead of light from the star(s) in that system, for example.

And I can think of other hypothetical explanations for the conflicting phases of those two "moons".


But I don't want to have to think of those hypothetical explanations. It is very simple to depict two astronomical bodies close together in the sky with identical phases, and it is so obvious that two astronomical bodies appearing close together in the sky would almost always have almost identical phases, that depicting two astronomical bodies appearing close together in the sky with radically different phases is disregarding all the probabilities. And without any payoff story wise in this episode.

And I find that annoying.

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Maybe there is something deflecting light or causing a shadow. I saw a full moon as a crescent moon. This shouldn't be possible without there being something wrong with me, but I also took photos of the phenomenon, so then something would have to be wrong with my camera as well.

But later I found out, it was just our good friend, planet Terra, that happened to be blocking the light that would otherwise have reached the moon surface, causing a visible shadow. Yes, it was an eclipse.

Have you ever heard of mirages in deserts? Space is a wonderous and more vast and interesting setting than a mere desert. If a humble mirage can happen in a desert, how much more amazing phenomena can happen in space?

Maybe there's a huge spotlight - maybe the light is reflecterd off of one of the moons into the other, perhaps the other moon is just a hologram in the sky, perhaps it's just a virtual reality, and not a real one (after all, it IS just a TV show..)

How meta do you want to get?

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