Alexander Ren Eldritch

Inspired to do so by this post; making my own post so as to not do weird things to other people's notes should I wish to respond to questions.

What we know from the current episode: Ruidus does not have phases (ie, doesn't wax or wane), and is visible for half the Exandrian year. It also sometimes flashes.

These two things are incompatible if we assume Ruidus's light works the same way as our (Earth's) moon or Catha presumably does, ie, as reflection of sunlight; the flashing is definitely weird. Therefore, we can determine Ruidus's light source is not reflection from the sun:

Visibility for only half the Exandrian year implies one of two possible orbits. One is an orbit slightly off from a true geosynchronous orbit (geosynchronous=in sync with Earth. In this case it would be an orbit that is very close to the length of the Exandrian 24-hour day, but not exactly the same). In that case it would be almost but not quite synced up with the planet's rotation and therefore would appear to move very slowly across the sky over the course of the year, relative to people on the planet. In this case, it is truly not visible to those on the opposite side of the planet, not even during the day. It would only appear to rise and set once per year; basically it makes its way across the sky bit by bit over the course of half the year, and then is not visible from that point for the other half of the year.

Alternately, it could have an orbit that is the same length as the Exandrian calendar year. This means it's technically up there in the sky during the day, since the planet makes a full rotation each day and Ruidus is, with this slow orbit, relatively stationary compared to the rotation of the planet; but it would be only visible at night for about half the year for most latitudes (tbh I do not have it in me to figure out the details about polar latitudes. Also the Nein were in Eiselcross in summer and it still had night so I'm going to say we do not have the required information re: the tilt of Exandria nor the precise latitudes involved).

Episode 2x76 actually already confirmed that the latter case, where Ruidus orbits Exandria once an Exandrian year, is indeed true. Note that during the half of the year when Ruidus is considered not visible, it technically is there in the sky; it's just that it's above during daylight hours. Per the Explorer's Guide to Wildemount, page 9, it is "nearly impossible" to see Ruidus during the day.

Also, note that in both cases Ruidus is always visible at night to someone; it's just not always visible at night in a certain part of the planet. Presumably this is how the scholars of Exandria determined the orbital length; someone in eastern Wildemount, for example, would have different dates of visibility for Ruidus than someone on the other side of the world in Issylra, and then they could also try to see Ruidus during the day to verify which scenario was true.

However, in either of these cases, the position of Ruidus relative to the position of Exandria and the sun changes which means that if its light source were the sun, it would appear to wax and wane, albeit at very different rates than Catha.

To not have phases while reflecting the light of the sun, Ruidus would effectively need to be not a satellite of Exandria, but rather a planet with the same length year as Exandria, in an orbit slightly further from the sun. For an illustration of moon phases see the below image, credit Karl Tate/space.com:

As seen, a full moon occurs when the planet is between the sun and the moon. Therefore, for Ruidus to always be full it would need to always be on the outer side of Exandria relative to the sun. However, in that case, it does not orbit Exandria; it orbits the sun (and the 'only visible for half the year' thing falls apart as well).

And a glass of water, sweetheart, my socks are on fire!

birdcats are my new favorite animal hello

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