# World with frequent lunar eclipses?

I am working on a world where an event, like a celebration, occurs during every lunar eclipse.

I would like to have lunar eclipses occurring more frequently--maybe even once a month--in order for this ceremony to be a fairly regular phenomenon. However, my limited knowledge of astrophysics is holding me back in the process of envisioning if something like this could be realistically accomplished.

Could such a solar system exist and sustain life similar to our own?

• Do you want just frequent lunar eclipses, or having frequent solar eclipses as well would be Ok? Commented Apr 9, 2020 at 18:24
• @Alexander I think that would work. I could make a seperate event for that correlation.
– DVNO
Commented Apr 9, 2020 at 18:28

Take Earth and Moon, and make the orbital plane of the Moon around the Earth to be in the orbital plane of the Earth around the Sun.

In this way each lunar month you will get a solar eclipse and a lunar eclipse.

The price would be that you would never get a full moon.

• I think it would be better if you could elaborate on this a bit more (or include relevant links). It would be also great if you could include some pictures. It would be of great help to those of us who are not sufficiently versed in astronomy and/or have difficulties visualising things. Commented Sep 23, 2021 at 18:54

In my answer to this question:

I suggested that a habitable planet could have a ring of 7 to 42 identical moons sharing a single orbit. They would be identically sized and evenly spaced 8.57 to 54.428 degrees apart along the shared orbit. Thus there could be solar and/or lunar eclipses much more often than if a single moon orbited the planet.

If the moons orbited the planet in the same plane as the planet orbited its star, there would be solar eclipses every time a moon came between the planet and the star, and lunar eclipses every time a moon passed exactly on the far side of the planet from the star.

If the Moon’s orbit around the Earth was in the plane of the ecliptic and the Moon’s orbit was circular, there could be a lunar eclipse every night.

If the Moon’s orbit was suitably elliptical there could be a lunar eclipse once a month at the Moon’s closest approach.

• "lunar eclipse every night" - not exactly. Lunar eclipse may happen only when the Moon is on the opposite side of Earth, during full Moon phase. Commented Apr 9, 2020 at 19:03
• If the Moon's orbit around the Earth were circular and in the plane of the ecliptic then the Moon would pass into Earths shadow once every 24 hours. The eclipse would be visible from the hemisphere that is in darkness at the time that the Moon is in Earth's shadow. True there would be no visible eclipse during a New Moon as the Moon would be fully in shadow, but all other phases would produce an eclipse. Commented Apr 9, 2020 at 19:58
• in that case what Moon's orbital period would be? Commented Apr 9, 2020 at 20:23
• Yes true it would have to be a lot closer than it is now as well, although still beyond the Roche limit. The Moons orbital period would be 24 hours prograde or retrograde. Commented Apr 9, 2020 at 21:59
• Do you want to get it tidally locked with Earth? Commented Apr 9, 2020 at 22:44

In brief, I see no reason why this this couldn't work...with a few caveats.

Eclipses are very localized events, usually clear from only small portion of the Earth. Eclipse cycles also run on cycles, but these cycles are not monthly because the near monthly lunar cycle is one rotation of the moon around the Earth.

Eclipses result from specific alignments of the Sun-Moon-Earth and this cycle is about 18 years. Multiple eclipses can occur over this time period, but the Eclipses will not be in the same location, nor at the exact same time in the cycle. This is because of two factors; the eccentricity of orbit (orbits are not circular and predicting the alignment of elliptical paths is more complicated than predicting the alignment of circular paths), and the precession of the Earth-Moon system. This means changing these two things in the right way could get the desired effects.

In summary if the Earth's orbit about the sun, and the Moons orbit about the Earth were more circular, and if the Earth-Moon system did not precess, you could in theory get a system were an eclipse happened at consistent intervals and even perhaps with the eclipse happening once in a lunar cycle. But then come the caveats...lunar eclipses would only be view-able from one side of the Earth, and Solar eclipses only view-able from a specific locality on Earth, everyone else would not experience these events, so they would have to be cultural significant based upon locality. Also a lack of precession in both the Earth and Moon and a circular lunar orbit would affect climate, and rather severely. A lack of seasons and no tide cycle would become a problem and uneven temperatures would result in rather extreme weather. Of course, this could all be downplayed, but the climate differences would be an important consequence of having getting the desired eclipse cycle.

• I think that you are describing the situation for solar eclipses when the moon eclipses the Sun. I think that DVNO was asking about lunar eclipses, when the moon passes though the shadow of the Earth. Lunar eclipses are visible more or less from the entire night side of the Earth when they happen. Commented Apr 10, 2020 at 4:49