By The Many Moons of Munnopor ...

I have been asked to talk about planets with multiple moons and how those moons might effect conditions on the planet around which they orbit. It’s a big topic, and one which must be mostly speculative because of the limited work that’s been done empirically on the subject.

I am also going to talk mainly about the effects of multiple moons in the fantasy milieu because the genre of science fiction, by its very nature, can take us to places where things are happening catastrophically. Planetary-grade catastrophes are not conducive to the existence of life at all and worlds without sophisticated life forms (i.e. sentient) are pretty boring from a writer’s perspective.

Divine intervention aside, the development of an environment suitable for sustaining complex life forms unassisted, takes a very long time. For example, such conditions on Earth only came about well after the larger bodies of the solar system had become stable in their orbits around the sun and each other.


Basically, the energies involved in planetary-level catastrophes are far too great to believe that ecologies for complex organisms would survive. In fact, it could be argued that the Earth’s current biosphere has only developed since the solar system quietened down (i.e. became stable). As evidence for this argument, it is now commonly believed that of all the extinction events that have occurred in the fossil record only one was caused by an impact from space (see the references).

With regard to the subject of this article, this reasoning implies that any sentient life forms must live in an environment of planetary stability, or be artificially protected from such upheavals. Therefore, on planets with multiple moons where sentient life has developed, the moons will be in stable orbits and have predictable and gradual effects on the environment of the planet, otherwise the chances of survival without intervention is, in my opinion, remote.

This probably reads like a bit of a cop out, but as I said at the start this is a big topic, so I have had to limit the scope of the discussion to even start on it. Next week I shall look at some of the effects stable-orbiting, multiple moons might have on the planets they orbit.


A no-prize to those who recognise the first title

About extinction events in Earth’s history

A good, in my opinion, account of an impact event in fiction

  “Lucifer’s Hammer” - Larry Niven and Jeremy Pournelle.

N.B. Please note that I although I use the Wikipedia (and WikiMedia Commons) a lot for references, this is for expediency and the familiarity of my readers. Anyone interested in further studies should make use of the references where available and understand that the Wikipedia is a co-operative project contributable to by anyone and must always be looked at in that light.

Phill Berrie, September, 2008.