In my curiosity, I looked up what the galaxy age setting does when generating a new map... To my surprise, younger galaxies have MORE habitable planets, and fewer volcanic/hostile planets.



http://endlessspace.wikia.com/wiki/Planet_probabilities





Based on my undergrad astronomy courses, I believe this is backwards. Younger solar systems/galaxies should lead to a greater frequency of large/hot stars with more volcanic/desolate planets.



Hotter "blue" stars have shorter life-spans in a cosmological sense than yellow (sun) type stars. They also explode violently on death, creating supernova which are believed to be required to generate heavy elements necessary for life. (All elements heavier than Iron require supernova to be created. Hence the phrase "we are all dust of the stars".) Thus, a younger galaxy would have a larger number of main-sequence blue stars and fewer black holes, nebula, supernova, and a lower concentration of heavy elements necessary for jungle/ocean/terran planets/ecosystems.



As galaxies age, the number of smaller stars (yellow/brown dwarf) would rise, as the blue stars exploded and created new stars from the remains (such as our sun).



Also, from a solar system perspective, younger solar systems would contain more volcanic planets, which become cooler and (probably) more habitable as they age. This fits with our understanding of the earth's creation: Initially violent and volcanic, slowly as the core cools, it becomes life sustaining (over billions of years).



TLDR: Galaxy age should be reversed - young galaxies should have more blue stars and more volcanic/hostile planets. Older galaxies should increasingly have habitable planets or barren (cooled) ones.



Just a minor detail that might be worth changing for a little consistency.

I would expect that the game considers our status in time as "normal" or "medium." You're absolutely right, to an extent. A 'young" galaxy, in my mind, represents one still in its formative years, so I would expect more lava planets and asteroid belts, perhaps more barren, arid, and desert, but considerably fewer "habitable" planets and perhaps fewer Gas Giants (it takes time to accumulate all that mass).



However, the probability for habitable planets should peak at "medium" age. In an "old" galaxy, the stars are beginning to cool (those that haven't nova'ed), so there would be fewer habitable planets and considerably more tundra, arctic, and barren. Maybe fewer asteroid belts as they would have coalesced or dispersed.

I think part of what I'm a little confused by is how to relate a planetary scale timeline (ie: Earth's formation process) vs a galaxy scale timeline (the creation and death of stellar generations).

I would actually expect a younger universe to have less aggregated heavier elements, so I would expect a younger universe to have more gas giants, fewer terrestrial planets and what terrestrial planets there are I would expect to be tiny/small.



Its my understanding that over time, the predominant change in elements is from lighter elements to heavier ones, so early on there wouldn't be as much of the heavier elements to form terrestrial planets but later on, there would be less hydrogen (and what there is would be more spread out) so probably fewer gas giants.

Chalk me up as one more person who has at least read a bit about stellar life cycles and thinks it's odd that the "young" galaxy has more life than the "old" galaxy, when the old one should have both more heavy elements (which are, as it turns out, pretty important to life) and will have had more time for rocky planets to coalesce. Furthermore, an old galaxy should have had more time for life to evolve on those wonderful, lush terran planets.