Re: @Destroy All Monsters
" this corresponds to 0.14 kg/s in case of perfect backconversion. So you are really looking at a few billion of years full-out collection."
Excellent math. But, not having seen the episode yet I had a question: Was this space egg thing specified as growing solely due to energy collection?
Leaping ahead to baseless speculation: There's a lot of useful mass on the moon to feed a hungry space egg if it's not a breatharian. Lunar soil has been demonstrated as a basis for growing terrestrial crops, albeit with lots of fertilizer and nutrients. More alien critters could get all sorts of material from the soil. Which is moot if it just likes its sunlight and "moon energy." :)