I decided to make a thoughrough[i]er[/i] analysis on the subject. [b]NOTE[/b]: WHAT HALO AS A FICTION DOES NOT DEFINE, I TRY TO THEORISE ABOUT, so don't take everything as a [i]fact[/i]. [quote][b]Lets star off with the ringworlds[/b], in this case Installation 04:[/quote][b]Day/night cycle[/b]: The installation is tilted so that only half of its inner surface--the far side--is exposed to the planetary systems star. Rotation speed determins cycle time. If the installtion orbits its gas giant, it would end up being eclipsed (how long is determined by the speed it travels). A lot of light will be reflected from the bright side to the dark (constant full moon). [b]Energy[/b]: It harvests gas from the gas giant it orbits/stays near via [url=http://images.wikia.com/halo/images/a/ae/Gasgiant.jpg]satelite installations[/url]. [b]Gravitation[/b]: Since the installation spins, objects within are pushed outwards. This is called a [i]centripetal force[/i]. [b]Atmosphere/how it keeps it[/b]: The ringworld maintains its atmosphere partially because of the centripertal force; a wall of [i]hard light[/i] at the edge of the ring helps to keep it in (trying to find picture of this). [url=http://www.slickpic.com/s/jUjAzjkN3jjm2d/_201209150207/photo#1888949]Paint infographic for Ringworld[/url] [quote][b]Installation 00[/b] aka The Ark:[/quote][b]Energy[/b]: A possible theory is that it harvests its captured planetoid for helium-3 or something. The Forerunners seem to rely heavily on gas. [b]Day and night cycle[/b]: The Ark has got an artificial sun that is surrounded by what seems to be some kind of [url=http://images1.wikia.nocookie.net/__cb20080713193922/halo/images/2/20/Artificial_sun.jpg]parabolic mirroring device[/url]. My theory is, that since it has to rotate anyway, in order to maintain its centripetal based gravitational pull, the installation will only be partially lit. [b]Gravity[/b]: Since it is not thick enough to accuire a genuin gravity, it relies on a centripetal force to do the job. It would be similar to spinning a bowl of water; the liquid is pressed out on the sides. The this method does not allow for any gravitation in the center, but since there's a hole there anyway, that doesn't matter. Atmosphere: There are a lot o blue lights on its corners, I assume these project hard light (trying to fid an image). [url=http://www.slickpic.com/s/AMDDzMOMkM33Q5/_201209150207/photo#1888950]Paint infographic for The Ark[/url] [quote][b]Micro Dyson Sphere[/b], in this case the one [i]within[/i]Onyx:[/quote][b]Day/night cycle[/b]: The installation has got a sun that's slightly smaller than Sol. This is possible since the MSD is freaking huge (150x10^6km diameter). How and if it recreates a day/night cycle is unknown. But Halsey and entourage did wander around for [u]days[/u], but nothing about night is mentioned (Ghosts of Onyx). A possible solution would be something similar to this: [url=http://www.larryniven.net/media/ringworld1024x768.jpg]Larry Niven's Ringworld[/url]. [b]Gravity[/b]: The most plausible theory is that it has enough mass to maintain a [i]genuin[/i] gravity. If it is aided by a centripetal force, the gravity at the poles is most likely lower. Atmosphere: It's a en enclosed area. [b]Energy[/b]: The sphere is essentially a huge [i]greenhouse[/i]; the more the sun radiates, the warmer it becomes, converting and redistrubuting that energy would be the most logical way of going about. [url=http://www.slickpic.com/s/N4MNTD3u1Q2MTE/_201209150207/photo#1888947]Paint infographic for Onyx MDS[/url] [quote][b]Requiem[/b]:[/quote][b]Day/night cycle[/b]: We have not yet seen a sun - a singular device, nor anything capable of lighting vast areas, but neither did we within Installation 04 (Control Room Canyon). So it is safe to say that it might solv lighting the same way as there, however that was done... There are clear shadows though, so it is likely that there is a dominating source of light, or is the graphics engine to blame for that (meta problem). [b]Gravity[/b]: Now this is where it becomes truely annoying... Requiem is supposed to be even bigger than the Onyx MDS! This means that there is a possibility for genuin gravity. However, there is just as much mass above as there is bellow. Presumably, it is impossible to know right now, but I'll speculate anyway (ties into energy). [b]Energy[/b]: If Requiem is indeed a onion of a dyson sphere (muliple layers), there could very well be a star at the center. If there is, the gravitation would always be superior inward. [url=http://www.slickpic.com/s/DMMLzY0MzV44MT/_201209150207/photo#1888948]Paint infographic for Requiem[/url] [quote]Finishing words:[/quote][i]Why is day/night cycle important[/i], I hear you say, [i]Forerunners don't even sleep[/i]? Well, I'd say that there are several reasons for why it might be practical. The strongest reason however, has be that most Forerunner installations are buildt to house the species that they collect, day and night would allow this flora and fauna (and James Mason knows what else) to live in a way that is familiar to them. Another reason is that nature needs a cooldown period, it would get rather hot if it didn't flux. Weather is also determined by a fluxuating temperature. Please do correct me if I'm wrong about something, but keep it clean :P [Edited on 09.14.2012 5:32 PM PDT]