I was thinking about my aliens and their generation ship. I did a lot of research on light in general as well as sunlight in particular. Since the aliens are moving away from the sun and facing away from the sun and towards the outer planets when they start their trip with the humans in space, that already dramatically decreases the amount of sunlight that reaches them. But that intensity goes down with the square of the distance. So if you go twice as far from the light source the light source will be 4 times dimmer and if you go 3 times as far the light source will be 9 times dimmer, etc. It eventually gets to a point where it is not visible anymore because only individual photons are reaching you. This dimming as you go further until you can't see it is why I thought of having, at least in some rooms, sunlight-mimicking LEDs So I did some research on LEDs and it turns out that different LEDs need different voltages to work. An infrared LED needs less than 1.6 volts so it could easily be powered by a AA battery(or any 1.5 volt battery for that matter). Ultraviolet LEDs on the other hand need 3 to 4.1 volts depending on the type of ultraviolet LED which is equivalent to 2-3 AA batteries. Then I did some research on how much sunlight reaches the surface and it turns out to roughly be in these proportions: 53% infrared 44% visible 3% ultraviolet And I did some more research on ultraviolet light and it turns out that no UVC reaches the surface, it is all absorbed by the time it reaches the stratosphere. Of the UV that does reach the surface, it is in roughly these proportions: 95% UVA 5% UVB So I figured that the aliens should have lightbulbs with lots of LEDs in them(like thousands) so that they can get the LEDs in roughly those proportions and as close as possible to evenly distributed. Of course that won't be a problem with the infrared and visible light. It is really the ultraviolet that they have to worry about getting evenly distributed. And I also figured that these LEDs should vary in duration and intensity over a 24 hour period to mimic the day-night cycle. Infrared and Ultraviolet LEDs should always be on and be at their lowest intensities at night. Visible light LEDs should be off at night and be on at varying intensities throughout the 2 twilights(morning and evening twilight) and be at their highest intensities after morning twilight and before evening twilight. Infrared should rise in intensity during morning twilight and lower in intensity during evening twilight and also be at its highest intensity at the same time the visible light is at its highest intensity. Ultraviolet should spike up during morning twilight and then stabilize until midmorning when it should spike up again and then stabilize. When it is late afternoon/early evening the ultraviolet should spike back down and stabilize until the end of evening twilight when it should spike back down to night intensity. With visible light it is a bit more complicated but basically, all the rainbow colors should be off at night and then as morning twilight starts the red LEDs should turn on first, closely followed by orange, yellow, green, and blue. Purple should be the very last light to turn on and since it only increases the intensity of already white light, it can rise in intensity slower than the other colors. Anyway, what do you think about having these sunlight-mimicking LEDs on the generation ship?