While we were in the Tucson area, we made a pilgrimage to the hippy-nerd mecca of Biosphere 2. You may remember the news sensation this experiment caused in the 90s, or maybe you only know and love it from the Pauly Shore movie Biodome. How there has not been a more serious film treatment of this story I have no idea, because it's just about the greatest story ever told.
Basically, a science-oriented theater troupe teamed up with a Texas billionaire to build a Mars colony on Earth: a totally self-contained 3 acre greenhouse. The troupe would live in it for a year, growing all their own food (I don't believe they planted popcorn) and recycling all their air and water, as if they were on the surface of another planet. The project had every kind of problem you could imagine, from the oxygen slowly disappearing, to a lack of food, ant infestations, to the Biospherians splitting into warring factions that wouldn't talk to each other. All the glory and dread of the experience is very well told in Jane Poynter's book the Human Experiment.
The media edified the project, then eviscerated it as a scam. But hey- this thing really happened, even if many mistakes were made. It was asking a really important question: can you create a sealed off ecosystem that survives long-term? There isn't much work being done to answer this now, so far as I know. The scale of the experiment is prohibitively large. We do know the answer is yes on the scale of the Earth, since life has survived here for billions of years. Earth might be considered materially closed because it really only gets sunlight in, and releases heat out to space. But Earth's biosphere is just a thin film coating on a massive dynamic rock, with volcanoes bringing gases and soils up to the surface all the time, so maybe it's silly to call it a closed system. Here's a recent article questioning if life needs a planet with plate tectonics. I'm both attracted and repulsed by the idea of living in domes, but fortunately we don't have to. Still, wouldn't it be neat to know if we could?
Also, Carl Zimmer wrote a great NYTimes piece on Biosphere just last weekend.
The mechanical lung, to prevent the windows from exploding or imploding as the building heats and cools.