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The next question is evident: How big a bottle closed to outside flows, filled with what kind of living organisms, would you need to support a human inside?

When human daredevils ventured beyond the soft bottle of the Earth's atmosphere, this once academic question took on practical meaning. Could you keep a person alive in space -- like shrimp in an Ecosphere -- by keeping plants alive? Could you seal a man up in a sunlit bottle with enough living things so that their mutual exhalations would balance? It was a question worth doing something about.

Every school child knows animals consume the oxygen and food that plants generate, while plants consume the carbon dioxide and nutrients that animals generate. It's a lovely mirror, one side producing what the other needs, just as the shrimp and algae serve each other. Perhaps the right mix of plants and mammals in their symmetrical demands could support each other. Perhaps a human could find its proper doppelganger of organisms in a closed bottle.

The first person crazy enough to experimentally try this was a Russian researcher at the Moscow Institute for Biomedical Problems. In 1961, during the heady early years of space research, Evgenii Shepelev welded together a steel casket big enough to hold himself and eight gallons of green algae. Shepelev's careful calculations showed that eight gallons of chlorella algae under sodium lights should supply enough oxygen for one man, and one man should generate enough carbon dioxide for eight gallons of chlorella algae. The two sides of the equation should cancel each other out into unity. In theory it should work. On paper it balanced. On the blackboard it made perfect sense.

Inside the airtight iron capsule, it was a different story. You can't breathe theories. If the algae faltered, the brilliant Shepelev would follow; or, if he succumbed, the algae would do likewise. In the box the two species would become nearly symbiotic allies entirely dependent on each other, and no longer dependent upon the vast planetary web of support outside -- the oceans, air, and creatures large and small. Man and algae sealed in the capsule divorced themselves from the wide net woven by the rest of life. They would be a separate, closed system. It was by an act of faith in his science that a trim Shepelev crawled into the chamber and sealed the door.

Algae and man lasted a whole day. For about 24 hours, man breathed into algae and algae breathed into man. Then the staleness of the air drove Shepelev out. The oxygen content initially produced by the algae plummeted rapidly by the close of the first day. In the final hour when Shepelev cracked open the sealed door to clamber out, his colleagues were bowled over by the revolting stench in his cabin. Carbon dioxide and oxygen had traded harmoniously, but other gases, such as methane, hydrogen sulfide, and ammonia, given off by algae and Shepelev himself, had gradually fouled the air. Like the mythological happy frog in slowly boiling water, Shepelev had not noticed the stink.

Shepelev's adventuresome work was taken up in seriousness by other Soviet researchers at a remote and secret lab in northern Siberia. Shepelev's own group was able to keep dogs and rats alive within the algae system for up to seven days. Unbeknownst to them, about the same time the United States Air Force School of Aviation Medicine linked a monkey to an algae-produced atmosphere for 50 hours. Later, by parking the tiny eight-gallon tub of chlorella in a larger sealed room, and tweaking the algae nutrients as well as the intensity of lights, Shepelev's lab found that a human could live in this airtight room for 30 days! At this extreme duration the researchers noticed that the respirations of man and algae were not exactly matched. To keep a balance of atmosphere, excess carbon dioxide needed to be removed by chemical filters. But the scientists were encouraged that stinky methane stabilized after 12 days.

By 1972, more than a decade later, the Soviet team, directed by Josepf Gitelson, constructed the third version of a small biologically based habitat that could support humans. The Russians called it Bios-3. It housed up to three men. The habitat was crowded inside. Four small airtight rooms enclosed tubs of hydroponically (soil-less) grown plants anchored under xenon lights. The men-in-a-box planted and harvested the kind of crops you might expect in Russia -- potatoes, wheat, beets, carrots, kale, radishes, onions and dill. From the harvest they prepared about half of their own food, including bread from the grain. In this cramped, stuffy, sealed greenhouse, the men and plants lived on each other for as long as six months.

The box was not perfectly closed. While its atmosphere was sealed to air exchanges, the setup recycled only 95 percent of its water. The Soviet scientists stored half of their food (meat and proteins) beforehand. In addition, the Bios-3 system did not recycle human fecal wastes or kitchen scraps; the Bios-dwellers ejected these from the container, thereby ejecting some trace elements and carbon.

In order not to lose all carbon from the cycle, the inhabitants burned a portion of the inedible dead plant matter rendering it into carbon dioxide and ash. Over weeks the rooms accumulated trace gases generated by a number of sources: the plants, the materials of the room, and the men themselves. Some of these vapors were toxic, and methods to recycle them unknown then, so the men burned off the gases by simply "burning" the air inside with a catalytic furnace.

NASA, of course, was interested in feeding and housing humans in space. In 1977 they launched the still-going CELSS program (Controlled Ecological Life Support Systems). NASA took the reductionist approach: find the simplest units of life that can produce the required oxygen, protein, and vitamins for human consumption. It was in messing around with elemental systems that NASA's Joe Hanson stumbled on the interesting, but to NASA's eyes, not very useful shrimp/algae combo.

In 1986 NASA initiated the Breadboard Project. The program's agenda was to take what was known from tabletop experiments and implement them at a larger scale. Breadboard managers found an abandoned cylinder left over from the Mercury space shots. This giant tubular container had been built to serve as pressure-testing chamber for the tiny astronaut capsule that would spearhead the Mercury rocket. NASA retrofitted the two-story cylinder with outside ductwork and plumbing, transforming the interior into a bottled home with racks of lights, plants, and circulating nutrients.

Just as the Soviet Bios-3 experiments did, Breadboard used higher plants to balance the atmosphere and provide food. But a human can only choke down so much algae each day. Even if algae was all one ate, chlorella only provides 10 percent of the daily nutrients a person needs. For this reason, NASA researchers drifted away from algae-based systems, and migrated toward plants that provided not only clean air but also food.

Ultra-intensive gardening seemed be what everyone was coming up with. Gardening could produce really edible stuff, like wheat. Among the most workable setups were various hydroponic contraptions that delivered aqueous nutrients to plants as a mist, a foam, or a thin film dripping through plastic holding racks matted with lettuce or other greens. This highly engineered plumbing produced concentrated plant growth in cramped spaces. Frank Salisbury of Utah State University discovered ways to plant spring wheat at 100 times its normal density by precisely controlling the wheat's optimal environment of light, humidity, temperature, carbon dioxide, and nutrients. Extrapolating from his field results, Salisbury calculated the amount of calories one could extract from a square meter of ultradensely planted wheat sown, say, on enclosed lunar base. He concluded that "a moon farm about the size of an American football field would support 100 inhabitants of Lunar City."

One hundred people living off a football field-size truck farm! The vision was Jeffersonian! One could envision a nearby planet colonized by a network of Superdome villages, each producing its own food, water, air, people, and culture.

But NASA's approach to inventing a living in a closed system struck many as being overly cautious, strangulatingly slow, and intolerably reductionistic. The operative word for NASA's Controlled Ecological Life Support Systems was "Controlled."

What was needed was a little "out-of-control."