© CDO courtesy of the University of Arizona
© CDO courtesy of the University of Arizona

How Living Inside Biosphere 2 Changed These Scientists' Lives

© CDO courtesy of the University of Arizona
© CDO courtesy of the University of Arizona

Taber MacCallum and Jane Poynter witnessed the most affecting solar eclipse of their lives in 1992. That's because as they watched the Sun disappear behind the Moon’s shadow, they were also watching their oxygen supplies slipping away.

At the time, they and their six teammates were sealed inside Biosphere 2, a 91-foot-tall, 3.14-acre experimental complex outside Tucson, Arizona. “We were all just glued to the monitors,” MacCallum recalls, “because you can see when the Sun was hidden away by the Moon, for that half hour period, the CO2 started going up. The oxygen started going down. You could see the actual, palpable effect.”

Without the Sun, the plants around them had stopped photosynthesizing and producing oxygen. Earth’s atmosphere is so huge that half an hour of this during a solar eclipse doesn’t have a noticeable effect. But inside an atmosphere 19 trillion times smaller than Earth’s, MacCallum and Poynter noticed.

“It's very hard on the Earth to get that tight a visceral connection between your behavior and the environment,” MacCallum says.

Today, the imposing white dome of Biosphere 2 still rises above the Arizona desert like a cross between a greenhouse and the Taj Mahal. Now, it’s a research station maintained by the University of Arizona where researchers study Earth processes, global environmental change, weathering, landscape evolution, and the effect of drought on rainforests, among many projects. Because of its systems and size, scientists can do controlled experimentation at an unprecedented scale in Biosphere 2.

Another view of Biosphere 2. Image credit: © CDO courtesy of the University of Arizona

MacCallum and Poynter returned to Biosphere 2 in May 2016 for the One Young World Environmental Summit to speak to young environmental leaders from around the world. But in the early 1990s, they and six others were sealed inside it for two years and 20 minutes, from September 26, 1991 to September 26, 1993, in a life-changing experiment that was equal parts humility and hubris—both shortsighted and ahead of its time.

“The big questions of the two-year mission,” says MacCallum, were, “Can we build artificial biospheres? Can these be objects of science? Can we learn from them?”

We could and did. As a result of their voluntary containment, we learned how to seal a giant building so that it loses less air than the International Space Station, manage damaged coral reefs, feed eight people on a half-acre of land, and recycle water and human waste in a closed system, among other things.

The structure itself, built from 1987 to 1991, is a technological marvel even today. The idea was to build a miniaturized biosphere completely separated from Earth, see if humans could live inside it, and see how they affected the animals and plants around them and vice versa. (Why call it Biosphere 2? Because Earth is Biosphere 1.) It’s roughly as tightly sealed as the space station and separated from the soil around it by a 500-ton steel liner.

In the early '90s, when the mission started, the ideas that humans were causing climate change or even that Earth was a biosphere at all were much less accepted than they are today. “When we started this project, I was spelling the word ‘biosphere’ down the phone,” says MacCallum.

Much the way a botanical garden's conservatory is, Biosphere 2’s glass-walled domes and pyramids were filled with different biomes: rainforest, ocean (with a coral reef), savannah, desert, mangrove swamp, and agricultural fields in which the team grew all their crops. They ate so many sweet potatoes that Poynter turned orange, but their world also included domestic animals: goats (their only dairy source), chickens, pigs, and tilapia. They had only enough coffee plants to make one cup of coffee per person every few weeks.

The desert biome in Biosphere 2. Image credit: © CDO courtesy of the University of Arizona

Problems quickly developed. The coral reef became overgrown with algae. Most of the pollinating insects died. A bush baby in the rainforest biome got into the wiring and was electrocuted. Each of the crew members had a primary job: Poynter was in charge of the farm and farm equipment, and MacCallum was in charge of the analytical chemistry lab inside Biosphere 2. The crew had to do all their research, farming, and experiments while hungry because they weren’t getting enough calories.

More dangerous was the decline in oxygen. That night in 1992, their oxygen levels dipped temporarily, but overall their oxygen levels declined from 20.9 percent to 14.5 percent. (Any environment below 19.5 percent oxygen is defined as oxygen-deficient by the Occupational Safety and Health Administration, or OSHA.) The low oxygen made them lethargic. For months they couldn’t sleep properly because it gave them sleep apnea. Scientists were monitoring them and communicating with them from the outside, and finally in August 1993, just a month before the crew left Biosphere 2, they decided to start pumping in oxygen.

Taber MacCallum tests air conditions in Biosphere 2. Image credit: © CDO courtesy of the University of Arizona

Later, scientists figured out that the culprits were microbes proliferating in the Biosphere’s compost-rich soil, combined with the building’s concrete. The microbes themselves were not harmful, but they converted oxygen into carbon dioxide, which then reacted with the building’s concrete to form calcium carbonate and irreversibly remove oxygen molecules from the Biosphere's atmosphere.

Still, looking back more than two decades years later, MacCallum and Poynter view the experiment as a success. Its initial science findings have been developed on in the years since—the University of Arizona has owned the facility since 2007—and its research focus remains as big picture as it ever was: global environmental change.

Beyond the science, even just seeing Biosphere 2 could change people’s perspectives. Poynter recalls getting an email while she was inside Biosphere 2 from a man who walked around the perimeter of the structure as part of the monitoring effort, who said, “'I get it now, because I walked around Biosphere 2, this miniature version of planet Earth, and it smacked me in the face: you guys only have what you have in there, and you have nothing else.'”

“That is fundamentally the message: that it's finite,” Poynter says. “And also very resilient.”

When after two years they finally emerged, Poynter had lost virtually all the enzymes to digest meat from eating so little of it. Nevertheless, she says, “Physically, we were in pretty decent shape. I had spent every day farming, so I was pretty strong.”

Jane Poynter checks on the goats in Biosphere 2. Image credit: © CDO courtesy of the University of Arizona

Still, it was a huge change. “The experience of coming out of Biosphere 2 was amazing in that it was like being reborn into this world and seeing it with fresh eyes,” she recalls. That night they had a big party with friends they hadn’t seen in two years. “And then the next morning there was this giant pile of garbage. It was this stark reminder of this consumable world that we live in.”

Poynter and MacCallum, who were dating when they entered Biosphere 2, married nine months after leaving it. Together with three others, they formed Paragon Space Development Corporation. Over the years, they developed a range of aerospace technology, including temperature control and life support systems for NASA and SpaceX that could be used to support people on the Moon or on Mars.

Their current company, World View Enterprises, spun out of Paragon in 2013. Key staff include chief scientist Alan Stern, head of the New Horizons mission to Pluto, and astronaut Mark Kelly (twin brother of astronaut Scott Kelly), who is the director of flight crew operations. World View sends uncrewed vehicles high up in the near-space stratosphere to research weather and other phenomena, and aims to one day bring people up to where the sky is black, the Earth looks curved, and it’s visibly clear that Earth is the home we share.

The curvature of the Earth as captured by a World View craft. Image credit: World View

It's that big-picture view that Poynter and MacCallum want to share with others. After talking with astronauts, they think that the “overview effect” astronauts feel when seeing the Earth from space is not unlike what they felt in Biosphere 2. Like Poynter and MacCallum, astronauts describe feeling deeply moved by the experience to do something to help Earth and its people.

Poynter says the company’s technology is proprietary and has to do with buoyancy control. “The basis of it is our ability to do very accurate altitude control,” she says, which allows their vehicles to take advantage of prevailing winds at different altitudes to travel exactly where they want.

World View Enterprises is particularly interested in taking leaders and influencers up to the stratosphere. Because you can’t just lock world leaders inside a biosphere in the desert for two years to give them the insight that Poynter and MacCallum know so deeply: We, as humans, are fully connected to and dependent on our environment.

“In the biosphere," Poynter says, "I really fell in love with the Earth."

Dean Mouhtaropoulos/Getty Images
Essential Science
What Is a Scientific Theory?
Dean Mouhtaropoulos/Getty Images
Dean Mouhtaropoulos/Getty Images

In casual conversation, people often use the word theory to mean "hunch" or "guess": If you see the same man riding the northbound bus every morning, you might theorize that he has a job in the north end of the city; if you forget to put the bread in the breadbox and discover chunks have been taken out of it the next morning, you might theorize that you have mice in your kitchen.

In science, a theory is a stronger assertion. Typically, it's a claim about the relationship between various facts; a way of providing a concise explanation for what's been observed. The American Museum of Natural History puts it this way: "A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts."

For example, Newton's theory of gravity—also known as his law of universal gravitation—says that every object, anywhere in the universe, responds to the force of gravity in the same way. Observational data from the Moon's motion around the Earth, the motion of Jupiter's moons around Jupiter, and the downward fall of a dropped hammer are all consistent with Newton's theory. So Newton's theory provides a concise way of summarizing what we know about the motion of these objects—indeed, of any object responding to the force of gravity.

A scientific theory "organizes experience," James Robert Brown, a philosopher of science at the University of Toronto, tells Mental Floss. "It puts it into some kind of systematic form."


A theory's ability to account for already known facts lays a solid foundation for its acceptance. Let's take a closer look at Newton's theory of gravity as an example.

In the late 17th century, the planets were known to move in elliptical orbits around the Sun, but no one had a clear idea of why the orbits had to be shaped like ellipses. Similarly, the movement of falling objects had been well understood since the work of Galileo a half-century earlier; the Italian scientist had worked out a mathematical formula that describes how the speed of a falling object increases over time. Newton's great breakthrough was to tie all of this together. According to legend, his moment of insight came as he gazed upon a falling apple in his native Lincolnshire.

In Newton's theory, every object is attracted to every other object with a force that’s proportional to the masses of the objects, but inversely proportional to the square of the distance between them. This is known as an “inverse square” law. For example, if the distance between the Sun and the Earth were doubled, the gravitational attraction between the Earth and the Sun would be cut to one-quarter of its current strength. Newton, using his theories and a bit of calculus, was able to show that the gravitational force between the Sun and the planets as they move through space meant that orbits had to be elliptical.

Newton's theory is powerful because it explains so much: the falling apple, the motion of the Moon around the Earth, and the motion of all of the planets—and even comets—around the Sun. All of it now made sense.


A theory gains even more support if it predicts new, observable phenomena. The English astronomer Edmond Halley used Newton's theory of gravity to calculate the orbit of the comet that now bears his name. Taking into account the gravitational pull of the Sun, Jupiter, and Saturn, in 1705, he predicted that the comet, which had last been seen in 1682, would return in 1758. Sure enough, it did, reappearing in December of that year. (Unfortunately, Halley didn't live to see it; he died in 1742.) The predicted return of Halley's Comet, Brown says, was "a spectacular triumph" of Newton's theory.

In the early 20th century, Newton's theory of gravity would itself be superseded—as physicists put it—by Einstein's, known as general relativity. (Where Newton envisioned gravity as a force acting between objects, Einstein described gravity as the result of a curving or warping of space itself.) General relativity was able to explain certain phenomena that Newton's theory couldn't account for, such as an anomaly in the orbit of Mercury, which slowly rotates—the technical term for this is "precession"—so that while each loop the planet takes around the Sun is an ellipse, over the years Mercury traces out a spiral path similar to one you may have made as a kid on a Spirograph.

Significantly, Einstein’s theory also made predictions that differed from Newton's. One was the idea that gravity can bend starlight, which was spectacularly confirmed during a solar eclipse in 1919 (and made Einstein an overnight celebrity). Nearly 100 years later, in 2016, the discovery of gravitational waves confirmed yet another prediction. In the century between, at least eight predictions of Einstein's theory have been confirmed.


And yet physicists believe that Einstein's theory will one day give way to a new, more complete theory. It already seems to conflict with quantum mechanics, the theory that provides our best description of the subatomic world. The way the two theories describe the world is very different. General relativity describes the universe as containing particles with definite positions and speeds, moving about in response to gravitational fields that permeate all of space. Quantum mechanics, in contrast, yields only the probability that each particle will be found in some particular location at some particular time.

What would a "unified theory of physics"—one that combines quantum mechanics and Einstein's theory of gravity—look like? Presumably it would combine the explanatory power of both theories, allowing scientists to make sense of both the very large and the very small in the universe.


Let's shift from physics to biology for a moment. It is precisely because of its vast explanatory power that biologists hold Darwin's theory of evolution—which allows scientists to make sense of data from genetics, physiology, biochemistry, paleontology, biogeography, and many other fields—in such high esteem. As the biologist Theodosius Dobzhansky put it in an influential essay in 1973, "Nothing in biology makes sense except in the light of evolution."

Interestingly, the word evolution can be used to refer to both a theory and a fact—something Darwin himself realized. "Darwin, when he was talking about evolution, distinguished between the fact of evolution and the theory of evolution," Brown says. "The fact of evolution was that species had, in fact, evolved [i.e. changed over time]—and he had all sorts of evidence for this. The theory of evolution is an attempt to explain this evolutionary process." The explanation that Darwin eventually came up with was the idea of natural selection—roughly, the idea that an organism's offspring will vary, and that those offspring with more favorable traits will be more likely to survive, thus passing those traits on to the next generation.


Many theories are rock-solid: Scientists have just as much confidence in the theories of relativity, quantum mechanics, evolution, plate tectonics, and thermodynamics as they do in the statement that the Earth revolves around the Sun.

Other theories, closer to the cutting-edge of current research, are more tentative, like string theory (the idea that everything in the universe is made up of tiny, vibrating strings or loops of pure energy) or the various multiverse theories (the idea that our entire universe is just one of many). String theory and multiverse theories remain controversial because of the lack of direct experimental evidence for them, and some critics claim that multiverse theories aren't even testable in principle. They argue that there's no conceivable experiment that one could perform that would reveal the existence of these other universes.

Sometimes more than one theory is put forward to explain observations of natural phenomena; these theories might be said to "compete," with scientists judging which one provides the best explanation for the observations.

"That's how it should ideally work," Brown says. "You put forward your theory, I put forward my theory; we accumulate a lot of evidence. Eventually, one of our theories might prove to obviously be better than the other, over some period of time. At that point, the losing theory sort of falls away. And the winning theory will probably fight battles in the future."

This Just In
Yes, Parents Do Play Favorites—And Often Love Their Youngest Kid Best

If you have brothers or sisters, there was probably a point in your youth when you spent significant time bickering over—or at least privately obsessing over—whom Mom and Dad loved best. Was it the oldest sibling? The baby of the family? The seemingly forgotten middle kid?

As much as we'd like to believe that parents love all of their children equally, some parents do, apparently, love their youngest best, according to The Independent. A recent survey from the parenting website Mumsnet and its sister site, the grandparent-focused Gransnet, found that favoritism affects both parents and grandparents.

Out of 1185 parents and 1111 grandparents, 23 percent of parents and 42 percent of grandparents admitted to have a favorite out of their children or grandchildren. For parents, that tended to be the youngest—56 percent of those parents with a favorite said they preferred the baby of the family. Almost 40 percent of the grandparents with a favorite, meanwhile, preferred the oldest. Despite these numbers, half of the respondents thought having a favorite among their children and grandchildren is "awful," and the majority think it's damaging for that child's siblings.

Now, this isn't to say that youngest children experience blatant favoritism across all families. This wasn't a scientific study, and with only a few thousand users, the number of people with favorites is actually not as high as it might seem—23 percent is only around 272 parents, for instance. But other studies with a bit more scientific rigor have indicated that parents do usually have favorites among their children. In one study, 70 percent of fathers and 74 percent of mothers admitted to showing favoritism in their parenting. "Parents need to know that favoritism is normal," psychologist Ellen Weber Libby, who specializes in family dynamics, told The Wall Street Journal in 2017.

But youngest kids don't always feel the most loved. A 2005 study found that oldest children tended to feel like the preferred ones, and youngest children felt like their parents were biased toward their older siblings. Another study released in 2017 found that when youngest kids did feel like there was preferential treatment in their family, their relationships with their parents were more greatly affected than their older siblings, either for better (if they sensed they were the favorite) or for worse (if they sensed their siblings were). Feeling like the favorite or the lesser sibling didn't tend to affect older siblings' relationships with their parents.

However, the author of that study, Brigham Young University professor Alex Jensen, noted in a press release at the time that whether or not favoritism affects children tends to depend on how that favoritism is shown. "When parents are more loving and they're more supportive and consistent with all of the kids, the favoritism tends to not matter as much," he said, advising that “you need to treat them fairly, but not equally.” Sadly for those who don't feel like the golden child, a different study in 2016 suggests that there's not much you can do about it—mothers, at least, rarely change which child they favor most, even over the course of a lifetime.

[h/t The Independent]


More from mental floss studios