Avatar: the real-life science behind the fantasy

Fireflies are perhaps the most obvious example, but the bioluminescent fish of the deep sea tell a different story – that nature, when deprived of light, sometimes creates its own.

On Pandora, where the nights can be many Earth days long, Cameron has suggested that an entire bioluminescent ecosystem could emerge.

This is where Cameron’s decision to make Pandora a moon – and not a planet – comes in. Moons, including Earth’s, are typically “locked” to their planets, with one side eternally facing the planet and one side eternally facing out into space. What this means is that one day on a moon equals the time it takes to orbit its parent planet – a long time.

To watch the phases of our Moon is actually to watch the lunar day in real time. A full moon is midday for the side of the Moon facing the Earth. A new moon is midnight for the side of the Moon facing the Earth. In other words, a lunar day takes more than 27 Earth days. And that means a very long night.

Home Sweet Moon

But could a moon hold life?

Potentially, yes. Actually, making Pandora a moon appears to be an acknowledgment of recent science. Astronomers are still looking for planets like Earth – small and rocky – within the so-called “Goldilocks zone”: Not so close to its star that its life-giving water evaporates, yet not so far away that it freezes into ice.

But small planets are hard to find. Instead, scientists have found gas giants like Saturn in the habitable zone around stars. Those planets are not inhabitable – but their moons could be.

That makes moons a good place to start looking for alien life. "All of the gas giant planets in our solar system have rocky and icy moons," Lisa Kaltenegger of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., told AP. "That raises the possibility that alien Jupiters will also have moons. Some of those may be Earth-sized and able to hold onto an atmosphere."

The problem is that gas giants emit tremendous amounts of radiation. The daily radiation on Jupiter’s Io, for instance, is 4,000 times the lethal dose.

Yet here again, Cameron uses science to solve science’s own problems. The robust magnetic field created by Pandora’s superconductivity deflects the radiation.

At one point in the film, a spectacular aurora dances overhead. Striking filmmaking, yes. But also pure science. The companion book, “Avatar: A Confidential Report on the Biological and Social History of Pandora,” adds that the interaction of the magnetic fields of Pandora and its parent planet “causes a giant increase in electrical activity on both bodies, with massive auroral storms and other electromagnetic phenomenon.”

Such a magnetic field could also be responsible for the telltale arcing formations of rock apparent at the climax of the film.

Other tidbits

• Everything on Pandora – including the 10-foot, blue-skinned Na’vi – is big because the gravity is 80 percent of what it is on Earth.

• Cameron has put Pandora and Polyphemus in the real Alpha Centauri star system, the closest star system to Earth. The system is actually three stars all revolving around one another. The biggest is 20 percent larger than the Sun, the second is 15 percent smaller than the Sun, and the third is a red dwarf 80 percent smaller than the Sun.

• Polyphemus is named for the one-eyed Cyclops in Homer’s “Odyssey.” In the film, a gigantic storm similar to Jupiter’s Great Red Spot is visible.

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