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"Good science is good observation."—Dr. Max Patel, Avatar
When Avatar was released in December 2009, I chose not to write about it in part because it was already receiving a great deal of attention. Now that an extended edition has been released and the original has been available on DVD for some time, your students will likely be familiar with the storyline. I'll examine a couple of items from A Confidential Report on the Biological and Social History of Pandora, a book on the science and social science of Avatar, as well.
Avatar is set in the year 2154 on a moon of a Jupiter-like planet being mined by humans for a substance called "unobtainium" (more on that later). Jake Sully is a former marine now paralyzed from the waist down, who is sent to the moon, Pandora, in place of his identical twin brother, to participate in a scientific project using avatars. Avatars are genetically engineered hybrids of human and Na'vi, the indigenous people on Pandora, controlled remotely by the humans whose DNA they share.
The very tall, slender Na'vi look quite human except for their large mobile ears and blue skin. Jake is cognitively connected to his avatar through a coffin-like box full of sensors and flashing lights. The project scientists use the avatars to interact with the Na'vi, and have apparently been doing so for some time. Jake is recruited by the head of security at the base to provide intelligence on the Na'vi for a likely future battle. On Jake's first trip into the forest "in" his avatar, he is separated from the party and nearly killed by indigenous wildlife. Jake survives the night in the jungle only with the help of Neytiri, a Na'vi woman who takes pity on his childlike behavior. Neytiri's clan orders her to teach Jake survival skills, and the film depicts the highlights of the following three months. Of course, Jake and Neytiri fall in love, and Jake's loyalty to the human race is called into question when the mining operation heads for the Na'vi Hometree. In the end, the message to humanity is clear: Living in harmony with the natural world is better than chasing profits at the detriment of the environment.
Jake Sully contemplates his avatar.
When Jake is stuck out in the jungle overnight, he sees that nearly every plant in the forest—and many of the animals—glow in the dark. Presumably, this is bioluminescence, or naturally occurring chemoluminescence, a process occurring in many organisms on Earth as well. Chemoluminescence is the process of changing chemical potential energy into visible photons in a chemical reaction. Bioluminescence is much more common in the oceans than it is on land, with algae near the surface and fish in the deep oceans producing light this way. On land, the main producers of this "living light" are fungi commonly known as foxfire and insects like fireflies. The University of California, Santa Barbara, has an excellent website on bioluminescence.
As Jake quickly discovers on his night out, humans on Pandora are under almost constant attack from indigenous predators. They include armor-plated, doglike creatures; large tiger-like creatures; and at least two kinds of very large pterodactyl-like creatures.
Based on what we see in Avatar, I'm concerned about the predator/prey balance on Pandora. The only herbivores we see are horselike creatures the Na'vi ride, but we see only a few, and we don't see them in the wild. Plant life is abundant, but no creatures are eating it. Unless the predators primarily eat one another, Pandora doesn't seem to have enough meat to go around. One of the big ideas of biology is the concept of trophic levels and the loss of energy when moving up the food chain. Since plants make their own food through photosynthesis, they are producers; herbivores are primary consumers. Carnivores are secondary consumers because they mostly eat herbivores. A tertiary consumer is a predator that mainly eats other predators. (On Earth, a killer whale is a good example of a tertiary consumer.) Each step up this chain causes a loss of energy: Plants only convert a fraction of the Sun's energy into food energy, herbivores only get a fraction of the energy from the plants they consume, and carnivores gain only a fraction of the energy from the flesh they eat. This means you need a lot of grass to support one lion. The ecosystem portrayed in Avatar seems close to collapse given the overabundance of producers and high-level consumers combined with the lack of primary consumers. With the attention to detail given to the Na'Vi language, I was hopeful that the science in Avatar would receive a similar careful treatment, but I was disappointed.
James Cameron (the film's writer, director, and producer) had another chance to get the science correct in an accompanying text, A Confidential Report on the Biological and Social History of Pandora, apparently in consultation with some scientists. I have not been able to read the whole book, but sections are available at Amazon.com, and I am not impressed with the physical science present there.
Humans have traveled to Pandora to mine unobtainium, and the only explanation the film provides is that it is very, very valuable. I actually appreciate that strategy, as that is all we need to know for the film to make sense. In Report, we learn unobtainium is a room temperature superconductor, which means it would have no electrical resistance, and thus be very valuable. Unfortunately, the book then states that only liquid helium temperature (about 4 K, or –269°C) superconductors exist on Earth. This is incorrect, as even in 2010 we have liquid nitrogen temperature (77 K, or –196°C) superconductors. That difference of 73 K may not seem like much, but consider that liquid nitrogen costs roughly 10 cents per liter; liquid helium costs more than $10 per liter. That factor of 100 makes a big difference when using superconductors in large scientific or engineering projects.
The book isn't much better on the large-scale issues, either. In Avatar, we learn Pandora has weaker gravity than Earth does; presumably that explains why the Na'Vi are so tall. The book provides a table comparing Earth and Pandora, stating the diameters, relative masses, and gravitational force at the surface. This is great because it enables physics students to check the author's understanding of gravity. The force of gravity between any two masses is given by Newton's law of universal gravitation:
where G is the gravitational constant, m1 and m2 are the two masses, and the r is the distance between them. Near the Earth's surface, we often write
F = mg,
which is about 9.8 m/s2.
With the diameter of Pandora and its mass compared to Earth, we can calculate g on Pandora:
This value of g is about 90% of the value on Earth, which means Pandora would have weaker gravity than Earth does. Unfortunately, the book lists Pandoran gravity as 80% of that on Earth.
Avatar delivers a similar message to that of 2009's Wall-E: We need to take care of the Earth's environment because it will be pretty difficult (maybe even impossible) to find another planet to live on. Night scenes on Pandora can be used to initiate discussion of bioluminescience, and biology teachers might ask students to find the problem of predator/prey imbalance shown in the film. Physics teachers can have students verify the plausibility of the numbers given for Pandora, then ask for planetary parameters that would produce the listed value for gravity there.
Jacob Clark Blickenstaff is Assistant Professor of Physics and Assistant Director of the Center for Science and Mathematics Education at the University of Southern Mississippi. He can be reached at email@example.com.
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