"Too much garbage in your face? There's plenty of space out in space!"—Line from commercial in WALL-E

With nominations for the 81st Academy Awards to be announced in late January, I thought I’d take a look at the one science fiction film that appears on many critics’ top-10 lists for 2008. No, it is not the Keanu Reeves remake of The Day the Earth Stood Still or M. Night Shyamalan’s The Happening. It’s Pixar’s latest animated feature, WALL-E, a shoo-in for best animated film and a potential nominee for best picture. WALL-E was in theaters over the summer and released on DVD in November, so it’s widely available for students to watch at home. There’s a lot in the movie for science teachers to like, but it has a few of the usual problems that film makers have with depicting space travel.

WALL-E has been described as an animated, science fiction romance, and extensive plot summaries are available online in case you’re not familiar with the story. The basic premise is that humans have left a polluted Earth. For this review I need to describe a few of the main characters: WALL-E (short for Waste Allocation Load Lifter, Earth class), is one of millions of robots left behind on Earth to clean up huge piles of trash. WALL-E’s routine is interrupted by the arrival of EVE (or Extraterrestrial Vegetation Evaluator) who is looking for a living plant, as that would indicate the Earth is ready for the humans to return from the space voyage they have been on during the cleanup. WALL-E falls in love with EVE, and the remainder of the film takes the pair to the Axiom, the flagship of the Buy-N-Large corporation. There, they help the human Captain to regain control of the ship from the robot autopilot (named AUTO.)

Science teachers should draw attention to the message of sustainability that the opening scenes of the film drive home. Humans leave Earth because they have covered it with garbage and refuse to take real responsibility for over-consumption fueled by the advertising of the Buy-N-Large mega-corporation. If students are not convinced to begin recycling by the giant towers of trash covering the Earth, no public service announcement will move them. The dusty, desolate surface of the planet contrasts with the rendering of stars, nebula, and galaxies when the action moves to space.

One of the most beautiful scenes in the film shows WALL-E and EVE rocketing around outside the Axiom ship in a ballet of applied physics. EVE uses her mysterious propulsion system to get around, but WALL-E makes good use of a CO 2 fire extinguisher to move. His first few blasts with the extinguisher show his experiments to figure out how to speed up, slow down, and turn. This scene could be used to show that a force is required to change the speed or direction of a moving object: WALL-E continues to drift in a straight line until he uses the “rocket” to change his motion.

Another bit that I think many physics teachers will enjoy is WALL-E’s recycling of old parts of one device to improve another. Over the many years of cleanup work, WALL-E has become obsessed with the movie Hello Dolly and watches clips of it over and over on a jury-rigged iPod. The screen on the iPod is too small to see well, so WALL-E uses a lens to magnify it and make the action visible. From the very thin, flat shape of the lens, it appears that he took it from an old overhead projector, like the one you might have gathering dust in the corner of your classroom. In that application, the lens spreads the light from the projector bulb over the whole glass surface. The lens is that thin piece of plastic between the lightbulb and the glass “bed” that was so hard to clean. This sort of lens was invented by Augustin-Jean Fresnel for use in lighthouses in the early 19th century. The credit-card shaped “pocket magnifiers” sometimes given away at trade shows are another example of a Fresenel lens. It’s comforting to think that they may still be useful in the future.

An uncomfortable part of the movie, though, was the classic sci-fi blunders made by the animators when the action moved to space. Virtually every film and television show that takes place in space makes the same mistakes I noticed in WALL-E. First, there is the issue of gravity. When in orbit around the Earth, or traveling at constant speed far from the Earth, objects in a ship would appear weightless. We have seen video of liquid drops forming spheres that “float” in front of the shuttle crew, and the challenges astronauts face simply keeping tools from wandering off. It is very difficult to simulate this weightlessness on Earth, so live-action movies and TV shows have some sort of artificial gravity created by the scriptwriters to explain how people can walk around as though the ship was on Earth.

You might think that an animated film would be able to get away from the gravity problem, but life on the Axiom is meant to be as much like a water-borne cruise ship as possible, and that requires a swimming pool, driving range, and other items that need gravity to seem normal. Everything on the ship behaves as though it was on Earth, falling when dropped and following parabolic paths when thrown. Objects just outside the ship float as expected in the absence of gravity. The troublesome scene is when AUTO tilts the ship to throw the Captain off balance. Everything on the ship slides to one side, as though the ship were on Earth, but the artificial gravity should keep pulling toward the floor, even though the ship is tilted. I can understand the cinematic reason to tilt the ship (in part because it calls to mind a similar scene in Titanic) but the physics is inconsistent.

Second, sound is a wave phenomenon that requires a material to carry the wave energy from one place to another. On Earth, that material is usually the atmosphere, but solids and liquids also carry sound waves well. In space, there is essentially no material to carry sound, so we wouldn’t be able to hear explosions, space ships going by, or WALL-E’s fire extinguisher as he and EVE fly around. Another space issue that the filmmakers ignored is the effect of near vacuum and very low temperature on living systems. WALL-E saves his plant from destruction in an explosion, but then carries it in his (non-pressurized) body exposed to space for a few minutes. The low temperature (-450 F°/-268°C) would cause the water in the plant to freeze, and the vacuum would cause gasses in the plant to evaporate through the leaves. In the end, it would be a very limp, probably dead plant that EVE took back onto the Axiom.

Physics teachers could use scenes of WALL-E with his fire extinguisher as an introduction to or follow up after performing the demonstration themselves; they could also explain that sound is not transmitted in space. Biology and environmental science teachers could encourage students to watch the film at home and have a family discussion about actions everyone can take to reduce, reuse, and recycle instead of contributing to the global problem of waste disposal.

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 jacob.blickenstaff@usm.edu.

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