Hannah: And rubies!
Professor Anderson: Feldspar!
When a new film adaptation of a classic work of science fiction appears in the theater I have to check it out, and in this case, the plot synopsis is right there in the title. Brendan Fraser stars as Professor Trevor Anderson in the latest version of Jules Verne’s A Journey to the Center of the Earth. Fraser is joined by Josh Hutcherson playing his nephew Sean, and Anita Briem playing the Icelandic mountain guide Hannah Asgeirsson. Though characters have been added and deleted from the source text, the basic plot remains the same: the Professor and his companions descend deep into the Earth through a volcano in Iceland, encounter various prehistoric plants and animals, sail across an underground sea, and finally return to the surface through a second volcano in Italy.
We all know that a trip to the center of the Earth has to be science fiction, but one of the goals of this column is to help teachers use current films (sci-fi, fantasy, or action) to motivate students to think about science when they are outside the classroom. This film can certainly be used to stimulate discussion of Earth science, physics, and even physiology.
When Verne wrote the novel in 1864, very little was understood about the interior structure of the Earth, so I am willing to forgive him for populating the deep places with prehistoric animals and plants. While humans still have not gone more than a few miles into the Earth’s crust, we know a great deal about the structure of the planet through seismic data. The way earthquake waves are reflected and refracted (bent) as they travel through the Earth tells us that the crust varies from just a few miles thick under the oceans to over 50 miles under continents. The next layer, the mantle is many thousands of miles thick, with the liquid outer core and solid inner core below that. Prof. Anderson’s comment early in the film that there are volcanic tubes that go “past the mantle” is ridiculous, but provides an opening to talk about the actual structure of the Earth.
While his structural statements may be suspect, Professor Anderson does use the names of several real (and important) minerals. On their adventures, the group encounters muscovite (a kind of mica), feldspar, and every 7th grader’s favorite rock, schist. Unfortunately, the plot also turns on the explosive behavior of pure magnesium, a substance not found in nature. The very reactivity that makes magnesium burn so vigorously means that it cannot be found as a pure element underground, and the minerals it forms are not explosive. This is one of many basic science “flubs” presented in the film, and it might be a fun end-of-semester task for a general science class to try to find them all. For instance, middle school students who have studied just a bit about volcanoes will likely catch the professor’s sloppy use of the terms “magma” and “lava.” While he uses them interchangeably, magma is molten rock below the surface, and lava the molten rock after it has erupted from a volcano.
Given the title of the film, a central question is just how close to the center of the Earth the adventurers get. The majority of their journey downward is accomplished in a single 90-second free-fall through a volcanic pipe. Calculating speed and distance fallen are common questions for physics students to work out, but physics teachers often tell students to ignore wind resistance so that acceleration is constant and the calculation simplified. This assumption is valid at relatively low speeds, or short falls, but after a person has fallen for several seconds, he or she is moving fast enough that wind resistance becomes very important. Twelve to fifteen seconds is enough to reach “terminal velocity,” when the wind is pushing up just as hard as gravity is pulling down. Skydivers typically reach about 100 mph (or 150 kph) in free fall. An individual’s terminal velocity is determined by how much the skydiver weighs and his or her wind resistance. Prof. Anderson, Hannah, and Sean all weigh very different amounts, so they wouldn’t stay together as they fell (or be able to hold a conversation while falling). In the end, their 90 seconds of free fall would take them less than 3 miles into the planet, or about 3900 miles short of the center.
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A few final notes: When talking about temperatures and distances an Icelander and a scientist would both use SI units (Centigrade temperature and meters) rather than the British system. I realize Americans would be confused, but perhaps movies like this could help ease us into the metric system by using the right units.
In my earlier review of Nim’s Island, I noted that the kinds of adventures boys and girls have in movies are quite often fundamentally different, and this film fits the pattern I described. Sean Anderson spends several hours separated from his uncle and Hannah while they are underground. Sean is presented with difficult challenges and very real dangers, which he overcomes mostly on his own. Nim, on the other hand, was never in physical danger, had silly challenges to overcome, and spent much of the movie waiting for a male rescuer.
This film is presented in 3-D in some theaters, so life science or physiology teachers could use this to talk about how stereo vision works. For us to see depth, or "in 3-D," our eyes must see two slightly different views of a scene. Normal films look flat because both eyes are seeing the same image. Stereoscopes and systems for 3-D movies are designed to get one view to your left eye and another to your right. (The colored glasses from the 1950’s are one way to do this.) The two different views are usually filmed with two cameras set a few inches apart so that each records a slightly different image. This modern version of 3-D movie uses polarizing filters to deliver the two images to viewers left and right eyes.
While there are quite a few examples of poor science in this science fiction film, I think teachers could use excerpts to generate student interest in the actual history and structure of the Earth and to talk about some basic ideas about the physics of falling through the air. I will continue to be on the lookout for films that present positive, strong role models for girls and young women who are interested in science.
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 firstname.lastname@example.org.
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