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Aug. 11, 2004
Journey to Earth's Center
The idea that Earth might be hollow, with winding underground passages and vast underworlds of fantastic creatures, has been around for a long time. Such an Earth has been the setting for a variety of thrilling stories, movies, and TV shows.
One of the earliest examples is the science fiction novel Journey to the Center of the Earth by French writer Jules Verne. He wrote it in 1864.
In the story, a group of adventurers travel to Iceland and descend into the crater of an extinct volcano. The explorers encounter various hazards as they trek deep into Earth. They end up at a vast underground sea, where they stumble upon prehistoric animals and a forest of 40-foot-tall mushrooms. Building a raft, they cross the ocean, battling gigantic sea monsters along the way. After further adventures, the explorers hurtle back to Earth's surface atop a river of lava. They eventually find themselves on a mountainside on the island of Stromboli in Italy.
Verne's heroes actually didn't get very far toward Earth's center. And if they had, they would have faced intense heat, immense pressure, and an iron core. Even without these factors, gravity would have been an issue.
When you drop a stone, it falls to the ground, pulled by Earth's gravity. In fact, there's a gravitational attraction between any two bodies. The strength of this force depends on the mass of each of the two bodies and how far apart they are. A larger mass means a larger force, so the sun has a much larger gravitational attraction than does Earth or an apple. Also, the farther apart two objects are, the less force they exert on each other.
Earth's gravitational force keeps the moon in orbit around Earth, governs the arcing path of a baseball, ensures that a dropped apple hits the ground, and keeps you from floating away.
At Earth's surface, you're attracted by all of Earth. As you travel toward Earth's center, you're attracted by parts of Earth that are both above and below you. So, the force pulling on you gets smaller as you get closer to the center of Earth. At the center itself, you would be weightless. You're attracted equally in all directions, so there would be no net gravitational force acting on you. Everything cancels out.
It would be interesting to imagine what Verne's heroes might have done if they had made it all the way to Earth's center and encountered weightlessness.—I. Peterson
The full text of an English translation of Journey to the Center of the Earth by Jules Verne can be found at www.online-literature.com/verne/journey_center_earth (Literature Network).
You can find an interesting reader's guide to Journey to the Center of the Earth at www.wsu.edu/~delahoyd/sf/verne_jce.html (Michael Delahoyde, Washington State University).
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