For Science!
5 Obsolete Theories That Scientists Once Widely Accepted

CJ Miozzi | 2 Jul 2014 15:00
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5. Hollow Earth Hypothesis

Ancient folklore and mythology across the world is filled with beliefs of subterranean realms deep below the Earth's surface, often strongly tied to religious ideas. But even scientists ascribed to various theories that called for a hollow Earth, including Edmond Halley - the man after whom Halley's Comet is named. In 1692, in an attempt to explain anomalous compass readings, Halley proposed that the Earth consisted of a hollow shell, some 500 miles thick, with inner shells that each had their own magnetic poles.

Variations of this idea were put forth by other scientists up and until the 20th century, when the study of seismic waves gave us the current picture we have of the interior of the Earth. A seismic wave is a wave of energy, often caused by an earthquake or explosion, that travels through the Earth. Using instruments, we're able to measure the properties of these waves, including how fast they travel through different materials. The denser the material, the more quickly the wave travels.

When traveling through air, seismic waves move at the speed of sound - Mach 1. Through water, they travel over four times as fast, and through a hard rock like granite, over 15 times as fast. Because we have observed the travel speeds of seismic waves through the Earth, we know that the only thing beneath our feet are layers of dense material, not large pockets of air or empty space. Sorry, Verne fans, but the only journey we're taking to the center of the Earth lies in the realm of fiction.

While many of these theories seem silly to us today, some of history's most respected individuals have held to them in the past. It's easy for us to scoff at old theories when we possess the accumulated knowledge of thousands of years of critical thinking. Doubtless, our ancestors will one day look back on some of our widely-held modern beliefs and find them just as quaint.

Science, and our understanding of the universe, is constantly evolving, and we must never forget that we stand on the shoulders of giants.

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