Earth, a Giant Pinball Machine

An anonymous reader writes "Scientists have long probed Earth's interior by monitoring seismic waves (if earthquakes don't make them, they can be induced with explosives, and one nuke test actually triggered an earthquake!), which reveal the inner structure of the planet. But what if the method is wrong? LiveScience reports on a new study suggesting Earth is like a pinball machine, with sound waves careening around before they get to the surface. What is interpreted as a broad layer change could be nothing more than a localized density variation."

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Smallest Pinball machine ...

[xmas2003]

Since the submitter talked about a giant pinball machine, here's the world's smallest pinball machine