We just learned about the Seismic Wave that moves through the earth.
The main tool for measuring earthquakes is called a Seismometer.
A simple way to think of a seismometer is like a weight hanging from a string.
When there is an earthquake, the weight will bounce up and down, and might also sway from side to side.
Most seismometers are electric now, like some of them that use magnets to hold a thing floating in the air, and when the thing gets moved around by the earthquake they measure how much it moves, and whether it moves forward, backward, side to side or up and down.
Older measuring tools were sometimes called seismographs or seismoscopes.
(from: wikipedia - seismometer)
Kid Facts - Blast from the past: Lathe
