The Schiehallion Experiment (1774) was a landmark scientific effort to estimate Earth’s density. By measuring how the mountain Schiehallion’s mass subtly deflected a plumb line from true vertical, astronomer Nevil Maskelyne and collaborators inferred the strength of Earth’s gravity and compared it with the mountain’s pull. The work combined careful surveying, astronomy, and mathematics, and helped turn gravitational measurement into a practical tool for understanding the planet’s interior.

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Schiehallion Labs is the online home of hobby projects by James McKay.