Calculating the circumference of the Earth by Eratosthenes
The first person to measure the size of the Earth was Eratosthenes, an ancient Greek scientist about 2,000 years ago. From basic geometry and the shadow of a tower he calculated the circumference of the Earth to be about 46,000 km. This value is slightly larger than the value measured today of about 40,000 km.
Foucault's pendulum is a device invented by the French scientist Leon Foucault to test the Earth's rotation.
Introduction to Deep Earth Science
Sensing Planet Earth – Water and Ice
Introduction to Astrophysics