How the Ancient Greeks Measured Earth’s Shape and Size @BobtheScienceGuy

Uploaded January 2025 | Updated September 2026, 3 weeks ago

Ancient Greek astronomy moved from philosophical ideas about a spherical Earth to direct observational and mathematical tests. This video covers evidence from ships and lunar eclipses, changes in the visible stars with latitude, early measurements of Earth’s circumference, and the development of geocentric and heliocentric models.

How the Ancient Greeks Measured Earth’s Shape and Size

Testing Whether Atmospheric Pressure Follows Temperature or Altitude

What Does It Take to Become a Scientist?

$Why Laser Tests Over Water Can Mislead Earth-Curvature Measurements Long-distance laser tests over water are often treated as simple curvature measurements, but the laser beam itself is affected by atmospheric refraction and its height above the water may be poorly constrained. This video compares laser observations with an optical auto-level method that establishes a local horizontal and directly measures vertical offset.$