In the 11th century, Al-Biruni successfully determined the radius of the Earth by measuring the dip of the horizon from the top of a hill.
In the 21st century, we can easily repeat the same experiment with practically no effort. All we need are a smartphone and an opportunity to observe the horizon from a high altitude, like during a flight.
Continue reading “Al-Biruni’s Method to Determine the Radius of the Earth”
There are two kinds of the horizon:
- Astronomical horizon: the horizon at the eye level.
- True horizon: the line that visually divides the Earth and the sky.
Because the Earth is a sphere, the true horizon always lies below the astronomical horizon, or the eye-level. The higher the observer, the larger the dip of the horizon.
Flat-Earthers claim there’s no dip of the horizon. They are wrong. It is not hard to observe the drop of the horizon and prove the curvature of the Earth.
Continue reading “The Dip of the Horizon”
As the Earth is spherical, the horizon is below the eye-level (or the astronomical horizon). The angle between the eye-level and the horizon is the dip of the horizon. The angle becomes larger as we go higher.
Flat-Earthers often claim that “the horizon always rises to eye-level”, and thus ‘proving’ the flat Earth claim. Despite their insistence to use a water level to ‘prove’ water is flat, the same device can be used to demonstrate the dip of the horizon, proving the water surface has curvature, and consistent with the spherical Earth model.
Continue reading “Water Level Demonstrates The Dip of the Horizon and Proves Earth’s Curvature”