Empirical Earth · Shape, Curvature & the Horizon

The horizon drops — it doesn’t rise to eye level

The claim

“The horizon always rises to meet your eye, however high you go — proof it’s flat.”

What is true

The horizon does look like it rises to meet your eye as you climb. That is a real impression and a common one.

What is measured

The horizon sits below eye level, and it drops more the higher you climb. It is about 0.045° at the shore and about 3° (2.98° with refraction ) from a jet at 33,000 ft. A flat Earth says 0° at every height. The measured dip is what a sphere gives. More on refraction and the curve.

What would show this is wrong

a calibrated scope or leveling app that shows the horizon exactly at eye level (0° dip) from high altitude.

Sources

  1. Dip of the horizon. The visible horizon lies below true horizontal by θ = arccos(R/(R+h)); about 1° from a 1,000 m hill and ~3° at jet altitude, reduced ~8% by refraction. A standard celesti link
  2. Visual, optical, radio and radar horizons. Each horizon is the distance at which Earth’s surface curves out from under the line of sight. Light bends slightly in air (the optical horizon rea link
  3. Samuel Rowbotham (“Parallax”), Zetetic Astronomy: Earth Not a Globe , 1865. The founding text of the modern flat-Earth movement, and the source of most of the arguments answered in this refe link
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