Empirical Earth · Shape, Curvature & the Horizon

Long-range photography & infrared

The claim

“Zooming in brings back a boat or skyline that should be hidden 'below the curve.'”

What is measured

Standing 2 m up, your horizon is only about 5 km away. Past it, the bottoms of distant things are hidden by the curve, and no amount of zoom brings them back.

What would show this is wrong

a target whose hidden base comes back when you zoom in, instead of staying cut off from the bottom up.

Sources

  1. Refraction, Snell's law & refractive index of air/water. Standard optics; refractive index of air via the Ciddor/Edlén equations. E. Hecht, Optics ; NIST refractive-index references. Snell's link
  2. Longest line-of-sight photograph. M. Bret, Pic de Finestrelles (2,826 m) → Pic Gaspard (3,883 m), 443 km, 16 Jul 2016 (Guinness World Record); a ~493 km shot has since been recorded. Photogr link
  3. Atmospheric scattering & infrared imaging. Rayleigh scattering ∝ 1/λ⁴ (haze penetration of near-IR); standard atmospheric optics (Bohren & Huffman; near-IR landscape/haze-cut photography ref link
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