Empirical Earth · Test It Yourself

The skip zone — a ring of radio silence that measures the Earth

The claim

“The ionosphere does all the work, so radio says nothing about the shape of the ground below.”

What is measured

A flat Earth sets no limit on how far one bounce can reach, and no limit on how high a frequency the ionosphere will return. Both limits are measured worldwide, every hour. A single F2 bounce tops out near 4,000 kilometers. The frequency multiplier tops out near 3.4. Both numbers follow from one ratio: the radius of the Earth divided by the height of the layer.

What would show this is wrong

a routine single F2 bounce of 8,000 kilometers on an ordinary day, or a measured M(3000)F2 above about 4, or an ionosonde network that returns correct layer heights from a formula with no Earth radius in it. None of these has ever been reported.

Sources

  1. Sky-wave propagation: the curvature of the Earth limits both the MUF and the skip distance. University lecture notes deriving the secant law and the grazing-incidence limit, showing that the link
  2. One-hop ceilings by ionospheric layer. The maximum ground distance spanned by a single reflection is about 4,000 km from the F2 region, with shorter ceilings from the lower layers, because t link
  3. Shimazaki (1955): F2 peak height from the measured MUF factor. hmF2 = 1490 / M(3000)F2 − 176 km, where M(3000)F2 is the maximum usable frequency for a 3,000 km path divided by the vertical c link
  4. Single-hop F2 paths beyond 4,000 km near solar maximum. Rappaport, Campbell & Pocock (1990) report single-hop F2 contacts exceeding 4,200 km at 50 MHz during the peak of sunspot cycle 22, ex link
The full entry, with the working →

This is one card from Empirical Earth, a free reference that states each flat-Earth claim at its strongest and then answers it with sourced measurements. Nothing is for sale and there are no advertisements.