These are the directions from north, in degrees, you need to point a directional antenna to get maximum signal strength at your location from a remote location.
Most people who believe the earth is flat follow the Gleason Map model. This is an azimuthal equidistant projection centred on the geographic North Pole. It is not intended to represent an actual flat earth.
From this we can see that the beam headings for:
- London to New York is around 210 degrees
- London to Tokyo is around 135 degrees
- and London to Sri Lanka around 345 degrees
If we now look at a round earth model and use a great circle map (azimuthal equidistant projection) centred on London:
We can see that the approximate beam headings would be:
- London to New York 275 degrees
- London to Tokyo 30 degrees
- London to Sri Lanka 87 degrees
These two sets of results are vastly different. Tokyo is in a completely different direction.
If we try pointing an antenna to a signal coming from Tokyo we find that it peaks in the direction given by the great circle map, around 30 degrees. Exactly what we would find if the earth was spherical.
How could flat-earthers get round this evidence?
They could look at this evidence and say:
Well the world IS flat, its just like a great circle map centred on London rather than the Gleason map centred on the north pole.
We can double check this by looking at a great circle map centred on Tokyo :
- This gives a beam heading of Tokyo to London of around 220 degrees
Compared to the Gleason map which would give this result:
- Tokyo to London is around 135 degrees
If we test it from Tokyo we find that it is, indeed, around 220 degrees. Exactly what we would expect if the earth were round. Lets keep an open mind though. This could happen if one of the following hypotheses were correct:
1. The earth is spherical
2. Radio waves travel in a way that is different to the way we currently think they travel.
However, if radio waves travelled differently it would mean that light also travelled differently and we literally see no evidence of that. Light is just visible radio spectrum after all.
We can further prove that the earth is round by using another aspect of radio wave propagation.
If I point my antenna to Tokyo at 30 degrees from North this is known as "short path". If conditions are right I can also (or sometime only) make contact by pointing my antenna to 210 degrees, which is "long path" - going right over South America and over the pacific to Tokyo.
There is no flat earth model that would explain these experimental results. The only shape of planet that fits this is spherical.