I posted this in an earlier thread, I think it's worth repeating that flat earthers just don't do well at maths.

From the time of Rowbotham, the flat earth believers quote chapter and verse on the distances to lighthouses, claiming they are visible much further out to sea than what curvature calculations predict.

Here is a plot of lighthouse visibility versus height of the light above sea level, taking into account standard correction for refraction and a bridge height of 30 ft above the water line.

The formula for calculating distance to the horizon, including refraction correction for standard atmosphere is D = 3.86 * sqrt ( h ) h = height in meters, D = distance in km.

The Planier lighthouse is 66 meters asl, and is visible for 43 km, calculated distance is 43 km, Flat Earthers claim the calculated value is 29 km

The Jeddah lighthouse is 113 meters asl, and is visible for 46 km, calculated distance is 53 km, Flat Earthers claim the calculated value is 38 km

The Ile Vierge lighthouse is 82.5 meters asl, and is visible for 50 km, calculated distance is 47 km, Flat Earthers claim the calculated value is 33 km

The Genoa lighthouse is 76 meters asl, and is visible for 46 km, calculated distance is 45 km, Flat Earthers claim the calculated value is 31 km

The conclusion is that if you do the calculations properly, the flat earth argument, falls flat on its face ( once again )

For details of the formula derivation go to ...

http://web.archive.org/web/20131717132700/http://mintaka.sdsu.edu/GF/explain/atmos_refr/horizon.htmlhttp://en.wikipedia.org/wiki/HorizonCalculation of ducting effects.

http://web.archive.org/web/20131717125400/http://mintaka.sdsu.edu/GF/explain/atmos_refr/bending.html