"Col" wrote

From this distance to the horizon calculator:

http://www.boatsafe.com/tools/horizon.htm

I love that website. It gives the answer to 15 decimal places. (that's to
an accuracy of micro metres). Wow!

Is that measuring to the front of the eye or to the back? (or to the front
of the cornea or to the back?)

Why do people persist in trying to impress Joe Publish with perceived levels
of accuracy that just aren't possible?
Incidentally, tomorrow's maximum temperature is forecast to be 17.3975720273
degrees Celsius
(not 17.3975720274 as has been widely suggested)

Jack