Maths regarding the dimensions of a force field.

[Kepler20f]

This question mixes the fantastical notion of a force field with some down to Earth mathematics, and it’s the latter I need help with please!

Assuming the following:

• a truly huge force field capable of shielding a continent, i.e. along the coastline,
• it is visible as a coloured shimmer,
• it reaches roughly as high as the definition of the edge of space, say 100km,
• all of this on a planet the size of Earth (say exactly the same for the sake of calculations),

and taking into account the curvature of the planet, how far away would the force field be visible? I’m wondering about observers on neighbouring continents, or on ships, how close would they have to be to see it?

 

[pbuk]

As you said yourself the notion of a force field is fantastical so you can attribute any properties to it you like.

However if you are simply asking how distant an object has to be to be hidden by the curvature of the earth, google "horizon distance".

 

[Kepler20f]

Yes that was exactly what I was asking for, thank you. I thought I'd made that pretty unambiguous actually! I was not in any way asking about properties of force fields. I don't know where you got that from...
The answer of 1133.9 km was not as high as I'd hoped but there you go.