How We Know the Earth is a Sphere

And after these things I saw four angels standing on the fourcorners of the earth, holding the four winds of the earth, that the wind should not blow on the earth, nor on the sea, nor on any tree.

Revelation 7:1-3

Yes, yes, it's like shooting fish in a barrel, but still it is valuable to consider how we know things:

I would add we know the Earth is not flat for many other obvious reasons, like, if it were flat gravity would be markedly greater in its center, tidal forces would tear the Earth apart, meteorites or comets could make holes the Earth (depending on how thick the Earth was and how large the meteorite or comet), seismological tests would not make any sense (since they disprove the flat Earth), plate tectonics would not make much sense, satellites would not orbit the Earth in the manner they do ... we could just go on and on.