>>5769459 Show them this video.
Also, you can use trigonometry:
Let's say that Bob is one mile above the surface and that the radius is about 4,000 miles (it's really 3,959 but let's round) Draw to tangent similar tangent lines to Bob and then draw a straight line from the points where the tangent lines touch the surface to the core. Use inverted sin/cos/tan equations (sin(x/y)^-1) to calculate the side distances calculate of the sides of the triangles that you've made. Then, use regular sin/cos/tan equations to calculate the angle measurement of the two angles of the triangles that connect bob to the tangent lines. Find the angle degrees then add.
Afterward, do the equation (X/360)(2πr) - X being the sum of the two angles and 360 the total degrees of a circle, Pi being ~3.14, and r being the radius. This will give you the arc length - the portion that Bob could actually see being one mile above the ground. After you find this number, you want to do the same but with the remaining degrees in the circle, subtract the angle measurement from 360 and insert it into the (x/360)(2πr) equation again. Add the sums and you will get the rough circumference of the circle.
After you get the circumference, plug it into the equation (A=C^2/4π): Area equals the circumference squared divided by four times pi.
This will give you a rough surface area of the earth.
This will debunk their entire argument.
