Flat earth

Bad Flat Earth Arguments: Compasses won’t work on a globe

As explained here I want to challenge some arguments I think are of low quality. and today I wanted to tackle the argument that compasses would only work on a flat plane.

The idea

On a globe, the needle of a compass would point down into the ground rather than horisontally. See chart

Incorrect idea about how compasses work
The idea is that on a flat plane, the magnetic field would make the needle point north without digging itself into the ground.

The problem

The problem is that magnetic fields are not straight but do curve like this:

Magnetic field by Windel Oskay @ flickr.com

As you see in the middle between the two poles, there are rather straight lines, which would make a compass work on a flat plane. But also notice that the lines farther away curve in a circle, leaving ample room for a spherical object where the magnetic field would still creep along the surface and make compasses point horizontally.

The globe model does explain why compass needles do not point downward. Attribution: TStein @ wikimedia.org

Conclusion

I chalk this up to a lack of knowledge of magnetic fields. If you are into the flat earth theory then I'd expect a better grasp of magnetic fields than this. Besides, both theories explain this equally well. Using this as a proof of a flat earth will only get you ridicule and discredit the whole idea.