These rays are obviously hitting earth at a triangle shape which, to be fair, ought not to happen if the sun is massively bigger than the earth,

Well sort of. It depends where you are on the ball The image is silly and cannot be used to demonstrate anything. The sun is showing through an opening in the clouds. It has nothing to do with the sun's size in relation to the earth. The sun 'broadcasts' and spreads out in that image, just like you expect it to. Remove the clouds and the light is all over uniform for the angle you are looking at. If you're on the north pole, the sun rays are at a low angle. If you're at the equator, it's above you. Simple.