I am perpetually annoyed by the argument "the Sun's rays are parallel" made here and many other places. They tell you to take a single point on the sun, and draw a big skinny triangle from there to different points on the Earth, showing that the angle is very small.<p>But any child can look at the sun (with eye protection :) and see that it is a disc, not a point of light. The disc is about 0.5 degrees, which is not so small.<p>So, two rays emanating from opposite ends of the Sun and arriving at your eye are clearly not "effectively parallel." Of course, 0.5 degrees often is small enough to not matter in some contexts, but it's just annoying to me that the "start from a single point on the Sun" reasoning is used to draw a conclusion that flies in the face of simple observation.<p>Sorry, rant over (: