answer:The rainbow that you see is for your eyes only. Someone standing off to your left or right will be seeing an entirely different rainbow in a slightly different position in the sky. The rainbow that you see is actually built, so to speak, around the axis line extending through the sun and your head. The shadow of your head, if you could see it, would always fall right at the center point of the arc of the rainbow (i.e. if the arc had been drawn by a giant compass, the point where that pivot point of the compass would have been). The primary rainbow will appear to lie about 40 degrees off of that sun/head axis. Because that axis line will be different for all viewers, each one effectively gets their own rainbow. Also, because that axis line will vary when the sun is higher or lower in the sky, you’ll see more or less of the arc at different times of the day. If the sun is more than 40 degrees above the horizon, then you won’t see any of the arc at all (assuming flat terrain).