When I See a Rainbow, Can People See the Other Side?
The whole point is that there really is no other side to the rainbow, all rainbows are full circles, and however, the average observer only sees approximately the upper half of the arc, the illuminated droplets above the horizon from the observer’s line of sight. To see a rainbow, you must be watching from just the right angle.
You can see a rainbow only when the sun is behind you and the sky in front is filled with rain drops. Anyone trying to look at the other side of the rainbow would simply be looking toward the sun. A rainbow is due to the bending and reflection of the sun’s rays when they are shining on raindrops in the air.
The size of the bow depends upon how much water is in the air, as well as on the position of the sun. The higher the sun is in the sky, the smaller the arc of the bow.