April 15, 2006 | Weather | WGNTV.com | WGN TV

April 15, 2006

Dear Tom, Is the parabolic curve of a rainbow the same for all rainbows? Carl Johnson, suburbs of Washington, D.C. Dear Carl, The arc of a rainbow is the same for all rainbows, but the arc is always circular and is never parabolic. Triton College astronomer Dan Joyce explains, "Most of the time, because we see only a fraction of the full rainbow, it is tempting to perceive what we do see as a parabola or some other non-spherical conic section--but it's a circle." Because a rainbow always appears at an angle of 138 degrees from the sun, it is seen on the opposite side of the sky from the sun. The best view of a rainbow's spectacular color display is afforded not from the ground, however, but from high-flying aircraft. Occupants of jet planes can sometimes see a rainbow's entire full circular sweep from top to bottom.