Would "rainbows"...

[Piscivore]

...form a circle if that pesky horizon were not in the way?


Just something I've always wondered.

[Hydrogen Cyanide]

I have a vague recollection of seeing a circle rainbow... I think I was in an airplane.... or it might have been a photograph.

I did find a couple of references:
http://www.earthsky.com/scienceqs/browsefaq.php?f=188
and
http://www.wonderquest.com/rainbow-circle.htm

A few summers ago we did take a picture of a double rainbow near Durango, CO.

[geni]

yes there are a number of ways you can move the horizon out the way. The clasic way is to fly in a plane but it is far less effort to make you own rainbow with a garden hose sprayer (set the water to really fin droplets you get a circular rainbox a couple of feet in diamiter).

[phildonnia]

Originally posted by Piscivore
...form a circle if that pesky horizon were not in the way?

Just something I've always wondered.

They form a circle even with that pesky horizon in the way. You generally don't notice this because

a) the scene not as clear as the sky, so there's too much other stuff cluttering up your view
b) the ground is more likely to be in shade, and
c) there's not as much rain between you and the nearest obstruction in the direction of the ground, so it's much fainter.

Circular rainbows are commonly seen from airplanes under the right conditions.

[BillC]

Originally posted by Piscivore
...form a circle if that pesky horizon were not in the way?Yes. A rainbow is a circle centred about a point opposite to the direction of the sun.

[CBL4]

Here are few pictures but none of them are impressive.

http://www.jlindquist.com/MPimages/dal10a.jpg
http://www.extrospection.com/archives/2003/10/circular_rainbow.html
http://www.bobtilden.com/1B02.htm

Create your own:
http://www.physics.umd.edu/lecdem/services/demos/demosn1/n1-43.htm

CBL

[Luke T.]

Well this certainly explains why I've never been able to find the pot of gold at the "end" of a rainbow!!!