I was taking an airplane today, and as I looked out the window I noticed something strange. I could see the shadow from the plane on the clouds, and there was a circle in rainbow colors around it.
How come?
All rainbows are circular, but because we’re usually on the ground we only see the top half.
You were in the air and saw the complete thing! Caused by thesun shining through droplets in the clouds, just like other rainbows.
What you saw is called a glory. Here’s some informations from The Bad Astronomer’s website:
So was it only coincidence that the rainbow was centered exactly on the airplane shadow?
No; this happens because you are directly between the light source and the shadow.
Another related phenomenon is that the plane’s shadow on the ground often appears to be surrounded by a brightly-lit zone - this is because you can’t see the shadows of any of the surface features and is particularly noticeable when the shadow falls on a field of wheat stalks - because you are viewing the shadow from the exact same direction as the light source, the shadows of the wheat stalks near to the plane’s shadow are hidden behind the stalks themselves, making the whole area look brighter.
Nope - a glory is always centered on the aircraft shadow. If things weren’t lined up that way, you wouldn’t see a glory.