[quote author=Fu-Kwun Hwang link=topic=44.msg4208#msg4208 date=1241401601]
The rainbow in the above simulation is due to light enter raindrop/waterdrop , refracted twice and reflected once or twice.
The angle of the rainbow is nearly 42 degree.  And the rainbow is always at the same relative position no matter how you move. You can not pass it. Because see rainbow from different raindrop when you move.
However, there are several way to produce rainbow light pattern. e.g. light pass through a prism, the image in the URL you have provided, ...etc.

May I know what is the direction of the sun when you saw the rainbow? Is there any other strong light source around?

Mr. Hwang,
I do hope you have not dismissed my experience (or perhaps I did not understand your answer), some of the peripheral info may be in error, but I assure you the basic info is fact - I stood in that rainbow and passed through it twice. On the back side I did not see any other rainbow nor did I see a different bow at any time during the experience. That bow I did see was stationary the entire time.

1. I stood in the bow and it was stationary
2. Standing in front of the bow, on the sun side, I could see the air 'slowly dancing' all the way to the ground. It was obvious, there was a rippling effect which distorted the air.
3. The cedar tree behind the bow had shaded towards grey when looking thru the bow and had a rippled effect.
4. The colors of the bow faded to clear from a few feet above my head (at least I could see no colors from ten feet down)

The following is a copy of an email I sent, in response to a request for additional info, to Kathy Coil @ noao.edu, there is more info:


I'll do the best I can, below, from memory, most of the info will only be
close. I have a rough understanding of  rainbow formation and the various
angles involved..., but, no understanding of how I am able to stand in a
rainbow. Is there any known explanatory geometry of a rainbow that would
allow for this???
.....I assure you, I stood in that rainbow, walked thru it and observed the
'wavy' effect in the air very closely (standing close I pondered what effect
it might have if I walked into it, so I first put my hand into the bow)...
as well as its effects on the cedar tree, as described, behind the bow.
.....The bow had faded its color from about ten feet off the ground and what
I was seeing was an obvious wavy effect in the air - no colors, just 'slow
dancing' air.

Time of day, not certain, but early afternoon in summer - sun had to be to
the NW. Weather: A light rain had passed from west to east, cloudy bright
and the sun was coming full - the remainder of the rain clouds were thin and
passing. It was not raining on me and the rain had passed by about a mile.
There were no other light sources, large trees or obstacles near, the
closest, a tree, at about forty yards to the NW and well below the angle of
the sun. (Sun angle? - I think it was in June near the equinox. Angle of the
arc to the sun (?), not sure, seems it was not straight on. It appeared to
me the bow was 90 degrees to the ground, or straight up. )

Stepping from a covered deck, going east, I saw the bow and that its end was
twenty yards from me to the SE. As I walked to the bow, it did not change
position, it remained stable.The bow ran from NE to SW, I was at the SW end
with the other end disappearing over a hill (width of the bow inknown - no
real reference) at perhaps a half mile. (I was in a valley approx a quarter
mile wide, on the west side of the valley.) Drawing a line from the base, to
the NW, of the bow perpendicular to the arc and calling it 90 degrees with
zero degrees being inside the arc, I approached the bow from 120 to 135
degrees and then stood directly in front of it within two feet observing the
interference in the air..

The base of the bow was narrow, about four feet wide, and the bow was very
thin from front to back, only a few inches. I stepped back and forth thru it
twice, slowly, before it disipated... and as I remember the sun was coming
full at that time.