Ever sailed in a rainbow ?

[Goodge]

Took this picture going up the Chenal Du Four last week.

A few minutes later the rainbow moved over us and the water went purple for a moment.

Bit weird really !

 

[Deleted member 478]

Unless science has changed since I was at school, I don't understand how this could have happened. Please educate me.

 

[brianhumber]

Lucky you - how much did you find in the pot of Gold then?

 

[Goodge]

I don't know either... that's why I took the photo.... it was a bit weird.

I saw the boat sailing along as you can see. Then the rainbow got a bit more intense and seemed to move / pass over us and the water looked purple for a while.

I'm no scientist and I haven't got paintshop either ... but that's what appeared to happen.

Anyway gave us soemthing to talk about for a few minutes

 

[RupertW]

Dunno about the science but I've seen the sun shining through the rain in the middle of a squall and the light is very colourful, changeable and odd - perhaps it's all the fat raindrops like little moving prisms.

 

[Goodge]

Pot of gold

I think the thieving French yacht nicked it first !

 

[snowleopard]

There's more than one way to form a rainbow. The common type involves light coming from behind the observer and being reflected once within each water droplet. Secondary rainbows seen inverted outside the normal one are formed by two reflections.

The one in the picture is, I think, formed in the same way as a coloured halo seen around sun or moon through thin high cloud. The light source is in front of the viewer and there are two reflections per drop.

 

[Becky]

When Cornish Maid was sailing upwind in 35+ knots of wind just north of Cape Finisterre, the wind was blowing the tops off the breakers, and the spray was making a beautiful rainbow on the sunny side of the boat. It would have been very pretty if I hadn't felt so b***dy awful.

I now strongly subscribe to the 'never again sail to windward' club. /forums/images/graemlins/grin.gif

 

[PaulJ]

I'm not sure about the science either but I once saw a very bright, fully circular rainbow when flying into Funchal. It was down Sun of us and our shadow was in the middle. Very pretty but I only saw it the once in 30 yrs of flying.

Paul.

 

[TonyD]

I've often seen this from commercial aircraft. The circular rainbow usually appears to be above the clouds and you are looking down on it, with the aircraft's shadow nearby. No idea how its caused though. /forums/images/graemlins/confused.gif

Tony

 

[PaulJ]

Tony, I think what you are describing is a different phenomenon. When I saw this circular rainbow we were quite low (I think about 1500ft) and there was a heavy rainshower out to one side of us and the cloud from which the rain was falling was above us. What I saw was definitely a "conventional" rainbow inasmuch as we were directly in the line between the sun and the rainbow. I suspect that all rainbows would be circular if it was not for the fact that we are usually at ground level and the Earth gets in the way of the bottom half...... /forums/images/graemlins/wink.gif

 

[snowleopard]

[ QUOTE ]
I suspect that all rainbows would be circular if it was not for the fact that we are usually at ground level and the Earth gets in the way of the bottom half...... /forums/images/graemlins/wink.gif

[/ QUOTE ]

Exactly so. The rainbow forms when light reflects through droplets that are on a precise angle between the source of light and the observer. The positions of droplets that meet this criterion lie on a circle opposite the sun from the observer. If you are high up you can see the full cirecle. Your shadow will fall at the precise centre of the circle.

To see the effect, set your garden hose to a fine spray and stand with your back to the sun.

I'm working on a graphics program to display rainbow effects at the moment so it's all a bit close to home.

 

[TonyD]

Thanks guys. You learn something new every day on Scuttlebutt! /forums/images/graemlins/cool.gif

Tony