I do know but am not sure that I can explain properly! It is caused by the sun shining through raindrops and the light is diffracted into the different colours. The position of the rainbow is fixed by your relationship to the sun (source of light) so, as you change your position the position of the rainbow changes. Hence, there may well be a pot of gold at the end of the rainbow but you willalways be in the centre of the arc!
Right, now someone explain it better!!!

A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun. More simply put, you see a rainbow when it is raining and the sun is also shining at the same time. There is nothing magical and mysterious about them in that sense, we regularly see in Moray where it is often raining and sunny at the same time. I think a bird would find it hard to fly 'over' a rainbow but could easily fly through such.

That's very interesting. I normally see them in summertime, immediately after a thunderstorm if it occurs at evening when the sun is just above the horizon.

You can sometimes see small ones in the spray form a waterfall or even in the spray from a garden hose.

the 7 colours are due to the wavelength of each colour of light. These form the spectrum of light and is part of the electromagnetic spectrum: red has the shortest wave length and is on the outside of the rainbow and violet the longest so is on the inside.

the rainbow forms when the sun is behind you and usually occurs when the sun is a specific angle to the horizon [that bit of science escapes me]. and the curve is pretty much that of the Earth. I remember making rainbows for the children with the mister part of the hose sprayer. mum was pure magic then :o)
Sadly you will never catch the rainbow but it is not an illusion in that sense.

They are an amazing phenomena especially when it's right above your head.

Think of dew drops--or, where I live, sprinkler drops!--on the grass. When the morning sun hits one just right, you see a spark of pure color. Move your head a fraction of an inch, and the spark disappears, or changes from purple to blue, to green, etc. Now imagine millions of drops, a mile or few away, with the ones at exactly the right angles from the sun and your eyes all showing sparks of color.
Rainbows are one of those things that develop from simple, predictable rules of optics and refraction, into nature's great works of art.

That's really amazing -the physics of it. It's not random

Saw a rainbow cloud the other day....quite magical, I'd read of them never expected to see one

I love to see a half rainbow, the sky inside the bow often darker than outside

We live on a wonderful world and thanks to folk like you on here, and brian cox...☺
I'm slowly beginning to understand physics a tiny bit

I've always understood that to see a rainbow (or a shooting star) it's very lucky. Often when I've had a problem I will see one or the other but the rainbow means it's there just for me. Fanciful? Probably but it's also quite comforting.

Apparently, if one is very high up on a mountain top one can see a rainbow as a complete circle with the shadow of the person in the middle. I have such photos in various books. Also, a rainbow lies in a certain direction , tho' never in a place, so head out boldly towards your rainbow. Who knows what you will find!

That's really fascinating Feverfew - a complete circle? That must be something to see. There seems to be so much folklore & mystery attached to them. Something about them makes me smile. Sometimes I'll see a halo around the moon on a foggy night - there's the complete circle.

I've seen double rainbows too. They're fascinating.

Feverfew, your suggestion to head out boldly could have you walking off a cliff!:o)

Yep, heading out boldly for a full circle rainbow (aka a "glory") requires skydiving gear! :D

What you are describing, Feverfew, is called a 'Brocken Spectre'. It is not actually a rainbow but occurs when the mountaineer is looking down into a mist filled gorge and the light is behind him, so effectively a shadow but with a halo. They are about as common as hens teeth.

A phenomenon of nature . . . sunlight and raindrops - I love them!

Just found a marvellous pic of a Brocken spectre on google - wow. Imagine being alone on a mountain top and seeing that if you didn't know what it was...

You don't even needed to be up a mountain to see at times, Bubla and I have seen from Troop Head on the Moray coast.

I added a new picture showing the 'ever present' rainbow at Niagara Falls. It's even visible at night during full moon (lunar bow). This was a very interesting discussion. Thanks to everyone who participated.

Great new pic, Paul . . . how fabulous it would be to see that at night! Fascinating subject, and one of the few things I can think of which are impossible to paint realistically.

I agree, good point.

Love the Falls picture, Paul. Do you live near there or were you just visiting?

Thanks Arbuthnot. I'm about a 6 hour drive to Niagara Falls. I was up visiting friends in Buffalo, then we all drove out to see the falls-which is a 'must see.' Very scenic up there and lots of farms, farms, farms. Too many cows for this city boy, lol.

I love the fact that I can produce the colours of the rainbow on the wall by my computer . . . just by positioning a crystal glass object with many facets for the sun to shine through. In fact anything that has all the colours of a rainbow makes me smile :))