h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

sorry, i didn't get the cone part
i don't see anything cone-shaped in a rainbow!
and i really don't like the idea of having a huge cone stuck in my eyeball

oh, i don't get the two-eye-thing too.
i mean, a rainbow and its shape have nothing to do with the number of eyes we use to observe it

It isn't a cone because it isn't a solid object. Pass light through a prism and what do you get? A rainbow! What therefore is a rainbow? It is the light refracted into individual frequencys of the electro magnetic spectrum. Is light a cone? No! So a rainbow is therefore not a cone!
In real world terms the other day I was waiting in a queue for the car wash, when the spray came on a rainbow appeared in front of me, I could quite clearly see the end of this rainbow where it terminated in the ground, I also know if I moved to the spot where the rainbow ended and looked across to the other end I wouldn't see the rainbow, because a) it's not 3D b) the light scource would have moved.

Sorry to be so long replying -- yes, a cone is a solid but you're splitting hairs there. The shape of the rainbow is the shape of the surface of a cone, which can reasonably be described as conical.

More precisely the rainbow's shape is the shape of the mirror that shows it to us.

It's not logical to describe what we see as 'light' and derive conclusions from that. Look at this page on your screen. What do you see? Light. Is light a page? No! So a page is therefore not a page!

"Conical" describes the shape of the selection of (ever-changing) water-droplets that show us reflections of the sun, in the form of a rainbow.

It could be said that the cone is formed by the wave/particle nature of light, so the cone that ends in your eye is made up of the light particles (photons) travelling towards you. The reason it's cone shaped is that it starts off widely dispersed, and ends up on your eyeball.

The thing is, though, is that then the number of rainbow cones that exist depends on the number of viewers. They all will have their own cone attached(!) to their eye(s), with different geometry for each one.

I prefer to think of them as intangible non-objects, no more a corporeal entity than the prism light, or sunlight (or solar wind?).
String Theorists may have a different view.

Another possibility is that there is and has ever been only one sunlight rainbow seen on earth, each viewing of which is a viewing of millions of reflections of our one and only sun, under the unique and always identical conditions that make it appear as a rainbow.

Yeah ole jon brown ee solde iz farme,with hiss minting crisps and His say me ALL are,ordered hiself to a manager and edittered his disgraceful race of words away in light like touche of "touch a microscope once and yuoull forget everything"turner traps laid before you reach Bombay"hillbilly indian pot of ink"Gale gaul snowman ski pole ice IM as cold as ice,cant read no farenhiet,ho-ho.Silkworms.o

Now that comes over as west country. "cant read no" distractingly US but west country equally. Shades of the Goons: Bombay Biddy for a char in Bloodnok's Rock'n'Roll Call. Curses, not available on CD yet.

Got it at last: the Goons songs on CD. My son gave it to me for my birthday.

The shape of the rainbow has Everything to do with the number of eyes observing, since each cone is essentially created by the eyes that are observing it.
Imagine, if you will, all the little photons (red-loking ones, through to Violet ones) streaming into your eye: if you close one eye, the rainbow is still there, if you close the other eye and reopen the first - Still There!
Logically, then, there must be a virtual cone for each eye &lt.

...../<-rainbow you can see
..../
.../
&lt
...\_____________<- horizon
.........\<- rainbow you cannot see

think about this drawing in 3d, and you'll see what I mean.

That is the solution I ascribe in my entry to "stiff-necked scientists". Now read on.

and after all that, i still haven't a clue about the cones!

maybe my dad was right; i should've taken physics...

are the scientists stiff necked because they spend their lives looking up at rainbows? i don't think i'll be a scientist.

What's the problem with the cones? The visible shape of the rainbow is the shape of the mirror: a "conical" selection of raindrops, selected by their position, namely where your sight lines meet the sun's rays at an angle of c.42 degrees. Sketch it on paper.

Not literally conical, as pointed out above, if you restrict the word to denoting a solid; but describing the surface of a cone, which I suggest is a properly meaningful use of the word "conical". In the same way people call a witch's hat conical, and everyone knows what they mean.

Now, do you see one rainbow, or two side by side? "Don't think, look!" as Wittgenstein A1024156 was fond of saying.

no, i still don't understand.

i get what conical means, now you mention a witch's hat. my immediate reaction was to think about a conical flask, but am i right in thinking that that is less of a nice topic?

anyway, cones. come rainbows are single, some double and some tripple. Does that have anything to do with cones? are the droplets of water in the shape of a cone or the light or are my eyes the cones? i don't understand at all.

All rainbows are double, though sometimes the outer(?) one is very faint. They may be triple; but I think the third ring is not in a visible direction.

The cones are emanating like witches' hats with their points in your eyes. The rainbow you see is a collection of millions of reflections of the sun.

The sun is reflected by every droplet in the cloud of mist in front of you. However you only see some of these reflections, those that come in at the critical angle. An angle measures the divergence between two lines; the lines in question are between sun and drop (one line) and drop and eye (the other line). I believe it is around 42 degrees for the principal rainbow.

Draw a rough sketch, it becomes perfectly clear on paper. The sun is behind you, you are looking away from the sun, the mist is in front of you. The sun's rays come in parallel lines (hitting your back) and are reflected back from the mist to enter your eyes. The reflections that you see appear to make up part of a circle; but these reflections are in fact coming from a selection of droplets that make up part of (the surface of) a cone.

oh! all becomes clear! as clear as a rainbow in a cloudless sky!

cheers x

Wow -- it's gratifying to a teacher (like me) to explain something to someone's satisfaction!

About "stiff-necked" -- it's my favourite word from the Old Testament.

See http://www.gracecathedral.org/enrichment/brush_excerpts/brush_20040609.shtml for a bit of dramatic action involving stiff-necked people.

lol