BS: Why are rain clouds Black

Subject: BS: Why are rain clouds Black
From: GUEST,Muppett
Date: 21 May 10 - 10:22 AM

Here's a thought, why are rain clouds black, when the rain that falls from them is colourless, any ideas?

Cheers

Subject: RE: BS: Why are rain clouds Black
From: Ebbie
Date: 21 May 10 - 10:24 AM

Sounds like the kind of question I might pose! I'll be reading with interest.

Subject: RE: BS: Why are rain clouds Black
From: GUEST,Janie
Date: 21 May 10 - 10:46 AM

They look dark because they block light. Rain clouds are more dense than other clouds because they hold more moisture, so they block more light.

Subject: RE: BS: Why are rain clouds Black
From: Bill D
Date: 21 May 10 - 10:49 AM

However, being dark does not necessarily indicate rain..... that cloud coming from Iceland ain't gonna make your grass grow.

Subject: RE: BS: Why are rain clouds Black
From: wysiwyg
Date: 21 May 10 - 10:51 AM

Black is Beautiful. It means the plants are gonna make oxy.

~Susan

Subject: RE: BS: Why are rain clouds Black
From: Dave the Gnome
Date: 21 May 10 - 11:03 AM

Because if they were pink they would be flamingos...

Subject: RE: BS: Why are rain clouds Black
From: GUEST,muppett
Date: 21 May 10 - 11:11 AM

So why aren't clouds that have less rain in them, rainbow coloured?

Subject: RE: BS: Why are rain clouds Black
From: Stu
Date: 21 May 10 - 11:29 AM

There's s holes in the sky
where the rain gets in
they're ever so small
that's why rain is thin.

Spike

Subject: RE: BS: Why are rain clouds Black
From: Newport Boy
Date: 21 May 10 - 12:30 PM

If you're worried about this, Muppett, how about:

If a brown cow eats green grass, why does it give white milk?

Phil

Subject: RE: BS: Why are rain clouds Black
From: bobad
Date: 21 May 10 - 12:34 PM

"So why aren't clouds that have less rain in them, rainbow coloured?"

They are.

Clouds are white because their water droplets or ice crystals are large enough to scatter the light of the seven wavelengths (red, orange, yellow, green, blue, indigo, and violet), which combine to produce white light.

Subject: RE: BS: Why are rain clouds Black
From: Mrrzy
Date: 21 May 10 - 12:54 PM

I saw a rainbow-cloud once, it lasts for mile and miles and luckily I was the passenger, not the driver, and he being both color-blind and too tall didn't get to see it, and yes it was really there.

Subject: RE: BS: Why are rain clouds Black
From: Amos
Date: 21 May 10 - 02:13 PM

Muppett:

Get a basic physics text book and study up some on the fundamentals of light propogation.

White light is a rainbow happening all at once.

A

Subject: RE: BS: Why are rain clouds Black
From: Stu
Date: 21 May 10 - 02:33 PM

I've never seen a purple cow
I never hope to see one
but from the milk we're getting now
there certainly must be one.

Subject: RE: BS: Why are rain clouds Black
From: Little Hawk
Date: 21 May 10 - 03:59 PM

If we can call an orange an "orange", why don't we call a banana a "yellow"?

The clouds that really freak me out are the ones that turn the sky a sort of deep bottle-green colour. Those generally indicate the strong possibility of a tornado...or at least a very severe storm. When you see them, take cover, preferably in a basement.

Subject: RE: BS: Why are rain clouds Black
From: gnu
Date: 21 May 10 - 04:07 PM

Amos... how is a rainbow "made"?

Subject: RE: BS: Why are rain clouds Black
From: Amos
Date: 21 May 10 - 07:06 PM

Traditional Newtonian optics indicate that is by refracting the differing frequencies of white light so they come out of a medium at separate angles so they are visible as ROYGBIV instead of as white light. Water droplets will serve. Ya? You have some other answer in mind, you wily Canuck?


A

Subject: RE: BS: Why are rain clouds Black
From: gnu
Date: 21 May 10 - 08:28 PM

Leprechauns. Everybody knows that. Geeeeeze oh eh?

Subject: RE: BS: Why are rain clouds Black
From: gnu
Date: 21 May 10 - 08:31 PM

Say.... that bit about color blindness and the your last post, Amos.

When youse see a rainbow, do youse see more than three colours?

Subject: RE: BS: Why are rain clouds Black
From: Little Hawk
Date: 21 May 10 - 08:43 PM

There are visible variations of colour in a rainbow from red to orange to yellow to green to blue to violet to indigo. Interestingly enough, these colour variations are seen in exactly the same order as the ones indicated in the Eastern traditions for the seven chakras (energy centers) in the human body, all of which are associated with the functioning of the endocrine gland systems.

Subject: RE: BS: Why are rain clouds Black
From: gnu
Date: 21 May 10 - 09:15 PM

I am partially colour blind, so I can only see only the three primary colours of a rainbow, as can 99.9% of all colour blind people. Very few fail a lantern test.

On the other hand, I can spot a Birch Partridge (Ruffed Grouse) against a "camo" background and point it's location out to others who cannot see it, even when it is in "full view". I have spotted them when all I could see was part of their head at twenty yards.

Subject: RE: BS: Why are rain clouds Black
From: Ed T
Date: 21 May 10 - 11:26 PM

An interesting site with pictures:
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

Subject: RE: BS: Why are rain clouds Black
From: JohnInKansas
Date: 22 May 10 - 05:17 PM

Somewhere up above someone suggested that rain clouds are black because they block the light. For some cases - when the light is behind the cloud - this is "an answer" but not an explanation.

A spherical blob, such as a raindrop, that's even slightly transparent will pass some light from behind, and when the light comes from the front will "turn around" part of the light and reflect it back. Neither effect is 100 per cent, so if there's "a sufficient density of blobs" the object (the cloud) looks darker when lighted from behind, and may be "somewhat grey" when the light is from the front.

When the light is on the front, the cloud looks really black only when the individual drops get too big to remain spherical, and the light is just "scattered" within the cloud instead of being reflected straight back.

Small water drops that can remain suspended by "normal" air motions are very nearly spherical due to surface tension. When the drops get big enough to remain "up there" only in the presence of strong rising air currents, the air blast "warps them" to irregular shapes that no longer are "good reflectors." The light is no longer reflected straight back to where it came from, but instead goes off into "somewhere else" in the cloud. Multiple - less than 100% - reflections results in all the light being absorbed in the cloud.

If a cloud starts to look black when the light is on the front side of the cloud, it means that the individual drops are big enough to require strong up-flowing air to remain in the cloud, which is a condition conducive to their eventual "falling down" as rain.

John

Subject: RE: BS: Why are rain clouds Black
From: Georgiansilver
Date: 23 May 10 - 04:02 AM

One explanation here which seems plausible

Subject: RE: BS: Why are rain clouds Black
From: GUEST,leeneia
Date: 24 May 10 - 01:00 AM

"The clouds that really freak me out are the ones that turn the sky a sort of deep bottle-green colour."

Hi, Little Hawk. From what I have read, green clouds produce hail. So don't just get under cover - put your car in the garage if you can.

I share your fear of tornados, but they also fascinate me. I read every tornado and storm book I see in the library. It still baffles and amazes me that they can even form.

As for rainbows, I have been seeing explanations all my life, and I have yet to see one that's convincing. The tiny droplets in the cloud are whizzing around like mad, right? Brownian motion? So how do they send the light rays (once split) out in order, all sorted into bands?

I go with the leprechaun theory.

Subject: RE: BS: Why are rain clouds Black
From: GUEST,muppett
Date: 24 May 10 - 04:20 AM

Some very interesting answer, but Amos, come on chill out and be more creative and imaginative with your answers, there's no fun in reading basic physics books.

I liked the link you sent Georgian Silver and Newport Boy, you're on my wavelength and a similiar quandry to yours, you eat food all different colours, why doesn't come out all brown.

Amos please don't ask me to read a Biology book, Nay only joking your answers were very informative and thanks.

Subject: RE: BS: Why are rain clouds Black
From: GUEST,keith A o Hertford
Date: 24 May 10 - 04:30 AM

Rain clouds look white from above.
They only look black from below because they are so dense.
Why things look any colour is to do with how they reflect.
Snow and clouds look white because they reflect and scatter all colours equally.
White is not a real colour but how we perceive a mixture of all colours of light.
We are even fooled into thinking we see all colours and white on TV when really only 3 colours are present.

Subject: RE: BS: Why are rain clouds Black
From: Micca
Date: 24 May 10 - 06:51 AM

There is a slightly more in depth answer Here

Subject: RE: BS: Why are rain clouds Black
From: GUEST,Muppett
Date: 24 May 10 - 08:50 AM

Cheers Micca very interesting, couldn't click open the example of the optical illusion though (pitty)

Subject: RE: BS: Why are rain clouds Black
From: gnu
Date: 24 May 10 - 01:09 PM

The scariest looking clouds for me are the really tall and dark ones I see when I look out the airplane window of a commercial turboprop.

I was returning home with my boss once in a Dash-8 and immediately noticed when the pilot made a turn on a short hop... then another. I was in a window seat and I could see fairly well what was coming. I gulped my drink and said to my boss, "Better drink up. We are flying into a storm." He pooh-poohed that and about thirty seconds later was wearing his drink.