[privacy] U.S. OMB: 'People are Losing Data'

[Drsolly]

On Thu, 2 Nov 2006, Gadi Evron wrote:

> On Thu, 2 Nov 2006, Fergie wrote:
> > And in other news, scientists say the sky is blue. :-)
> 
> I wonder what the real colour of the sky is. I am sure it is not blue!
 
That depends what you mean by that question. What is a "real colour"?

But you can do the following experiment that shgows you how come the sky 
is blue.

Get a glass box (like an aquarium, for example), and blow some smoke into 
it (you might burn some paper and blow the smoke into theglass box. Then 
put a lid on it, to keep it in place.

Then shine a torch through the box. You'll see that the beam coming out 
the far end is reddish, and the smoke looks blueish. That's because the 
small particles of solid suspended in the air (the smoke), scatters blue 
light more strongly than red, because the red has a longer wavelength. The 
blue light, scattered in all directions by the smoke particles, is what 
makes the smoke look blue. And the blue sky is for the same reason.

So, next time you kid asks you "why is the sky blue", you can show her the 
reason.

And if you took the suspended particles out of the air, then there 
wouldn't be any scattering, and it would be black.

The other big question is, why is the sky black (as can be seen at night, 
when there's no scattering effect). Hint - this is 
called Olber's paradox.