Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: The color of snow



Leigh, are you referring to "white-out?" The conditions you describe
seem to be those that give rise to white-out conditions, but if so,
your comments below confuse me. And since I don't now live somewhere
where I can expect significant snow in the winter (nor do I expect
that many others on the list do, except for you Canadians and an
occasional Minnesotan), I guess you'll just have to tell us what you
are describing, if not white-out.

I have had a couple of experiences with white-out, the most memorable
was in the early sixties. I was flying a DC-3 inbound to Little
America. When we broke out below the clouds it was like flying into a
bowl of milk. There were no shadows, and no horizon. We could see the
buildings of the camp ahead of us but they appeared to be floating,
not anchored to anything, much less the ground. We set up for a
controlled descent, planning to just fly the plane until it hit the
ground, figuring that once we got on the ground we could just taxi to
wherever the buildings were. Unfortunately, about halfway through the
descent the radar operator informed us that we were about three miles
from some large crevasses dead ahead. Since we couldn't tell where
the ground was we had no idea how much farther we had to fly on our
glide slope before we landed. The radar altimeter was of no use
because it penetrated an indefinite distance into the ice before the
reflected signal was strong enough to be detected in the airplane. So
we leveled off, and flew back to our starting point at the same
altitude and started the descent again, hoping to land before we got
too close to the crevasses, and this time we did. But it was a most
unnerving experience--just like being in a cloud except that the
visibility was unlimited, but because there were no shadows or
horizon lines, we had no visual references for our orientation.
Interestingly, by the time we got into camp, the clouds had thinned
enough that there was enough sun penetrating the clouds to create
some shadows and the condition had passed. When we took off, there
was a clear horizon.

I guess I'm glad I had the experience and nothing bad came of it, but
I don't think I want to do that again.

Hugh

One of my favorite illusions involves the apparent color of snow
lying on the ground. One day next winter, after snow has fallen
and covered the ground, and when the sky is still leaden with
thick cloud, thick enough so that you can't tell where the Sun
is, go outside and look carefully at the snow and the sky. There
will be a quiz afterward!

Quiz:

1. What color is the snow?

2. What color is the sky?

3. Which is brighter, the snow or the sky?

4. Explain your observation.

This is a remarkable illusion. You can make it even more dramatic
if you can view the sky with a horizon of snow, say over the top
of a hill. It goes away for me if I view it upside down by looking
between my legs, the same technique that makes the Moon illusion
go away.

Leigh

--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

Let's face it. People use a Mac because they want to, Windows because they
have to..
******************************************************