[bizerl (OP)]

I'm afraid this is not something I have dilligently documented, but it seems to me that clouds look the same whether the sun is shining on them, or from behind them.
In an aeroplane above the clouds, we are viewing them from the same side as the sun, yet they look the same if we are underneath them, viewing them from the opposite side of the sun.
Is there something in this? Or is it just my flawed, human brain ignoring the inconvenient data to make a convenient pattern?

[RD]

In an aeroplane above the clouds ... they look the same if we are underneath them

Anvil clouds wouldn't look anvil shaped if viewed from directly above ...


https://en.wikipedia.org/wiki/Anvil_cloud

Clouds can have self-similarity so can look similar when viewed at different scales.

[bizerl (OP)]

Love that picture!

I should clarify what I mean by "the same". Obviously clouds are different shapes from different angles, but I would have thought that there would be some difference in colour/ opacity etc. from an observation with a light source behind the cloud, and one with a light source in front.

Whilst their shape may vary, clouds of a similar type will have the same (for example) "white fluffiness" whether the light is behind or in front.

[damocles]

White fluffy clouds are aerosols of such density (particles per unit volume) and thickness (metre top to bottom) that sunlight is scattered only once or twice in a fairly isotropic (all directions equal) way in its passage via cloud to the eye. These clouds look much the same from top or bottom. However denser and/or thicker clouds that look grey from below because sunlight is scattered many times before a small remnant of it reaches the viewer's eye, look much lighter from above than below, for fairly obvious reasons. Other issues are the amount of sky that is covered by cloud (for viewing from below) and the way that our pupils adjust to let in more or less light depending on the overall brightness of viewing conditions.

I've looked at clouds from both sides now, from up and down, but still somehow it's clouds' illusions I recall. I really don't know clouds at all. (couldn't resist)

[cheryl j]

I like to paint, and when clouds are fairly low in the sky, I think they look different depending on where the sun is. When the sun is behind you the center of the cloud tends to be white and fluffy with darker blue edges. When clouds are back lit, its the opposite - the center is darker and the edges kind of glow, as in the picture below.

 http://upload.wikimedia.org/wikipedia/commons/thumb/7/71/Cloud_in_nepal.jpg/220px-Cloud_in_nepal.jpg