But my question is a bit different. If one goes outside during a fog, that’s a good demonstration of what a cloud is like on its inside. I’m more curious about the outside of a cloud.
More specifically, thick, heavy, cumulus clouds seem to have very clear and defined surfaces, especially on their bottoms. But how well-defined is it when one is close up? If one were able to get very close to one without creating any wind (could it happen when mountain climbing?), could you actually see and touch the surface of the cloud? Without moving your feet, could you take your hand and move it, and say, “Now my hand is inside the cloud… And now it’s not.”
Related question, or perhaps it is really the same question:
We know that fog varies widely in density. Sometimes you’ll be in a fog where the visibility is limited to a half-mile, and sometimes you’ll barely see 50 yards. How dense is the bottom or top of a cumulus cloud?
(I have tried to find the answer to some of these questions when carefully watching out the window of an airplane, but we were moving just way too fast.)
I moved through the clouds (in airplane) and have clouds move past me (in high mountains) and it’s really just like fog. It’s kinda hazy on the edge and when you are “entering” the cloud your range of sight gets gradually (but quite fast) shorter as fog thickens. Densest cloud I was into I could see ground in, like two hundred feet ahead. Possibly there are denser ones, but I haven’t experienced them.
I’ve done this with fog on a calm night. The air six feet above the ground was full of droplets; everything within five feet of the ground (and warmed by the earth) was clear. The boundary wasn’t a hard and fast thing, but there was a definite difference in a foot’s height.
It’s also a good demonstration of moving into a cloud! During the next fog, open the door and start walking out. There’s your cloud surface. In fact, it would be sharper than a real cloud. So maybe open a garage door, wait a minute and then start “touching the clouds.”
Quite often when I’ve been skiing I’ve seen well-defined fluffy white cumulus clouds drifting across the mountain, and have skied through them. The edges aren’t “sharp” close up, but you pass into the cloud pretty noticeably within the space of a few feet. It feels colder and damper and you can’t see as far, but that’s about it.
I have to disagree with Cecil (Sorta). Many years ago, when I took my first lessons in an Ultralight, we happened to be flying in a layer of low level (1500-2000 feet) scattered clouds. I had been steering aroung the clouds when the instructor told me to get close enough to the next one to put a wing in it. When I did he said “Stick out your hand and grab a piece of cloud.” This was easy, as the doors were off the plane here in Florida. I will tell you that this was almost a spiritual experience for me, and nothing like touching fog. I’ve done it many time since, and it’s always a neat thing to do.
That’s because of the distance. Have you ever seen a fogbank roll in? From a mile away, it appears to have an edge, but the closer it gets, the fuzzier that edge becomes.
Similar phenomenon, on a vastly larger scale: look at this picture of a nebula. What you’re looking at is huge, almost unimaginably vast. The formation is big enough to contain several stars. From here, it looks like a big, thick cloud with a sharp edge. And in the movies, when a spaceship enters a nebula, it looks the same way; the ship appears to be navigating through colored fog. But in reality, it’s so incredibly large and so diffuse you’d barely recognize you’d passed the boundary.
Flying an Ultralight for the first time was exciting enough in itself, a lot more fun than “Real” airplanes. Then, reaching out and grabbing a handful of cloud, priceless. Surreal, spiritual, whatever. You had to be there.
A really serious fog can have quite distinct edges. I saw one that perched just below head level (you had to duck if you wanted to avoid it), and it was almost totally opaque. Perfectly clear beneath. Stick your hand in there, and it’s suddenly cool and wet.
Not as good as previous posts, but I once saw an airliner drop out of a cloud at night just as it was lowering its gear and landing lights on final approach. That was pretty cool.
The mist that forms over water when you drop dry ice in it can have a pretty distinct edge. And I’ve seen small patches of fog blowing off of a warm lake that looked as sharply defined as ghosts in a movie.
And once (don’t do this!), I burned a chunk of crystalline Iodine (under a fume hood), creating wisps of poisonous purple gas that floated around in remarkably coherent blobs.
