You probably don't, but I have another one from today.
It's from the local Children's Museum. Ours has a motto: "play to learn learn to play". We go because it's fun for my toddler, and he may even learn something from it some day, but only because I understand every experiment and instruct him on what's going on. The other kids are playing, surely, but none are learning.
The Children's Museum is a busy place most days. Typically they have 5 or 6 school field tripping classrooms present each day. The more people present, the less anyone gets anything out of it, because it's impossible to carefully control the exhibits well enough to produce a useful effect. The elementary kids there are a rowdy bunch, pushing buttons, flipping switches. They are discovering nothing. There is no one to help them learn anything at any table, so instead, they fiddle aimlessly.
In one room, they have a lot of water pipes. At one table, they have water pipes with valves. Done correctly, you can turn the valves and demonstrate:
1. sometimes, you can make an object rise without lifting it yourself--so the ping pong ball can start at the bottom of a pipe and be raise
2. sometimes, you can make an object that normally floats on top of the water get sucked down into a pipe--so the ping pong ball can be lowered even though it has no water pushing down from above
3. you can use these in conjunction to raise and lower ping pong balls in interesting ways.
But in all of my over a dozen trips to that exhibit, with more than an hour in that room per trip, only once did I manage to get the kids to set the valves in such a way to do the above, and tell them what they were doing, and why it happened.
Today was the rule, not the exception. I was trying to demonstrate how to get the ball to go down into the pipe by turning the valves so water would flow down and suck the ball with it. But a boy was interfering, constantly rotating the valve as if it were a screw (which it wasn't) so it would open/close/open/close/open/close.
I asked "what are you trying to do?" his honest response: "I don't know."
I then asked "would you like to try and do something instead? Something interesting?"
But I didn't succeed. I needed the kids to stop fiddling, and actually perform the experiment, recognizing action and reaction. Too many kids, too many controls to fiddle with. I fear what they learned was science has something to do with fiddling switches.
PS. Not only are there no instructors ever present, but the explanations on the exhibits are flat-wrong, and worse, they are irrelevant. In each case, there are a dozen things more interesting to say that could be pointed out, but aren't.