There are many reasons for this. Not everybody knows the same things. It can be surprisingly valuable to go over the basics even when you already know them. And then there's the "stupid question" that so often is far from stupid—often everyone else in the room is wondering the same thing. It usually isn't obvious in advance whether a question is deep or shallow.
Asking simple foundational questions out of interest isn't a problem around here. The finest conversations always welcome them. It's the intellectually petty discussions, where people try to one-up each other with displays of knowledge, that can't handle them.
"I googled, and found differing opinions on whether perpetual motion is possible. Is this an example that shows that it is?" would be a better question. It still would surprise me that there are people on HN who would pose such a question about such a simple device, but it would show some intelligence and a will to make an effort to learn. The OP still may have both, but the way the question is posed doesn't show it.