What is really pushing the blades and making them spin?

Air is really what pushes the pinwheel's blades and makes them spin, even though you can't see it happening. When you blow, moving air pushes against the angled blades, and because they're tilted, that push makes them rotate round and round instead of just moving straight back.

Sunlight doesn't push on physical objects the way moving air does, and sound is just vibrations traveling through the air rather than a steady push, so neither one could spin the blades the way a puff of breath does.

Wind turbines that make electricity work on this exact same idea, just using much bigger blades and real wind instead of a puff of breath from your mouth.