When a child spins a top for the first time, she begins a dialog - "What if I do this?" - to which the top quickly responds "Then I do this." After a few tries the top stands up as it spins, defying both gravity and the child's expectations. She replies next with a slightly different spin, and it answers with slightly different behavior. The dialog goes back and forth until the child develops an intuitive sense of what the top will do.
This kind of conversation is something I'm always trying to create when designing playful learning activities. In the Playing with the Sun construction kit, the phenomena under investigation is energy - both generation and expression. Today children are used to gadgets that spend energy from batteries or wall sockets by moving, or lighting up, or making noise. But the generation side of the equation is much less familiar. I want to help children create an intuitive sense of how energy is created to act as a foundation for their understanding as it develops in the future.
An important part of inviting a child into a Tinkering dialog with any phenomena is designing or selecting materials that can respond in the same timescale as the child. This is why it’s difficult for a child to have a good exploratory dialogue with a solar panel. The kind she sees on rooftops don’t appear to do much of anything. Even if she could play with them directly, they probably wouldn't respond in any way that she could understand.