Solar toys are animated by the sun. Of course, with modern technology, it's tempting to connect a motor to a solar cell via wires and a microprocessor to power the toy. But that's inelegant (though effective). These solar toys directly convert sunlight to motion through mechanical linkages and elementary physics. The magic is visible.
Early solar toys include the famous "drinking bird", radiometer and Galilean thermometer. Genuine Ideas has developed a "solar diver", by careful modification of the well-known "cartesian diver". Here, sunlight replaces external pressure changes as the motive force behind the bobbing capsule in a column of liquid. Click on the image for more information, and try our physics simulator to demonstrate the diver's properties.
Solar Pivots are desktop toys which turn slowly in the sun, meant for gentle amusement rather than active play. If the device completes a full circle, I call it a "solar wheel", otherwise it is a "solar rocker".
Both versions rely on the related general concept of sunlight creating heat, the heat impelling a weight to move, and the moving weight unbalancing a pivoting wheel. There are three ways to convert sunlight to motion: thermoscopic (e.g. heat evaporates a liquid that subsequently moves the weight), thermal expansion (e.g. heat causes a material to expand or bend, moving the weight), or a stirling engine (e.g. heat increases the pressure in a gas, which moves a weight or piston). Toys based on each of these mechanisms are shown below- movies and more information are available by clicking on the images.