Photolith

The Photolith is a metal object in Pikmin Forever.. It is a Crookes radiometer. It is found in the Mycelial Burrow, after the section in which Mushroom Pikmin are found, on a ledge that requires activating a light sensor to reach. When Mushroom Pikmin or leaders approach the Photolith with their light, the foil fins inside rotate, since the object measures light.

Olimar's Notes
''A recent expedition inside a cave overgrown with fungus has led us to this strange object. If we had not discovered friendly illuminant Mushroom Pikmin, we wouldn't have been able to see it in action. The vanes inside rotate in response to light. The interior of the research pod has very little light at all, so we explorers have been taking turns running up and shining it with our beacons. This planet never ceases to marvel me with its creations, although I'm not sure I've spent more hours studying any other object than I have with this one.''