This works for a surprising range of sunlit things, including rooftops (sure), highway surfaces (probably not), sailboats (maybe), and jets, cars, and wild deer (haha good luck).

"Solar Panels", by Randall Munroe, licensed under Creative Commons Attribution-NonCommercial 2.5 License

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This works for a surprising range of sunlit things, including rooftops (sure), highway surfaces (probably not), sailboats (maybe), and jets, cars, and wild deer (haha good luck).