Astronaut and chemist Dr. Don Pettit does physics demos that are out of this world. Currently on board the International Space Station, Dr. Pettit presents fantastic physics that can only be demonstrated in micro-gravity.
Challenge Question: Why do plants appear red in infrared pictures and cities grey?
Challenge Answer: Plants reflect IR light. This picture was probably taken during the day,
so the plants are reflecting IR, while the concrete cities are
absorbing it. At night, the cities will be visible as they release heat
in the IR spectrum, while the plants will be dark.