Our planet looks very different, when viewed in infrared light from space. Astronaut Don Pettit shoots footage of huge swathes of our planet from the International Space Station — first using a regular camera, and then using a camera that films in infrared. Take a look at glowing red forests and strangely blue lakes.

We need to keep people doing basic-yet-cool-looking science demonstrations in space forever.

The infrared camera shows our cities as dull gray, while forests and fields appear bright red. This is strange — until you consider that concrete does reflect infrared. Famously, spy satellites would fly over aircraft testing sites and, even through spy planes were wheeled away, pick out their shapes by recording which bits of pavement were left in the sun and were radiating infrared light, and which had been in the plane's shadow and were dark.

But it's all a matter of degree. Plants, since they absorb certain wavelengths of light and reflect others, reflect infrared very well. They shoot it, mirror-like, right back up. This is why they are seas of red during daylight hours. But infrared also is radiated by a hot object, the way heating a coil of wire enough will make it glow with visible light. Since plants are selective in their absorption, they don't radiate as much during the night. They're also fairly thin and shed their excess heat quickly. Concrete, on the other hand, will get hot during the day, and shed its heat gradually, making it show up more during the night, when other sources of infrared will go silent. Also, a city is lit up during the night with lights that give off all different kinds of light. Although a lot depends on the kinds of gradations that the camera is set to pick up, and where you are shooting from, this is generally why plants look 'hotter' in infrared than cities do. At least, while we're watching them during the day.

Via Physics Central.