Have you ever worn a dark T-shirt on a sunny day and felt the fabric warm in the Sun’s rays? Most of us know dark colors absorb sunlight and light colors reflect it – but did you know this doesn’t work the same way in the Sun’s non-visible wavelengths?
The Sun is Earth’s power source, and it emits energy as visible sunlight, ultraviolet radiation (shorter wavelengths), and near-infrared radiation, which we feel as heat (longer wavelengths). Visible light reflects off light-colored surfaces like snow and ice, while darker surfaces like forests or oceans absorb it. This reflectivity, called albedo, is one key way Earth regulates its temperature – if Earth absorbs more energy than it reflects, it gets warmer, and if it reflects more than it absorbs, it gets cooler.
The picture becomes more complicated when scientists bring the other wavelengths into the mix. In the near-infrared part of the spectrum, surfaces like ice and snow are not reflective – in fact, they absorb near-infrared light in much the same way a dark T-shirt absorbs visible light.
