Unless an object has a temperature of absolute zero (-273 °C) it reflects, absorbs, and emits energy—called electromagnetic radiation—in ways that depend on its physical and chemical properties. The amount of electromagnetic radiation an object emits depends primarily on its temperature. The higher the temperature of an object, the faster its electrons vibrate and the shorter the peak wavelength of the emitted radiation. Conversely, the lower the temperature of an object, Light the slower its electrons vibrate, and the longer its peak wavelength of emitted radiation. Given the wide range of temperatures in the universe, it should be clear that electromagnetic radiation has wavelengths that span a very wide range.
Using sensors on orbiting satellites, designed to detect multiple spectral-band combinations, scientists can “tune in” to study various aspects of Earth’s surface in ways not possible from a simple color photograph. Just as soils, different plant types, plant health, the presence of water, bare rock, ice, and many other types of land cover each have unique “signatures” in the electromagnetic spectrum, different sources of light (e.g., incandescent lamps and LEDs) have their own unique signatures in the electromagnetic spectrum. Over time, scientists can observe and analyze changes in spectral signatures to detect changes in the Earth’s surface and identify various phenomena taking place, sometimes based on lighting patterns.
About Light
The electromagnetic spectrum is the range of traveling waves of energy that run from very short gamma and X-rays through ultraviolet light, visible light, microwaves, and out to long radio waves. Visible light is the quite narrow band that human eyes are adapted to see. But as noted earlier, humans are proficient at developing tools to extend the range of their capabilities.Using sensors on orbiting satellites, designed to detect multiple spectral-band combinations, scientists can “tune in” to study various aspects of Earth’s surface in ways not possible from a simple color photograph. Just as soils, different plant types, plant health, the presence of water, bare rock, ice, and many other types of land cover each have unique “signatures” in the electromagnetic spectrum, different sources of light (e.g., incandescent lamps and LEDs) have their own unique signatures in the electromagnetic spectrum. Over time, scientists can observe and analyze changes in spectral signatures to detect changes in the Earth’s surface and identify various phenomena taking place, sometimes based on lighting patterns.
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