All objects on earth give out energy as microwaves. Microwaves are a type of low-energy radiation that is not related to the temperature of the object. Since all objects naturally radiate this energy they can be passively detected by sensors on satellites, hence the term: "passive microwaves." The low-energy microwaves can give us some information about the composition of the object they come from. The types of atoms in an object and how these atoms are arranged affects the energy they give out. For example, solid sea ice gives out more microwave energy compared with the ocean water around it. When the satellite data detects this higher energy area, it tells us that there is sea ice on the ocean. Clouds in the sky do not give out much microwave energy, and this makes it easy to "see through" the clouds to find sea ice using satellite equipment that can detect passive microwaves. This is an improvement over using satellites to take "regular" pictures of the earth in the visible light range, because when clouds cover the sky, visible light, which is the energy we can see with the naked eye, is blocked.

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