Glossary of Astronomical Terms/albedo

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Albedo is a ratio of the intensity of light reflected off an object over the intensity of light that object received. Given that white light is comprised of all frequencies of visible light, objects that appear white reflect a great deal of the light that's cast upon them, hence their albedo is close to 1. Conversely, dark objects absorb most of the light they receive, hence have a low albedo, something close to 0.

Albedo values cannot be inferred merely from observation. For example the full moon may appear bright, but this is due to the fact that the only reference is the night sky which has a very low albedo value. In fact, the soil of the moon has a low albedo at 0.1, which is the same albedo value as road asphalt.