albedo - definition - light, astronomy, nuclear and particle physics

Definition: light: Photometric term for the fraction of incident light that is diffusely reflected from a surface.

planetary astronomy: the fraction of incident sunlight that is reflected from a planet. This is believed to have a serious impact on climate.

nuclear and particle physics: Ratio of the neutron flow density out of a medium free from sources to the neutron flow density into it.

Examples: During Ice ages, the Earth is covered by a reflective layer of ice, which greatly increases its albedo, further lowering temperatures.