Whiteness, actually. A calculation of a planet's reflection power in proportion to its absorptive ability, represented in a formula measuring the amount of light reflected from an unpolished surface in proportion to the total amount of light that falls on it.

The albedo is 7 for the moon and mercury; 59 for Venus; 44 for Earth; and 15 for Mars. The changeable character manifested by Moon and Mercury is thus shown to be due to their poor reflective potential in some manner.

An entirely different set of Lunar properties comes from the fact that the surface temperature increases some 70-odd degrees above boiling point as the Moon reaches an opposition to the Sun, and as a result it emits a wide band of infra-red frequencies that are many times more intense than all of the rays reflected by the Sun.

The temperature of the surface decreases to a sub-zero level within the first few minutes of a Lunar eclipse and the infra-red emanation stops. At Lunation, the dimly-lit surface of the Moon is attributed to light reflecting back from the Planet, which will look to the Moon-dweller four times bigger and several times lighter than the Moon when viewed from Earth with its high albedo.

There are some suggestions that, aside from its reflected light, Jupiter emits a ray of its own, but astrophysicists are not yet in consensus on that issue.