# Do the earth and the moon reflect the different fractions of total solar radiation proportionally?

Reading on this website that: "All of the energy from the Sun that reaches the Earth arrives as solar radiation". "Solar radiation includes visible light, ultraviolet light, infrared, radio waves, X-rays, and gamma rays".

Here Albedo is explained to refering to the entire spectrum of solar radiation.

The earth and the moon obviously reflect different amounts of total solar radiation, but question is if they reflect the different solar radiation fractions proportionally?

(Proportional reflection is when all the different light spectrum fractions increases, or decreases, with the same percentages.)

Or do earth and/or moon reflect light dis-proportionally?

Rephrasing the question: We know how much the difference in visible geometric albedo between earth and the moon is, but is that figure the same when comparing reflection of infrared, or any of the other parts of the light spectrum?

• +1 good question (and asked with a somewhat different title than previously). There is actually an answer in the vote-closed thread which indicates the exact spectral differences. astronomy.stackexchange.com/questions/26780/… has a comparison of sun and moon Feb 22, 2021 at 13:25
• @planetmaker. Exactly where is it on that page? Feb 22, 2021 at 14:29

The obvious answer is: "of course". Different colour simply means different wavelength-dependent reflection; different brightness means different wavelength-independent reflection. Earth and moon have different colours when viewed from space.

The real question is by how much does it differ as a function of wavelength. There are already here nice comparisons of the solar spectrum and the Moon's spectrum.

There's a relative measurement of Earth's reflectance by Björn et al (2009). Similarily Turnbull et al (2006) discuss the reflectance of Earth compared to the Moon. Reality is complicated as exact reflectance depends on the observation angle and angle of incidence - and the exact materials looked at which varies slightly for the Moon and can vary a lot for Earth, especially when considering cloud and ocean coverage. Earth might be slightly redder due to increased thermal radiation, especially in the absorption bands of water in the atmosphere.

• Do you buy saying “of course” mean that the earth and the moon do reflect the different sun wavelengths proportionally? And that if the reflection of say visible light is up, infrared light has to be down with the same corresponding figure? Feb 22, 2021 at 22:41
• No two things have exactly the same colour, especially if they have different chemestry. So no, colours are different. But not much. Feb 22, 2021 at 23:08

Essentially the amount of radiation reflected per spectrum band (UV, X, visible etc.) depends on atmospheric and object surface chemical composition. In the case of the Moon you have no atmosphere, so this is already a great difference with respect to Earth. But since there's also a different surface composition between Earth and Moon you can't say a priori: "if the Earth reflects x amount of UV radiation from the Sun because of the atmosphere, then the Moon reflects all of it cause atmosphere is absent". Of course it's just an example.

Answer edit for rephrasing: no, that difference can't exactly be visible light. The albedo is estimated from the amount of reflected light, which includes the whole spectrum of radiation.

• Not exactly, albedo refers to the entire spectrum of radiation.
– Zebx
Feb 23, 2021 at 1:54