Moon does not have its own light, it just reflects the sunlight. The moon that we are talking about, Earth’s moon is not a good reflector as compared to the other planets or moons as it reflects only around 13 per cent of the light that falls on it. We just see it brighter than other planets because of its closeness with the Earth.
The moon appears blue when the atmospheric particles are of the right size (size close to the wavelength of blue light) to selectively scatter the blue light. This happens mostly in the regions where there is the availability of particles having such size. For instance, aerosols produced from coniferous plants can react with ozone to give such sized particles. The place with an abundance of coniferous plants is likely to visualize the blue moon.
The colour that we see is just a result of the scattering of light (Rayleigh scattering), the same reason due to which the sky is blue. The scattering of reflected sunlight can result in different colours of the moon.
The moon appears mostly yellow at night and white during daytime as we see from Earth. The yellow colour is seen since yellow light is one of less scattered light as the light travels through the atmospheric particles. The red colour though scattered least is not seen because yellow is relatively scattered more in proportion with greater abundance. During the day the moon appears white due to excess sunlight (white light) coming directly from the Sun.
Blue moon, this phrase is often referred to as the moon which is not actually blue to see but a rare moon. Each year offers usually 12 full moons and each full moon occurs every 29 and half days. So in a year, there are approximately 11 more days. That means in three years an extra moon can occur. This moon is called ‘the blue moon’.
The smokes created by factories and fires can produce particles in the atmosphere with a size close to the wavelength of red light. This moon is called ‘the red moon'.
Credits: Sabitha
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