The phenomenon of the Moon appearing red on certain days without an eclipse is known as a "red Moon" or "blood Moon." There are a few different reasons why this can occur:
Atmospheric Effects: When the Moon is near the horizon, its light has to pass through a thicker portion of Earth's atmosphere. The Earth's atmosphere scatters shorter wavelengths of light, such as blue and green, more than longer wavelengths, such as red. As a result, the red part of the spectrum is less scattered and can reach the Moon, giving it a reddish appearance.
Rayleigh Scattering: The Earth's atmosphere contains tiny particles, such as dust and aerosols, which can scatter light. During certain atmospheric conditions, such as after volcanic eruptions or wildfires, there can be an increased amount of these particles in the atmosphere. This scattering can filter out shorter wavelengths of light and allow more red light to reach the Moon, causing it to appear red.
Lunar Illusion: Sometimes, the Moon can appear reddish due to an optical illusion caused by the surrounding sky. When the sky near the horizon is colored by atmospheric effects, such as during sunrise or sunset, the Moon can appear to take on similar colors due to the contrast with its surroundings.
It's important to note that the specific appearance of a red Moon can vary depending on local atmospheric conditions and the presence of particles in the air. Additionally, there may be cultural or historical interpretations associated with the phenomenon in different societies.