Some people, inclusive of a body of astronomers, believed the moonlight was just another kind of light possessed by that satellite of the Earth itself, admittedly a more soft and mellow light. Those few who could discern that it was reflected light attributed the source to the neighbouring planet Venus, the brightest object in the night sky. For hundreds of years scientists knew about this phenomenon where the Moon acts as a form of mirror that reflects light in a fairy-like aura of luminance. This reflected sunlight from the Earth increases and decreases depending on the change of seasons. Land mass, like the Asian continent in any season or the snow covered northern hemisphere in winter, is responsible for deep glowing reflection.
Oceans cause relatively faint reflected light.
This reflected light from the Earth, called by astronomers earthshine', and which can be seen from outer space and on photographs, can vary in brightness by as much as 20 per cent. What is of interest to scientists is that recent colour photographs show earthshine is turning from its usual brightness to a pale luminosity. What is not clear is the reason for this dimness. Some scientists wonder if it is the global warming which is responsible. Others speculate the cause may be the 11-year cycle of the Sun's magnetic activity.