The understanding that the moon has no light of its own but reflects sunlight is not a recent discovery but rather a longstanding observation made by early astronomers. The ancient Greeks were among the first to propose that the moon shines by reflecting sunlight.
One of the earliest recorded instances of this understanding can be traced back to the Greek philosopher Anaxagoras in the 5th century BCE. He argued that the moon does not emit its own light but instead reflects the light of the sun. This idea gained further support from later philosophers and scientists, including Aristotle.
The evidence for this observation is readily apparent to anyone who has observed the moon. Its phases, from the full moon to crescent shapes, are a result of the relative positions of the sun, moon, and Earth. During a full moon, the moon is positioned opposite the sun in the sky, and its entire sunlit side is visible from Earth. During a crescent moon, only a portion of the moon is illuminated, depending on its position relative to the sun and Earth.
Furthermore, the shadows observed on the moon's surface during a lunar eclipse also indicate that the moon reflects sunlight. During a lunar eclipse, the Earth blocks direct sunlight from reaching the moon, resulting in a reddish glow caused by sunlight bending through Earth's atmosphere and reaching the lunar surface.
Over time, advancements in scientific understanding and technology have further confirmed the moon's reflective nature. For example, astronauts who visited the moon during the Apollo missions brought back rock samples that were found to be composed of materials similar to those found on Earth, reinforcing the notion that the moon reflects sunlight like any other non-luminous object.
In summary, the understanding that the moon has no light of its own but only reflects sunlight can be attributed to ancient observations made by philosophers and later supported by scientific evidence and space exploration.