Leonardo da Vinci explained the phenomenon in the early 1500s when he realized that both Earth and the Moon reflect sunlight. Light is reflected from the Earth to the Moon and back to the Earth as Earthshine.
Leonardo Da Vinci is generally known to many as an artist above all accomplishments, however he excelled in other areas including mathematics, engineering, and oddly, astronomy. Leonardo Da Vinci’s works remain undiminished, as does his mind which was restlessly inquiring for higher knowledge. His deep understanding of nature and the world and his quest for understanding, led him down an illuminated path. He fashioned flying machines, crossbows, and cannons, using his deep interest in science to figure out any technical matter. Using his wild imagination, he turned his sights to the moon. Leonardo Da Vinci pushed forward using his ideals of shadow and light to observe the moon, thus formulating the Codex Leicester explaining earthshine and his contrasting beliefs, leading to what earthshine really is defined as.
As with photography and art, light and shadow can define an object, area, or even a planet. Placing yourself in a specific location can cause an object to appear different, thus your perspective of an object that’s unchanging, becomes fluid. Leonardo Da Vinci’s perspective, although appropriately geared more towards an artistic sense, heavily relied on the Earth and the planets themselves. His works, more importantly his paintings, always reflected the correct light and shading of the background to produce the perfect outcome. Shading and light were the sources that drove Da Vinci to look to the Moon, thus prompting him to study the Moon in its crescent stage.
In the beginning, it was about observing the light in the sky when the Sun sets on the Moon. It gets dark--but not entirely dark. There's still a source of light in the sky: Earth. Our own planet lights up the lunar night 50 times brighter than a full Moon, producing the ashen glow or what some people may call "the old Moon in the new Moon's arms". Of course, Leonardo Da Vinci didn’t realize the technical aspects of his observations, although he did proceed to sketch exactly what he saw in the sky.
Already during the 16th century, Leonardo da Vinci had correctly gathered enough information and drawings to explain the nature of earthshine. In Da Vinci’s Codex Leicester, published in the early 16th century, he states his belief that the Moon possessed an atmosphere and oceans, and that it was a fine reflector of light because it was covered with so much water. He also speculated about how storms on Earth could cause the earthshine to become brighter or dimmer, which is indeed observable with modern instrumentation.
Once again, using his observations of the secondary light phenomenon, he formed these provocative words within his Codex Leicester.
Some have believed that the moon has some light of its own, but this opinion is false, for they have based it upon that glimmer visible in the middle between the horns of the new moon...this brightness at such a time being derived from our ocean and the other inland seas -- for they are at that time illuminated by the sun, which is then on the point of setting, in such a way that the sea then performs the same office for the dark side of the moon as the moon when at the full does for us when the sun is set.
Although Da Vinci’s assessment about the Moon is both revolutionary and in some aspects accurate, there are certain statements that have been proven to be erroneous. First of all, the moon has no oceans. This statement was clear when astronauts traveled to the Moon in 1969 on the Apollo 11 mission. They didn’t step out on a fluid foundation, although the term “Sea of Tranquility” alludes to that aspect. They stepped out onto solid rock.
Observers in space, such as the Apollo 11 astronauts, were never able to experience earthshine because they never stayed overnight to view the nightfall. They may have been able to see nearby objects illuminated by earthshine, as things on earth may be illuminated by moonlight. However, in direct sunlight, it was nearly impossible to experience the direct effects of earthshine, which would have been a ghostly glow of the moon at their feet.
If neither the Earth nor the Moon is the source of earthshine, than something in the atmosphere has to be the source of light. In fact, earthshine is actually the Moon’s night side reflected from the surface of the Earth, and to be more specific, the clouds are creating the reflection. When we observe a crescent moon, we can clearly see a type of grayish luminosity. No one could really explain what this glow was until Leonardo Da Vinci looked up at the moon and placed himself on the surface.
If an average person desires to investigate earthshine, it’s not completely impossible, although you have to know what you’re looking for. For instance, when the Moon is a thin crescent, it is visible as a pale-gray ghostly glow over the remainder of the disk. If you look between the horns of the crescent, you will see the entire shadow of the moon. This is called earthshine.
Earthshine can be difficult to see less than a day after new Moon because the Moon is lower in the sky. It is, however, most noticeable between one and four days before or after the new Moon. Astronomers and scientists believe it’s best seen at about two days, as the Moons moves away from the Sun in the darker night sky, and before the area of brightly lit Moon overpowers the Earthshine, and the lit face of the Earth toward the Moon diminishes.
The intensity of earthshine varies as the level of cloud cover changes over the Earth, and is an indicator of climate change. In fact, climatologists have studied earthshine, or rather the Earth’s albedo in conjunction with the concept of earthshine. According to Geophysical Research Letters, to derive the long term anomalies in the earthshine effective albedo, ES measurements had to take place. These measurements allow the astronomers, scientists, and researchers to examine ground based astronomical observations of the bright and dark side of the Moon, thus allowing them to take large-scale instantaneous measurements of the Earth’s effective albedo, typically over a third of the Earth’s surface at a given time.
In the case of earthshine, Leonardo believed that the surface of an object reflects the color of the light which illuminates it. Therefore, the atmosphere which lies between the eye and the object is the transparent medium. What does this all mean? It means that it is quite possible that Da Vinci might have known how the clouds and atmosphere reflected light, however he didn’t consider this a source of earthshine.
Leonardo Da Vinci recognized the fact both Earth and the Moon reflect sunlight. What he didn’t realize was that when the Sun sets anywhere on the Earth-facining side of the Moon (this happens every 29.5 Earth-days) the landscape remains lit -- illuminated by sunlight reflected from our own planet-NASA.
This perspective of the planets allows astronauts today to look upon the Moon as Leonardo Da Vinci once did over five centuries ago, with an open mind. His immense reputation and the articulation of his hands and mind left others with a lifetime of understanding.
Earthsine Sketch By Da Vinci Source
Lauren Axelrod is a full time student working towards a Ph.D. in Medieval European Archaeology and History, with an emphasis on the Templars, Free Masons, Crusades, and the time period spanning 500-1565.