An “EPIC” animation of the Moon transiting the Earth created with actual satellite images of the far side of the moon, illuminated by the Sun. The images are taken by NASA’s Earth Polychromatic Imaging Camera (EPIC), a four-megapixel CCD camera and telescope attached to the Deep Space Climate Observatory (DSCOVR). While the moon was crossing between the DSCOVR and the Earth, EPIC took these beautiful photos almost one million miles (1.6 million kilometers) from Earth.

The distance between the Moon and Earth varies from around 356,400 km to 406,700 km at the extreme perigees (closest) and apogees (farthest).

Video: Moon Transiting the Earth

EPIC View of Moon Transiting the Earth
This animation features actual satellite images of the far side of the moon, illuminated by the sun, as it crosses between the DSCOVR spacecraft’s Earth Polychromatic Imaging Camera (EPIC) and telescope, and the Earth – one million miles (1.6 million kilometers) away.

The Moon is in synchronous rotation: it rotates about its axis in about the same time it takes to orbit Earth. This results in it nearly always keeping the same face turned towards Earth. The Moon used to rotate at a faster rate, but early in its history, its rotation slowed and became tidally locked in this orientation as a result of frictional effects associated with tidal deformations caused by Earth.

The side of the Moon that faces Earth is called the near side, and the opposite side of the far side. The far side is often inaccurately called the “dark side”, but in fact, it is illuminated as often as the near side: once per lunar day, during the new moon phase we observe on Earth when the near side is dark (I am sorry, Pink Floyd, there is no “dark side of the moon”).

Why there wasn’t a solar eclipse?

Why wasn’t there a solar eclipse when this was shot, while Moon transiting the Earth? Because, when these pictures were taken, the Sun was not directly behind the satellite. In fact, NASA purposefully keeps DSCOVR at least 4 degrees away from the Sun-Earth line – the direct path between our planet and the star. It allows researchers to more easily receive satellite data.

DSCOVR conducts its primary mission of real-time solar wind monitoring for the National Oceanic and Atmospheric Administration (NOAA). It was originally developed as a NASA satellite proposed in 1998 by then-Vice President Al Gore for the purpose of Earth observation. It is at the Sun-Earth L1 Lagrangian point, 1,500,000 km (930,000 mi) from Earth, to monitor variable solar wind condition, provide early warning of approaching coronal mass ejections and observe phenomena on Earth including changes in ozone, aerosols, dust, and volcanic ash, cloud height, vegetation cover, and climate.

Moon transiting the Earth - EPIC
When these pictures were taken, the Sun was not directly behind the Moon. So there wasn’t a solar eclipse while Moon transiting the Earth.

Why the Moon looks so dark in this EPIC video?

A lot of people think the video above (EPIC view of Moon Transiting the Earth) is fake because the Moon looks so dark. Why does the Moon look like that?

Because the moon is dark. Despite the fact that it sometimes seems to shine very brightly, the moon reflects only between 3 and 12 percent of the sunlight that hits it. Compared to Earth, which has an average albedo of 30-35% (it widely varies locally across the surface because of different geological and environmental features), our satellite is way less reflective.

The object with the highest albedo in the Solar System is Saturn’s moon Enceladus, which has an albedo of 0.99 (99 percent), which means that it reflects almost all the light it receives from the Sun. Because Enceladus is covered with very reflective snow and ice. The Moon is much more similar to a very dark object, like an asteroid.

NASA published a series of images from DSCOVR showing the Moon passing in front of the Earth. What’s been amazing is the number of people who think that it looks wrong, because they think the moon is lighter than it actually is.


M. Özgür Nevres
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