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 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).
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 wasn’t there a solar eclipse when this was shot? 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 the satellite’s 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 on W
- “That Moon and Earth GIF is totally real: debunking Twitter’s conspiracy theories” by Loren Grush on The Verge