# Why clouds are not moving in NASA's video of the Moon passing in front of the Earth?

I recently saw a short video from NASA. It shows the moon passing by the Earth as it rotates.

The video itself looks quite fake, but that can probably be attributed to the fact that it was reconstructed from sensor data as opposed to a regular camera.

My question is, why do the clouds not appear to move at all? According to the website, the images span approximately 5 hours.

There are a lot of people online saying the video is fake. I believe the Earth is a globe, but I can see why people have their doubts about this particular video.

• I see some of the clouds change a little. – farrenthorpe Jan 24 '17 at 18:39
• See this article for a good writeup of this NASA-created animation and a brief overview of the satellite that captured the images. There is also a NASA page dedicated to this satellite and its mission. – brichins Jan 24 '17 at 21:41
• The problem is that many people are not able to visualise different perspectives. The only experience they have is watching clouds move overhead here on Earth. They are not able to visualise how that would look from a million miles away. They further cannot visualise the difference between the micro level they observe, across a few tens of mils, versus the macro level seen here. They also cannot visualise relative motion. Tell them to try seeing the clouds move when flying at 36,000 feet. Does the fact that they cannot mean that they don't or perhaps that the flight is fake? – Simon Jan 25 '17 at 8:32
• The clouds "don't move" for the same reason waves and boats "don't move" on the ocean when looking at them from a jet liner. Hint: What's the distances in the image? What's average cloud speed? – Peter - Reinstate Monica Jan 25 '17 at 9:21
• A ‘regular camera’ also reconstructs its pictures from sensor data (and generally performs quite a lot of post-processing in-camera) :). The most salient difference is that NASA’s Earth Polychromatic Imaging Camera exposes the R, G, and B channels sequentially rather than simultaneously, producing the green edge on the moon. But regular cameras can also produce artefacts due to non-instantaneous exposure. – Pont Jan 26 '17 at 22:56

They are moving, but not fast enough to notice at the distance shown. From the NASA page:

These images were taken between 3:50 p.m. and 8:45 p.m. EDT on July 16, showing the moon moving over the Pacific Ocean near North America. The North Pole is in the upper left corner of the image, reflecting the orbital tilt of Earth from the vantage point of the spacecraft.

In five hours, clouds may move some hundreds of kilometers at most. The half-disk of the Earth is nearly 13,000 km across, so over the period the pictures were taken, the clouds should only be expected to move a small fraction of the width of the disk.[1] Add to that the fact that the Earth is rotating and it is not readily apparent that they move at all.

1: Say the clouds in a huge hurricane move in a straight line at 100km/hr; over this 5-hour animation, that's 500 km movement which is just under 4% of the Earth's 12,742 km diameter. The Earth is about 550px in this image and 550 × .04 = 22 pixels maximum change.

• In addition to this, if you look at vortex formations movement is slightly more apparent as those changing shape rather than moving with respect to a mostly blue ball. It might be confirmation bias but it looks like there's a slight change to me. – Kaithar Jan 24 '17 at 16:00

The clouds can be seen moving but of course it's subtle at first glance.

Frame 16:


Frame 20:


• Nice spotting! I was searching for tiny movements myself but with the low frame rate I wasn't sure if my eyes were playing tricks on me. I appreciate you taking the time to hunt down a relatively noticeable change! – Chris Parton Jan 24 '17 at 20:25
• It can be hard to tell which changes are actual movement, and which are due to the perspective changes from rotation. – Barmar Jan 24 '17 at 21:06
• @Barmar I agree but I took frames that are very close together to reduce that effect (20 is the last frame). I also chose this area because one area can be observed thinning which is not likely to be perspective. – Adam Caviness Jan 25 '17 at 13:26
• The "foot" of the sphinx-shaped cloud that ends right near the reflection of the sun changes quite a lot. As does the cloud just south-west of the hole-in-the-clouds that the moon passes under. – naught101 Jan 27 '17 at 1:58

The image is real, and the clouds are moving, they just move slow, as clouds do. The unnatural appearance arise because they are taken by DSCOVR at an extraordinarily large distance, from a place called L1, more than one million kilometers away!!!. The rotation of the Earth in the animation makes it difficult to distinguish the movement of the clouds, but if you just track one single area as shown in the animation below, the movements of the clouds becomes evident:

The zoom area shown in the right was extracted from the circled area in the left. For the above animation I downloaded the original frames at high resolution from here. The resolution was reduced so that it is smaller than the limit of SE (2MB), but you can see it at full resolution here.

Here you can see a closeup on the cropped section:

The changes and movements of the clouds are quite obvious now. Aren't they?

The overall deformation is mostly due to perspective changes as Earth's rotates, but it is clear how some clouds change, and some dissolve completely during the video, like the elongated one in the upper left corner of the cloudless patch shown in the crop. If you put attention the vanishing of that cloud can be seen in the original video.

Another effect that might make the image looks weird, is the fact that the images used for the red, green and blue channels of the image are taken 30 seconds apart, and due to the displacement of the Earth and specially the Moon during that period, it creates an edge effect that is very clear in the full resolution image and might contribute to the fact that the moon seem to be pasted in the image, and the overall weirdness of the image. Here a close-up to the Moon showing very clearly the edge effect: