Every few months, like clockwork, someone sends us a content on whatsApp/ email about a lovely picture/ video they’ve seen. We recently received a video from around 15 people on the same day (May 26, 2021) asking whether it is authentic or not. The video claims that it shows the Moon moving across the sky as seen from some place between Russia and Canada in Arctic with a giant Moon looming hugely over the horizon. Perhaps you’ve seen it via whatsapp or a social network; the video is really stunning, as you can see for yourself (https://youtu.be/pyNsIARgOBo)
But it has one teeny tiny problem: It’s an artistic impression (created using computer simulations)!
And if you see this without attribution to the artist, and don’t know the astronomy behind the scene, it’s hard to say whether it’s real or not.
So how can I tell it’s NOT REAL? Ah. Glad you asked.
SIZE DOES MATTER:
The size of the Moon in the video compared to the size of the Sun is a dead giveaway this isn’t a real photograph. In the real sky, the Moon and Sun appear to be the same size.
The angular size of an object — that is, how big it looks in the sky — depends on its physical size and its distance. Things look bigger the closer they are, and if two objects are at the same distance, the physically bigger one will look bigger. There’s some simple math that governs this: the angular size of an object is actually its diameter divided by its distance. So let’s do the math for the Sun and Moon:
Moon size / Moon distance = 3474 km / 384,000 km = 0.00905
Sun size / Sun distance = 1.4 million km / 150 million km = 0.0093
As you can see, the two ratios are almost exactly the same! The Sun is about 400 times bigger than the Moon, but it’s also 400 times farther away. Because of that, they appear to be the same size to our eye.
In fact, the Moon and Sun being the same apparent size is why we can have such beautiful solar eclipses. If the Moon were so much larger than the Sun as depicted in the drawing, we’d never see the Sun’s ghostly corona during an eclipse; the huge Moon would block it completely.
Therefore, the video is not actually a photograph/ recording of the real Moon.
