No, the super blood moon isn't a harbinger of the apocalypse!

This article was written by Alan Duffy from Swinburne University of Technology, and was originally published by The Conversation.

For many people, the sight of the Moon turning deep red - some would say blood red - during a lunar eclipse is a wonderful sight. And that’s precisely what many millions of sky gazers will be able to see this Sunday or Monday, depending on their location on Earth.

But for a dedicated few, this is a sign of something much more terrifying: nothing less than the apocalypse itself.

Lunar eclipses are an impressive and visible reminder that the night sky isn’t a static backdrop but a dynamic show filled with worlds that move and interact. In this case, the Moon’s orbit will take it directly behind the Earth, opposite the sun and into our shadow, which will carve out evermore of the Moon’s face until it’s entirely dark.

Or, at least, it would be if Earth’s atmosphere wasn’t bending (refracting) light into that shadow region, known as the umbra. After passing through so much air, the bluer colours are scattered out and all that remains is red. We see this effect in the reddening of the sunlight every sunrise and sunset.

In other words, this blood moon is nothing less than all the sunrises and sunsets of Earth, reflected back at us from the surface of the Moon. Sadly, this romanticism will be lost on a dedicated few who will instead greet it with fear as a portent of terrible events.

Enter the tetrad: a rare event?

This latest event marks the fourth lunar eclipse in a row with no partial eclipses to spoil the run. Such a run of eclipses is known as a tetrad. While not uncommon – there have been eight such tetrad eclipses in the 21st century – they are unusual, with none between 1400 to 1900.

What makes this final of the four a little different is that it’s during a super moon. This is when the full moon occurs when the Moon is closest to Earth in its orbit, thereby appearing about 14% bigger and 30% brighter than when furthest from us.

The last time there was a blood super moon (or less poetically: a perigee lunar eclipse) was in 1982, with the next not until 2033.

This was originally published by Science Alert.