Chances are, you might have seen a viral Facebook post or image doing the rounds this month claiming that, on the night of Wednesday April 20 and again on May 29, the almost full moon will glow green for a whole 90 minutes.

We can't believe we actually have to tell people this, but no, that's not going to happen. That sounds pretty obvious, but with more than 38,000 shares on one Facebook post alone, and considering how many people have written to science pages asking whether it's real or not, it's clear that there are a lot of confused people out there. So what's actually going on?

Depending on which version of the post you read, the hoax explains that on either April 20 or May 29, several planets are going to align.

As part of this fictional event, the Moon will only be 4 degrees from the green-tinged Uranus in the night sky - and, somehow, that will cause our lunar satellite to glow green for around an hour and a half.

Screen Shot 2016-04-20 at 3.58.05 pmFreia L.S/Twitter

According to the real funny team behind the image, this event is so rare that the last time it happened was in 1596, so they're encouraging everyone to mark the event in their calendar and share it so their friends can marvel at the event too.

Spoiler: nope, none of that is going to happen.

But as you've probably figured out, this Wednesday is also 4/20 AKA national weed day. So what seems to have happened is that some fun-loving internet prankster created the original May 29 hoax - for reasons that escape us - which was then picked up by a group of green-loving people who tweaked the event to be more weed-appropriate.

You may have also noticed that the time-frame in between green moon is, you guessed it, 420 years. Ha ha, good one guys, you got us.

To be fair, the creators of the hoax probably didn't expect quite so many naive people to jump on the bandwagon and believe that the Moon really would turn green, but as we all know, people are willing to believe anything online.

We mean anything - in the past year alone we've had to debunk myths that an asteroid is about to wipe out Earth, or that Mars will look as big as the Moon in the night sky.

"What I personally find most distressing about the 'green moon' and other hoaxes are all of the emails I receive from seemingly knowledgeable and intelligent people," writes Joe Rao, a columnist over at "These missives all start out with some variant of the following: 'I know this probably isn't true, but can you verify this?'" 

"Use your critical-thinking skills: If something sounds too weird, crazy or amazing to be true, it probably isn't true," he adds.

We'll second that advice, and also remind you that there are plenty of scientifically proven things in our night sky that do actually appear green - such as twin comets and the aurorae. While these might not go viral on Facebook, they're even more spectacular because they're real. 

So do the world a favour and stop sharing all the crap out there, okay? Space is cool enough without it.