Mark your calendars. April 20 is a big day for strange happenings in the night sky. Due to a highly improbable interaction with Uranus, the moon will glow in a shade of green. It sounds spectacular, but it's completely false.
Snopes, a site dedicated to debunking strange and unusual rumors, last week traced the origin of the green-moon claim to a now-deleted Facebook post on March 25 that included an altered photo of the moon and the message "Save the date - May 29th, 2016. Green moon visible for first time since 1847."
The green-moon concept has spread through sharing on Twitter and Facebook. Since the original post, the date has morphed to April 20, likely in reference to the 4/20 date and its unofficial significance as a day to celebrate marijuana, which is often known by the slang term "420." Some tweets about the supposedly green moon also note that this is the first time in 420 years the phenomenon will occur. Just in case you didn't get the hint from the date alone.
An involved description of Uranus coming close to the moon accompanied the original Facebook post and gave it just enough science flair to make it believable to those who want it to be true. Uranus is an ice giant with a blue-green hue thanks to methane gas in the planet's atmosphere, but it won't make our moon look green.
So how hard is it to fake a green-moon photo? It took me about three seconds using Google's Picasa app to add some tint to a NASA moon image provided by the Apollo 11 spacecraft. Our only natural satellite looks good in green.
This isn't the first oddball space rumor to gain traction on the Internet. Last year, NASA felt compelled to step in and assure people that a doomsday asteroid would not be slamming into Earth in September 2015. As you can see by our continued existence, NASA was right. The green-moon idea doesn't have the same fear factor as an Earth-shattering asteroid, but it does fall into the same "don't believe everything you read online" category.