Though it sounds like some type of superhero—specifically the unlicensed off-brand kind that hangs in Times Square—the “green flash” is actually a real thing that you can see in the sky with your own eyes. And while we know the green flash exists (there is plenty of photographic evidence), it has reached more of a mythical status because it’s not something seen on a regular basis.
Unlike certain meteor showers or moons, you can’t mark your calendar to see the green flash: it just has to happen. But, there are ways to improve your chances of catching a glimpse at the elusive natural light show. Here’s what to know.
What is the green flash, exactly?
The first thing to know is that while there are several natural phenomena lumped together and referred to as “the green flash,” most fall into one of two forms, both of which were identified by English physicist James Prescott Joule in 1869. The first form is what Joule referred to as the “last glimpse” and is a bluish-green flash that appears at the last moment before the sun dips below the horizon.
The second form is associated with a mock mirage and is mainly seen from elevated positions, according to Andrew T. Young, an astronomer, green flash expert and professor at San Diego State University. (If you want to learn more about the green flash, Young maintains a website full of information and links to photos.)
How to catch the green flash
You don’t need any kind of fancy equipment to see the green flash, but do you need to be in the right place at the right time. Like most of the exciting things taking place in the sky, your best chance of seeing the green flash is when conditions are clear. It also helps to have a view of a very distant horizon, like an ocean or a sea, according to an article on EarthSky.
Most of the green flashes people report seeing are of the “last glimpse” variety, occurring at sunset, the very last second before the sun sinks below the horizon. And yes, the green flash usually only lasts for one second—maybe two (it’s not called the “green lingering light”). It’s also possible to see the green flash immediately before sunrise, but the timing is harder.
The key to catching the green flash at sunset is not looking too soon. This is important because a) looking directly at the sun any earlier (or anytime, really) can damage your eyes; and b) that will cause you to miss the green flash. Instead, look away until the thinnest rim of the sun is visible above the horizon.