The green flash phenomenon at the ocean horizon

You’re out the back, watching the sun dip into the drink. Just as the last sliver of gold vanishes, there’s this legendary emerald spark that flickers for a heartbeat. It’s not a trick; the atmosphere is acting like a giant glass lens.

Think of the air like a heavy swell that bends light. As the sun hits the horizon, the atmosphere acts like a prism, curving the red colors away and leaving a sharp, green glow. It’s a rare bit of timing, like catching the perfect barrel before dark.

Wait, if the air's a prism, why don't we get a blue flash?

Spot on, mate. Technically, blue light bends even more than green, so it should be the very last thing we see. But the atmosphere is a messy break.

See, blue light is like a tiny, fragile ripple. As it travels through all that thick air at the horizon, it gets scattered and bounced around—basically wiped out—long before it hits your eyes. It’s the same reason the sky looks blue during the day.

Green is the sweet spot. It’s got just enough muscle to make it through the 'whitewater' of the atmosphere while still bending enough to stay visible after the long red waves have already dipped below the line.

Hold up, if blue is scattered, why does the sun turn fiery red?

Think of it like waves hitting a messy break. Blue light is like small, choppy ripples—they get broken up by the thick air near the horizon until they're spent.

What’s left are the heavy rollers: red and orange waves. These long-distance travelers have the 'weight' to push through that atmospheric soup without getting knocked off course.

By the time the sun hits the horizon, you’re only seeing the survivors. The air filters out the lightweights, leaving only that deep, glowing red.

But why isn't the sun blood-red when it's high in the sky?

It’s all about the length of the paddle, mate. At noon, the light takes the shortest route straight down. There’s hardly any 'whitewater' to push through, so it’s a quick, easy trip for every color.

Since the path is short, those blue ripples don't get scattered away. When all the colors arrive together at full strength, they mix into that blinding white-gold light we see during the heat of the day.

The red-out only kicks in when the sun is low. The light has to trek sideways through hundreds of miles of thick air, which finally tires out the lightweights.

If the sun's a white-gold mix, why is the sky still blue then?

It’s a bit of a trick, mate. While most of the blue makes it through in that main beam, a tiny fraction still gets caught in the 'chop' of the air.

Think of the atmosphere kicking up a bit of 'spray' off the top of the light wave. Those blue ripples are so small they’re easily knocked off course by air molecules, bouncing around until they fill the sky.

So while the sun stays white, the rest of the sky glows blue from those scattered leftovers.