Starship Asterisk*

A Green Flash of Spring

Explanation: Taken on March 20 from the top of Haleakala on the isle of Maui, planet Earth, the first sunrise of northern spring is pictured in this vacation snapshot. The telephoto view from the volcanic caldera above a sea of clouds also captures an elusive green flash near the Sun's upper limb. Atmospheric layers with sharp temperature changes cause the colorful flash as the Sun rises behind a distant cloud bank. Refraction along sight lines through the layers creates multiple distorted images of the Sun, and for a moment, can visibly deflect shorter wavelength green light.

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The reason a green flash is rare is not that green light is short wavelength. It's kind of mid-range in the visible spectrum in fact. It's that the range of wavelengths the eye/brain perceives as green is pretty narrow compared to the reds/oranges/yellows on the long wavelength side and the blues/violets on the short side. So whatever atmospheric phenomenon produces the flash has to scroll through that very narrow range very slowly in order for us to pick it up as green, just as we never see a green sky, only a blue or red.

GeeBee wrote:The reason a green flash is rare is not that green light is short wavelength. It's kind of mid-range in the visible spectrum in fact. It's that the range of wavelengths the eye/brain perceives as green is pretty narrow compared to the reds/oranges/yellows on the long wavelength side and the blues/violets on the short side. So whatever atmospheric phenomenon produces the flash has to scroll through that very narrow range very slowly in order for us to pick it up as green, just as we never see a green sky, only a blue or red.

The green flash is not particularly rare. The caption used "elusive", which is a good word given that the flash is brief. But if you're on the lookout, you can see it quite frequently.

The wavelengths aren't "scrolled through". The green flash is caused by dispersion, which causes the atmosphere to act like a prism. We barely notice the wavelengths longer than green, because they blend with the orange Sun. We don't see the shorter wavelengths because they are scattered by the atmosphere (the same reason the sky is blue). But there is a blue flash phenomenon. It has the same cause, but the atmospheric conditions that create it are unusual. So it's not just elusive, but truly rare.

What do you get if you cross Green Lantern with The Flash? GREEN FLASH!!!!!

Well, OK, my bad...

Yet another example of this phenomena of light and atmosphere....

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The "Murray Schukar" link in the credit is dead on the two browsers that I've just tried. I wonder if that is the case for others or is it just a problem with my internet connection?

DavidLeodis wrote:The "Murray Schukar" link in the credit is dead on the two browsers that I've just tried. I wonder if that is the case for others or is it just a problem with my internet connection?

The error says "The requested URL /apod/mjk.3 [at] me [dot] com was not found on this server." from which you can see that the link is wrong. If you manually enter /apod/mjk.3@me.com, you'd still get an error because it's a mixture of a URL at the apod server and an email address. I suppose the link should just be mjk.3@me.com, without the /apod/ bit. That would open your mail program with a new message addressed to mjk.3@me.com.

Rob

rstevenson wrote:

DavidLeodis wrote:The "Murray Schukar" link in the credit is dead on the two browsers that I've just tried. I wonder if that is the case for others or is it just a problem with my internet connection?

The error says "The requested URL /apod/mjk.3 [at] me [dot] com was not found on this server." from which you can see that the link is wrong. If you manually enter /apod/mjk.3@me.com, you'd still get an error because it's a mixture of a URL at the apod server and an email address. I suppose the link should just be mjk.3@me.com, without the /apod/ bit. That would open your mail program with a new message addressed to mjk.3@me.com.

Rob

Thanks for your help Rob .

From it I've now found the mjk.3@me.com link brings up a blank email form that is preaddressed to that email address.

Murray Schukar can be found on facebook.

A rare blue flash has been photographed by James Westlake. It has been posted by Sandgirl in the Recent Submissions thread. You have to scroll down a bit to see it; James Westlake's image is the twelfth picture posted in this thread.

Ann