APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

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APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by APOD Robot » Wed Dec 02, 2015 5:06 am

[img]http://apod.nasa.gov/apod/calendar/S_151202.jpg[/img] Golden Gate Sunset: Green Flash

Explanation: The setting is San Francisco Bay, the time is sunset, and the bridge is the Golden Gate. What you are about to see is an unexpected double sunset ending with a rare green flash. Watch closely -- in the recorded time-lapse sequence, unusually warm air created by bridge traffic refracts sunlight toward the Earth, causing a superior image of the top of the Sun to form. This image will disappear -- marking the first "sunset" -- only after the main image has dipped below the deck. All the while, boats pass in the foreground, cars pass over the bridge, and clouds reflecting sunlight drift by in the distance. The scene ends with Earth's turbulent atmosphere itself creating a path that only higher-energy visible sunlight can traverse, making the last glimpse of our home star appear to flash green.

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by Boomer12k » Wed Dec 02, 2015 5:14 am

As they say in Science Class...."Sure enough...." :lol2:

Great video. Congrats on getting this phenomena.

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by neufer » Wed Dec 02, 2015 12:22 pm

I'm confused. :-?

Is this a true green flash

or a bridge induced pseudo-green flash :?:
Art Neuendorffer

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by WindChaser114 » Wed Dec 02, 2015 2:36 pm

While the Golden Gate Bridge at sunset presents itself as a superior image, I believe what you meant to say that a Superior Mirage is created by the bridge traffic/rising air.

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by Chris Peterson » Wed Dec 02, 2015 3:07 pm

neufer wrote:I'm confused. :-?

Is this a true green flash

or a bridge induced pseudo-green flash :?:
First, you'll need to create a working definition for "true green flash" and "pseudo-green flash". An exercise that will probably answer your own question.
Chris

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by neufer » Wed Dec 02, 2015 4:02 pm

Chris Peterson wrote:
neufer wrote:
I'm confused.

Is this a true green flash

or a bridge induced pseudo-green flash :?:
First, you'll need to create a working definition for "true green flash" and "pseudo-green flash". An exercise that will probably answer your own question.
I'm confused. :-?

Was that an answer or a pseudo-answer :?:
Art Neuendorffer

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by Chris Peterson » Wed Dec 02, 2015 4:05 pm

neufer wrote:
Chris Peterson wrote:
neufer wrote:
I'm confused.

Is this a true green flash

or a bridge induced pseudo-green flash :?:
First, you'll need to create a working definition for "true green flash" and "pseudo-green flash". An exercise that will probably answer your own question.
I'm confused. :-?

Was that an answer or a pseudo-answer :?:
It was a meta-pseudo-answer. (Are you more confused than usual today?)
Chris

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by neufer » Wed Dec 02, 2015 4:19 pm

Chris Peterson wrote:
It was a meta-pseudo-answer.
I never meta-pseudo-answer I didn't like.
Chris Peterson wrote:
(Are you more confused than usual today?)
I'm, at least, being less profuse than usual.
Art Neuendorffer

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by Rusty Brown in Cda » Wed Dec 02, 2015 5:14 pm

Congrats on getting this phenomenon.

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by starsurfer » Wed Dec 02, 2015 6:42 pm

neufer wrote:
Chris Peterson wrote:
It was a meta-pseudo-answer.
I never meta-pseudo-answer I didn't like.
Chris Peterson wrote:
(Are you more confused than usual today?)
I'm, at least, being less profuse than usual.
You guys are hilarious! :lol2:
This gives me an idea for a Starship Asterisk stage show musical! :idea:

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by Ron-Astro Pharmacist » Wed Dec 02, 2015 7:59 pm

"Pseudo" (not genuine, sham) could be a whole variety of possibilities but I might bet Art is diffracting the definition to bend our minds and Chris is bending it back the other way to straighten him out. :wink:
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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by Astronymus » Wed Dec 02, 2015 9:26 pm

So someone escaped his locker. Arrrrr.
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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by saturno2 » Wed Dec 02, 2015 9:29 pm

I think the sun´s rays are distorted in the atmosphere
and then redistorting by reflection on the surface
of the water.
The green flash would be the distortion of the distortion
from sunlight.

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by NateWhilk » Wed Dec 02, 2015 10:46 pm

Great video! Congrats to Mr. Rivest.

Green flashes at the South Pole can last for minutes. A video of that would be great.

This video mentions them but doesn't show any.

This video claims to show them, but I don't see any that really qualify.

Roger

Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by Roger » Thu Dec 03, 2015 1:44 am

This is an excellent video of the green flash. From the standpoint of documenting the green flash, the bridge's effect is superfluous and the mention of it appears to have misled some of the readers who have posted here.

The green flash is caused by the refraction by Earth's atmosphere of the light from the Sun. Blue light refracts more than green, so that, to reach the observer's eye, the blue light has to follow a higher curved path through the atmosphere. Thus, when the Sun is very low, the top edge of the sun may look bluer than the rest of the Sun, while the bottom edge of the Sun may look redder than the rest of the Sun. As the Sun sets, and only the top limb of the Sun is visible, the glare of the bright disk is mostly obscured by the horizon so that the fainter, refracted blue light at the top edge is detectable. The blue light makes the last sliver of the Sun's disc to appear green -- that is, yellow plus extra blue makes green.

I have seen many images of the full disc of the Sun at very low altitude that show a greenish color of the upper part of the Sun or of some clouds just above the Sun, and the greenish clouds are called a green flash. They are not a green flash. The green flash is what's seen in this video at the last sliver of the upper edge of the Sun, as it disappears behind the horizon.

liebencrantz

Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by liebencrantz » Thu Dec 03, 2015 2:35 am

very cool shot. i was thinking that the bridge traffic probably had a smaller contribution to the thermocline compared to the sun-warmed steel and concrete span itself suspended over very cold water. then again, underestimating car exhaust can be risky.

Tre Gibbs

Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by Tre Gibbs » Thu Dec 03, 2015 3:08 am

Technically, the bridge is The Golden Gate BRIDGE. The Golden Gate is the waterway between the two landforms (the south landform being San Francisco County and the north being Marin County) which The Golden Gate Bridge crosses. To say the "bridge is The Golden Gate" is incorrect.

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by neufer » Thu Dec 03, 2015 2:08 pm

Roger wrote:
This is an excellent video of the green flash. From the standpoint of documenting the green flash, the bridge's effect is superfluous and the mention of it appears to have misled some of the readers who have posted here.

The green flash is caused by the refraction by Earth's atmosphere of the light from the Sun. Blue light refracts more than green, so that, to reach the observer's eye, the blue light has to follow a higher curved path through the atmosphere. Thus, when the Sun is very low, the top edge of the sun may look bluer than the rest of the Sun, while the bottom edge of the Sun may look redder than the rest of the Sun. As the Sun sets, and only the top limb of the Sun is visible, the glare of the bright disk is mostly obscured by the horizon so that the fainter, refracted blue light at the top edge is detectable. The blue light makes the last sliver of the Sun's disc to appear green -- that is, yellow plus extra blue makes green.

My understanding is that the yellow/orange gap between the [weakly bent] red sun set and a [strongly bent] green flash and is caused naturally by the Chappuis ozone absorption band and NOT by some artificially induced thermal heating line such as from the Golden Gate Bridge.

I see very little color dispersion at all is this particular monochromatic APOD sun set :!:

It is all artificially induced monochromatic distortion, IMO.
Art Neuendorffer

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by geckzilla » Thu Dec 03, 2015 7:11 pm

What exactly do you mean by artificially induced monochromatic distortion, Art? Your opinion would seem to not matter here, since the camera has recorded notably greener fringes around the top tip of the sun as it sets. A few simple measurements show that the image is both not monochromatic and that the green color is indeed there whether your eyes are able to perceive these facts or not.
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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by neufer » Thu Dec 03, 2015 7:45 pm

geckzilla wrote:
What exactly do you mean by artificially induced monochromatic distortion, Art?
The primary distortion is caused by the warm air right around (and just above) the Golden Gate Bridge.

There is very little spectral color dispersion taking place (as necessary for a Green Flash).
geckzilla wrote:
Your opinion would seem to not matter here,
So what else is new?
geckzilla wrote:
... since the camera has recorded notably greener fringes around the top tip of the sun as it sets. A few simple measurements show that the image is both not monochromatic and that the green color is indeed there whether your eyes are able to perceive these facts or not.
I wouldn't say that the top tip of the sun has "notably greener fringes" as it sets
...at least not enough to qualify as a Green Flash.
Art Neuendorffer

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by geckzilla » Thu Dec 03, 2015 8:45 pm

neufer wrote:
geckzilla wrote: ... since the camera has recorded notably greener fringes around the top tip of the sun as it sets. A few simple measurements show that the image is both not monochromatic and that the green color is indeed there whether your eyes are able to perceive these facts or not.
I wouldn't say that the top tip of the sun has "notably greener fringes" as it sets
...at least not enough to qualify as a Green Flash.
I drew an arrow pointing to the green part. The green of the arrow was sampled from the green flash.
greenflash.jpg
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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by neufer » Thu Dec 03, 2015 9:18 pm

https://en.wikipedia.org/wiki/Flash_pan#.E2.80.9CFlash_in_the_pan.E2.80.9D wrote:
<<The flash pan or priming pan is a small receptacle for priming powder, found next to the touch hole on muzzleloading guns. The ignition of the main charge from the flash pan was not a guaranteed operation, however, and sometimes it failed. In those cases the spark would flash in the pan, but the gun would fail to fire. This led by the end of the 17th century to the expression “flash in the pan” to mean a failure after a brief and showy start, or momentary sensation of no real importance.>>
http://www.scientificamerican.com/article/fact-or-fiction-if-sky-is-green-run-for-cover-tornado-is-coming/ wrote:
<<Researchers remain undecided about the exact mechanisms that cause the sky to appear green in certain thunderstorms, but most point to the liquid water content in the air. The moisture particles are so small that they can bend the light and alter its appearance to the observer. These water droplets absorb red light, making the scattered light appear blue. If this blue scattered light is set against an environment heavy in red light—during sunset for instance—and a dark gray thunderstorm cloud, the net effect can make the sky appear faintly green.>>
Art Neuendorffer

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Re: APOD: Golden Gate Sunset: Green Flash (2015 Dec 02)

Post by RJN » Fri Dec 04, 2015 3:23 pm