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.
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.