by APOD Robot » Wed Feb 28, 2024 5:06 am
Shades of Night
Explanation: How does the sky turn dark at night? In stages, and with different characteristic colors rising from the horizon. The
featured image shows, left to right, increasingly late
twilight times after sunset in 20 different vertical bands. The picture was taken last month in
Syracuse,
Sicily,
Italy, in the direction
opposite the Sun. On the far left is the pre-sunset upper sky. Toward the right, prominent bands include the
Belt of Venus, the
Blue Band, the
Horizon Band, and the Red Band. As the dark shadow of the Earth rises, the colors in these bands are
caused by direct sunlight reflecting from air and
aerosols in the
Earth's atmosphere, multiple reflections sometimes involving a
reddened sunset, and
refraction. In practice, these bands can be diffuse and hard to discern, and their colors can depend on
colors near the setting Sun. Finally, the Sun
completely sets and the sky becomes dark.
Don't despair -- the whole thing will happen in reverse when the
Sun rises again in the morning.
[url=https://apod.nasa.gov/apod/ap240228.html] [img]https://apod.nasa.gov/apod/calendar/S_240228.jpg[/img] [size=150]Shades of Night[/size][/url]
[b] Explanation: [/b] How does the sky turn dark at night? In stages, and with different characteristic colors rising from the horizon. The [url=https://www.facebook.com/photo/?fbid=10231968620107561]featured image[/url] shows, left to right, increasingly late [url=https://apod.nasa.gov/apod/ap230506.html]twilight[/url] times after sunset in 20 different vertical bands. The picture was taken last month in [url=https://youtu.be/zopIdrtkbVE]Syracuse[/url], [url=https://youtu.be/NnKs9NDzvVs]Sicily[/url], [url=https://en.wikipedia.org/wiki/Italy]Italy[/url], in the direction [url=https://apod.nasa.gov/apod/ap190624.html]opposite the Sun[/url]. On the far left is the pre-sunset upper sky. Toward the right, prominent bands include the [url=https://apod.nasa.gov/apod/ap230626.html]Belt of Venus[/url], the [url=https://twanight.org/gallery/the-elusive-bands-of-anti-twilight/]Blue Band[/url], the [url=https://epod.usra.edu/blog/2023/01/anti-tiwilight-colors-and-belt-of-venus.html]Horizon Band[/url], and the Red Band. As the dark shadow of the Earth rises, the colors in these bands are [url=https://www.eso.org/sci/publications/messenger/archive/no.178-dec19/messenger-no178-51-56.pdf]caused[/url] [url=https://opg.optica.org/ao/fulltext.cfm?uri=ao-56-19-G156&id=367436]by[/url] direct sunlight reflecting from air and [url=https://en.wikipedia.org/wiki/Aerosol]aerosol[/url]s in the [url=https://climate.nasa.gov/news/2919/earths-atmosphere-a-multi-layered-cake/]Earth's atmosphere[/url], multiple reflections sometimes involving a [url=https://apod.nasa.gov/apod/ap170120.html]reddened sunset[/url], and [url=https://en.wikipedia.org/wiki/Refraction]refraction[/url]. In practice, these bands can be diffuse and hard to discern, and their colors can depend on [url=https://apod.nasa.gov/apod/ap061221.html]colors near the setting Sun[/url]. Finally, the Sun [url=https://www.weather.gov/lmk/twilight-types]completely sets[/url] and the sky becomes dark. [url=https://qph.cf2.quoracdn.net/main-qimg-ad89b5e5f33336dc569bfe095c1342df-lq]Don't despair[/url] -- the whole thing will happen in reverse when the [url=https://apod.nasa.gov/apod/ap231019.html]Sun rises[/url] again in the morning.
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