Comments and questions about the
APOD on the main view screen.
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Ann
- 4725 Å
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by Ann » Sun Jun 09, 2019 8:45 am
This is a spectacular image with rich deep colors and a fantastic optical effect.
Ann
Color Commentator
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De58te
- Science Officer
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by De58te » Sun Jun 09, 2019 11:40 am
I don't think that perspective isn't the only explanation for the triangle shape. Unlike railroad tracks, I don't think many volcanoes have parallel cube shape sides. I think that volcanoes are mostly cone shaped with the wider part at the base. Now a cone pictured in two dimensions looks like a triangle. Now why a volcano takes on a cone shape is physics due to fluid flow in gravity. Unlike solids an erupting lava flow would flow down the sides of a volcano because it is fluid. When it gets to the bottom it cools and then turns solid. Solids then usually don't move anymore and stay in place. As time goes on and more fluid lava flows it tends to bunch up at the bottom so then an old volcano tends to have much more mass at the bottom than the top and so it shapes like a cone.
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orin stepanek
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by orin stepanek » Sun Jun 09, 2019 11:43 am
Nice! I thought there was a similar one where the moon was within the shadow!

Orin
Smile today; tomorrow's another day!
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orin stepanek
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by orin stepanek » Sun Jun 09, 2019 3:05 pm
Thanks Art; That's the one!
Oh; Guess I should have clicked on commonly seen in the write up!
Orin
Smile today; tomorrow's another day!
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rustybrown@live.ca
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by rustybrown@live.ca » Sun Jun 09, 2019 3:24 pm
The triangle shadow phenomena is not unique...
It's a phenomenon, really.
Just to clarify.
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neufer
- Vacationer at Tralfamadore
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by neufer » Sun Jun 09, 2019 5:10 pm
rustybrown@live.ca wrote: ↑Sun Jun 09, 2019 3:24 pm
The triangle shadow phenomena is not unique...
It's a phenomenon, really.
Just to clarify.
https://www.etymonline.com/search?q=phenomenon wrote:
phenomenon (n.) 1570s, "fact, occurrence," from Late Latin phænomenon, from Greek phainomenon "that which appears or is seen," noun use of neuter present participle of phainesthai "to appear," passive of phainein "bring to light, cause to appear, show." Meaning "extraordinary occurrence" first recorded 1771. Plural is phenomena.
..........................................................
phenomenal (adj.) 1803, "of the nature of a phenomenon," a hybrid from phenomenon + -al. Meaning "remarkable, exceptional" is from 1850.
[Phenomenal] is a metaphysical term with a use of its own. To divert it from this proper use to a job for which it is not needed, by making it do duty for remarkable, extraordinary, or prodigious, is a sin against the English language. [Fowler]
Art Neuendorffer
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JKent@APD
- Asternaut
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by JKent@APD » Sun Jun 09, 2019 9:48 pm
Been there Done That!
MoonRise Through Mount Teide's Shadow; © Casado (TWAN)
A Triangular Shadow of a Large Volcano
Image Credit & © Juan Carlos Casado (TWAN)
Why does the shadow of this volcano look like a triangle? The Mount Teide
volcano itself does not have the strictly pyramidal shape that its geometric
shadow might suggest. The triangle shadow phenomena is not unique to the Mt.
Teide, though, & is commonly seen from the tops of other large mountains &
volcanoes. A key reason for the strange dark shape is that the observer is
looking down the long corridor of a sunset (or sunrise) shadow that extends to
the horizon. Even if the huge volcano were a perfect cube & the resulting
shadow were a long rectangular box, that box would appear to taper off @ its
top as its shadow extended far into the distance, just as parallel train
tracks do. The above spectacular image shows Pico Viejo crater in the
foreground, located on Tenerife in the Canary Islands of Spain. The nearly
full moon is seen nearby shortly after its total lunar eclipse last month.