After watching this youtube short, an idea occured to me. This town of Viganella is in darkness for 83 days per year because of the relatively low position of the sun in the sky. However, if the position of the sun never changed because there was no axial tilt, could we get in a situation where there are valleys in the extreme north and south that never experience daylight? Or if they do, only for afew short hours at special times of the day. Now, the star I am working with is a small red dwarf, much dimmer than our own sun, so the satr takes up about 3 degrees in the sky instead of the suns .5 degrees. This makes the planet slightly warmer then earth. What I am thinking is that these valleys of eternal shadow could end up being much, much colder than the surrounding environment (they are already surrounded by mountains, atleast on the side facing the sun), and warmer air might not always be able to reach them, so I was thinking these might be able to host quickly growing glaciers if they happen to be in a region where enough rain falls. Is the idea of glacier valleys in temperate regions facing away from the equator reasonable?

  • $\begingroup$ I'm not going to work-up an answer at present because - time. It might be worth taking a look at Switzerland's glaciers for inspiration. It's quite close to the Viganella area. $\endgroup$ Commented Mar 4, 2022 at 2:32
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    $\begingroup$ ? It is very easy to design and dig a ditch, oriented east-to-west, sufficiently narrow or sufficiently deep so that the sun never shines directly on its bottom. You just need to take into account the maximum elevation of the sun (for example, about 67 degrees here at 45 degrees latittide north, or about 53 degrees at 60 degrees latitude north) and use simple geometry to make sure that not a single ray of sunlight falls on the bottom of the ditch at any time during the year. (In the case of zero axialt tilt, the maximum elevation of the sun is 90 degrees minus the latitude.) $\endgroup$
    – AlexP
    Commented Mar 4, 2022 at 2:34
  • $\begingroup$ @AlexP if you were to turn that into an answer, I would make that the accepted answer most likely cause you give me the calculation I need. to figure it out aswell. $\endgroup$
    – skout
    Commented Mar 5, 2022 at 2:47

1 Answer 1


What you ask is totally possible. Even in my garden, the South side has a shed to the East, a fence to the South and the house to the West, making so that there is a strip about 2 meters wide which only gets direct light from May till August, well past the equinox. An heaven for fern and moss.

In a situation with 0 axial tilt it will be even easier, you just need something shaped like a コ with proper height that stops light from East, South and West (in the North emisphere, in the South one just swap South with North).

  • $\begingroup$ That's a very northern-hemisphere-centric answer! $\endgroup$ Commented Mar 4, 2022 at 5:24

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