Let's say you have a planet tidally locked to its star (a red dwarf), with an atmosphere that makes it habitable around the area halfway between the point closest to the star and the point furthest away. All the life in this area would live in perpetual twilight.

Could life very similar to humans survive such an existence? I'm specifically wondering what the effect would be on our bodies of always being in the sun, but at the same time never having full sunlight, only a setting sun. Would our skin need to be different? Would we have evolved to need less sleep (being that it's always light and therefore we would always be able to do work so sleeping is less practical)?

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    $\begingroup$ So basically you ask us to design a whole ecosystem for you? $\endgroup$ – Mołot Oct 18 '16 at 15:10
  • $\begingroup$ what is the orbital inclination of your aforementioned extreme axial tilted planet? not that I'm intending to answer(mine is littered with broken English) but there will be significant temperature variation away from the equator... and the experts here REALLY scrutinized your question through and through you've been welcomed! $\endgroup$ – user6760 Oct 18 '16 at 15:41
  • $\begingroup$ @user6760 oops! I can see how my use of the word "poles" could be confusing in this context, so I edited it out. The axis of rotation is perpendicular to the orbital plane, and the period of rotation is the same as the period of revolution, so that only one side ever faces the star. $\endgroup$ – Tori Oct 18 '16 at 15:48
  • $\begingroup$ @Tori I think this question is too broad, and it has too many sub-questions embedded in it. The purpose of this site is for you to start with your own design and then ask specific reality-check questions about the validity of your designs. I am voting to close, but I hope you break it down into more specific questions and repost. $\endgroup$ – kingledion Oct 18 '16 at 16:11
  • $\begingroup$ Put on hold? I was going to say possible duplicate: How extensive could a habitable twilight zone be on a tidally locked planet? - see also: Could (and how would) life develop and survive in a place of 24 hours of darkness? $\endgroup$ – Theraot Oct 18 '16 at 18:10

It would not have a dark/light side. You are describing the planet Gliese 581 c

The Planet to is tidally locked, but there is hope for life on such a planet. While the ''day'' side would always be burning and the ''night'' side would freeze your internal organs, the dawn and dusk ring around the planets latitude would theoretically be habitable. So no, there would be no life on the day or the night side, but in between.

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