# Circadian rhythms underground

**URL:** <https://boards.straightdope.com/t/circadian-rhythms-underground/781713>\
**Category:** Factual Questions\
**Created:** [March 8, 2017, 6:38pm UTC](https://boards.straightdope.com/t/circadian-rhythms-underground/781713 "2017-03-08T18:38:06Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Malleus\_Incus\_Stapes](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/malleus_incus_stapes/32/3293_2.png) [@Malleus\_Incus\_Stapes](https://boards.straightdope.com/u/Malleus_Incus_Stapes)\
**Post date:** [March 8, 2017, 6:38pm UTC](https://boards.straightdope.com/t/circadian-rhythms-underground/781713/1 "2017-03-08T18:38:06Z")

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Deep in caves, where there’s no sunlight, is there any sort of day/night cycle that might be perceptible to the organisms within? Something like a consistent change in atmospheric pressure or humidity or something?

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**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\
**Post date:** [March 8, 2017, 6:44pm UTC](https://boards.straightdope.com/t/circadian-rhythms-underground/781713/2 "2017-03-08T18:44:30Z")

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Funny you should ask it like this, because there is [a famous experiment](https://en.wikipedia.org/wiki/Stefania_Follini) involving circadian rhythms and caves.

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**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\
**Post date:** [March 8, 2017, 8:29pm UTC](https://boards.straightdope.com/t/circadian-rhythms-underground/781713/3 "2017-03-08T20:29:28Z")

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I have seen aquarium coral isolated from sun light close up for the night in late afternoon, when the aquarium lights are still on.

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**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\
**Post date:** [March 8, 2017, 9:06pm UTC](https://boards.straightdope.com/t/circadian-rhythms-underground/781713/4 "2017-03-08T21:06:41Z")

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> [@carnivorousplant](#):
>
> I have seen aquarium coral isolated from sun light close up for the night in late afternoon, when the aquarium lights are still on.

Isn’t that a deleted line from Roy Batty’s death scene?

(Back on topic, it looks like Mexican blind cavefish, at least, [lost](https://www.sciencenews.org/blog/wild-things/blind-cavefish-got-no-circadian-rhythm) their circadian rhythm.

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**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\
**Post date:** [March 9, 2017, 12:28am UTC](https://boards.straightdope.com/t/circadian-rhythms-underground/781713/5 "2017-03-09T00:28:13Z")

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> [@Darren\_Garrison](#):
>
> Isn’t that a deleted line from Roy Batty’s death scene?

I doubt it.