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Asked by anon-221225 on 26 Jun 2019.
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Rebecca Moon answered on 26 Jun 2019: last edited 26 Jun 2019 1:33 pm
Great question! At the start of the day, a human can be about a centimetre taller than at the end of the day. The spine is comprised of the bony vertebrae which are separated by spongy intervertebral discs. During the day, the weight of the head and upper body on the spine causes compression of these intervertebral discs and that’s why people are shorter at the end of the day than on waking it. But it wouldn’t matter is you had spent the day walking or sitting, youd still be slightly shorter, and due to the lack of gravity in space, astronauts would not be different heights throughout the day 🙂
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David Wilson answered on 26 Jun 2019:
Nice answer Rebecca, the answer is you do, but it might be tricky to notice.
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A great (an entertaining) way to see this exaggerated is if you know someone who is running a marathon where someone can lose up to 3cm over the course of the distance! If you know someone who is about the same height or slightly taller this is noticeable and well worth pointing out to them now that they are shorter than you! -
Matthew Bareford answered on 26 Jun 2019:
Short answer is yes.
Essentially during the day our spines compress (bones push down on each other) as we walk. During the night our spines then decompress (bones move back apart) so in essence we do all grow in our sleep.
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Nina Rzechorzek answered on 26 Jun 2019: last edited 26 Jun 2019 10:13 pm
As the others have explained nicely; if you are upright for long enough the compression of your vertebral column (spine) as result of gravity will allow some temporary height loss. You can elongate your spine by up to 3 % if go space travelling!
https://www.nasa.gov/audience/forstudents/5-8/features/F_How_Youve_Grown_5-8.html
And of course, if you are a quadruped (e.g. a dog), gravity is not acting on spine length to the same extent, so dogs don’t get longer when they sleep!
Comments
Rebecca commented on :
Wow David, that is a cool fact! I’m only 5ft 3 at best so its a good thing I don’t/haven’t/won’t ever run a marathon or I’d be really short at the end of it!