I’ve learnt a little about sleep cycles and remember that every 90 minutes is when we move through the 5 stages of sleep, but I’ve also heard it’s recommended to have 8 hours of sleep. Wouldn’t that make you feel drowsy if you’re interrupting the sleep cycle when you wake up after 8 hours?
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The eli5 is that *all* of these numbers are vague, rounded approximations. Human biology doesn’t happen to run exactly in sync with round units of time.
Just listen to Joe Rogan’s podcast #1109 with Matthew Walker. All you need to know about sleep and it’s benefits
8 is a magic number which is divisble by 24. 24 is the number of hours of the day.
8 hours go to sleep/in bed.
8 hours go to work/travel to and from work.
8 hours go to free time, dinner, friends, entertainment.
You don’t mess with the holy trinity. You (sleep) gets a piece, your boss gets a piece and you yourself (as a person) gets a piece.
This is why decimal time won’t ever get implemented. It’s based on 10 hours a day. A brilliant concept. But it is not divisible by 3.
Prediction: 6-hour work day will be the norm in the near future.
Funny you should ask:
Before the wide spread use of artificial lights, there was a first sleep and a second sleep. Some scientists believe that “bi-modal” sleep is what humans are most accustomed to.
Until the early 18th century, people would go to bed more or less at sundown. They would then wake up in the middle of the night and spend an hour or so thinking, praying, reading, making love, etc. Then they would go back to sleep for another few hours.
Here is an article providing more in-depth information about first sleep, second sleep, and the 8 hour sleep:
[https://www.bbc.com/news/magazine-16964783](https://www.bbc.com/news/magazine-16964783)
For about 10 years now I’ve heard it as 9 hours instead – 6 sleep cycles.
People said 8 hours before they knew much about sleep cycles, I think. And now, many people remember the old stand-by and haven’t learned about the sleep cycles, so the old saying doesn’t die.
Don’t know if it was commented before, but I think I saw something on the internet before about certain fitness braces who can somehow sense in which stage of the sleep cycle you are and wake you up when it’s the easiest to be woken up.
I found this app, looks interesting!
https://www.sleepcycle.com/how-sleep-cycle-works/
You know that when you wake up at 5 am and feel ready to stand up even though you could sleep till 6.30? And if you do go back to sleep you feel like shit afterwards? I guess there’s something to it. Had that recently when I couldn’t find my phone to put my alarm on and I woke up by myself from subconsciously knowing I’d lose my job lol.
there is a lot of misleading information in here. if you want to learn more about our current understanding of sleep from a laymans perspective i urge you to watch a few Matthew Walker videos. i like the Joe Rogan one, but there are plenty of others including TED talks. few youtube videos have made me pause and reevaluate my self like his have.
The time on the cycles isn’t *exactly* 90 minutes. The time will vary per person – and per cycle.
Some people can feel refreshed after a 30 minute power nap… others can sleep all day and not feel refreshed.
Everyone is different… find what works best for you.
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