> So all I’m saying is try it. If you have and it didn’t work, fine. But you’ll never know if you don’t try.
This is good advice, especially when -- as others in this thread have mentioned -- blue light exposure may be making artificial night owls out of larks. I personally have tried this without success. I use f.lux to avoid making my situation any worse.
> Also if you say you are so very tied to signals for the sun.
That's not quite what I said, but I understand why that was your takeaway.
> What happens in the summer when it’s light out from 6am to 9pm? Do you also start waking up earlier? What about in winter when it’s light only from 9am to 4pm? How do you cope?
This is a good question. I would categorize this under "second-order effects", because I'm certainly delayed year-round, and I haven't noticed any obvious seasonal variation. It would be interesting to see whether earlier dusk correlates with going to sleep earlier more easily. Thanks for the idea!
> What do you do if you live in Finland and it’s light out for 6 months? Do you just not sleep?
Like I said, the circadian rhythm is just one mechanism the body uses to regular sleep. Another is the build-up of adenosine accrued while awake. Mentioned elsewhere in this thread, the book "Why We Sleep" by Matthew Walker is a wonderful exploration of the complexity of our sleep subsystem.
As for myself, although I've never lived in Finland, I have been a grad student living like a hermit in a room with almost solely artificial lighting. My sleep cycle starts to wander: every "night", I go to bed later and later, and wake later and later. It sometimes got to the point that I would wake at 4pm and sleep at 7am -- and eventually I would cycle back around to a lark's early morning schedule. This is pretty consistent with experiments in which people live underground and never see light, although it's certainly not so extreme as the results they saw.
(This, by the by, is also how I know what my natural sleep period is when unconstrained by scheduled obligations: nine hours. I've noticed that seven hours is the absolute minimum I need to be remotely productive the next day, and even then I'm likely to do low-effort things like discuss sleep on Hacker News.)