1. I am surprised how 15-19°C could be the temperature range for sleeping. That's just too cold; at least here in India. It's usually around 22°C (72°F) minimum

1. I am surprised how 15-19°C could be the temperature range for sleeping. That's just too cold; at least here in India. It's usually around 22°C (72°F) minimum people who have ACs, or the room temperature in temperate places like Pune and Bangalore. My friends say the same thing about SF at least. Is it common to sleep at this relatively cold (15-19°C) temperature in the USA? Also, there must be places/states where people don't use ACs, right? 3. I used to run at night for almost a year. Around 2-4 hours before sleep and very light dinnner after cooling down and then read a bit or so, or listen to soft/light music and fall asleep like a baby at around ~11PM and wake up at ~7pm (never set any alarms; still don't unless I've to catch an early flight or so). That was my best sleeping routine in a long time and I used to feel so awesome throughout the day. I've known people go for for a walk or so and then fall asleep after dinner. 5. Couldn't agree more. If I fall sleep during day it just pushes my sleeping rhythm off the track like anything. Very short naps (esp. after lunch or heavy lunch are quite nice) 9. That I have noticed in many people. I myself though could never really sleep in late, after college (in college or before I could sleep whenever I had an opportunity or wanted - like a lecture, bus, pillion riding etc - what blissfull times!), except some scenarios on some days that I could never pinpoint the reason for sleeping in late (but I feel exceptionally good on those days). So generally I am wide awake by 6.45-7.15AM no matter how late I fall asleep like an alarm clock :( So I try to fall sleep by 11PM. Are these points your own observations like I've listed mine or established results from research?