The theory of biphasic sleeping is quite simple. By sleeping 2 times in a day, totalling 3, 4.5, 6, 7.5, or 9 hours of sleep (or, if you prefer, by completing a certain amount of entire sleep cycles), you should sleep better and be less tired when you wake up that if you slept for any amount of time in between, that is not a multiple of 90 minutes. As Glen Rhodes brilliantly exposes, ''The secret is NOT the amount of sleep, but rather the number itself; a multiple of 90 minutes will change your life.''. For instance, you will feel a lot more better if you slept 7.5 hours and had 5 complete sleep cycles than if you slept 8.5 hours, and that the alarm clock brutally interrupted the cycle. Have you ever been so groggy after the alarm clock rang that you could barely move? Well, there's 90% chance that it's because you didn't finish your last sleep cycle.
That's the key to become a biphasic sleeper. Instead of sleeping in one big chunk during the night, you divide your daily sleeping time into 2 (bi-phasic), and you end up with being a lot less tired and a lot more productive than the people who don't complete sleep cycles. I've been researching a lot about this, and I didn't find any medical side-effects. In fact, cavemen were polyphasic sleepers (sleeping a very small amount of time several times in the day) because they couldn't afford to rest with all the predators. We later became biphasic (look at all the babies who take a nap during the afternoon and sleep during the night), and finally monophasic because lightning wasn't working very well, and we had to maximise working hours during daytime, and rest when the sun went down. When artificial lighning was invented, we could have go back to biphasic, which is a healthier way of life, but the new way of life was already instaured. All this to say that we are naturally biphasic when we are born, and that society (at least in the northern hemisphere) forces us to become monophasic.
The benefits of biphasic sleep, from what I saw, seems really awesome: you sleep less, but you become more productive and it's even healthier! The only negative side is that it can somehow affect your social life, and you sometimes find people who quit biphasic sleep because they it just wasn't compatible with their way of life (ex: Tim). Nevertheless, nearly all the bloggers that have experimented it say it's a great experience that really works, so why not give it a shot? For a teenager who has no other choice than work very late every day, waking up in the morning without being tired seems almost too good to be true. This is why I decided to become a biphasic sleeper. And even if it doesn't work, it looks like a great experiment to try, and I have to admit that I love it when people think I'm crazy, while I could actually sleep better than them ...