By now, you know whether you’re a night owl or an early bird, but if you want to know more about your body’s more subtle rhythms, try a new book “Sex Sleep Eat Drink Dream,” by Jennifer Ackerman. It’s a tour through 24 hours in the life of a typical body and here are some of the findings: most of us are mentally sharpest three hours after waking, when concentration and problem-solving abilities may be up to 30 percent better than at other times of day. This makes late morning the best time to puzzle through a complex decision or absorb new information. On the other hand, the best time to brave the dentist’s chair is in the afternoon, when the pain threshold in teeth is highest. If you’re going for a personal best, schedule your run for early evening, when your perception of exertion is low and your muscles are at their most powerful. And the next time you’re having a drink at happy hour, be thankful that the liver best detoxifies booze between 5 and 6 p.m.