Sleep fact and fiction: does counting sheep work?

Is an hour’s sleep before midnight as good as two after? Can a lie-in at the weekend make up for late nights during the week? We separate the fact from the fictionA siesta is not the same thing as a power nap. Siestas are a cultural norm in certain places (particularly in hot countries) where people take a brief rest after lunch. We can do this because our circadian biology (body clock) has a natural dip in the afternoon and there is a natural lull in our alertness. If we are extremely sle