One-third of our lives is spent not having any idea what we are doing.

All right, admittedly many of us spend even greater percentages of our lifetimes clueless. But officially, we all have one-third of our lives basically unaccounted for.

Why? Because we are sleeping.

Sleeping is required by every creature with even the most rudimentary or remedial brain stem. Yet we really don’t understand why we sleep or what sleep is for.

All we really know about sleep is that if deprived of it for just ten days, we’re dead. That’s right — dead. Three minutes without air. Three days without water. Ten days without sleep. These are the physical limits of life.

Sleep isn’t just a big shut-down, a turn off, The Great Reboot. Sleep has degrees of depth. Sometimes we are all but comatose. Other times w…