Steven Strogatz in Quanta Magazine:
Why do we sleep anyway? We spend about a third of our lives asleep, so it seems like it must be pretty important. But there’s still so much about it that we don’t understand. One thing that sleep researchers are pretty sure of is that every system in our body seems to be impacted by sleep. When we miss out on sleep, it impairs our circulation, our digestion, immune system, metabolism, and of course, brain function. And sleep deprivation doesn’t need to be long term to do damage. In fact, if you go without sleep long enough, you will die. But why, exactly?
…Rogulja (02:07): Well, you’re probably sitting right now and kind of resting in some way. But you’re definitely not sleeping, right? So, yeah, what is it that’s so different? And I would say that, for me, what is the kind of most defining characteristic of sleep is that kind of loss of awareness of the external environment and of your internal state, in many ways.
More here.