Paul McCartney had a baby when he was 61; Rod Stewart was 66; Rupert Murdoch was a stunning 72. Not only does that mean they'll have less stamina than the average dad, that means they'll, well, check out a lot sooner too.

What makes spinal-cord injuries as devastating as they are is that everything about them plays out in absolutes: they are instantaneous, utterly disabling and horribly permanent.

Identical twins are ideal lab specimens for studying the difference between learned and inherited traits since they come from the womb preloaded with matching genetic operating systems. Any meaningful differences in their behaviors or personalities are thus likely to have been acquired, not innate.

Indeed, the best way to think of willpower is not as some shapeless behavioral trait but as a sort of psychic muscle, one that can atrophy or grow stronger depending on how it's used.

The mind and the body are inextricably entwined, and rarely are their inseparability clearer than when we're under some kind of mental pressure. The moment we start trying to learn a new skill, make a decision or otherwise think on our feet, our nervous system reacts - with accelerated pulse rate, increased respiration, even sweating.

Suffering is always hard to quantify - especially when the pain is caused by as cruel a disease as Alzheimer's. Most illnesses attack the body; Alzheimer's destroys the mind - and in the process, annihilates the very self.

Sadoway does more than entertain; he gives you a glimpse into the future of energy.