“Once I saw the Crab Nebula through a powerful telescope. The nebula is the expanding debris of an exploded star, a wreath of shredded star-stuff eight light-years wide and 5000 light-years away. What I saw in the telescope was hardly more than a blur of light, more like a smudge of dust on the mirror of the scope than the shards of a dying star. But seeing through a telescope is 50 percent vision and 50 percent imagination. In the blur of light I could easily imagine the outrushing shock wave, the expanding envelope of high-energy radiation, the torn filaments of gas, the crushed and pulsing remnant of the skeletal star. I stood for a quarter of an hour with my eye glued to the eyepiece of the scope. I felt a powerful sensation of energy unleashed, of an old building collapsing onto its foundations in a roar of dust at the precise direction of a demolition expert. As I watched the Crab Nebula, I felt as if I should be wearing earplugs, like an artilleryman or the fellow who operates a jackhammer. But there was no sound.”