It was over in less than a second. I let out the breath I didn't know I'd been holding. My God, I thought dully, how fast did those things come down? I ran a quick mental calculation. Assume they were traveling at orbital velocity when they hit the atmosphere. What would that be? Something like 35,000 kilometers per hour —in other words, 10 klicks per second or thereabouts, maybe 10 times the speed of a rifle bullet. And Thor projectiles were a lot bigger than rifle bullets, of course. I'd heard them described as "smart crowbars." Assume each one massed a nominal one kilo. How much kinetic energy was contained in one kilo of mass traveling at 10,000 meters per second? If I remembered my high-school physics—and hadn't slipped a decimal place somewhere—that would be something like 100,000,000 joules of energy: one hundred megajoules . Per crowbar . And how many crowbars had been in the burst we'd just seen?