Rocket
Rockets remain inherently unreliable despite decades of engineering refinement. The space shuttle programme achieved a 98.5% success rate, meaning one in sixty-seven missions ended catastrophically. Modern commercial rockets fare somewhat better, yet each launch carries genuine risk. Components number in the millions, any of which might fail. Weather, materials fatigue, and human error conspire against success. Each successful launch represents a minor miracle of maintained tolerances.
Time
Time has never once failed to proceed. In 13.8 billion years of continuous operation, not a single second has been skipped, reversed, or lost due to technical difficulties. Time requires no maintenance, no quality control, and no contingency planning. It operates with absolute consistency whether observed or not, whether convenient or catastrophic. Physicists occasionally suggest time might behave strangely near black holes or at quantum scales, yet even these variations occur reliably, predictably.