10 things most people don't know, that engineers think about constantly: 1. CORRELATION IS NOT CAUSATION Two things happening together does not mean one causes the other. Engineers test this. Most decisions aren't made by people who do. 2. SYSTEMS FAIL AT INTERFACES The individual components usually work fine. It's where they connect that disasters happen. 3. MORE SAFETY FEATURES CAN MAKE THINGS LESS SAFE Adding redundant systems increases complexity. Complexity increases the number of ways things can go wrong. This is called the safety paradox, and it's why nuclear plant design is not simply "add more backups." 4. THE ABSENCE OF EVIDENCE IS NOT EVIDENCE OF ABSENCE Something hasn't failed yet. That doesn't mean it's safe. It may mean you haven't run it long enough. 5. TOLERANCE STACKING Each component has a tolerance: ±0.1mm. Put 20 components together, each at the worst end of their tolerance, and you have a 2mm error. Many products fail not because any part is bad, but because all the parts are slightly wrong in the same direction. 6. THE MAP IS NOT THE TERRITORY Every engineering model is wrong. Some models are useful. The model that causes disasters is the one someone believed was exact. 7. FEEDBACK LOOPS CHANGE SYSTEMS Adding a monitoring system changes the behaviour of the system being monitored. Adding safety incentives changes what engineers report. Measuring performance changes what people optimise for. 8. ENTROPY IS ALWAYS WINNING Everything degrades over time. Maintenance is not optional, it's the only reason anything works. Every structure, machine, and system is a continuous battle against the second law of thermodynamics. 9. THE HUMAN IN THE LOOP IS BOTH THE STRONGEST AND WEAKEST COMPONENT Human adaptability is extraordinary, humans solve problems no designer anticipated. Human error is the root cause of most major failures. Designing for humans means accounting for both. 10. FIRST-PRINCIPLES THINKING IS RARE Most decisions are made by analogy: "we did it this way before." The engineers who change things ask: what does physics actually require here? The answer is almost always different from what tradition suggests.