@bonzoesc Reminds me of a time when I half-jokingly critiqued the phrase “it’s not rocket science” to mean “it’s not complex”. I argued rocket science was really pretty simple (TL;DR version: “conservation of momentum”) and the really hard part was rocket engineering (finding ways to use that concept that didn’t explode, incinerate the crew, or poison half the planet on the way up). Someone brought up Tsiolkovski’s rocket equation as a counterexample; it’s a first principle that’s not immediately visible from conservation of momentum (though of course it’s part of the derivation of the equation). Ok, fair, but as KSP enthusiasts can attest to: getting a usable spacecraft within the constraints of the rocket equation takes a lot of rocket engineering as well.