Indeed there are. Dark Matter. Dark Energy. Quantum gravity. Proton decay. The origin of life. Etc. Etc. Even some quite everyday things - lightning, DNA repair, why some people are so much more badly harmed by beryllium than others - that aren’t as well understood as we’d like. But conversely there are a load of things that we do know. Putting your head in the fire is bad for it. House-bricks sink in water. Night follows day (and vice versa). Without oxygen to breathe we die.
All of the first world and most of the second and third ones are filled with electronics. A good deal of it is designed and built by hundreds of thousands (millions ?) of smart people using well-established principles they learned at uni. It just works. Honestly it does. Large corporations don’t go unexpectedly bust because today transistors suddenly aren’t behaving the way they behaved yesterday (never mind, they’ll be OK again next week). In regular, everyday electronics there aren’t any surprises any more. Cardiac pacemakers don’t just stop. Airport radar systems don’t have off days. My electronic alarm clock wakes me at the same time every morning. I’d notice if it didn’t.
Change in temperature ? The kit I worked with was so temperature sensitive that we would go into the room with it as infrequently as possible, and when we did go in we took a small torch to avoid switching the lights on (they warmed the room up).
If I’m measuring the distortion from something like a Quad II I’ll leave it to settle for 10-15 minutes after switch-on before starting the measurement. The result can be half (or twice) what it was when the valves were still cold.
