This evening I learned that the oven will only heat up if you turn it on. Oh, sure, I had known that in theory for many years, but now I know it through experience.
I've made another discovery in recent months. If you frequently take a cup of coffee with you to the car then let the empty mug roll around on the floor of the car for weeks, clanking into other mugs you've carried out to the car, then the mugs sometimes become damaged by chipping, cracking, or having the handle fall off. Who would have seen that coming?