I was turning this over in my mind during my morning walk, when it occurred to me that perhaps all of you collectively might be able to answer some questions that have nagged at me for years. I could of course try Google, but that is so 2012. The new thing is crowdsourcing, so let's see whether it works. Here are three things that puzzle me. Can anyone shed light on one or another of them?
1. How does soap work? I mean, I understand why rinsing your hands in water, rubbing as you rinse, might shake loose some bits of dirt and carry them away, but why does it help to use soap? By way of contrast, my Dental Hygienist has counseled me that the proper way to clean my teeth is to start by flossing, which if done well loosens the plaque that has built up; then to brush with a bare brush to complete the removal of the plaque, and then to apply the prescription fluoride toothpaste [after which one is not to eat or drink for twenty minutes, an injunction I honor more in the breach than the observance.] She says using toothpaste just confuses things and does not do any additional good. So, if that is true, what good is soap?
2. How can stunt planes at aerial circuses fly upside down? I learned all about Bernoulli's Principle and the differential pressure under and over the wing created by the curved upper surface of the wing, thus creating upward pressure that lifts the airplane, but if all of that is true, why doesn't an airplane crash when it flies upside down?
3. How does friction work? Friction is a ubiquitous phenomenon, as common as gravity. But I have no idea how it works. Why do some things produce friction when rubbed against one another whereas other things do not? Why is ice virtually frictionless? In the summer, when it is very warm here in North Carolina even early in the morning during my walk, I am liable to return home sweaty, whereupon friction gets in the way of my taking my T-shirt off, whereas in the Winter, it comes off easily. How come?
I await your collective enlightenment.