Thus we can get the correct answer for the probability of partial reflection by imagining (falsely) that all reflection comes from only the front and back surfaces. In this intuitively easy analysis, the 'front surface' and 'back surface' arrows are mathematical constructions that give us the right answer, whereas .... a more accurate representation of what is really going on: partial reflection is the scattering of light by electrons inside the glass.

I think it's much more interesting to live not knowing than to have answers which might be wrong. I have approximate answers, and possible beliefs, and different degrees of uncertainty about different things, but I am not absolutely sure of anything. There are many things I don't know anything about, such as whether it means anything to ask "Why are we here?" I might think about it a little bit, and if I can't figure it out then I go on to something else. But I don't have to know an answer. I don't feel frightened by not knowing things, by being lost in the mysterious universe without having any purpose - which is the way it really is, as far as I can tell.

All mass is interaction.

Nature uses only the longest threads to weave her patterns, so that each small piece of her fabric reveals the organization of the entire tapestry.

We are lucky to live in an age in which we are still making discoveries.

Nature does not care what we call it, she just keeps on doing it.

I learned very early the difference between knowing the name of something and knowing something.