If you thought that science was certain - well, that is just an error on your part.

No! Not for a second! I immediately began to think how this could have happened. And I realized that the clock was old and was always breaking. That the clock probably stopped some time before and the nurse coming in to the room to record the time of death would have looked at the clock and jotted down the time from that. I never made any supernatural connection, not even for a second. I just wanted to figure out how it happened.

This is not very important what I'm doing. I'm just proving something.

The present situation in physics is as if we know chess, but we don't know one or two rules.

Science is uncertain.

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.

It is odd, but on the infrequent occasions when I have been called upon in a formal place to play the bongo drums, the introducer never seems to find it necessary to mention that I also do theoretical physics.