Why You Keep Seeing Me

Yesterday afternoon I ran into a friend, by chance, for the third time that day.


“Why do I keep seeing you?” he asked.


“Good question,” I said, “you see, about eight light-minutes in that direction is a giant ball of gas called the sun. Inside, hydrogen under high pressure and temperature fuses into Helium. The Helium nucleus is lighter, so by E=mc^2 energy is given off in the form of photons…” and went on discussing atmospheric scattering, optics, the physiology of the retina, nerve impulses, a hierarchy of vision-processing mechanisms in the brain, the fusiform gyrus, grandfather neurons, and the nature of consciousness, all contributing to why he saw me.


But I was a bit surprised, as I dragged the joke on for a few minutes, how often I didn’t really understand what I was saying (and said it rather poorly). Hydrogen fuses to form Helium in the sun? Why does it do that? I thought I knew most of what there is to know about a single Hydrogen atom from my quantum mechanics courses, but put two of them together (and give the nucleus actual degrees of freedom) and i have no idea why they do what they do.


Today I ran across this quote from Tom Stoppard’s Arcadia:

It makes me so happy. To be at the beginning again, knowing almost nothing…. The ordinary-sized stuff which is our lives, the things people write poetry about—clouds—daffodils—waterfalls….these things are full of mystery, as mysterious to us as the heavens were to the Greeks…It’s the best possible time to be alive, when almost everything you thought you knew is wrong.

(quoted in Melanie Mitchell’s Complexity: A Guided Tour)

There is a lot of mystery in something as mundane as seeing a face you recognize. Fortunately, today many of the answers to these mysteries are known, if not in full detail, then at least in much greater detail than I know now. It’ll be interesting to find a few of these things out.


2 Responses to “Why You Keep Seeing Me”

  1. Rod Vance Says:

    I use this kind of humour with my children all the time – my seven year old daughter thinks it is hilarious. I began this kind of thing as a parry to my daughter’s constant demands – children genuinely take many years to learn someone else’s point of view so they’re genuinely not being thoughtless when they bark out constant demands and its rather unproductive to tell them that they are being “selfish” or “thoughtless”. So, when I got a one word demand for “milk” (implicitly, “may I have some milk, Papa?”), I would say something like: “milk: that’s a protein laden liquid secreted by the female of endothermic amniotes of the class mammalia to feed her young with, isn’t it?”. She quickly caught on and now simply enjoys the humour of the many characters we dream up together (amongst which the geek so utterly absorbed in their own thoughts as to think it socially acceptable to speak like this in everyday life).

    On the question of learning things anew, I am finding much joy in helping out at the science room at my daughter’s school. Little seven year olds burn with curiousity when you show them the Dirac belt trick and say that there are only two ways wherein things can “be changed by a full turn” and that this governs which “stuff” takes up space and which, like light, does not. I don’t have a good explanation for them as to why this is so – this is the other half of the spin statistics theorem of course – the best I can so far do is to tell them that *how* things rotate has a bearing on how they fit together and give an example of left and right handed nuts and bolts – one has to be turned one way, the other in the opposite sense, to do them up. Nonetheless it is still amazing that one can thus describe a spinorial object through the Dirac trick in a way that a seven year old understands deeply. They also love the Mobius strip, especially after you ask them to imagine what a piece of paper with one side would look like. Olber’s paradox washes well with a little person learning all this stuff for the first time.

  2. vk Says:

    The first thing I thought when I read this nice post was the following comic on xkcd https://xkcd.com/1145/ which you might already know but matches to the topic

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