DJ Strouse

My Goodreads rating: 4 of 5 stars

I love reading explanations of biology from physicists; what once were magic and collections of ‘just-so’ stories become explanations of how and why processes occur the way they do. This book was single-handedly responsible for convincing dozens of physicists to chase issues biological and given I already had the bug, I figured it would be interesting to see what sparked it in so many others.

Here’s the conversation that runs through my brain when I think about this book:

The Children: Grandpa Schroedinger, Grandpa Schroedinger! Tell us about biology!

Grandpa Schroedinger: Well, what do you want to know?

TC: What’s an organism?

GS: An organism is a 4D pattern that consumes negative entropy to maintain order.

TC: Huh?

GS: It’s something that’s alive.

TC: Oh. Why are organisms so much bigger than atoms?

GS: Ho, ho, ho! If organisms were close to the size of atoms, life would be intolerable! We’d all be buffeted about by the quantum chaos and never have a chance at predicting our environment. Think about it: your sensory organs would be useless if all they could pick up was Brownian motion. That’s one hell of a signal-to-noise problem! We have to be big so that life is more predictable.

TC: How come we don’t know how life works? If physicists are so smart, why haven’t they figured out the genetic code yet?

GS (grave face): You should learn not to run your mouth. But if you must ask, it’s because physicists like things that are easy to study, such as the relatively simple and elegant structures produced by statistical mechanics. But statistical mechanics produces statistical structures – periodic crystals and such. Organic molecules are aperiodic and quite foreign to physicists. We shouldn’t expect that our physical models will carry over so easily; in fact, ‘it is well-nigh unthinkable that the laws and regularities thus discovered should happen to apply immediately to the behaviour of systems which do not exhibit the structure on which those laws and regularities were based.’ Reductionism is hard. There are many steps on the ladder between physics and phenomena, each one possibly best describable in a completely different language.

TC: I heard the biologists are going to discover DNA in 7 years, but I want to know now! How does it work?!

GS: Well fortunately I’m a flippin’ genius and probably one of the smartest grandpas in the world so I can tell you how this DNA stuff works seven years before anyone else will know. Here’s the trick: it’s an aperiodic crystal stored in your chromosomes.

TC: But if it’s so tiny, how do we fit the recipe for a whole human being in there?

GS (pats child on head): Combinatorics, my boy! Combinatorics! If you have 25 letters and want to make a 25-letter word using just 5 different letters, you know how many words you can make? More than 62 trillion!

TC: Wow… but if the DNA is so tiny, how does it remain stable? You told us that tiny things get buffeted about in the quantum storm!

GS: Silly child! Quantum theory can save the day again! Since molecules are only stable in discrete quantum states, these aperiodic crystals will only be stable in certain patterns. They’ll need a minimum amount of energy to pop out of place, kind of like a marble stuck in a thimble. You can poke it and flick it without knocking the marble out but if you smack it too hard, kapoot! That’s why high temperatures and x-ray radiation are not particularly conducive to your health. They sometimes provide enough energy so that, kapoot!, your little aperiodic DNA crystals pop out of place and mutate!

TC: Wait.. I look nothing like my mom and dad. How can I be just a copy of them?

GS: Well, it turns out your DNA isn’t perfectly stable. It’s just instable enough that mutations can occur here and there. Think of it like an optimization problem: your DNA mutates just often enough to explore different design possibilities, but just rare enough that evolution can isolate the mutation responsible when we make a good or bad move. With too many changes at once, it’s impossible to judge which were ‘good’ and which were ‘bad’, but with no changes at all, the whole world would be like one big personality-less fraternity. Either that or your parents adopted you.

TC: Oh… [one child walks away from crowd with head down:] So we dip into the quantum storm just often enough to be helpful.. neat! How does every cell know how to follow the recipe? Is there a DNA dictator who tells everyone what to do?

GS: Nope! Organisms are more democratic than that. Every cell gets a cloned copy of the recipe. It’s a bit like a collection of local governments all based on the same constitution but that each make decisions based on local conditions.

TC: Wow… you really are the smartest grandpa in the world!

GS: Ho, ho, ho! [pats child on head again:] Yes, I know. Now, here; take this bratwurst and run along! I have to go solve the mysteries of dark matter and energy, explain consciousness, and prove P=NP.

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