Thursday, May 26, 2016
How do you say "physics" in the tongue of biology?
Okay, so we have our chimpanzee banging away at typewriters. Each keystroke is assumed to be random (this is a thought problem, not a hiring problem). Let’s limit the keys to the twenty six letters of the alphabet so I don’t have to count the keys on my laptop. How long does it take our pan troglodytes to produce Shakespeare’s Richard the Third?
Well, our hairy scribe will produce one “n” about every twenty-six strokes. Multiply 26 by 26 and that is how many strokes will be needed to produce the first two letters “no”. Assuming that Bonzo types 260 letters a minute, how long will it take him to turn out Now is the Winter of Our Discontent Made Glorious Summer by this Son of York?
I once actually calculated this out and quickly determined that it would take more time than the kosmos has existed for our chimp or indeed a whole army of chimps to get even halfway through that first line.
I like to use this popular thought problem to test my philosophy students. Could chimpanzees produce a Shakespeare play by random typing? The answer is that not only could they do so but they would inevitably do so, given enough resources including time. The problem is that the requirements are so vast as to be, for all practical purposes, impossible. She who agrees with what I have just said is capable of thinking logically. He who refuses to acknowledge even the contingent possibility is not.
One might say that Darwin explained how it was not only possible but actual that that random typing produced chimpanzees. What you need is some means of saving the good letters. If every good letter survives and every bad letter perishes, then every twenty six strokes will get you one letter closer to My Kingdom for a Horse!
Darwin can explain how you get from the simplest replicating organisms to certified public accountants because replicating organisms, by definition, have a means of saving and compiling the good letters in the DNA (or RNA) script. But how do you get from inorganic chemistry to those UR organisms?
Physicist Jeremy England has an intriguing guess. His work is discussed in “How do you say “life” in Physics” by Alison Eck in Nautilus. England addresses the problem that life presents to physicists.
To the physicist steeped in statistical mechanics, life can, in this sense, appear miraculous. The second law of thermodynamics demands that for a closed system—like a gas in a box, or the universe as a whole—disorder must increase over time. Snow melts into a puddle, but a puddle does not (on its own) spontaneously take the shape of a snowflake. Were you to see a puddle do this, you’d assume you were watching a movie in reverse, as if time were moving backward. The second law imposes an irreversibility on the behavior of large groups of particles, allowing us to play with words like “past,” “present,” and “future.”
The arrow of time points in the direction of disorder. The arrow of life, however, points the opposite way. From a simple, dull seed grows an intricately structured flower, and from the lifeless Earth, forests and jungles. How is it that the rules governing those atoms we call “life” could be so drastically different from those that govern the rest of the atoms in the universe?
England’s guess is that the solution turns on irreversible shifts in states of atoms. Here is my version, which mixes the metaphors in the Nautilus articles. Someone jumping a fence with a pogo can jump back, given that she has enough energy to do so. That’s a reversible change in state. Someone being shot out of a canon cannot return. His flight is irreversible.
How does this work at the atomic level?
A group of atoms could take a burst of external energy and use it to transform itself into a new configuration—jumping the fence, so to speak. If the atoms dissipate the energy while they transform, the change could be irreversible. They could always use the next burst of energy that comes along to transition back, and often they will. But sometimes they won’t. Sometimes they’ll use that next burst to transition into yet another new state, dissipating their energy once again, transforming themselves step by step. In this way, dissipation doesn’t ensure irreversibility, but irreversibility requires dissipation.
Now, if I understand the argument, a shift in a configuration of atoms that dissipates the energy required to effect it is a means of saving information. If the configuration acquires more energy and then jumps to yet another new configuration, then information is in effect compiled. The third configuration has a history. To really understand what it is, you would have to know the steps that led up to it. To the extent that that is true, the history involves the compiling of information. The gaggle of atoms is saving the good letters.
This is a very long way from explaining how genuine organisms emerge out of the inorganic soup. It doesn’t give us any idea of the chimpanzee typing odds. It does give us an idea of how the simplest mechanics might have produced a selection pressure that tilted inorganic processes towards the emergence of life.
The origin of life is one of the major mysteries. The fact that life did emerge on planet Earth tells us that inorganic nature contained within it the seeds of life. I like that idea. England may be onto an important clue as to where those seeds lay and how they germinated.