Life's Greatest Secret Read Online Free Page A

closed system, energy will dissipate until it reaches a constant and even level: physicists explain this in terms of the increasing amount of disorder, or entropy, that inevitably appears in such systems. Organisms seem to contradict this fundamental law because we are highly ordered forms of matter that concentrate energy in a very restricted space. Schrödinger’s explanation was that life survives ‘by continually sucking orderliness from its environment’ – he described order as ‘negative entropy’. This apparent breach of one of the fundamental laws of the Universe does not cause any problems for physics, because on a cosmological scale our existence is so brief, our physical dimensions so minute, that the iron reality of the second law does not flutter for an instant. Whether life exists or not, entropy increases inexorably. According to our current models, this will continue until the ultimate heat death of the Universe, when all matter will be evenly spaced and nothing happens, and it carries on not happening forever.
    Schrödinger encountered far greater difficulties when he came to discuss his second topic: the nature of heredity. Like Koltsov and Delbrück before him, Schrödinger was struck by the fact that the chromosomes are accurately duplicated during ordinary cell division (‘mitosis’ – this is the way in which an organism grows) and during the creation of the sex cells (‘meiosis’). For your body to have reached its current size there have been trillions of mitotic cell divisions and through all that copying and duplicating the code has apparently been reliably duplicated – in general, development proceeds without any sign of a mutation or a genetic aberration. Furthermore, genes are reliably passed from one generation to another: Schrödinger explained to his audience that a well-known characteristic such as the Hapsburg, or Habsburg, lip – the protruding lower jaw shown by members of the House of Hapsburg – can be tracked over hundreds of years, without apparently changing.
    For biologists, this apparently unchanging character of genes was simply a fact. However, as Schrödinger explained to his Dublin audience, it posed a problem for physicists. Schrödinger calculated that each gene might be composed of only a thousand atoms, in which case genes should be continuously shimmering and altering because the fundamental laws of physics and chemistry are statistical; although overall atoms tend to behave consistently, an individual atom can behave in a way that contradicts these laws. 44 For most objects that we encounter, this does not matter: things such as tables or rocks or cows are made of so many gazillions of atoms that they do not behave in unpredictable ways. A table remains a table; it does not start spontaneously turning into a rock or a cow. But if genes are made of only a few hundred atoms, they should display exactly that kind of uncertain behaviour and they should not remain constant over the generations, argued Schrödinger. And yet experiments showed that mutations occurred quite rarely, and that when they did happen they were accurately inherited. Schrödinger outlined the problem in the following terms:
    incredibly small groups of atoms much too small to display exact statistical laws … play a dominating role in the very orderly and lawful events within a living organism. They have control of the observable large-scale features which the organism acquires in the course of its development, they determine important characteristics of its functioning; and in all this very sharp and very strict biological laws are displayed.
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    The challenge was to explain how genes act lawfully, and cause organisms to behave lawfully, while being composed of a very small number of atoms, a significant proportion of which may be behaving unlawfully. To resolve this apparent contradiction between the principles of physics and the reality of biology, Schrödinger turned to the most