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What Is Life?

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For other uses, seeWhat Is Life (disambiguation).
What Is Life? The Physical
Aspect of the Living Cell
Title pages of 1948 edition
AuthorErwin Schrödinger
LanguageEnglish
GenrePopular science
PublisherCambridge University Press
Publication date
1944
Publication placeUnited Kingdom (UK)
Media typePrint
Pages194 pp.
ISBN0-521-42708-8
OCLC24503223
574/.01 20
LC ClassQH331.S357 1982

What Is Life? The Physical Aspect of the Living Cellis a 1944 science book written for the lay reader by physicistErwin Schrödinger.The book was based on a course of public lectures delivered by Schrödinger in February 1943, under the auspices of theDublin Institute for Advanced Studies,where he was Director of Theoretical Physics, atTrinity College, Dublin.The lectures attracted an audience of about 400, who were warned "that the subject-matter was a difficult one and that the lectures could not be termed popular, even though the physicist’s most dreaded weapon, mathematical deduction, would hardly be utilized."[1]Schrödinger's lecture focused on one important question: "how can the events in space and time which take place within the spatial boundary of a living organism be accounted for by physics and chemistry?"[1]

In the book, Schrödinger introduced the idea of an "aperiodic solid" that contained genetic information in its configuration ofcovalent chemical bonds.In the 1950s, this idea stimulated enthusiasm for discovering the chemical basis ofgeneticinheritance.Although the existence of some form of hereditary information had been hypothesized since 1869, its role in reproduction and its helical shape were still unknown at the time of Schrödinger's lecture. In 1953,James D. WatsonandFrancis Crickjointly proposed thedouble helixstructure ofdeoxyribonucleic acid(DNA) on the basis of, amongst other theoretical insights,X-ray diffractionexperiments conducted byRosalind Franklin.They both credited Schrödinger's book with presenting an early theoretical description of how the storage of genetic information would work, and each independently acknowledged the book as a source of inspiration for their initial researches.[2][3]

Background[edit]

The book, published in 1944, is based on lectures delivered under the auspices of theDublin Institute for Advanced StudiesatTrinity College, Dublinin February 1943, attended byÉamon de Valeraand hiscabinet.[4]At that time, although DNA was known to be a constituent of cell nuclei, it had not yet been identified with certainty as the molecular basis of inheritance, and the concept of a "heredity molecule" was strictly theoretical, with various candidates. One of the most successful branches of physics at this time wasstatistical physics.Schrödinger himself is one of the founding fathers ofquantum mechanics,a theory which is also very statistical in its nature.

Max Delbrück's thinking about the physical basis of life was an important influence on Schrödinger.[5]However, long before the publication ofWhat is Life?,the American geneticistHermann J. Muller,who would later win a Nobel Prize in 1946, had in his 1922 article "Variation due to Change in the Individual Gene"[6]already laid out all the basic properties of the "heredity molecule" (not yet known to be DNA) which Schrödinger re-derived in 1944 "from first principles" inWhat is Life?(including the "aperiodicity" of the molecule), properties which Muller specified and refined additionally in his 1929 article "The Gene As The Basis of Life"[7]and during the 1930s.[8]Muller himself wrote in a 1960 letter to a journalist[citation needed]regardingWhat Is Life?that whatever the book got right about the "hereditary molecule" had already been published before 1944 and that Schrödinger's were only the wrong speculations; Muller also named two famous geneticists, including Delbrück, who knew every relevant pre-1944 publication and had been in contact with Schrödinger before 1944. DNA as the molecule of heredity became foremost only afterOswald Avery's bacterial-transformation experiments published in 1944; before those experiments, proteins were considered the most likely candidates. DNA was confirmed as the molecule in question by the Hershey–Chase experimentconducted in 1952.

Content[edit]

In Chapter I, Schrödinger explains that most physical laws on a large scale are due tochaoson a small scale. He calls this principle "order-from-disorder". As an example he mentionsdiffusion,which can be modeled as a highly ordered process, but which is nevertheless caused byrandom movementof atoms or molecules. As the number of atoms is reduced, the behaviour of a system becomes increasingly random. He states that life greatly depends on order and that a naïve physicist may assume that the master code of a living organism has to consist of a large number of atoms.

In Chapter II and III, he summarizes what was known at the time about the hereditary mechanism. Most importantly, he elaborates on the rolemutationsplay in biologicalevolution.He concludes that the carrier of hereditary information has to be both small in size and permanent in time, contradicting the naïve physicist's expectation. This contradiction cannot be resolved byclassical physics.

In Chapter IV, Schrödinger presentsmolecules,which are indeed stable even if they consist of only a few atoms, as the solution. Even though molecules had long been known to exist, their stability could not be explained byclassical physicsdue to the discrete nature of quantum mechanics. Furthermore, mutations are directly linked toquantum leaps.

He continues to explain, in chapter V, that truesolids,which are also permanent, are composed of highly orderedcrystals.The stability of molecules and crystals is due to the same principles, and a molecule might be called "the germ of a solid". On the other hand, anamorphous solid,without crystalline structure, should be regarded as aliquidwith a very highviscosity.Schrödinger writes that the heredity material is likely to be a molecule, which unlike a crystal does not repeat itself. He calls this an "aperiodic crystal". Its aperiodic nature allows it to encode an almost infinite number of possibilities with a small number of atoms. He finally compares this picture with the known facts and finds it in accordance with them.

In Chapter VI, Schrödinger states:

...living matter, while not eluding the "laws of physics" as established up to date, is likely to involve "other laws of physics" hitherto unknown, which however, once they have been revealed, will form just as integral a part of science as the former.

He anticipates that this statement will be open to misconception and tries to clarify it. The main principle involved with "order-from-disorder" is thesecond law of thermodynamics,according to whichentropyonly increases in aclosed system(such as the universe). Schrödinger explains that living matter evades the decay tothermodynamical equilibriumby homeostatically maintainingnegative entropyin anopen system.

In Chapter VII, he maintains that "order-from-order" is not absolutely new to physics; in fact, it is even simpler and more plausible. But nature follows "order-from-disorder", with such exceptions as the predictable movement of thecelestial bodiesand the behaviour of mechanical devices such as clocks. Even those are influenced by thermal and frictional forces. The degree to which a system functions mechanically or randomly depends on the temperature. If sufficiently heated, a clock melts into a puddle of randomly moving molecules. Conversely, if the temperature approachesabsolute zero,any system behaves more and more mechanically. Some systems, such as clocks, approach this mechanical behaviour even at room temperature.

Schrödinger concludes this chapter and the book withphilosophicalspeculations ondeterminism,free will,and the mystery of humanconsciousness.He attempts to "see whether we cannot draw the correct non-contradictory conclusion from the following two premises: (1) My body functions as a pure mechanism according to Laws of Nature; and (2) Yet I know, by incontrovertible direct experience, that I am directing its motions, of which I foresee the effects, that may be fateful and all-important, in which case I feel and take full responsibility for them. The only possible inference from these two facts is, I think, that I – I in the widest meaning of the word, that is to say, every conscious mind that has ever said or felt 'I' – am the person, if any, who controls the 'motion of the atoms' according to the Laws of Nature". Schrödinger then states that this insight is not new and that theUpanishadsconsidered this insight of "ATMAN=BRAHMAN"to" represent quintessence of deepest insights into the happenings of the world. "Schrödinger rejects the idea that the source of consciousness should perish with the body because he finds the idea" distasteful ". He also rejects the idea that there are multiple immortal souls that can exist without the body because he believes that consciousness is nevertheless highly dependent on the body. Schrödinger writes that, to reconcile the two premises,

"The only possible alternative is simply to keep to the immediate experience that consciousness is a singular of which the plural is unknown; that there is only one thing and that what seems to be a plurality is merely a series of different aspects of this one thing…:

Any intuitions that consciousness is plural, he says, are illusions. Schrödinger is sympathetic to theHinduconcept ofBrahman,by which each individual's consciousness is only a manifestation of aunitary consciousnesspervading theuniverse— which corresponds to the Hindu concept of God. Schrödinger concludes that "...'I' am the person, if any, who controls the 'motion of the atoms' according to the Laws of Nature." However, he also qualifies the conclusion as "necessarily subjective" in its "philosophical implications". In the final paragraph, he points out that what is meant by "I" is not the collection of experienced events but "namely the canvas upon which they are collected." If a hypnotist succeeds in blotting out all earlier reminiscences, he writes, there would be no loss of personal existence — "Nor will there ever be."[9]

Schrödinger's "paradox"[edit]

See also:Entropy and life

In a world governed by thesecond law of thermodynamics,allisolated systemsare expected to approach a state of maximum disorder orentropy:an irreversible state ofthermodynamic equilibrium,wherefree energyis no longer available to dowork.It has been argued that, since life approaches and maintains a highly ordered state, it violates the aforementioned second law, implying that there is a paradox. However, since thebiosphereis not an isolated system, there is no paradox. The increase of order inside an organism is more than paid for by an increase in disorder outside this organism by the loss of heat into the environment. By this mechanism, the second law is obeyed, and life maintains a highly ordered state, which it sustains by causing a net increase in disorder in the Universe. In order to increase the complexity on Earth—as life does—free energy is needed, and in this case is provided by the Sun.[10][11]

Editions[edit]

See also[edit]

References[edit]

  1. ^abMargulis, Lynn.&Sagan, Dorion.(1995).What Is Life?(pg. 1). Berkeley: University of California Press.
  2. ^Watson, James D.(2007),Avoid Boring People: (Lessons from a life in science),New York: Knopf, p.353,ISBN978-0-375-41284-4.Page 28 details how Watson came to appreciate the significance of the gene.
  3. ^Julian F. Derry (2004)."Book Review:What Is Life?By Erwin Schrödinger ".Human Nature Review.Retrieved2007-07-15.
  4. ^"Erwin Schrödinger in Dublin: Physicist, womaniser, fugitive".The Irish Times.Retrieved2022-12-15.
  5. ^Dronamraju KR (November 1999)."Erwin Schrödinger and the origins of molecular biology".Genetics.153(3): 1071–6.doi:10.1093/genetics/153.3.1071.PMC1460808.PMID10545442.
  6. ^Muller, Hermann Joseph (1922)."Variation due to change in the individual gene"(PDF).The American Naturalist.56(642). Electronic Scholarly Publishing Project (1996): 32–50.doi:10.1086/279846.S2CID31573243.Retrieved3 January2021.
  7. ^Proceedings of the International Congress of Plant Sciences 1 (1929)
  8. ^Schwartz, James (2008).In Pursuit of the Gene. From Darwin to DNA.Cambridge: Harvard University Press.ISBN978-0-674-02670-4.
  9. ^Schrödinger referencesThe Perennial PhilosophybyAldous Huxleyas a "beautiful book" leveling with the view he has taken in the last chapter.
  10. ^What is Life?p. 91
  11. ^The Entropy Law and the Economic ProcessNicholas Georgescu-Roegen p. 11

External links[edit]

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