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.Leafing through a math book, his eyewas caught by an esoteric nineteenth-century mathematical func-tion devised by mathematician Leonhard Euler.Veneziano sawthat the Euler beta function, as it is called, seemed to describemany of the strong reactions among elementary particles.Thiswas the starting point for an entirely new way of looking at theuniverse.Quantum physics was running into all kind of prob-lems at the time, and younger physicists quickly became inter-ested in this fresh theoretical direction.Bit by bit, additionalaspects of what would become string theory began to emergethroughout the 1970s.There appeared to be a lack of internalconsistency in the material, however, and it was not until JohnSchwarz of the California Institute of Technology and MichaelGreen of Queen Mary s College in London were able to show in1984 that self-consistency was attainable that string theory trulytook off.What are strings? They are entities that vibrate throughoutthe universe, everywhere, so infinitesimal that it takes 10 millionbillion of them to make up a quark which is itself so small wecan only infer its existence from experiments.We are going downto a level that underlies the subatomic world of quantum physics,a realm of activity so infinitesimal that the word  micro seemsutterly inadequate.Some readers may be reminded here of themedieval debates about how many angels can dance on the headof a pin, or of the Henry Hasse short story recounted in chapter19, in which a scientist disappears into a tabletop and reappears asa giant in Lake Erie.Many eminent physicists had the same initialreaction and some are still very dubious.c20.qxd 6/19/01 2:32 PM Page 200200 UNSOLVED MYSTERIES OF SCIENCEString theory does have something important going for it,however.The intractable problem of how to work the gravita-tional force into quantum physics disappears.It doesn t simplyprovide a formula that unites the two, either.String theory insiststhat gravity must exist.Indeed, Edward Witten, the acknowl-edged leader of the string-theory contingent, goes further:  Stringtheory has the remarkable property of predicting gravity. BrianGreene explains what is meant by this:  Both Newton and Ein-stein developed theories of gravity because their observations ofthe world clearly showed them that gravity exists, and that, there-fore, it required an accurate and consistent explanation.On thecontrary, a scientist studying string theory even if he or she wascompletely unaware of general relativity would be inexorablyled to it by the string framework.Even Greene, a major backer of string theory, sees a problemhere, noting that because we already know all about gravity, stringtheory s prediction of it is more of a  postdiction. Given that themathematics used in elucidating string theory are new in them-selves, and that mathematics in general can be forced to desiredconclusions (corporations and governments do it all the time),there was considerable resistance to Witten s sense of triumph inthis regard.Even so, the fact that string theory united gravitywith the other three fundamental forces (the electromagnetic andthe strong and weak nuclear forces) with relative ease certainlyput it one up on quantum theory.Still, there is the matter of those extra dimensions.Stringtheory, it was quickly apparent, demanded the existence of anadditional 6 spatial dimensions beyond the 3 we are conversantwith in our daily lives.When Einstein s dimension of time isadded, that produced a total of 10 dimensions a nice round num-ber.These additional dimensions, like the vibrating subsubatomicstrings, were of course invisible to us and destined to stay thatway until our technology catches up.Edward Witten has alsosaid that string theory is twenty-first-century science that was dis-covered too soon for it to be proved with our existing means ofinvestigation.This, too, can sound convenient, but it should beremembered that Charles Babbage had laid down all the funda-mental laws of computing by 1830, but because he was stuck withc20.qxd 6/19/01 2:32 PM Page 201How Many Dimensions Are There? 201the entirely inadequate technology of punch cards, his work wasforgotten for more than a hundred years.Scientific theory oftendoes get ahead of the level of technology available to eitherimplement or prove it.Nevertheless, it must be asked what things look like in thisinfinitesimal world with 10 dimensions.The string theorists haveanswers to that, up to a point.Throughout The Elegant Universe,there are illustrations that attempt to depict what are called Calabai-Yau spaces [ Pobierz całość w formacie PDF ]