rmans。”
as it was； the europeans had their hands full trying to understand the strange behavior ofthe electron。 the principal problem they faced was that the electron sometimes behaved like aparticle and sometimes like a wave。 this impossible duality drove physicists nearly mad。 forthe next decade all across europe they furiously thought and scribbled and offered petinghypotheses。 in france； prince louis…victor de broglie； the scion of a ducal family； found thatcertain anomalies in the behavior of electrons disappeared when one regarded them as waves。
the observation excited the attention of the austrian erwin schr？dinger； who made some deftrefinements and devised a handy system called wave mechanics。 at almost the same time thegerman physicist werner heisenberg came up with a peting theory called matrixmechanics。 this was so mathematically plex that hardly anyone really understood it；including heisenberg himself （“i do not even know what a matrix is ；” heisenberg despairedto a friend at one point）； but it did seem to solve certain problems that schr？dinger’s wavesfailed to explain。 the upshot is that physics had two theories； based on conflicting premises；that produced the same results。 it was an impossible situation。
finally； in 1926； heisenberg came up with a celebrated promise； producing a newdiscipline that came to be known as quantum mechanics。 at the heart of it was heisenberg’suncertainty principle； which states that the electron is a particle but a particle that can bedescribed in terms of waves。 the uncertainty around which the theory is built is that we canknow the path an electron takes as it moves through a space or we can know where it is at agiven instant； but we cannot know both。
3any attempt to measure one will unavoidably3there is a little uncertainty about the use of the word uncertainty in regard to heisenbergs principle。 michaelfrayn； in an afterword to his play copenhagen； notes that several words in german…unsicherheit； unscharfe；unbestimmtheit…have been used by various translators； but that none quite equates to the english uncertainty。
frayn suggests that indeterminacy would be a better word for the principle and indeterminability would be betterstill。
disturb the other。 this isn’t a matter of simply needing more precise instruments； it is animmutable property of the universe。
what this means in practice is that you can never predict where an electron will be at anygiven moment。 you can only list its probability of being there。 in a sense； as dennis overbyehas put it； an electron doesn’t exist until it is observed。 or； put slightly differently； until it isobserved an electron must be regarded as being “at once everywhere and nowhere。”
if this seems confusing； you may take some fort in knowing that it was confusing tophysicists； too。 overbye notes： “bohr once mented that a person who wasn’t outraged onfirst hearing about quantum theory didn’t understand what had been said。” heisenberg； whenasked how one could envision an atom； replied： “don’t try。”
so the atom turned out to be quite unlike the image that most people had created。 theelectron doesn’t fly around the nucleus like a planet around its sun； but instead takes on themore amorphous aspect of a cloud。 the “shell” of an atom isn’t some hard shiny casing； asillustrations sometimes encourage us to suppose； but simply the outermost of these fuzzyelectron clouds。 the cloud itself is essentially just a zone of statistical probability marking thearea beyond which the electron only very seldom strays。 thus an atom； if you could see it；would look more like a very fuzzy tennis ball than a hard…edged metallic sphere （but not muchlike either or； indeed； like anything you’ve ever seen； we are； after all； dealing here with aworld very different from the one we see around us）。
it seemed as if there was no end of strangeness。 for the first time； as james trefil has put it；scientists had encountered “an area of the universe that our brains just aren’t wired tounderstand。” or as feynman expressed it； “things on a small scale behave nothing like thingson a large scale。” as physicists delved deeper； they realized they had found a world where notonly could electrons jump from one orbit to another without traveling across any interveningspace； but matter could pop into existence from nothing at all—“provided；” in the words ofalan lightman of mit； “it disappears again with sufficient haste。”
perhaps the most arresting of quantum improbabilities is the idea； arising from wolfgangpauli’s exclusion principle of 1925； that the subatomic particles in certain pairs； even whenseparated by the most considerable distances； can each instantly “know” what the other isdoing。 particles have a quality known as spin and； according to quantum theory； the momentyou determine the spin of one particle； its sister particle； no matter how distant away； willimmediately begin spinning in the opposite direction and at the same rate。
it is as if； in the words of the science writer lawrence joseph； you had two identical poolballs； one in ohio and the other in fiji； and the instant you sent one spinning the other wouldimmediately spin in a contrary direction at precisely the same speed。 remarkably； thephenomenon was proved in 1997 when physicists at the university of geneva sent photonsseven miles in opposite directions and demonstrated that interfering with one provoked aninstantaneous response in the other。
things reached such a pitch that at one conference bohr remarked of a new theory that thequestion was not whether it was crazy； but whether it was crazy enough。 to illustrate thenonintuitive nature of the quantum world； schr？dinger offered a famous thought experimentin which a hypothetical cat was placed in a box with one atom of a radioactive substanceattached to a vial of hydrocyanic acid。 if the particle degraded within an hour； it would triggera mechanism that would break the vial and poison the cat。 if not； the cat would live。 but we could not know which was the case； so there was no choice； scientifically； but to regard thecat as 100 percent alive and 100 percent dead at the same time。 this means； as stephenhawking has observed with a touch of understandable excitement； that one cannot “predictfuture events exactly if one cannot even measure the present state of the universe precisely！”
because of its oddities； many physicists disliked quantum theory； or at least certain aspectsof it； and none more so than einstein。 this was more than a little ironic since it was he； in hisannus mirabilis of 1905； who had so persuasively explained how photons of light couldsometimes behave like particles and sometimes like waves—the notion at the very heart of thenew physics。 “quantum theory is very worthy of regard；” he observed politely； but he reallydidn’t like it。 “god doesn’t play dice；” he said。
4einstein couldn’t bear the notion that god could create a universe in which some thingswere forever unknowable。 moreover； the idea of action at a distance—that one particle couldinstantaneously influence another trillions of miles away—was a stark violation of the specialtheory of relativity。 this expressly decreed that nothing could outrace the speed of light andyet here were physicists insisting that； somehow； at the subatomic level； information could。
（no one； incidentally； has ever explained how the particles achieve this feat。 scientists havedealt with this problem； according to the physicist yakir aharanov； “by not thinking aboutit。”）above all； there was the problem that quantum physics introduced a level of untidiness thathadn’t previously existed。 suddenly you needed two sets of laws to explain the behavior ofthe universe—quantum theory for the world of the very small and relativity for the largeruniverse beyond。 the gravity of relativity theory was brilliant at explaining why planetsorbited suns or why galaxies tended to cluster； but turned out to have no influence at all at theparticle level。 to explain what kept atoms together； other forces were needed； and in the1930s two were discovered： the strong nuclear force and weak nuclear force。 the strong forcebinds atoms together； it’s what allows protons to bed down together in the nucleus。 the weakforce engages in more miscellaneous tasks； mostly to do with controlling the rates of certainsorts of radioactive decay。
the weak nuclear force； despite its name； is ten billion billion billion times stronger thangravity； and the strong nuclear force is more powerful still—vastly so； in fact—but theirinfluence extends to only the tiniest distances。 the grip of the strong force reaches out only toabout 1/100；000 of the diameter of an atom。 that’s why the nuclei of atoms are so pactedand dense and why elements with big； crowded nuclei tend to be so unstable： the strong forcejust can’t hold on to all the protons。
the upshot of all this is that physics ended up with two bodies of laws—one for the worldof the very small； one for the universe at large—leading quite separate lives。 einstein dislikedthat； too。 he devoted the rest of his life to searching for a way to tie up these loose ends byfinding a grand unified theory； and always failed。 from time to time he t