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verse that had a beginning。 it mighttherefore also have an end。
the wonder； as stephen hawking has noted； is that no one had hit on the idea of theexpanding universe before。 a static universe； as should have been obvious to newton andevery thinking astronomer since； would collapse in upon itself。 there was also the problemthat if stars had been burning indefinitely in a static universe they鈥檇 have made the wholeintolerably hot鈥攃ertainly much too hot for the likes of us。 an expanding universe resolvedmuch of this at a stroke。
hubble was a much better observer than a thinker and didn鈥檛 immediately appreciate thefull implications of what he had found。 partly this was because he was woefully ignorant ofeinstein鈥檚 general theory of relativity。 this was quite remarkable because； for one thing；einstein and his theory were world famous by now。 moreover； in 1929 albert michelson鈥攏ow in his twilight years but still one of the world鈥檚 most alert and esteemed scientists鈥攁ccepted a position at mount wilson to measure the velocity of light with his trustyinterferometer； and must surely have at least mentioned to him the applicability of einstein鈥檚theory to his own findings。
at all events； hubble failed to make theoretical hay when the chance was there。 instead； itwas left to a belgian priest…scholar （with a ph。d。 from mit） named georges lema？tre tobring together the two strands in his own 鈥渇ireworks theory；鈥潯hich suggested that theuniverse began as a geometrical point； a 鈥減rimeval atom；鈥潯hich burst into glory and hadbeen moving apart ever since。 it was an idea that very neatly anticipated the modernconception of the big bang but was so far ahead of its time that lema？tre seldom gets morethan the sentence or two that we have given him here。 the world would need additionaldecades； and the inadvertent discovery of cosmic background radiation by penzias and wilsonat their hissing antenna in new jersey； before the big bang would begin to move frominteresting idea to established theory。
neither hubble nor einstein would be much of a part of that big story。 though no onewould have guessed it at the time； both men had done about as much as they were ever goingto do。
in 1936 hubble produced a popular book called the realm of the nebulae； whichexplained in flattering style his own considerable achievements。 here at last he showed thathe had acquainted himself with einstein鈥檚 theory鈥攗p to a point anyway： he gave it four pagesout of about two hundred。
hubble died of a heart attack in 1953。 one last small oddity awaited him。 for reasonscloaked in mystery； his wife declined to have a funeral and never revealed what she did withhis body。 half a century later the whereabouts of the century鈥檚 greatest astronomer remainunknown。 for a memorial you must look to the sky and the hubble space telescope；launched in 1990 and named in his honor。
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9 THE MIGHTY ATOM
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while einstein and hubble were productively unraveling the large…scale structure ofthe cosmos； others were struggling to understand something closer to hand but in its way justas remote： the tiny and ever… mysterious atom。
the great caltech physicist richard feynman once observed that if you had to reducescientific history to one important statement it would be 鈥渁ll things are made of atoms。鈥潯heyare everywhere and they constitute every thing。 look around you。 it is all atoms。 not just thesolid things like walls and tables and sofas； but the air in between。 and they are there innumbers that you really cannot conceive。
the basic working arrangement of atoms is the molecule （from the latin for 鈥渓ittle mass鈥潱�
a molecule is simply two or more atoms working together in a more or less stablearrangement： add two atoms of hydrogen to one of oxygen and you have a molecule of water。
chemists tend to think in terms of molecules rather than elements in much the way thatwriters tend to think in terms of words and not letters； so it is molecules they count； and theseare numerous to say the least。 at sea level； at a temperature of 32 degrees fahrenheit； onecubic centimeter of air （that is； a space about the size of a sugar cube） will contain 45 billionbillion molecules。 and they are in every single cubic centimeter you see around you。 thinkhow many cubic centimeters there are in the world outside your window鈥攈ow many sugarcubes it would take to fill that view。 then think how many it would take to build a universe。
atoms； in short； are very abundant。
they are also fantastically durable。 because they are so long lived； atoms really get around。
every atom you possess has almost certainly passed through several stars and been part ofmillions of organisms on its way to being you。 we are each so atomically numerous andso vigorously recycled at death that a significant number of our atoms鈥攗p to a billion foreach of us； it has been suggested鈥攑robably once belonged to shakespeare。 a billion moreeach came from buddha and genghis khan and beethoven； and any other historical figureyou care to name。 （the personages have to be historical； apparently； as it takes the atomssome decades to bee thoroughly redistributed； however much you may wish it； you arenot yet one with elvis presley。）so we are all reincarnations鈥攖hough short…lived ones。 when we die our atoms willdisassemble and move off to find new uses elsewhere鈥攁s part of a leaf or other human beingor drop of dew。 atoms； however； go on practically forever。 nobody actually knows how longan atom can survive； but according to martin rees it is probably about 1035years鈥攁 numberso big that even i am happy to express it in notation。
above all； atoms are tiny鈥攙ery tiny indeed。 half a million of them lined up shoulder toshoulder could hide behind a human hair。 on such a scale an individual atom is essentiallyimpossible to imagine； but we can of course try。
start with a millimeter； which is a line this long： …。 now imagine that line divided into athousand equal widths。 each of those widths is a micron。 this is the scale of microorganisms。
a typical paramecium； for instance； is about two microns wide； 0。002 millimet