It ISN’t EASY being an anism. In t knopost of t ain you,and even it    be pretty grudging.

        From ttom of t o trenco top of t mountain, t covers nearly t muc against t large.

        For    is even o tion of living t took t venturesome decision 400 million years ago to cra of t of table space by volume, acc to oimate, is fually—in practicalterms pletely—off-limits to us.

        It isn’t simply t    breater, but t    bear the pressures.

        Because er is about 1,300 times ly as you desd—by t of omospeers (ty-t) of depto top of a five- eminence—CologonMo, say—t as to be indisible. At ter, o te dimensions of a Coke . Amazingly, people do voluntarily dive to suc breatus, for t in a sport knoly ternal ans rudely deformed is t exing (tpresumably as exing as urn to to reac be dragged doe briskly,by a aalk about itafteralian named Umberto Pelizzari, ,lingered for a nanosed, and t back to terrestrial terms, 236 feet isjust sligy block. So even in our most exuberantstunts ers of the abyss.

        Oto deal    depte ery. t point in trenco over sixteen to send o t depturdy divingvessel, yet it is o ies of ampype of crusta similar to stranspareion at all. Most os are of course muc even at to being squasack of fourteen loaded t trucks.

        Nearly everyone, including t t,t to be ter ourselves, and er is“virtually inpressible,” in t of Oxford Uy, “t ter, and is not crus dept is ticularly in t cause trouble. t    tal is not knoil quite retly it    t anyone diving to one ers or so    tedly proved otappears, acc to As, t “ed.”

        Plenty else    go    t ed to times experienced a dreadedpo a catastrop. t    too literally, sucked up into t and hosepipe.

        o t is left in t are his bones and ss of flesh,”

        t J. B. S. e in 1947, adding for t of doubters, “this hashappened.”

        (Ially, t, designed in 1823 by an Englisended not for diving but for fire-fig    being made of metal it o enter burning structures in any form of attire, butmost especially not in somet ed up like a kettle and made to ttempt to save ment, Dearied it underer and found it error of t so muc, t nitrogen. Put t nitrogen istransformed into tiny bubbles t migrate into tissues. If too rapidly—as oo-quick ast by a diver—trapped o fizz ily ttle of y blood vessels, depriving cells of oxygen, and causing pain so excruciating tsufferers are proo bend double in agony—he bends.”

        tional imeimmemorial but didn’t attract mution in tern il teentury, and t     at all (or at least not very    andnot generally mu riverbeds to facilitate tru e piers. ten ended period ofificial pressure toms like tingling or it uable fe more insistent pain in ts and occasionally collapsedin agony, sometimes o get up again.

        It    puzzling. Sometimes o bed feeling fine, but imes t    all. As relates a story ing tors of a neunnel uory ba as tunnelneared pletion. to ternation to fizz o tantly to fizziness, memorably enlivening tive process.

        Apart from avoiding s alties are reliablysuccessful against t is to suffer only a very s exposure to t is o dept    ill effect. t stay under long enen iodissolve into tissues. tion is to asd by careful stages. ttle bubbles of nitrogen to dissipate harmlessly.

        A great deal of    surviving at extremes is oo traordinaryfateam of Jot and J. B. S. andards ofBritisellectuals, tstandingly etric. to an aristocratic Scottis    spent mostof ive modesty as a professor of p Oxford. -minded. Oer    airs to cy o return and ime. ion o travel to o study    grandson of t. ime, parodied oucist Edantamount in t ter Point .

        to diving o    t intervals necessary to manage an astfrom t getting t erests ranged across tudying altitude siess in climbers to tstroke iregions. icular i in ts of toxic gases on touand more exactly aking and measuring    only ion level —a level, as trevor Norton notes iaining ory of diving, Stars Beionally removed from nearly certaiy.

        o posterity as J.B.S., erest in    from infancy. At t is it oxyhaemoglobin or carboxyhaemoglobin?”

        t s. By time eeeed gases and gas masks togetaking turns to see    took to pass out.

        took a degree in sce (udied classics at Oxford),    stist in , mostly in Cambridge. t PeterMedaion of    of Brave New orld.

        Among many ots, ral role in marrying Darion to tic o produce ogeicists as thesis.

        Perted t unity of killing people.”

        er te ty-tific papers). ill tructive, t alo find. ic Marxist. It ed, not altoget t of apurely trarian instinct, and t if    Union e monarc. At all events, most of icles first appeared in t Daily orker.

        erests ed miners and poisoning, tsequences of ty funding    .” tal der into imecould be sealed and subjected to tests of various types, all painful and nearly all dangerous.

        Volunteers migo sit in ice er mosped to rapid . In one experiment, ed adangerously y ast to see alfillings i every experiment,” Norton es, “ended ing.” tually soundproof, sots to signal unress o tap insistently on to es to a small window.

        On anoted levels of oxygen,    so severe t ebrae. Collapsed lungs ine hazard.

        Perforated eardrums e on, but, as ed in one of , altdeaf, one    bloobaoke out of tion, w.”

        raordinary about t t o subject osu t of sce, but t rouble talkingcolleagues and loved ones into climbing into too. Sent on a simulated dest, t lasted teen minutes.    last sopped boung acrossto    a o cook dinner. o be around, including on one memorable occasion a former primeminister of Spain, Juan Negrín. Dr. Negrín plained afteringling and “acurious velvety sensation on t oto    io feeling in tocks and lower spine for six years.

        Among ien intoxication. For reasons tare still poorly uood, be a    nitrogen bees apooxit. Us influence divers o offer topassing fiso try to    also produced est, ed, t “alternated betion, at onemoment begging to be depressed because    ‘bloody a minutelaugtempting to interfere erity test.” In order to measurete of deterioration in t, a stist o go into teer to duct simple matical tests. But after a fees, as errecalled, “tester oxicated as testee, and often fot to press topco take proper notes.” tion is even noery. It is t t it may be t causes alcooxication, but as noone knoain     all events,    test care, it is easy to get in trouble once you leave the surface world.

        o our earlier observatio tplace to be an anism, even if it is tion of t’ssurface t is dry enougo stand on, a surprisingly large amount is too    or cold or dry orsteep or lofty to be of muco us. Partly, it must be ceded, t. In terms ofadaptability, ty amazingly useless. Like most animals,    muc places, but because    so freely and easily stroke,    circumstances—on foot    er in a    desert—most peopleo rise again, in neing    but—because    keeping it. Even in quitemild o keep your body er ties to a large extent by employing cloter, but even so tions of Earto live are modest indeed: just 12 pertof total land area, and only 4 pert of the seas.

        Yet tle of our pla but t    t    of. You o look at our oem—or, e to t, Eart certainperiods in its oo appreciate t most places are muco life tery globe.

        So far space stists    seventy plas outside tem, outof ten billion trillion or so t are t to be out tospeak y on tter, but it appears t if you able forlife, you o be just aobe. Various observers ified about ticularly    till to theyare:

        Excellent location.e are, to an almost uny degree, t distance from t sortof star, o is big enougo radiate lots of energy, but not so big as to burn itself outsly. It is a curiosity of p tar t burimes as massive, it self after ten million years instead of tenbillion and    be uo orbit woo mugwould have frozen.

        In 1978, an astrop named Mic made some calculations and cluded tEartable    been just 1 pert fartcloser to t’s not muc it    enougtle menerous—5 pert nearer and 15 pert fartto be more accurate assessments for our zone of ability—but t is still a narro.

        1to appreciate just o look at Venus. Venus is only ty-fivemillion miles closer to t just tesbefore it tou, Venus is very like Eart tal distance made all to    turned out. It appears tduring tem Venus ra    t Venus could not o its surface er, rous sequences for its climate. As its er evaporated,toms escaped into space, and toms bined o forma demospifling. Altime ropical verdure,    it is mucoofier enviro for any kind of life t s surfacetemperature is a roasting 470 degrees tigrade (roug),    lead, and tmosp ty times t ofEartand. e lack teake suitsor even spaces o visit. Our knoant radar imagery and some startled squa probe t ioned for barely an ly sting down.

        So t’s o travel fart and t    but cold, as Mars frigidly attests. It, too,    retain a usable atmospurned into a frozene.

        But just being t distance from t be tory, for oted and fair, ly it is not. For t you o have:

        t kind of pla.I don’t imagine even many geops, t en interior, but it’s a pretty nearcertainty t    all t magma s be here now.

        Apart from mucerior created tgassing t o build anatmospic field t sion. Italso gave us plate teics, ly smoot o a depters.

        t be life in t lonesome o, but tainly    be baseball.

        In addition to erior, s in tproportions. In t literal    stuff. to our o discuss it more fully in a minute, but first o sidertors, beginning    is often overlooked:

        1tremops of Yelloone and similar anisms found elses realize t actually life of a type could range muc-even, pero.    alking about ions t ures.

        e’re a t.Not many of us normally t,but t is in effect    is. Most moons are tiny iion to ter plaian satellites of Pance, are only about ten kilometers indiameter. Our Mooer of t in tem o itself (exceptPluto,    because Pluto is itself so small), and makes to us.

        it teadying influeop,    sequences for climate and eady gravitationalinfluence keeps t t speed and ao provide t of stabilitynecessary for t of life. t go on forever. t a rate of about 1.5 inc     keep us steady and ion, but in time you s as muc apleasaure in t sky.

        For a long time, astronomers assumed t toget tured t drifted by. e no about 4.5 billion years ago a Mars-sized object slammed i enougerial to create t especially so as it ime ago. If it    ednesday clearly    be nearly so pleased about it. oour fourt crucial sideration:

        timing.tful place, and our existence is a s stretc played out in a particular ma particular times—if, to take justone obvious insta been    by a meteor his in a burrow.

        e don’t really ko, but it seems evident t if you ely advay,you o be at t end of a very long es involving reasonable periodsof stability interspersed    t amount of stress and cobe especially otal absence of real cataclysm. As o us, o find ourselves in t position.

        And on t note, let us nourn briefly to ts t made us.

        ty-turally    elements oy or so ted in labs, but some of tely put to one side—as, in fact,cs tend to do. Not a fetleknoatine, for instance, is practically unstudied. It able ( door to Marie Curie’s polonium), but almost not stifidifference, but rarity. t isn’t mue out telusive element of all, o be francium,    is t tour entire pla may tain, at any given moment, fey francium atoms.

        Altoget ty of turally    elements are ral importao life.

        As you mig, oxygen is our most abundant element, ating for just under 50pert of t, but after t tive abundances are often surprising. a sili is t o oitanium is teo do y or utility to us. Many of ts are actually more on tter-kno or nitrogen. tinbarely makes it into top fifty, eclipsed by sucive obscurities as praseodymium,samarium, gadolinium, and dysprosium.

        Abundance also tle to do e. Aluminum is to oing for nearly a tent’s under, but its existence    even suspected until it eenturyby ime after t it reated as rare and precious. gressnearly put a sop ton Moo s aclassy and prosperous nation e silver dinner servid replaced it ting edge even if t.

        Nor does abundanecessarily relate to importance. Carbon is only teento, ating for a very modest 0.048 pert of Eart, but     it.    sets tom apart is t it is s isty animal of tomiany otoms (including itself) andigy robustrick of naturenecessary to build proteins and DNA. As Paul Davies ten: “If it    for carbon, lifeas     of life carbon is not all t plentiful even in ally depend on it. Of every 200atoms in your body, 126 are    19 are carbon.

        2Ots are critiot for creating life but for sustaining it. e need iron tomanufacture    it    is necessary for tion ofvitamin B12. Potassium and a very little sodium are literally good for your nerves.

        Molybdenum, manganese, and vanadium o keep your enzymes purring. Zinc—bless it—oxidizes alcohol.

        e o utilize or tolerate t even tance. Selenium is vital to all of us, buttake in just a little too muc    to e certais is a relic of tion. Stleno actually    mineral requirements. Modern cattleneed quite a lot of copper because ts of Europe and Africa olerance for elements is directly proportioen and tom is divided among all ts.

        abundan t. e o expect, and in some cases actually iny amounts of rare elements t accumulate in t . But step uptiny amount, and ly uood. No one kno ofarsenic is necessary for our . Some auties say it is; some not. All t iscertain is t too muc will kill you.

        ties of ts    beore curious still whey are bined.

        Oxygen and ance, are t bustion-friendly elements around,but put togetible er.

        3Odder still in bination aresodium, one of t unstable of all elements, and c toxic. Drop asmall lump of pure sodium into ordinary er and it o kill.

        Coriously rations forkilling micranisms (it’s c is lethal.

        C of c orld ar. And,as many a sore-eyed stest, even in exceedingly dilute form t appreciate it. Yet put ty elements toget do you get? Sodiumcable salt.

        By and large, if a doesn’t naturally find its o our systems—if it isn’tsoluble in er, say—end to be i of it. Lead poisons us because o it until o fas into food vessels and pipes for plumbing. (Notially, lead’s symbol is Pb, for tin plumbum, t of t to be. As o mention mercury, cadmium, and all trial pollutants inely dose ourselves) does not leave us a great deal of room for smirking. sdon’t ocaturally oolerance for tend to beextremely toxic to us, as onium. Our tolerance for plutonium is zero: t    going to make you    to lie down.

        I    you a long o make a small point: a big part of t Earting is t o suit its ditions.     is not t it is suitable to life but t it is suitable to our life—and    may be t many of t make it so splendid to us—ioned Sun, doting Moon, sociable ore magma tick at,and all t—seem splendid simply because t o t on. Noone    altogether say.

        Otingclouds of ammonia. ted t t doesn’t ssgrinding plates or spe rats in aperma onic tranquility. Any visitors to Eart certainly, att, be bemused to find us living in an atmen, a gassulkily disined to react ial to bustion t place fire stations t our cities to protect ourselves from its livelier effects.

        But even if our visitors self is not bustible; it merely facilitates tion of ot as ible, eacime you lit a matco flame. remely    bustible, as trated on May 6, 193 inLake, Neo flame, killing ty-six people.

        aovies, it is u t even give tain traanganese, selenium, zind otalparticles at least some of o t not seem a all.

        t Riake a joke about a posteriori clusions, as t amazing to me tonige AR 357.    you imagine? Of all tes in tate,    I    particular oonight?

        Amazing!” , of course,    it is easy to make any banal situatioraordinary if you treat it as fateful.

        So it is possible t ts and ditions t led to tquite as extraordinary as o till, traordinary enougain: to do until ter.
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