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

    From ttom of t ocean 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, according to one estimate, is fundamentally—in practicalterms completely—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 descend—by t of one atmospen meters (ty-t) of depto top of a five- eminence—Cologne CatonMonument, say—t as to be indiscernible. At ter, o te dimensions of a Coke can. Amazingly, people do voluntarily dive to suc breatus, for t in a sport knoly ternal organs rudely deformed is t exing (tpresumably as exing as urn to to reac be dragged doe briskly,by ance, t anyone o talk about itafteralian named Umberto Pelizzari, ,lingered for a nanosecond, 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 colonies of ampype of crustacean similar to stransparent, ection at all. Most oceans are of course muc even at to being squasack of fourteen loaded cement trucks.

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

    Plenty else can 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 some rags of flesh,”

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

    (Incidentally, 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, Deane tried 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 ascent by a diver—trapped o fizz in exactly ttle of ciny blood vessels, depriving cells of oxygen, and causing pain so excruciating tsufferers are prone to bend double in agony—he bends.”

    tional imeimmemorial but didn’t attract muctention in tern il teentury, and t   at all (or at least not very  andnot generally muc on riverbeds to facilitate truction of bridge piers. ten ended period ofificial pressure toms like tingling or itc an unpredictable fe more insistent pain in ts and occasionally collapsedin agony, sometimes never to get up again.

    It  puzzling. Sometimes o bed feeling fine, but imes t  all. As relates a story concerning tors of a neunnel under tory banquet as tunnelneared completion. to ternation to fizz o tantly to fizziness, memorably enlivening tive process.

    Apart from avoiding s altogetrategies are reliablysuccessful against t is to suffer only a very s exposure to t is o dept  ill effect. t stay under long enougrogen in tem todissolve into tissues. tion is to ascend 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 eccentric. to an aristocratic Scottis  spent mostof ive modesty as a professor of p Oxford. -minded. Once after  airs to cy o return and ime. ion o travel to Corno study  grandson of t. ime, parodied oucist Edantamount in t Counter Point .

    to diving o  t intervals necessary to manage an ascentfrom t getting t erests ranged across tudying altitude sickness in climbers to tstroke in desertregions. icular interest in ts of toxic gases on tounderstand more exactly aking and measuring  only ion level —a level, as trevor Norton notes in ertaining ory of diving, Stars Beneationally removed from nearly certain lety.

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

    t s. By time eenager, ten tested gases and gas masks togetaking turns to see  took to pass out.

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

    Among many ots, ral role in marrying Darion to tic o produce ogeneticists 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 contrarian instinct, and t if  Union e monarc. At all events, most of icles first appeared in t Daily orker.

    erests concerned miners and poisoning, tconsequences of ty funding  .” tal cylinder 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 cion. In one experiment, ed adangerously y ascent to see alfillings in eet 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 common, but, as ed in one of , altdeaf, one can bloobacco smoke out of tion, w.”

    raordinary about t t o subject osuc in t of science, but t rouble talkingcolleagues and loved ones into climbing into too. Sent on a simulated descent, t lasted teen minutes.  last sopped bouncing acrossto  and sent o cook dinner. o be around, including on one memorable occasion a former primeminister of Spain, Juan Negrín. Dr. Negrín complained afteringling and “acurious velvety sensation on t oto  ion left feeling in tocks and lower spine for six years.

    Among ions rogen intoxication. For reasons tare still poorly understood, beneat a  nitrogen becomes apooxicant. Under its influence divers o offer topassing fiso try to  also produced est, ed, t “alternated betion, at onemoment begging to be decompressed because  ‘bloody a minutelaugtempting to interfere erity test.” In order to measurete of deterioration in t, a scientist o go into teer to conduct simple matical tests. But after a fees, as errecalled, “tester oxicated as testee, and often forgot 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 observation t Eart tplace to be an organism, 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 conceded, 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 no more tgenerating  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 percentof total land area, and only 4 percent of the seas.

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

    So far space scientists  seventy planets 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 uncanny degree, t distance from t sortof star, one t is big enougo radiate lots of energy, but not so big as to burn itself outsly. It is a curiosity of p tar t burns. en times as massive, it self after ten million years instead of tenbillion and  be unate to orbit woo muchingwould have frozen.

    In 1978, an astrop named Mic made some calculations and concluded tEartable  been just 1 percent fartcloser to t’s not muc it  enougtle more generous—5 percent nearer and 15 percent 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 toucion, 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 consequences for its climate. As its er evaporated,toms escaped into space, and toms combined o forma dense atmospifling. Altime ropical verdure,  it is mucoofierce an environment for any kind of life t s surfacetemperature is a roasting 470 degrees centigrade (roug),  lead, and tmosp ty times t ofEartand. e lack teco make 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 need to have:

    t kind of planet.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 tectonics, ly smoot o a depters.

    t be life in t lonesome ocean, 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 considertors, beginning  is often overlooked:

    1tremops of Yelloone and similar organisms 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 in relation to ter planet. tian satellites of Pance, are only about ten kilometers indiameter. Our Moon, er ter of t in tem o itself (exceptPluto,  because Pluto is itself so small), and makes to us.

    it teadying influence, top,  consequences for climate and eady gravitationalinfluence keeps t t speed and angle to 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 apleasant feature 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 into Eart enougerial to create t especially so as it ime ago. If it  ednesday clearly  be nearly so pleased about it. oour fourt crucial consideration:

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

    e don’t really knoenceto, but it seems evident t if you ely advanced, ty,you need to be at t end of a very long ccomes 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 occurring elements on Earty 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 (next door to Marie Curie’s polonium), but almost not scientific indifference, but rarity. t isn’t mucatine out telusive element of all, o be francium,  is t tour entire planet may contain, at any given moment, fey francium atoms.

    Altoget ty of turally occurring elements are ral importance to life.

    As you mig, oxygen is our most abundant element, accounting for just under 50percent of t, but after t tive abundances are often surprising. ance, t silicon is t common element on Earttitanium is tenttle to do y or utility to us. Many of ts are actually more common 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 ection. Aluminum is tcommon element on Earting for nearly a tent’s underneat, but its existence  even suspected until it eenturyby ime after t it reated as rare and precious. Congressnearly put a sop ton Monument to s aclassy and prosperous nation e silver dinner service and replaced it ting edge even if t.

    Nor does abundance necessarily relate to importance. Carbon is only teentcommon element, accounting for a very modest 0.048 percent of Eart, but   it.  sets tom apart is t it is s isty animal of tomic co many otoms (including itself) andigy robustness—trick 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 critical not 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 certain elements 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 proportionate to trogen and tom is divided among all ts.

    abundance in t. e o expect, and in some cases actually need,tiny amounts of rare elements t accumulate in t . But step uptiny amount, and ly understood. 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 can become more curious still whey are combined.

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

    3Odder still in combination 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 microorganisms (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 an element doesn’t naturally find its o our systems—if it isn’tsoluble in er, say—end to be intolerant of it. Lead poisons us because o it until o fas into food vessels and pipes for plumbing. (Notincidentally, 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 occur naturally on Eartolerance 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 conditions.   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 carbon, more magma tick at,and all t—seem splendid simply because t o count on. Noone can altogether say.

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

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

    action movies, it is unlikely t t even give tain traces of manganese, selenium, zinc, and otalparticles at least some of o t not seem a all.

    t Rico make a joke about a posteriori conclusions, as t amazing to me tonige AR 357. Can you imagine? Of all tes in tate,  I  particular one tonight?

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

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