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第1页InNamibia,aboutone-quarterofchildrenhavestuntedgrowthrelatedtopoornutrition;about120,000childrenhavelostoneorbothparents,predominantlytoHIV/AIDS,and26%ofallwomenaged15to49havehadatleastonechilddie.Livingmoresanitarilymayhaveincreasedasthma,butintermsofscaleandimpact,that'stinycomparedwiththebenefitofnotdyingfromdiseaseforlackofhygiene,saysMichaelBell,aninfectiousdiseasespecialistanddeputydirectorofHealthcareQualityPromotionattheCentersforDiseaseControlandPrevention.Somescientistsaresearchingforwaystoharnesstheimmune-primingeffectsofmicroorganismswithoutthefataldiseases.Parasiticwormsknownashelminthesareleadingtheway.ClinicaltrialsareunderwayintheU.S.andEuropetestingTrichurisSuisOva(TSO)—-aspeciesofpigwhipworm—asatreatmentforpeanutallergies,ulcerativecolitis,Crohn'sdiseaseandMS.Astudyisbeingdesignedtotestitwithasthma.It'salsobeingtestedwithadultswhohaveautism,whichsomeresearchersbelievecouldberelatedtoimmunologicalfunction.EnlargeImageCloseChinaPhotos/GettyImagesAvendor'sbabysitsamidthechickensatamarketinWuhan,HubeiProvince,China.Preliminarystudiesseempromising:Inone,when29patientswithCrohn'sdisease,adisorderofthedigestivetract,weregivenTSOeverythreeweeksforsixmonths,symptomsimprovedin21ofthemwithnoadversesideeffects.Theovaaresuspendedinaliquid,invisibletothenakedeye.There'snotaste,nothingtofeel,saysDr.Weinstock,oneoftheearlydeveloperswhocouldshareintheproceedsifTSOprovessuccessful.Themicroscopiceggshatchintomicroscopicwhipwormsinthegastrointestinaltract,whichinteractwiththehost'simmunesystemandcandampenanoveractiveimmuneresponse,heexplains.Todate,therehavebeenfewsideeffects,hesays.Asfarasweknow,thisagentdoesn'tcausediarrhea,headds.Nothingcrawlsoutofyou.Forthosewhofeartheickfactor,Dr.Weinstocknotesthatevenundernormalconditions,peopleareteemingwithmicroorganisms,whichoutnumberhumancellsbyabout10to1,manyofwhicharenecessaryforhumanhealth.Manyfoods—fromyogurttocheesetobread—alsocontainlivebacteriaandfungi.Somedailyproductsnowwidelyadvertisethattheycontainprobiotics,orgoodbacteria.Butmostimmunologistssaythatthoseinfoodproductshavenotbeensufficientlystudiedorstandardizedtodrawscientificconclusionsaboutwhathealthbenefitstheyprovide.Scientistsarestillworkingonwaystoseparategoodgermsfrombadones;inthemeantime,theyhaveafewinsights:Studieshaveshownthatchildrenwhogrowupwithhouseholdpetshavefewerallergiesandlessasthmathanthosewhodon't.TheCDC'sDr.Bellsaysthatpeopleshouldbevigilantaboutwoundcaresincebacteriacancauseproblemsifitgetsintothebloodstream,andhestilladvocateshand-washing.Ifyou'renotdoingit10timesaday,you'reprobablynotdoingitenough,hesays.Butheandotherexpertssaythatregularsoapandwaterarefineinmostcases.Sterilizinghandsis第2页criticalmainlyforhealth-careworkersandinhospitals,wheredisease-causinggermsareprevalentandcaneasilyspread.Manyexpertsadvisecommonsense.Wedon'twanttosaytochildren,'OK,playbythedirtyriverbankandcatchwhateveryoucan,'saysDr.Weinstock.Butwecansaythere'snothingwrongwithkidsplayinginthedirt.Theydon'thavetoliveintotalsanitation,andtheywon'tdiefromeatingsomethingoffthefloor.It'sprobablymorehealthythannot.第3页Allyouneedisawormhole,theLargeHadronColliderorarocketthatgoesreally,reallyfast1Hello.MynameisStephenHawking.Physicist,cosmologistandsomethingofadreamer.AlthoughIcannotmoveandIhavetospeakthroughacomputer,inmymindIamfree.Freetoexploretheuniverseandaskthebigquestions,suchas:istimetravelpossible?Canweopenaportaltothepastorfindashortcuttothefuture?Canweultimatelyusethelawsofnaturetobecomemastersoftimeitself?1'Timetravelwasonceconsideredscientificheresy.Iusedtoavoidtalkingaboutitforfearofbeinglabelledacrank.ButthesedaysI'mnotsocautious.Infact,I'mmorelikethepeoplewhobuiltStonehenge.I'mobsessedbytime.IfIhadatimemachineI'dvisitMarilynMonroeinherprimeordropinonGalileoasheturnedhistelescopetotheheavens.PerhapsI'deventraveltotheendoftheuniversetofindouthowourwholecosmicstoryends.2Toseehowthismightbepossible,weneedtolookattimeasphysicistsdo-atthefourthdimension.It'snotashardasitsounds.Everyattentiveschoolchildknowsthatallphysicalobjects,evenmeinmychair,existinthreedimensions.Everythinghasawidthandaheightandalength.3Butthereisanotherkindoflength,alengthintime.Whileahumanmaysurvivefor80years,thestonesatStonehenge,forinstance,havestoodaroundforthousandsofyears.Andthesolarsystemwilllastforbillionsofyears.Everythinghasalengthintimeaswellasspace.Travellingintimemeanstravellingthroughthisfourthdimension.4Toseewhatthatmeans,let'simaginewe'redoingabitofnormal,everydaycartravel.Driveinastraightlineandyou'retravellinginonedimension.Turnrightorleftandyouaddtheseconddimension.Driveupordownatwistymountainroadandthataddsheight,sothat'stravellinginallthreedimensions.ButhowonEarthdowetravelintime?Howdowefindapaththroughthefourthdimension?5Let'sindulgeinalittlesciencefictionforamoment.Timetravelmoviesoftenfeatureavast,energy-hungrymachine.Themachinecreatesapaththroughthefourthdimension,atunnelthroughtime.Atimetraveller,abrave,perhapsfoolhardyindividual,preparedforwhoknowswhat,stepsintothetimetunnelandemergeswhoknowswhen.Theconcep