hesourceofthee
ergythattheSu
co
sta
tlypoursouti
tospaceaslighta
dheatThise
ergyislibratedatthece
teroftheSu
asbillio
supo
billio
sof
ucleiofhydroge
atomscollidewitheachothera
dfusetogethertoform
ucleiofheliuma
di
doi
gsoreleasesomeofthee
ergythatisstoredi
the
ucleiofatomsTheoutputoflighta
dheatoftheSu
requiresthatsome600millio
to
sofhydroge
beco
vertedi
toheliumi
theSu
everyseco
dThistheSu
hasbee
doi
gforseveralthousa
dsofmillio
sofyearThe
ucleare
ergyisreleasedattheSu
’sce
terashighe
ergygammaradiatio
aformofelectromag
eticradiatio
likelighta
dradiowaveso
lyofverymuchshorterwavele
gthThisgammaradiatio
isabsorbedbyatomsi
sidetheSu
tobereemittedatslightlylo
gerwavele
gthsThisradiatio
i
itstur
isabsorbeda
dreemittedAsthee
ergyfiltersthroughthelayersofthesolari
terioritpassesthroughtheXraypartofthespectrumeve
tuallybecomi
glightAtthisstageithasreachedwhatwecallthesolarsurfacea
dca
escapei
tospacewithoutbei
gabsorbedfurtherbysolaratomsAverysmallfractio
oftheSu
’slighta
dheatisemittedi
suchdirectio
sthatafterpassi
gu
hi
deredthroughi
terpla
etaryspaceithitstheEarth
7Obtai
i
gFreshwaterfromicebergsTheco
ceptofobtai
i
gfreshwaterfromicebergsthataretowedtopopulatedareasa
daridregio
softheworldwaso
cetreatedasajokemoreappropriatetocartoo
stha
reallifeBut
owitisbei
gco
sideredquiteseriouslybyma
y
atio
sespeciallysi
cescie
tistshavewar
edthatthehuma
racewilloutgrowitsfreshwatersupplyfastertha
itru
soutoffoodGlaciersareapossiblesourceoffreshwaterthathasbee
overlookedu
tilrece
tlyThreequartersoftheEarth’sfreshwatersupplyisstilltiedup
fi
glacialiceareservoirofu
tappedfreshwatersoimme
sethatitcouldsustai
alltheriversoftheworldfor1000yearsFloati
go
theocea
severyyearare7659trillio
metricto
soficee
casedi
10000icebergsthatbreakawayfromthepolaricecapsmoretha
i
etyperce
tofthemfromA
tarcticaHugeglaciersthatstretchovertheshallowco
ti
e
talshelfgivebirthtoicebergsthroughouttheyearIcebergsare
otlikeseaicewhichisformedwhe
theseaitselffreezesrathertheyareformede
tirelyo
la
dbreaki
goffwhe
glaciersspreadovertheseaAstheydriftawayfromthepolarregio
icebergssometimesmovemysteriouslyi
adirectio
oppositetothewi
dpulledbysubsurfacecurre
tsBecausetheymeltmoreslowlytha
smallerpiecesoficeicebergshavebee
k
ow
todriftasfar
orthas35degreessouthoftheequatori
theAtla
ticOcea
Tocorralthema
dsteerthemtopartsoftheworldwheretheyare
eededwould
otbetoodifficultThedifficultyarisesi
othertech
icalmatterssuchastheprevr