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How Cosmology
Became a
id the unverse begi, or bas it
always exsted? Sdentists long
regarded ths question as lyig
outside thei concer in the metaphysical
real of phiosophers and theolo-
gian. Not unti the middle of ths centu
did physidsts and astronomers
begi to equp themselves with theories
power enough and exerental
techques senitive enough to address
the issue.
Two competig cosmologies then
emerged. One, popularly caled the big
ban, assues tht the unerse evolved
from inti conditions so hot and dene
tht only radiation and elementar particles
could exst; the unverse then expanded
and cooled, predpitati the
star and galaxes. The opposing model
offers a unverse that has always exsted;
the dispersal of matter resultig
from the observed exanion of the
unerse is compenated by the contiuous
creation of matter.
The big bang theory bas prevaed
largely because of the prediction, observation
and interretation of a phenomenon
known as the cosmic background
radiation. Ths radiation, widely
regarded as the afterglow of the big
Science
The discovery of the cosmic microwave background
in the 1960s established the 'big bang theory
and made cosmology into an empirical science
STHEN G. BRUSH has taught the hitory
of sdence at the Uniersity of Marland
at College Park since 1968. Before
tht he conducted research in theoretical
physics at Lawrence Uverore Laboratory
and helped to wrte the tex for a
school physics coure developed at
hi
Hard University. He has wrtten
the development of the kietic theory
of gases, the origi of the solar system
and other topics in the history of moder
physical sdence. He is spendi the
1992-93 academc year at the Institute
for Advanced Study in Prceton, N.J.,
an how empircal tests afect sdentists'
choice of theories.
SCIC AMCA Augus 1992
by Stephen G. Brush
bang, suses the sky in al diections
at micrwave frequendes. Aro A. Penzias
and Rober W. Wilon of Bel laboratories
discovered the cosmic back-
ground in 1964-65 whie tr to
rid
thei radio anten of micrwave noise.
The steady state model of the unverse
predicted no such radiation and could
not plausibly account for it. Thus, for
the fist tie, hypotheses about the origi
of the cosmos bad faced an empircal
test tht left wier and a loser.
Rarely do theories stand or fal on
the outcome of a sine test. Th tie,
however, opinon shited alost overnit.
With a few year, most cosmologits
had either adopted the big bang
theory or ceased publihi in the field
Pens and Wilon won the Nobel Pre
in Physics in 1978 for their achevement.
Just ths past Apri, measurements
of miuscue varations in the
backound radition vidicated another
predicton of the big ban theory.
Yet no one could have appredated
the signcance of the cosmic microwave
backound without the legacy of
knowledge tht may other sdentists
bad been buidi thougout the centu.
The history of the discover yields
another kid of inight. By followi
the story past 1965 to see how the discover
afected the standig of rival
cosmological theories, we can test competi
ideas about the natue of scientic
progress.
Big ban cosmology began to come
into foc in the 1930s, after Edwi P.
Hubble, the ement Amercan astronomer,
showed tht galaxes appear
recede from one another and that the
most distant ones recede at the greatest
rate. Hubble fidi implies tht
the unverse is exandig. it was also
interreted to imply tht the cosmos
had once been concentrated in a ver
sma space at a defte tie. Alexander
A. Friedman, a Russia physidst,
and Georges Lemaitre, a Belgian priest,
each used Al Eitei' s general theory
of relatity to descre how such
an exandi unverse might evolve.
Nuclear physics played a role by providig
the tools with which to model
the sythesis of the elements frm fudamental
parcles. Those tools sered
not only George Gamow, chpion of
the big bang, and his colleagues Raph
A Alpher and Rober Heran but also
Fred Hoyle then at the University of
Camridge-who favored the rival '
steady state theory.
Vital to the theoretical work was the
COSMC AUDITRS Amo A. Pen.
(left) and Rob W. Win (riht) of Bej'
Laboratories pose on the micrwave.
horn anten (show on this page) tht .
fit cupped an ea to the big ba. '
contrl
Planck :
centu
of blad
gets its
er
tion ani
diated E
spect
ter pI
priOl!
would I
perect
radiatic
plosioD
the blal
Sti t
cuatioJ
patter

contrbution that Eistei and Max
Planck made around the tu of the
centu whie formulati the physics
of blackody radiation. The blackbody
gets its. name from its idealed propert
of absorbin al incomig radiation
and then reradiatig it. This reradiated
energy is distrbuted across the
spect in a high chacterstic patter
predicted by Planck. Because the
priordial fiebal, in its early phases,
would bave put energy and matter into
perfect thermal equbrium the fist
radiation liberated from the cooli explosion
would bave to have displayed
the blackody patter
Sti to be supplied was a predse calcuation
of how energetic that spectral
patter would appear today, many bil-
lions of years afer the fiebal began to
exand and cool. Wht was the temperatue
of the radiation in space? An answer
to that question could come only
after sdentists developed a quantitative
theory of the evolution of the fie-
bal after the big bang.
. The development of th quantitative
theory began with Gamow, a Russianborn
physicist who bad made his reputation
by exlai radioacte decay.
In the 1930s he came to the U.S., teachin
fist at George Washigton Uniersity
and then at the University of Colorado.
At George WasbIon, he concentrated
on the astrophysical and cosmological
as of nuclea reactonsabove
al the mechms by which the
fit elements bad bee sythesized.
Gamow looked for his answer at
both ends of the cosmic scale. In the
early 1930s astronomers showed tht
most stars were composed predominantly
of hydrogen andhelwn It was
reasonable to assue tht hydrogen
was the fist element to form because
its nucleus contai but sie proton
and tht hel-the nex heaviest element,
whose nucleus contai two protons
and two neutrons-was the fist
higher" element formed by the fusion
of hydrogen But protons wi fuse onl
if some force overcomes the imense
electrostatic repulsion between them
Th process seeed to requ so much
heat and pressue tht only a priordi
event or the interor of a star could bave
provided the rit conditions.
SCIC AMCA Augu 1992

i' ,.
- '- . ' ' - ' . --,"'" - , - - - . - '- . " , - . . ' - - - - - .-=-..= -:- =-.. ---
Sl AN NONSESE In a montage he made to amus
frends, George Gamow emerges, genete, frm a botte of
the prieva matter created in the big ba He is conju
The reigng theory of the nuclear
phy&ics of stars, which rem for the
most par vad today, bad been developed
in 1938 by the Ge-born physicist
Han Bethe of Cornel University.
Bethe wated to exlai how the
shies. He did so,by assum tht nuclear
fuion in stelar interors convers
mass into energy. Spedfcaly, Bethe
proposed tht two fusion reactons
could take place in stars lie the
one fuses protons into helum nuclei,
and another adds protons to carbon
nucleito form heavier elements.
But where did the carbon origite?
Tht question was not anwered unti
the 1950s, when Hoyle proposed a reacton
tht could produce carbon from
thee helum nuclei under the spedal
conditions found at the core of a star.
Tht recton and others needed to
ate heavier elements wer confed ex-
SCIC AMCA Augu 1992
perentaly, in a hi-eergy parcle
accelertor, by Wilam A. Fowler and
hi group at the Calorn Intitute of
Techology. Hoyle and E. E. Sapeter
provided important theoretical help.
19.57 a scheme exla how stars
might bave sythesized most of the elements
from hydrogen .and hel bad
been worked out by Fowler, Hoyle and
Margaret Bubidge of Caltech together
with Geoffey Bubidge, then at the
Mount Wilson and Paoma obsertories.
The work was done independently
by A. W. Camern, then at Atomic En
ergy of Canda. Yet the cosmic abundace
of hel remed a myster.
Gaow bad alady formulted a dain
hypthesi tht ultitel led to the
solution of the he1 puzzle. In his
verion of the big bang, Gamow suggested
tht the elements might bave
formed even beore the star came into
up by Robe Her (at left and Rah A. .Apher (at riht)".
wh showe ho such matter-whch they ca "yem
could have combin to form the lit elements
be, in a stupendously hot and den
gas of neutrons. Some of the neutrons
would then bave decayed into protons
and electons-the buidi bloc of
hydrogen In 1948 Gamow, known
hi impatience with detai as wel as .
hi brice, assigned the task of ,
velopin the theory to Raph Alpher,
graduate student at Gerge Was
ton. Alher later joined forces with It ,
er Heran of the John Hopki U
verity Applied Physics Laorato
Alphergave Gamow s intial sust
the nae "ylem" frm a Greek w
mean "priordi matter.
cordi to Gamow s theory
worked out by Alpher and
ma larer nuclei formed in
priev inero when smaer
begi with hydrgen grw
the successive captue of neutrIi.
process
free ne1
fel and
Hoyll
riva t(
io by co
attemp
was Sl
cates c
Alpl
thttl
el un
tr'
Moree
exax
atten
its tel
esti
ter b
pe1
atioI
five
solu
the
did
mic
sou
tak
the
Vel
pI,
fl'

process contiued unti the supply
free neutrons ran out, the tempeatue
fel and the parcles dispersed
Hoyle attempted to beltte ths new
riva to hi own steady state scenio
by cal it the big ban theory. The
attemt at ridicue backd: the phrse
was so vivid tht the theory s advocates
adopted it as thei own
Alpher and Her soon realed
thtthe radition perdi thei modelunverse
would maitai the spectr
of a blackod soure as it cooled
Moreover, they could calcuate how the
exansion of the unverse would bave
attenuated th radition and reduced
its tempeatu. The two scientits
estites of the present denty of matter
in the unverse to predict the tempetu
of the cosmic backun radiation
tody and dered a vae of abt
five kelvi (degrees Celsius above absolute
zer).
Astronomers did not ruh to conf
. the predicton, perbaps because they
did not knw how to pick out the cosmic
backgrund frm other raditie
soes or pebaps beau they di not
take serously the cosmology on which
the predicton was based The origi
on of the big ban theory bad two
ajor drawback. First, :it faied to ex-
'/ai the formation of the elements be
yond helum which bas a mass number
of four. Because there are no stable
isotopes bavig mass nums
five and eight, one canot mae heavier
elements out of hel by addi
neutrons one at a tie. Th problem
could be solved only by invoki the
stel nudeosythesi of Hoyle, Fowler
and thei collaborators, a concept associted
with the steady state theory.
Indeed, the moder version of the big
ban theory assues tht elements
yond helum arose only after the formation
of the fit generation of stars.
A second objecton to a big ban unverse
involved the question of age.
tronomical measuements of the distances
and recessiona speeds of galaxes,
in conjuncton with Hubble s law
of exanion, implied tht the unerse
was two bilon year old Yet the roc
of the ear' s surace prove tht the
planet is signcantly older th tht.
The steady state theory wa concei
to resolve ths apparent contradiction.
One night in 1946, thee youn sdentits
in Camridge, End-Hoyle,
Heran Bondi and Thomas Gold-
went to see a ghost story fi
Dead
l'Jht. As Hoyle later realed the movie,
bad four separate pars lied ingenously
together in such a way tht
the fi became cicuar, its end the
sae as its begig." Gold asked
friends whether the unverse might be
simarly constrcted In the
dicussion the worker sketched out a
dyc but noncydic model of the unverse
tht would always look the same
even thoug it is always ch:mEing
Accordi to Hoyle, Bondi and Gold,
the unvere bad no begi.They argued
tht the gales' rushig away
from \is does not imply a contiuous
attenuation of matter our own gal
wi never be left al alone, they sad,
beause matter is be crted contiuously,
at a rate just sudent to compente
for the matter tht is diappear
from the viible unvere. Ths
new matter wi eventuy form sta
an gaes so tht th unere wi always
look about the sae to any obserer
at any tie.
One might objec tht the cration of
matter out, of noth violates the law
of consertion of mass. and energy.
The riposte is obvious: the big ban
also violates th law and does so by
creati matter al at once, at the begini
of tie, when the act is bend the
reach of sdentic study. (In a later version
of the steady state theory, Hoyle
proposed-tht grvitationa energy creates
matter, a reement tht restores
the overal consertion of mass-eergy
but introduces other problem)
roponents of the steady state assered
tht thei theory wa more
sdentic th the big ban because
it postuted a process-contiuous
creation-tht might in pridple
be obsered Moreover, they argued,
thei theory made defte predictons
of a kid tht astrnomer could test
in the nea futue.
In sta thei moel on the outcome
of a sm nu of obsetions, Bondi
Gold and other proponents of the
steady state model exlicitly invoked
the doctre of Kal Popper, an Austran-born
phiosopher now livig in England
Popper defes science as a didplie
founded on the cration of hy-
potheses tht predict phenomenpreferably
new ones-tht can be tested
If a prediction fais, the scientit
abadons the hypthesi; if the hypthesi
surves, the sdentist does not
clai to bave proved it but merely to
bave establihed the hypothesis as a
basis for fuer research
Poppers priciple holds tht testabilty
rather th trth should be the
crteron for judgi sdentic theories.
For intance, Poppe dimisses Marism
and psychoanys as "pseudoscience"
because he beleves those theories
ar so flexle tht they can expla
any fact and thus elde any test.
Bondi proposed to cheie the
steady state theory by compar the
unerse as it is with the unerse as it
once was. Because the steady state theory
says the unverse always looks the
same, it predict tht galaxes formed
recentl wi resemle those formed
long ago. If you look out into spaceand
thus back in tie, because the
speed of lit is fite-and see tht
ditant gaes ar diert frm neaby
ones, Bondi conclded, "then the
steady-state theory is stone dead" Lie
other wrti before 1965, however,
Bondi faied to mention another test of
the steady state model it does not pre
dict 'a cosmic microwave backund
The theory faied the test Bondi had
set it. In the 1950s and early 1960s a
vaety of astrnomical obsertions
showed tht the unere bad ched
signcantl over tie. Ma Ryle of
Camridge counted both ditant and
neary radio soures, knowi tht the
more ditant sig had taken longer
to arve and thus refected an earlier
stage in cosmic hitory. Ryle conclded -
tht ther bad be fewer sources in
the past. Although some astronomers
argued tht he bad not proved hi cae,
additiona support evdence emered
when astronomer discovered wbat
seemed to be the oldest radiative
sources-quasistel objects, or qua-
SCIC AMCA Augu 1992

FR HOYL chpion of the steady state , conceived of the theory with
Her Bondi and Thomas Gold in 1946, afer the thee had seen a ghost story
fi whose plot ended in a retu to the ope scene.
sars. These objects bad no contemporar
paralel wbatsoever.
Meanwhie the awkward issue of the
disparty between the age of the unverse
and the age of the ear was resolved
in a way tht favored the big
ban. In 1952, followi the lead ofWalter
Baade of the Mount Wilson Observatory,
astronomers revised thei scale
of galctc distances upward by a factor
of two. The estiated age of the
unverse therefore doubled. Later work
raised it to a mium of 10 bilon
years, whereas the age of the ear remaed
fied at 4.5 bilon year.
Yet many sdentists, parcuarly in
Brtai lied the simplidty of the steady
state theory and so contiued to di
the concept. They pointed out tht one
did not bave to make arbitrar assuptions
about a big ban or worr about
wbat happeed before the big ba. Advocates
of the steady state model also
took hear from the faiure of earlier attempted
reftations, a record tht made
them suspidous of any new attack.
As the steady stater spt ever more
tie exlai away the evidence accumulati
agait thei theory, thei adherce
to Poppes methodology steadily
became less credible. Intead they
seemed to be ilustratig Planck's more
cycal view of sdence. Writig in
Sdentific Autobiography and Other Pa-
SCIC AMCA Augus 1992
pers (1949), the great physidst argued,
A new sdentic trth does nottrumph
by convidng its opponents ard
mak them see the light, but rather
because its opponents eventualy die
and a new genertion grows up tht is
famar with it.
lanck' s pridple, as historian of
science now cal it, contradicts
Poppers pridple by emphasizing
the human element in sdence to
the detrent of abstract logic. Just as
astronomers can weigh the big bang
agait the steady state as a descrption
of the unverse, so may historian of
sdence tr to dedde between Planck'
and Popper s descrptions of sdence.
Let us see which seem more accute
in ths' parcuar case, without undertak
to judge whether sdence always
works in ths way.
In 1959 a suey showed that a majority
of astronomers rejected contiuous
creation, although only a thd of
those voti actaly favored the big
ban. Even Hoyle abandoned his original
model and replaced it with a more
complicated hypthesis. In 1964 he concluded
tht the hi abundance of helum
in the unerse implied it bad been
cooked" at tempeatues exceedi
10 10 kelvi. Yet Hoyle refsed to abandon
the idea of the contiuous creation
of matter. A new shock was needed.
The discover of the cosmic microwave
backound provided tht shoc
Penas and Wilson made the discover
by measu the temperatue of
space or, as a physicit would say; by
detectig the Planck blackody spectral
distrbution tht corresponds to a
parcu temperarue. Electomagnetic
radiation perades the regions between
the planets and the stars, and it
can be detected by intrents on the
ear Much of th radition comes in
spedfc frequendes detered by the
physical and chemcal properes of astrnomical
soures. It th canot be accuately
chactered by a sine tempertue.
Intead investigators look for
radiation tht is in ther equri
at a parcuar temperatue. Tht is to
say, the radiation is contiuously ditrbuted
over dierent frequendes aC-
cord to the law dicovered by Plack
in 1900. .
The Plack ditrution ha a ch-
actertic sbape for ever temperatue
(see ilusation on opposie pagel. For
the unverse in which we live , the background
radition corresponds to a tempedtu
slitl less th th kel.
The distrution peak at a wavelen
of about 0.18 centieter, which is in
the microwave region of the spect
One can iner a tempertu of space
indiecty. As Arur Staney Eddion
pointed out in 1926, the amount of
light comi from al the stars-tht
is, the total energy denity-would be
equvaent to 3. kelvi if convered to
ther equrium But Eddion did
not propose a spedfc procedure for
testig hi predicton. .
At tht tie, even a sdentit of Eddigton
s cah"ber would bave found the
task daunti. Obviously, ordi ther- ,
mometers would be swamped by energy
comi from the su other celestial
objects and the ear' s atmosphere.
On excee senitie intrents
tued to wavelength between a milieter
and a centieter and inated
from local sources, can hope to detect
the cosmic micrwaves.
About 15 year afer Eddion made
hi presdent predcton, Andrw McKellar
of the Domion Astrophysical Obseratory
in Canada suggested a practical
way to measue wbat he caled the
efectie temperatue of space. McKel- .
lar, one of the fit astronomer to pro
pose tht molecues as wel' as atoms
could exst in intertelar space , sugested
tht the cyogen (CN) molecue '
be employed as a therometer. He not- .
ed tht cyogen emts spect lies
whose relatie intenity corresponds to
the num of electons in hier-eer- :
gy states itself a fucton of the tem-
:::
peratu
tht ten
ThesE
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Radar
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peratue of space; McKelar estiated
tht temp tU to be 2.3 kelvi.
These indiec approaches could not
rue out intererence frm local sources.
To do tht, one must detect the radition
itsel and map it across the sky.
Radar equpment developed at the Massachusetts
Intitute of Tecology duin
World War n was just barely capable
of senin the cosmc backound
diecty-for anyone who wated
look for it. .
In 1946 a group at M.lT., led by
Rober H. Dicke, reported annospheric
radiation measuements taken by a
microwave radiometer. The team noted
tht the "radiation frm cosmic matter
at the radiometer wavelen" was
qute spare-less th the equvalent
of 20 kel-but did not follow up
obsertion. Dicke, who susequently
moved to Prceton Uniersity, later recaled
tht "at the tie of ths measuement
we were not thg of the
big ban' radiation but onl of a possible
glow eJtted by the most ditant
gales in the unerse.
Steven Weig, in his book The
First Three Minutes, suggests two reasons
why no one made a systematic
search for the backound radiation
3efore 1965. First, the big ban bad
lost some crediilty when it faied to
exlai the formtion of elements heavier
th hel so tht it did not see
inportt to test the theory s other predictons.
In contrast, nucleosythes in
stars-a theory lied to steady state
cosmology-seemed to exlai how
heavy elements could bave been made
from hydrogen and hel even
though it did not exlai how the helum
bad formed in the fist place. .
Seond, Weierg points to a breakdown
of communcation between theorists
and exentalsts. The theorists
did not realze one could obsere
the radiation with exti equpment
and the exerentalts did not reale
the signcance of thei obsertions.
From ths perspective it is noteworty
that Dicke, who is both a theorist and
an exerentalst, played a major !:
role: together with P. James E. Peebles, 104
he helped to relate a pecuar micro-
wave noise to cosmological theory.
The most remkable mised op-
portty resuted from a mider-
standig between Gaow and Hoyle.
Although each crticied the other
theory, they could sti. bave frendly
dicussions. In the suer of 1956
\:;amow told Hoyle tht the unerse
' must be fied with microwave radiation
. at a temperatue of about 50 kelvis.
(He ared at th estite on hi own
afer Alpher and Her bad publied
thei predicton.)
. As itbappened, Hoyle Was famar
with McKelars proposa tht the temperatu
of space is about thee kelvi.
So Hoyle argued tht the tempertue
could not be as high as Gamow
claied. But neither of them realzed
tht if a diect measuement could confi
the thee-kelvi vaue and also establih
the Plackan spec it would
refte the steady state theory, whichas
Hoyle recognzed-predicts a zero
tempetue for space.
A dierent kid of communcation
problem-satelte relys-did lead to
the discover of the cosmic microwave
background. Bell Labs wated its sateltes
to convey as much inormtion
as possible at microwave frequendes, a
task tht requed its workers to fid
and elte noise from al sources.
The relay hadwae, dervi from the
fi' s War-relted work on radar, consisted
of a horn-sbaped receiver tht
Bel Labs eneers Harald T. Fri and
A. C. Beck bad buit in 1942. Another
Bel Las engieer, Arur B. Crawford,
cared the idea much fuer. In 1960
he buit a 20-foot horn receier at the
Crwford Hi facity near Holmdel,
NJ. Tht refector, oriy used to receie
signals bounced frm a plastic
baloon high in the annosphere, ' became
avaiable for other puroses just
in tie for Penzas and Wilson.
he two investigators wanted to
star a research progr in radio
astronomy. To prepare the hily
senitive intrent for thei work,
Pens and Wilson fist bad to rid it of
microwave noise. They faied in thei
fist few attempts. Finaly, in Januar
1965, Fens heard tht Peebles bad a
theory tht might exla the origi of
the stuborn peristent sig
106
102
103 10
108
Peebles was workig with DiCke at
Prceton, about 25 mies from the
Holmdel laboratory. Dicke rejected the
assuption tht the unerse necessa
ily began with the big ban. He thought
it more liely tht the unverse went
though pbases of exanion and contrcton.
At the end of each contrcton,
he conjectued, al matter would pass
though temperatues and denities intene
enoug to bre down the heavier
nuclei into protons and neutrons.
Thus, although Dicke s unverse did
not star with a big ban, each of its
cycles must begi in a simar cata-
clys Moreover, Dicke s cosmology im
plied an intial fiebal of high-temperatue
radiation tht retai its Plack
blackody chacter as it cools down
and he estited tht the present temperatue
of the radiation would be
kelvi. He evidently bad forgotten
own 1946 measuement tht suested
the exstence of backund radiation
at a temperatue less th 20 kelvi.
Peebles made fuer calcutions from
Dicke s theory and obtaied an estimate
of about 10 kelvi.
Dicke and Peebles, together with two
graduate students, 'P. G. Roll and D. T.
Wilon, then stared to constrct an
anten at Prceton to measue the
cosmic backund radiation. Before
they bad a chce to get any resuts,
Dicke receied a cal from Pen, suggesti
they get together to dicuss the
noise in the Crwford anten corr
spondi to a tempertu of about 3.
kel. It was soon apparent tht Pen
zias and Wilson bad aleady detected
the radiation predicted by Dicke and
Peebles and earlier by Alpher and Herman
But unti the two astronomers
taled to Dicke and Peebles, they did
not knowwbat they bad found The
FREQUENCY (CYCLES PER SECOND) 108 10w 1012
WAVELENGTH (CENTMETERS)
BlACKODY SPECTUM prected by the big ba theory implies tht the earlies
radition in the uner wi now appe to be emti frm a soe a few degrs
above absolute zer Pens and Win confed the sp at a sie
point; other have sice confed it for a wide rae of frencies.
SCc AMCA Augu 1992

Selection from George
Gamow's Mr Tompkins
in Paperback
Your years of toil,
Said Ryle to Hoyle,
Are wasted years, believe me.
The steady state
Is out of date
Unless my eyes deceive me
My telescope
Has dashed your hope;
Your tenets are refuted.
Let me be terse:
Our universe
Grows daily more diluted!"
Said Hoyle, "You quote
Lemaitre, I note,
And Gamow. Well, forget them!
That errarit gang
And their Big Bang-
Why aid them and abet them?
You see, my friend
It has no end
And there was no beginning,
As Bondi, Gold,
And I wil hold
Until our hair is thinning!"
Not so!" cried Ryle
With rising bile
And straining at the tether;
Far galaxies,
Are, as one sees,
More tightly packed together!"
You make me boil"
Exploded Hoyle,
. His statement rearranging;
New matter's born
Each night and morn
The picture is unchanging!"
Come off it, Hoyle!"
I aim to foil
You yet" (The fun commences)
And ina while,"
Continued Ryle,
ll bring you to your senses!"
Verses by Barbara Camow
theoretical interretation was essential
to tu mer detecton into tre dicover.
Tht discover came more th a
decade late because the scientic world
bad simply overlooked the earlier work
by Gamow, Alpher and Her
The reports of the groups from Bel
Labs and Prceton were sent to the As-
SCIC AMCA August 1992
trophysical Journal in May 1965 and
appeared together in the July 1 issue.
Publication uneashed a flood of arcles
in both the mass media and the
sdentic jourals. Even Hoyle admtted
tht the steady state theorY, at least
in its origial form
, "
wi now have
be discarded , n although he later tred
to han on to a modied version tht
could exlai the microwave radiation.
But Bondi's empbasis on the testabilty
of the steady state theory bad come
back to haunt its proponents. Any attempt
to twt the theory to exlai the
new discoveres riked beig labeled
pseudosdence.
Although the press was quck to condude
tht Penas and Wilson bad confied
the big ban defitively, sdentits
reed tht thei resuts were liitedJo
only a few wavelen clustered
atone end of the Planck cue. Other
exlanations of the background radiation,
such as a combintion of radio
sources, could exlai those data
points. It was not unti the mid-1970s
that enoug measuements at dierent
frequencies bad been made to convice
the skeptics tht the background radiation
actaly follows Planck's law. The
spectr of the CN molece played an
important par here, as astronomers
resuected and buit on the earlier
work of McKelar.
By the late 1970s nearly al the origina
supporters of the steady state model
had exlidtl abandoned it or simply
stopped publishig on the subject. A
surey of Amercan astronomers conducted
at tht tie by Carol M. Copp of
Calorna State University at Fuleron
found tht a large majority supported
the big ban over the steady state.
The rapid demse of the steady state
theory after 1965 shows tht Popper
pridple, rather than Planck's, applies
in th case. The dicover of the cosmic
microwave backound, combined with
arguents about helum abundance
and obsertions of ditant radio soures
and quasars, conviced most steady
staters that thei theory was no longer
wort pursuig. It bad been tred and
found wati.
Yet in 1990, when the steady state
theory was al but forgotten, Hoyle and
a few of his colleagues tred to revive it
as a "mi-big bang" theory, argug
tht the evidence d s not support the
hypothesis tht a single exlosion created
every. Geoffey Burbidge recently
sumarzed ths view in an essay
in these pages (see "Why Only One
Big Ban?"; Februar).
Although proponents of the big ban
could dismiss most such crtidsms,
some puzzles sti remaied unolved.
For exple, the microwave backund
seemed too smooth It lacked the slight
vaations in temperatue and, by implication,
in denty tht seemed necessar
to seed later gravitational clumpin.
Without such seedig, there would
not bave be sudent tie to produce
the galaxes and supergalactic strctues
now obsered.
hen, in Apri of ths year, George
P. Smoot and hi colleagues at
the University of Calorna at
Berkeley and at the Lawrence Berkeley
Laboratory released evidence tht may
fi ths gap in the big bang theory.
They anounced an anysis of measurements
of the cosmic backound
radiation gathered by an orbiti obsertory
caled the Cosmic Background
Exlorer (COBE).
The data showed slit
temperatue vaations in the cosmic
backound, just as bad been exected.
by big bang theorists. The researchers
interret these "rpples" as flctuations
in the denity of matter and energy in
a ver early pbase of cosmic hitory.
Such ripples may help exlai how
matter clumped under the force of its
own gravitY in tie to form the stars,
galaxes and larger strctus of the
contemporar unverse.
Did the unverse realy begi at the
big bang, or was there a previous contraction
phase-a "big crch" tht
led to the high temperatue and density?
Wil the unverse contiue to expand
forever, or wi it eventualy collapse
into a black hole? Does the creation
of the unverse involve quantu
theory in a fudamental way? These
ideas now domiate physical thought
(see "Quantu Cosmology and the Cre- .
ation of the Universe," by Jonath
Halwel; SOEC AMCA, December
1991). Tht sdentits consider such
questions worty of serous investigation
is itsel largely a consequence of
the dicover of the cosmic microwave
backgound,' which tranformed cosmology
into an empircal sdence.
RJTI REING
IN SEACH OF TI BIG BANG: QuAN
PHcs AN COSMOWG. John Gribin
Bantam Books, 1986.
'f COSMC MICROWAVE BACKGROUN:
25 YEA LATE. Edited by N. Mandolesi
and N. Vittorio. Klwer Academc Publishers,
1990.
MODER COSMOLOGY IN REOSPCI.
Edited by B. Berott et al. Camridge
University Press, 1990.
'f CA FOR TI RETIC HOT BIG
BANG COSMOLOGY. P. E. Peebles, D. N.
Scham E. L. Tuer and R. G. Kron
in Nature, VoL 352, No. 6338, pages
769-776; August 29, 1991.
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