bang ueory Is rrle IIru)] wrsEry eL
this: Fifteen to twenty billion years agq'a big bang'
began, and it Eoes to*utr,ing fike
infiniteiy
The
bif
The universe began as an
or explosion, o.rrrril, .r"lting tr,e universe.
the
of space and time. wthin the first second after
dense, hot fireball, a scramblinE
orpanded npidly-and becarne flooded
bang, gravity came into ueing.lhe universe
one another, forming protons and neuwith subatornic particles that siammed into
was a mere 500 billion deErees
trons. Three minutes later, when the temperature
piotons and neutrons formed the nuclei of
Fahrenheit (Zg0 biliion i.gr.* Ceisius),
(the simplest elements)'
iyarog.n, heiium, and iithium
300 million more
It took another 500 thousand years for atoms to form and
stars, condensed from
y..rr-ioi stars and gaiuies to begin to appear. Countless planets
came into being
its
l*rrr,.g nebulae, .ro-r*J *a ai.a before our own sun and
billion
one-half
vears ago
and
named trre uittrv Way. And it was onlv four
;;;
nat
;"i..r,
-our
gas.
solar system was formed from a cloud of dust and
Who found the
first evidence to support the big
bang theory?
called the
In 1929, American astronomer Ed*in Pou'ell Hubble made what has been
He found observable
most significant as[ronomical discove4' of the twentieth century'
those stars'
proof thlt stars exist in huf,e groups called gaiaxies. By tracing the light of
Milton Humahe also found that all matter in ,p... is movin$ away from each other'
gala:ries
that some
determined
and
distant
photographed
the
son, Hubble's colleague,
were moving at about one-seventh the speed of lighr The impiications of this
;;ft*
was proof that the universe was expanding. and it
discovery were enorTnous. Here
to be true. The work of these two
made the big bang theory seem much more likely
,rtrono*.t is widely credited wiLh usherin! in the era of modern cosmology, the
study of the origin, evolution' and structure of the universe'
What other evidence suPPorts
ihe big bang theory?
Best known for his work on nuclear fusion
and the big bang theory. Russian-born
American physicist George Gamow (19011968) furthered the argument in favor of
the big bang theory in t948. Ifa bang had
occurred, he stated. it would have left
traces of background radiatton that could
persist even after many billions of years.
He calculated that the radration would
have cooied to just a few degreas above ab-
solute zero. He was later proven correct
when radio engineers Amo Penzias and
Robert Wilson detected fatnt background
radiaticjn coming from all over lhe sk-v that matched Gamo,v's calculation. The presence
of this background radiatron remairu the single greatest piece of evidence in support of
the big bang. Gamow's work on the big bang theory contributed to making that theory
the most widely accepted explarution of how the universe began,
what was the steady-state theory of the universe?
has always been essentially the sarne
The steady-state theory claims that the universe
sterns from the Cosit iq today, and that it wilt continue that way forever- The theory
everyrvhere' tri pro'
same
the
is
",
irinciple. which states that the universe
gasses fill the universe from end to
other words, that the same objacts and
much different than the view from any
end and that the view from one galarry is not
this concept of same'
ot-i,., g"f*y. The originator of the steady-state theory applied
the
up with the steady-state theory claiming that
iii"gLf
;;;i;
to eome
-oc<
nEr: to
-- as well .r-r0"..
'- time
present'
not only in all places, but at all times-past'
same,
ti,e
toi,r
should
theory
major
th..gtY was.offered in response to the other
fn.
ljt;;r,
,t."ai-rt";;
i"i fr**.
beEan, the big banE theory'
universe
the
;fi"*
What was the first piece of evidence that seemed to nrle
out the steadY-state theorY?
uni'
The discovery ot quasars in 1963 arlued against the steady-state theory of the
Earth.
verse. These extremely bright objecls occur only at the farthest reaches from
if, as the steady-state theory suggests. the universe looks the same everyl/rhere, in all
directions. quasars should be distributed eveniy throughout space. Since quasars are
mostly old and distant. though. they'are not compatible with this theory.
Whieh discovery is considered
to have definitively ruled out
the steady-state theory of the
universe?
The most important piece of evidence for
the big bang theory was found in 1992,
when the NationalAeronautics and Space
Admi nistration's Cosrnrc B a ckgrothd'
fu-
plora (COBEt hoked fifteen billion light(the same as looking fif1.ears into space
reen billion years into the past). It
detected tiny temperature changes in the
cosmic background radiation, which may
be evidence of gravitational disturbances
in the early universe. These ripples or
Thc Connlc B.dgrornrd Elplorer (COBE) studlcd 0t
qivurr'r brdrywnd
out thc
!-adhtlon. tB conclusiou rulcd
of thc unrwnc'r origin.
st..{F$.rc tlrory
fluctuations of temperature, which are as
long as ten billion light'years. could have eventually come together to form the stars,
galaxies. and other pieces of the universe, indicating that the universe has changed
over time' This last piece of evidence has pushed the steady-state theory out of the
running for the explanation of how the universe began, at Ieast for now.