This paper outlines the theoretical arguments behind the prediction...
This is the paper for which Penzias and Wilson got awarded the Phys...
When Penzias and Wilson went to work at Bell Labs there was a very ...
If you go back and read the paper that precedes the result from Pen...
Before Penzias and Wilson started using the antenna to try to find ...
Today we know, thanks to the data from COBE, that the CMB radiation...
Arno Penzias and Robert Wilson were both radio astronomers who work...
19
65ApJ.
.
.142.
.419P
No.
1,
1965
LETTERS
TO
THE
EDITOR
419
high
pressure,
such
as
the
zero-mass
scalar,
capable
of
speeding
the
universe
through
the
period
of
helium
formation.
To
have
a
closed
space,
an
energy
density
of
2
X
10
-29
gm/cm
3
is
needed.
Without
a
zero-mass
scalar,
or
some
other
“hard”
interaction,
the
energy
could
not
be
in
the
form
of
ordinary
matter
and
may
be
presumed
to
be
gravita-
tional
radiation
(Wheeler
1958).
One
other
possibility
for
closing
the
universe,
with
matter
providing
the
energy
con-
tent
of
the
universe,
is
the
assumption
that
the
universe
contains
a
net
electron-type
neutrino
abundance
(in
excess
of
antineutrinos)
greatly
larger
than
the
nucleon
abun-
dance.
In
this
case,
if
the
neutrino
abundance
were
so
great
that
these
neutrinos
are
degenerate,
the
degeneracy
would
have
forced
a
negligible
equilibrium
neutron
abun-
dance
in
the
early,
highly
contracted
universe,
thus
removing
the
possibility
of
nuclear
reactions
leading
to
helium
formation.
However,
the
required
ratio
of
lepton
to
baryon
number
must
be
>
10
9
.
We
deeply
appreciate
the
helpfulness
of
Drs.
Penzias
and
Wilson
of
the
Bell
Telephone
Laboratories,
Crawford
Hill,
Holmdel,
New
Jersey,
in
discussing
with
us
the
result
of
their
measurements
and
in
showing
us
their
receiving
system.
We
are
also
grateful
for
several
helpful
suggestions
of
Professor
J.
A.
Wheeler.
R.
H.
Dicke
P.
J.
E.
Peebles
P.
G.
Roll
D.
T.
Wilkinson
May
7,
1965
Palmer
Physical
Laboratory
Princeton,
New
Jersey
REFERENCES
Alpher,
R.
A
,
Bethe,
H.
A
,
and
Gamow,
G
1948,
Phys.
Rev.,
73,
803
Alpher,
R
A.,
Follín,
J
W.,
and
Herman,
R.
C.
1953,
Phys.
Rev
,
92,
1347.
Bondi,
H
,
and
Gold,
T.
1948,
M
N.,
108,
252.
Brans,
C
,
and
Dicke,
R.
H
1961,
Phys.
Rev.,
124,
925.
Dicke,
R.
H.
1962,
Phys.
Rev.,
125,
2163.
Dicke,
R.
H
,
Beringer,
R.,
Kyhl,
R
L
,
and
Vane,
A
B.
1946,
Phys.
Rev.,
70,
340
Einstein,
A,
1950,
The
Meaning
of
Relativity
(3d
ed.;
Princeton,
N.J.:
Princeton
University
Press),
p.
107.
Hoyle,
F.
1948,
M
N
,
108,
372.
Hoyle,
F
,
and
Tayler,
R
J
1964,
Nature,
203,
1108
Liftshitz,
E
M.,
and
Khalatnikov,
I.
M
1963,
Adv.
in
Phys
,
12,
185.
Oort,
J
H
1958,
La
Structure
et
Involution
de
Vuniverse
(11th
Solvay
Conf
[Brussels:
Éditions
Stoops]),
p.
163.
Peebles,
P
J.
E.
1965,
Phys.
Rev.
(in
press).
Penzias,
A.
A.,
and
Wilson,
R.
W.
1965,
private
communication.
Wheeler,
J.
A
,
1958.
La
Structure
et
involution
de
Vuniverse
(11th
Solvay
Conf.
[Brussels:
Éditions
Stoops]),
p.
112.
1964,
in
Relativity,
Groups
and
Topology,
ed
C.
DeWitt
and
B.
DeWitt
(New
York:
Gordon
&
Breach).
ZePdovich,
Ya.
B.
1962,
Soviet
Phys.—J.E.T.P.,
14,
1143.
A
MEASUREMENT
OF
EXCESS
ANTENNA
TEMPERATURE
AT
4080
Mc/s
Measurements
of
the
effective
zenith
noise
temperature
of
the
20-foot
horn-reflector
antenna
(Crawford,
Hogg,
and
Hunt
1961)
at
the
Crawford
Hill
Laboratory,
Holmdel,
New
Jersey,
at
4080
Mc/s
have
yielded
a
value
about
3.5°
K
higher
than
expected.
This
excess
temperature
is,
within
the
limits
of
our
observations,
isotropic,
unpolarized,
and
©
American
Astronomical
Society
•
Provided
by
the
NASA
Astrophysics
Data
System
19
65ApJ.
.
.142.
.419P
420
LETTERS
TO
THE
EDITOR
Vol.
142
free
from
seasonal
variations
(July,
1964-April,
1965).
A
possible
explanation
for
the
observed
excess
noise
temperature
is
the
one
given
by
Dicke,
Peebles,
Roll,
and
Wilkinson
(1965)
in
a
companion
letter
in
this
issue.
The
total
antenna
temperature
measured
at
the
zenith
is
6.7°
K
of
which
2.3°
K
is
due
to
atmospheric
absorption.
The
calculated
contribution
due
to
ohmic
losses
in
the
antenna
and
back-lobe
response
is
0.9°
K.
The
radiometer
used
in
this
investigation
has
been
described
elsewhere
(Penzias
and
Wilson
1965).
It
employs
a
traveling-wave
maser,
a
low-loss
(0.027-db)
comparison
switch,
and
a
liquid
helium-cooled
reference
termination
(Penzias
1965).
Measurements
were
made
by
switching
manually
between
the
antenna
input
and
the
reference
termina-
tion.
The
antenna,
reference
termination,
and
radiometer
were
well
matched
so
that
a
round-trip
return
loss
of
more
than
55
db
existed
throughout
the
measurement;
thus
errors
in
the
measurement
of
the
effective
temperature
due
to
impedance
mismatch
can
be
neglected.
The
estimated
error
in
the
measured
value
of
the
total
antenna
temperature
is
0.3°
K
and
comes
largely
from
uncertainty
in
the
absolute
calibration
of
the
reference
termination.
The
contribution
to
the
antenna
temperature
due
to
atmospheric
absorption
was
ob-
tained
by
recording
the
variation
in
antenna
temperature
with
elevation
angle
and
em-
ploying
the
secant
law.
The
result,
2.3°
±
0.3°
K,
is
in
good
agreement
with
published
values
(Hogg
1959;
DeGrasse,
Hogg,
Ohm,
and
Scovil
1959;
Ohm
1961).
The
contribution
to
the
antenna
temperature
from
ohmic
losses
is
computed
to
be
0.8°
±
0.4°
K.
In
this
calculation
we
have
divided
the
antenna
into
three
parts:
(1)
two
non-uniform
tapers
approximately
1
m
in
total
length
which
transform
between
the
2f-inch
round
output
waveguide
and
the
6-inch-square
antenna
throat
opening;
(2)
a
double-choke
rotary
joint
located
between
these
two
tapers;
(3)
the
antenna
itself.
Care
was
taken
to
clean
and
align
joints
between
these
parts
so
that
they
would
not
sig-
nificantly
increase
the
loss
in
the
structure.
Appropriate
tests
were
made
for
leakage
and
loss
in
the
rotary
joint
with
negative
results.
The
possibility
of
losses
in
the
antenna
horn
due
to
imperfections
in
its
seams
was
eliminated
by
means
of
a
taping
test.
Taping
all
the
seams
in
the
section
near
the
throat
and
most
of
the
others
with
aluminum
tape
caused
no
observable
change
in
antenna
temperature.
The
backlobe
response
to
ground
radiation
is
taken
to
be
less
than
0.1°
K
for
two
reasons:
(1)
Measurements
of
the
response
of
the
antenna
to
a
small
transmitter
located
on
the
ground
in
its
vicinity
indicate
that
the
average
back-lobe
level
is
more
than
30
db
below
isotropic
response.
The
horn-reflector
antenna
was
pointed
to
the
zenith
for
these
measurements,
and
complete
rotations
in
azimuth
were
made
with
the
transmitter
in
each
of
ten
locations
using
horizontal
and
vertical
transmitted
polarization
from
each
position.
(2)
Measurements
on
smaller
horn-reflector
antennas
at
these
laboratories,
using
pulsed
measuring
sets
on
flat
antenna
ranges,
have
consistently
shown
a
back-lobe
level
of
30
db
below
isotropic
response.
Our
larger
antenna
would
be
expected
to
have
an
even
lower
back-lobe
level.
From
a
combination
of
the
above,
we
compute
the
remaining
unaccounted-for
antenna
temperature
to
be
3.5°
±
1.0°
K
at
4080
Mc/s.
In
connection
with
this
result
it
should
be
noted
that
DeGrasse
el
at.
(1959)
and
Ohm
(1961)
give
total
system
temperatures
at
5650
Mc/s
and
2390
Mc/s,
respectively.
From
these
it
is
possible
to
infer
upper
limits
to
the
background
temperatures
at
these
frequencies.
These
limits
are,
in
both
cases,
of
the
same
general
magnitude
as
our
value.
We
are
grateful
to
R.
H.
Dicke
and
his
associates
for
fruitful
discussions
of
their
re-
sults
prior
to
publication.
We
also
wish
to
acknowledge
with
thanks
the
useful
comments
and
advice
of
A.
B.
Crawford,
D.
C.
Hogg,
and
E.
A.
Ohm
in
connection
with
the
problems
associated
with
this
measurement.
©
American
Astronomical
Society
•
Provided
by
the
NASA
Astrophysics
Data
System
No.
1,
1965
LETTERS
TO
THE
EDITOR
421
Note
added
in
proof.—The
highest
frequency
at
which
the
background
temperature
of
the
sky
had
been
measured
previously
was
404
Mc/s
(Pauliny-Toth
and
Shakeshaft
1962),
where
a
minimum
temperature
of
16°
K
was
observed.
Combining
this
value
with
our
result,
we
find
that
the
average
spectrum
of
the
background
radiation
over
this
frequency
range
can
be
no
steeper
than
X
o
7
.
This
clearly
eliminates
the
possibility
that
the
radiation
we
observe
is
due
to
radio
sources
of
types
known
to
exist,
since
in
this
event,
the
spectrum
would
have
to
be
very
much
steeper.
A.
A.
Penzias
R.
W.
Wilson
May
13,
1965
Bell
Telephone
Laboratories,
Inc
Craweord
Hill,
Holmdel,
New
Jersey
REFERENCES
Crawford,
A
B.,
Hogg,
D.
C
,
and
Hunt,
L
E
1961,
Bell
System
Tech.
/.,
40,
1095.
DeGrasse,
R.
W
,
Hogg,
D
C
,
Ohm,
E
A
,
and
Scovil,
H.
E.
D
1959,
“Ultra-low
Noise
Receiving
System
for
Satellite
or
Space
Communication,”
Proceedings
of
the
National
Electronics
Conference,
15,
370.
Dicke,
R
H
,
Peebles,
P.
J.
E.,
Roll,
P
G.,
and
Wilkinson,
D.
T.
1965,
Ap
/.,
142,
414.
Hogg,
D
C
1959,
J
Appl
Phys
,
30,
1417
Ohm,
E
A
1961,
Bell
System
Tech.
J
,
40,
1065
Pauliny-Toth,
I
I
K.,
and
Shakeshaft,
J.
R.
1962,
M.N.,
124,
61.
Penzias,
A.
A
1965,
Rev
Sei.
Instr.,
36,
68.
Penzias,
A
A
,
and
Wilson,
R
W.
1965,
Ap
J
(in
press).
ERRATUM
In
the
paper
“Stellar
Evolution.
I.
The
Approach
to
the
Main
Sequence^
{Ap.
141,
993),
the
following
corrections
are
to
be
made:
page
993,
line
1,
replace
“popuation”
by
“population”;
page
997,
line
18,
delete
the
last
word
“energy”;
page
999,
line
2,
replace
“expanding”
by
“contracting”;
page
1007,
section
heading
VI—replace
“8”
by
“9”;
page
1007,
line
1,
replace
“Figure
12”
by
“Figure
17”;
page
1017,
line
5,
replace
“equation
(19)”
by
“equation
(B9)”;
page
1018,
line
6,
replace
“W.
Z.
Fowler”
by
“W.
A.
Fowler.”
Icko
Iben,
Jr.
June
7,
1965
Massachusetts
Institute
or
Technology
©
American
Astronomical
Society
•
Provided
by
the
NASA
Astrophysics
Data
System
Arno Penzias and Robert Wilson were both radio astronomers who worked at the Bell Research Labs. Penzias had been born into a Jewish family in Munich in 1933, but due to the rise of Naziism his family escaped to the USA in 1939. Penzias was interested in physics from an early age, and majored in the subject at the City College of New York. He then went to Columbia University to study for a Ph.D. in radio astronomy. His advisor at Columbia was Charles Townes, who would later win a Nobel Prize for his invention of the maser. Wilson had grown up in Texas, and majored in physics at Rice University in Houston, and had then gone on to Caltech in 1957 to study for a Ph.D.
When Penzias and Wilson went to work at Bell Labs there was a very special antenna lying around. This horn shaped antenna had been used to detect signals from the Echo balloon satellite, which had been launched in 1960. Its rare design had been optimized to pick up very weak signals from the high altitude Echo balloon, while minimizing the extraneous signals from any terrestrial sources.
These features made this antenna ideal to search the sky for astronomical radio sources.
This paper outlines the theoretical arguments behind the prediction of a background radiation. If you want to understand why this paper was published exactly before the Penzias and Wilson one please read the annotations below.
Today we know, thanks to the data from COBE, that the CMB radiation has a temperature of 2.72548 ± 0.00057 K, which is compatible with Penzias and Wilson's measurements.
Note that Penzias and Wilson only measured this excess at one wavelength - 7.35 cm. Later more data was collected at multiple wavelengths which proved that the CMB has a thermal black body spectrum, governed by the Stefan–Boltzmann law:
$$
P/A = \sigma T^4
$$
This is the paper for which Penzias and Wilson got awarded the Physics Nobel Prize in 1978. It's also one of the most understated titles of any scientific paper - the "excess temperature" mentioned in the title is in fact the **Cosmic Microwave Background (CMB) radiation**. The experimental detection of the CMB was a very important milestone in cosmology since it is a landmark evidence of the Big Bang origin of the universe, in which the CMB is the residual heat of creation--the afterglow of the big bang.
Before Penzias and Wilson started using the antenna to try to find radio sources in the sky they decided to analyze the "noise" the antenna could be being subject to. This would include: radio signals from the ground, local radio interference, or electronic noise in the detection equipment.
They even considered a pair of pigeons that were nesting in the horn of the antenna, and leaving a “white deposit” on the walls of the horn. Penzias and Wilson got rid of the pigeons and cleaned the horn to exclude any potential sources of noise.
If you go back and read the paper that precedes the result from Penzias and Wilson it concludes that, assuming the Big Bang theory is true, there should be a detectable afterglow radiation permeating today's Universe, with approximately the same temperature as the one detected by Penzias and Wilson. For anyone reading these two papers it might seem like an incredible coincidence that there happen to be two groups of researchers making two matching discoveries almost at the same time: the theoretical prediction of the CMB and it's experimental discovery.
**Here's the story of why these 2 papers came to be published in the exact same Journal issue.**
Near the end of 1964, Penzias went to a conference in Montreal where he talked about the "noise" problem with the horn antenna to the cosmologist Robert Burke. A few months after the conference Burke got a draft copy of a paper by his friends Robert Dicke and James Peebles of Princeton University in which they predicted that the Big Bang should have left an all-pervasive background radiation which today would be in the radio part of the spectrum.
When Burke got the preprint from Dicke and Peebles he called Penzias, who confirmed that the "noise" was the same radiation that was being predicted in the paper. Penzias then called Dicke informing him of the signal he and Wilson had detected. Dicke was stunned and the 2 teams decided to publish back-to-back articles in the Astrophysical Journal of 1965. The first paper, entitled “Cosmic Black-Body Radiation” outlining the theoretical arguments behind the prediction of a background radiation and the second paper talking about the experimental detection of the previously mentioned radiation.