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the sky. Operationally, the tilt was changed with the use of a dif-
ferential gear salvaged from a Model T Ford truck. He also
turned to a very different kind of design for the antenna itself.
Janksy had noted that radio signals from deep space were weak.
In order to focus them better, Reber decided to construct a par-
abolic antenna a dish with a sheet metal surface that would
reflect radio waves back up to a receiver located twenty feet
(6 m) above it. The receiver was designed to enhance the signals
by a factor of several million. An electronic stylus recorded the
radio waves on charts.
Reber s dish was thirty-one feet (9.5 m) wide. He didn t have
much choice in the matter, as he pointed out in a lecture: In
building the supporting superstructure the longest lumber avail-
able at the hardware stores in Wheaton was twenty feet, dictat-
ing a maximum diameter of 31 feet for the dish. A wooden
tower also had to be built to provide access to the receiver.
Reber did most of the work building his radio telescope by him-
self, with an occasional helping hand, over several months in
1937. The materials cost about $2,000, no small amount for that
time. The structure was, of course, the talk of Wheaton and
would have been anywhere else in the United States or around
the world. No one had ever seen anything like it, and it would
remain the largest and most sensitive radio telescope on the
planet until after World War II. Even the parabolic disks of
almost all modern radio telescopes are no more than 300 feet
(91.4 m) across; if they were any larger, Earth s gravity would
warp them, distorting reception.
An Astronomy Today article by Sancar James Fredsti, a research
engineer at the California Institute of Technology Owens Valley
Radio Observatory, gives a particularly clear picture of the dif-
ferences and similarities between radio and optical telescopes.
Grote Reber 123
The noise, or static, that streams through the universe has a vari-
ety of signal properties, such as frequency, phase, amplitude
and in some cases repetitive patterns. Both rapidly spinning
pulsars and very distant quasars, which emit as much energy as
one hundred galaxies and are believed to form around black
holes at the center of galaxies, give out signals that identify
them as separate point sources. A different kind of signal is
emitted by field sources, such as the vast clouds of gas and
dust that act as incubators for new stars. As information from
any kind of source is received, it must be mathematically ana-
lyzed to separate what is useful and significant from the sur-
rounding noise.
Both optical and radio telescopes are collecting electromag-
netic energy the same theories apply whether that energy
takes the form of light as viewed by optical telescopes or radio
waves collected by radio telescopes. There is a major difference,
however, in terms of the wavelengths that are being studied. As
Fredsti puts it, Optical telescopes operate at very high frequen-
cies and microscopic wavelengths, while their cousins the radio
telescopes work at lower frequencies and longer wavelengths.
That means that the beam width of a radio telescope is about
200,000 times that of an optical telescope, with a commensurate
reduction in resolution. Thus radio telescopes have their limi-
tations. On the other hand, they can detect objects that are im-
possible to view with an optical telescope and can reveal the
true nature of objects in ways that optical telescopes, even the
Hubble Space Telescope, cannot. Pulsars, for example, were dis-
covered in 1967 by Jocelyn Bell Burnell and Antony Hewish,
working at the Mullard Radio Astronomy Observatory in Cam-
bridge, England. Although pulsars can be detected visually, their
incredibly fast spin cannot. The search for black holes, which
allow no light to escape and thus are invisible, could not have
been carried out without radio telescopes.
While many of the factors described above had not yet been
grasped in 1937 when Grote Reber built the first dish telescope,
124 It Doesn t Take a Rocket Scientist
he was well aware that he needed to compensate for the weak
signals he would be collecting. That was the reason for the
paraboloid design, but it also carried over into other features of
his homemade radio telescope. Surmising that the objects Jan-
sky had detected must be very hot, Reber concluded that they
would be more easily detected at much higher frequencies. Jan-
sky had used a 20-MHz (15 m) wavelength; Reber started out
using a 3,300-MHz (11 cm) wavelength that he believed would
provide much greater detail. In fact, this approach did not work.
He built a second receiver with a 900-MHz (30 cm) wavelength,
but still had no luck. On his third try in 1938, at a 160-MHz
(1.85 m) wavelength, he detected radio emissions from the Milky
Way, confirming Jansky s original work in greater detail.
Reber faced other difficulties in his work. The sparks from
automobile engines created too much interference during the
day for successful results, even in Wheaton, so he found it nec-
essary to work almost entirely at night. These automobile sparks
created fuzzy spikes on his charts even at night, but the results
were still clear enough to be included in the articles on his work
that he began publishing in 1940. He presented other data as
contour maps, showing clearly that the strongest (brightest) sig-
nals in the Milky Way emanated from its center, corresponding
with the bulge found at the center of almost all galaxies in later
years. It wasn t until the late 1990s that astronomers came to the
conclusion that almost all galaxies have a vast black hole at their
centers, which creates enormous stellar activity as their massive
gravity pulls star systems toward them. Early clues to this phe-
nomenon were present in Reber s data, including bright radio
sources in Cygnus and Cassiopeia that his efforts revealed for the
first time.
Reber s first paper on his radio telescope discoveries ap-
peared in the Proceedings of the Institute of Radio Engineers, #28,
in 1940. This was a technical article describing the details of the
instrumental design of his radio telescope and the method he
Grote Reber 125
had used to reduce and record the data he was receiving. It
should be noted that he did not refer to his instrument as a
radio telescope. That term was not introduced until after
World War II. Reber simply called it an antenna system. A sec-
ond article, titled Cosmic Static, was published in Astrophysical
Journal, #91, later in the same year. Brief and in some ways ten-
tative as this article is, it marks the beginning of radio astron-
omy as a separate discipline. Several papers, Reber began,
have been published which indicate that electromagnetic distur-
bance in the frequency range 10 20 megacycles arrives approxi-
mately from the direction of the Milky Way. It has been shown
that black-body radiation from interstellar dust particles is not
the source of this energy.
In a footnote, Reber directed readers to the articles by Jansky
that had originally inspired him, as well as to a paper by two
other Bell Labs engineers on the same subject, published in
1937. His reference to black-body radiation was footnoted with a
citation of an article by Fred Whipple and Jesse Greenstein (with
whom Reber would later collaborate), which had appeared in
the Proceedings of the National Academy of Science, also in 1937.
This second citation makes clear that Reber fully grasped the
potential significance of what he was doing. Black-body radia-
tion would later prove to be a key element in establishing a the-
oretical proof for the Big Bang theory of how the universe
began, after Arno Penzias and Robert Wilson of Bell Labs stum-
bled on the steady hiss of cosmic background radiation in 1965
while they were developing a receiver for the first communi-
cations satellite, Telstar. This is not to suggest that Reber was
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