John Call Cook (April 7, 1918 – October 12, 2012) was an American geophysicist who played a significant role in establishing the field of ground-penetrating radar. He is widely recognized for contributing fundamental research that advanced its development. Cook also demonstrated that aerial surveys could map surface radioactivity, enabling more efficient prospecting for uranium ore. He invented electrostatic detection methods for identifying hazardous ice crevasses and developed additional techniques in remote sensing.
For most of his professional career, Cook specialized in remote sensing and the detection of underground objects.
Early years
John Call Cook was born on April 7, 1918, in Afton, Wyoming, to Carl and Ella Cook. His father worked as an attorney and farmer, and was the son of Phineas Wolcott Cook and his fourth wife, Johanna.
As a teenager, Cook constructed a number of devices, including a spark-gap transmitter, a batteryless crystal radio, a six-inch telescope, and an improvised diving helmet made from a cookie can with a bolted plastic sheet for vision. The helmet was supplied with air through a garden hose powered by three tire pumps connected together.
University
Undergraduate
Cook first studied at Brigham Young University before transferring to the University of Utah to study physics. In the spring of 1941, he began working as a laboratory assistant at the university and graduated later that year.
The war years
As a physics major during World War II, Cook was recruited to work at the Radiation Laboratory at MIT, where he was assigned to the "Experimental Systems Group – 44" under Dr. James L. Lawson in the Roof Laboratory. The group focused on advanced radar problems, including signal discernibility, anti-jamming methods, short pulses, and receiver design. Its experimental systems frequently set performance standards, with members continually expanding the range of radar capabilities.
They employed S-band (10 cm wavelength) and X-band (3 cm) radar sets, each with several types of display, and later obtained a K-band set (1 cm), which was capable of resolving the structure of nearby objects such as a gasholder. Each set contained about 300 vacuum tubes, 10 to 20 adjustment knobs, and numerous interconnecting cables. Vacuum tube failures occurred nearly every day, requiring extensive troubleshooting.
The group often tracked a B-17 bomber sent from Bedford Airfield, experimenting with frequency and polarization, the use of chaff, jamming countermeasures, and evaluating whether propeller modulation of signal amplitude could distinguish friendly from hostile aircraft.
MIT Rocket Research Society
Cook was elected president of the Rocket Research Society, a special-interest club at the Radiation Laboratory.
Although the American Rocket Society in New York had suspended activities during the war, the MIT group continued experimenting with liquid-propellant rockets. Cook built a portable test stand from a wooden box, which included a thrust gauge, fuel and oxidizer tanks, valves with long control rods, and an electric ignition system. Together with Bob Smith and other members, he built rocket motors from materials such as steel, aluminum, ceramics, and even silver coins, using the lathes and facilities of the MIT Student Model Shop.
Members obtained liquid oxygen from the nearby Arthur D. Little Company, which was developing a portable military LOX generator and discarding excess product. The group transported the liquid oxygen in five-gallon steel cans insulated with fiber mat. In one of their most successful tests, a rocket motor produced a ten-foot flame with standing shock waves, driving the thrust gauge off-scale for more than ten seconds. However, the aluminum motor burned out and ignited the test stand, which they extinguished with a Pyrene fire extinguisher. The carbon tetrachloride extinguishing agent produced phosgene and chlorine gases, which corroded the metal equipment.
With liquid oxygen still remaining, the group conducted a controlled explosion. The blast propelled a wooden board 50 feet into the air and embedded gravel in the chest of the person lighting the fuse, despite Cook's safety precautions. The incident was later exaggerated in MIT's humor magazine Voo Doo, which portrayed Cook as the nonchalant "Lon Crook".
In spring 1945, news arrived of German V-2 missile attacks on Britain. The German Rocket Society, supported by the government, had advanced far beyond American efforts, continuing the work of Robert Goddard. Their large rockets were used for military purposes, which Cook found disheartening. He subsequently lost interest in rocketry until the creation of NASA. Anticipating his departure from Cambridge, he resigned as president of the MIT Rocket Research Society and was succeeded by Robert Kraichnan, who later became prominent in the study of general relativity.
Master of Science
In the fall of 1945, Cook received a graduate assistantship at Penn State and began work on a master's degree. During his second year, he was appointed to teach Professor Weber's junior-level thermal laboratory course. Cook read extensively in the Physics Library on gravitational topics, developed a thesis plan, and conducted experiments using an Eötvös torsion balance, a highly sensitive gravity-sensing instrument owned by the Geophysics Department in the Mineral Industries Building. Professor Sylvain Pirson was impressed with the modifications Cook made to improve the sensitivity of the balance and with his administration of the course. However, Professor Duncan, the department head, advised him that due to difficulties in advanced mathematical physics courses, it was recommended that he graduate with the master's degree and not continue further.
Cook graduated in 1947 at age 29. After returning home, he met L. V. S. Roos of Texaco, who headed a seismic prospecting crew in Utah, and was hired as an assistant recorder at $300 per month. Each morning, the eight-member crew traveled with a recording truck, a drill rig, and a water tanker to survey sites. The drill team bored three-inch holes up to 150 feet deep, where dynamite charges were placed. Cables and geophones were laid out in a radius of about 1,000 feet from the recording truck. After a preliminary charge was set off to "spring" the hole, the main shot was fired, requiring careful sequencing of switches. Because each hole could be used only once, accuracy and precision were critical. Cook was soon promoted for obtaining high-quality data.
With his master's degree, Cook was regarded as a specialist by visiting Texaco officials and by Roos, who suggested he might advance to crew chief or join the laboratory staff in Houston. These early successes, combined with the support of his family, helped restore his confidence.
PhD
In late 1947, Cook received a telegram from Professor Sylvain Pirson at Penn State offering him a position as a research assistant in the Geophysics Department with a salary of $170 per month and the opportunity to pursue a doctorate in geophysics. With tuition costs nominal and fieldwork in colder weather becoming less practical, Cook accepted the offer and re-enrolled at Penn State. He moved back into the Graduate Club and entered the PhD program. He was placed in charge of the earthquake seismograph station, where he learned to operate the equipment, analyze the records, and send reports to Washington. At Pirson's request, he built the department's first vertical-component seismometer, which he connected to a visible-ink recorder in the department offices, eliminating the need for photographic development to monitor earthquakes.
During the winter of 1949, Cook attempted to extend his master's work by testing for a tangential gravitational field—a hypothetical effect purported to arise around a rotating body. He arranged to use the large turbine rotors at the Westinghouse Plant Apparatus Division near Pittsburgh, setting up an Eötvös torsion balance on the factory floor while the rotors were balanced at 3,600 rpm. Despite the stability of the cast-iron plate flooring, vibrations and thermal fluctuations hindered his measurements. Attempts to dampen interference, such as filling the instrument with alcohol, introduced further instabilities. On his final visit, Cook was approached by Westinghouse engineer Joseph Slepian, who questioned the theoretical basis of the experiment and noted that the effect was not predicted by general relativity. Unable to defend the hypothesis, Cook abandoned the project.
At Pirson's request, Cook also built a model oil well with an electric logging system, producing data that Pirson encouraged him to publish. Cook's article, Laboratory Tests of Electrolog Resistivity Interpretation, appeared in The Producers Monthly. On the basis of this work, Pirson nominated Cook for membership in Sigma Xi, the national scientific research society, of which he remained a lifelong member.
Pirson later arranged for Cook to assume a research project sponsored by the Penn Grade Crude Association, a consortium of oil firms in northwestern Pennsylvania. Cook was promoted to research associate with a salary of $300 per month. Along with another associate, Bacon, he assumed responsibility for teaching all of the department's geophysics courses; Bacon taught most classes, while Cook taught general geochemistry during the 1948–49 academic year. Pirson subsequently left Penn State for an industry position in Tulsa, Oklahoma, a departure that was widely regretted within the department.
As part of the Penn Grade project, Cook conducted fieldwork in the oilfields near Bradford, Pennsylvania. These fields, known for producing high-quality petroleum refined into brands such as Quaker State and Pennzoil, were largely aging operations with equipment 30–50 years old. Cook observed drilling and logging practices and conceived an improved electric logging method based on thin-sheet current paths controlled by "shielding-current" electrodes, similar to Kelvin potential shields. Although his model showed significantly improved vertical resolution, he discovered that similar methods had already been developed by other inventors and by Schlumberger, which was involved in related patent litigation.
Thesis
With the government offering favorable purchase guarantees for newly discovered uranium, aerial surveys for radioactive ore became an area of growing interest. Cook selected airborne detection of surface radioactivity as his dissertation topic. He examined questions such as detection limits, flight altitude and speed, minimum ore body size, attenuation by overburden and atmosphere, and interference from cosmic rays and natural background radiation. While many answers could be derived from theoretical calculations, Cook sought experimental verification.
The Geophysics Department had recently acquired a portable Geiger counter, which Cook used to measure gamma radiation from rock samples collected at the Mauch Chunk carnotite outcrop. He also profiled a uranium ore stockpile at a refinery in Rifle, Colorado, demonstrating detectability at distances up to a quarter mile. Recognizing the limitations of Geiger counters for airborne surveys, he experimented with a large Geiger–Müller tube and constructed supporting circuits. Using hydrogen-filled balloons from the Meteorology Department, he lifted detectors up to 300 feet to measure gamma radiation from ore boxes, the Mauch Chunk deposit, and a small radium sample borrowed from a hospital. These experiments, carried out in 1950–51, formed the basis of his dissertation.
Cook's thesis, An Analysis of Airborne Surveying for Surface Radioactivity, was over 100 pages long and included 29 figures. It was typed in triplicate by his wife, Vi, and accepted by his committee.