History of Force Measurement in the US – Part 22

Based on work out of Germany, France and Finland, and at the request of the US Weather Bureau, two researchers of the Bureau’s electrical division began an endeavor to devise a practical system of radiometeorography for the weather service. A similar request was made by the aerological division of the Navy’s Bureau of Aeronautics, this one being researched by a team from the radio laboratory. This second team’s offering seemed better suited to both requests, so the duo from the electrical division fitted the device they had developed with Geiger counters and began launching them 20+ miles up to gather cosmic ray data. Their findings would impact thinking on radiation and the effect of cosmic rays on radio communication as well as the study of atomic structure. Using data gathered from 18 launches of their device, Leon Curtiss and Allen Astin confirmed international reports proposing that the greater part of cosmic-ray phenomena was caused by secondary effects within the Earth’s atmosphere.

The team from the radio division, meanwhile, successfully devised a unit that transmitted continuous data on cloud height and thickness, temperature, pressure, humidity, and light intensity in the upper atmosphere. Dubbed the “radiosonde”, the device was effective at 15+ miles up and at distances up to 200 miles. By 1940, it completely changed the US weather and meteorological services with 35,000 units being built and launched each year.

During the 1930s and 1940s, the Bureau was party to nearly every expedition sponsored by the National Geographic Society, including visits to the polar regions and balloon flights 14 miles into the stratosphere. The Society and the Bureau co-sponsored an expedition to the USSR to observe and photograph the 1936 solar eclipse, capturing the first-ever natural color photographs of an eclipse using a 14-foot camera conceived and constructed at the Bureau. Both the camera and the Bureau would participate in several other solar eclipse expeditions around the globe over the next few years. Dr. Briggs even organized an eclipse expedition to Brazil in 1947 that comprised 76 researchers from the Bureau, armed forces and National Geographic Society.

Concurrent with this atmospheric research, huge breakthroughs were made across the world in the fields of physics and atomic research. The Bureau’s first studies in this vein were into atomic chemistry, not physics. The existence of isotopes (atoms of the same chemical element with different atomic weights) had been discovered, but researchers were having difficulty finding a heavy isotope of hydrogen using the existing technology. The Bureau stepped in to suggest use of its cryogenic lab to study liquid hydrogen where experiments confirmed the existence of the proposed heavy hydrogen isotope.

In a series of discoveries by American and European scientists, the existence of neutrons was confirmed and the first nuclear reactions were performed. Enrico Fermi experimented using uranium with an atomic weight of 238 and bombarding the atoms with neutrons to split the nucleus, but his results were inconclusive. Later experiments by others confirmed that the same isotope of uranium could be split and finally that it could be split into two nuclei of roughly equal size but producing enormous quantities of energy in the process. These findings were relayed to Albert Einstein by Niels Bohr, who also informed him that Hitler had control of the only known source uranium ore and had placed an embargo on it.

This news and its significance were conveyed to President Roosevelt, who immediately sought the advice of Dr. Briggs at the Bureau. Within a week, Dr. Briggs was chairman of the newly formed Advisory Committee on Uranium. The Committee’s task was to investigate uranium fission (faster than Nazi scientists could). Less than a month from Einstein’s initial letter to the President, the Committee issued a report indicating the distinct theoretical possibility of a chain reaction that would produce enough energy for an explosive weapon or to power a submarine.

As the Second World War began in Europe, and recognizing the potential implications of researching nuclear fission, Dr. Briggs hesitated as to what he and the Bureau should do next. Was this a line of research he and his organization would or should pursue? The Committee was absorbed, renamed and absorbed again into a series of other national defense programs created as Nazi Germany continued its European conquests, before finally becoming inactive under the umbrella of the Manhattan District division of the Army Corps of Engineers in 1942.

**The information presented here is drawn from “Measures For Progress: A History of The National Bureau of Standards” (Rexmond C. Cochrane)

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