Carbon 14 – Libby’s Luck

Carbon 14 - Libby's Luck

Willard Libby acknowledged his “most miraculous” good fortune in his 1967 paper History of Radiocarbon Dating.

The good fortune in many stages of this research was most miraculous.

As one example, it would have been difficult indeed to have done the research without Grosse’s thermal diffusion columns, which one could not have afforded to construct.

They just happened to be ready, and operating.

As a second example, without the experience in the measurement of small amounts of radioactivity which the group had gained in other connections over the years, it would not have been possible to measure even the most concentrated samples.
As a third example, the oceans do mix.

As a fourth, no one in Baltimore had used synthetic radiocarbon from the Atomic Energy Commission for research at the time of the study, so it was quite certain that the radiocarbon found in the sewage was natural.

History of Radiocarbon Dating – 1967 – Willard Libby
http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0336&numPages=23&fp=N

And Wikipedia clearly documents the good fortune of Willard Libby.

He received his B.S. in 1931 and Ph.D. in 1933 in chemistry from the University of California, Berkeley, where he then became a lecturer and later assistant professor.

Libby spent the 1930s building sensitive geiger counters to measure weak natural and artificial radioactivity.

In 1941 he joined Berkeley’s chapter of Alpha Chi Sigma.

Awarded a Guggenheim Fellowship, he spent most of 1941 at Princeton University.

After the start of World War II, he worked on the Manhattan Project at Columbia University with Nobel laureate chemist Harold Urey.

Libby was responsible for the gaseous diffusion separation and enrichment of the uranium-235 which was used in the atomic bomb on Hiroshima.

In 1945 he became a professor at the University of Chicago.

In 1954, he was appointed to the U.S. Atomic Energy Commission.

In 1959, he became Professor of Chemistry at University of California, Los Angeles (UCLA), a position he held until his retirement in 1976.

In 1960, Libby was awarded the Nobel Prize in Chemistry for leading the team (namely, post-doc James R. Arnold and graduate student Ernie Anderson, with a $5,000 grant) that developed carbon-14 dating.

http://en.wikipedia.org/wiki/Willard_Libby

But neither Wikipedia nor the smiling Willard Libby mention that it’s possible to give your luck a helping hand.

Origins: 1927-1940
Libby at Berkeley: GM Counter Development

Known at UCB as “Wild Bill Libby” for pushing “far out” ideas and undertaking “fast and rough” experiments

Radiocarbon Dating: A History
2009 Radiocarbon in Ecology and Earth System Science
University of California, Irvine
https://webfiles.uci.edu/setrumbo/public/2009_14C_class/UCI_C14HISTORY_2009.pdf

In many ways Willard Libby helped to make his own luck by playing the numbers game.

Like a good card player Libby counted his scientific cards and coolly calculated his chances of winning before he made a scientific gamble.

However, like other Settled Scientists before him, Willard Libby could also finesse a fudge, reverse engineer an equation [to fit the data], exploit privileged information and gain advantage by applying psychological pressure.

In fact, the entire Radiocarbon Dating edifice is based upon Libby’s Luck.

Where the story really starts has been lost in the fog of war.

However, one illuminating starting point is the way Willard Libby helped to establish a favourable baseline of “natural” Carbon 14 radiation for his Radiocarbon Dating theory.

During World War Two Willard Libby was a member of the Manhattan Project and he “was responsible for the gaseous diffusion separation and enrichment of the uranium-235 which was used in the atomic bomb on Hiroshima” [Wikipedia].

Libby knew [very well] that the world changed in 1945 after the nuclear genie had been explosively unleashed into the atmosphere.

Above Ground Explosions

Libby also knew [very well] that the Skies over America had begun to change in 1942 when the “first man-made self-sustaining nuclear chain reaction was initiated” at the University of Chicago [where Libby became a professor in 1945].

Chicago Pile-1 (CP-1) was the world’s first artificial nuclear reactor.

The construction of CP-1 was part of the Manhattan Project, and was carried out by the Metallurgical Laboratory at the University of Chicago.

It was built under the west viewing stands of the original Stagg Field.

The first man-made self-sustaining nuclear chain reaction was initiated in CP-1 on 2 December 1942, under the supervision of Enrico Fermi.

Fermi described the apparatus as “a crude pile of black bricks and wooden timbers.”

Made of a large amount of graphite and uranium, with “control rods” of cadmium, indium, and silver, unlike most subsequent reactors, it had no radiation shield and no cooling system.

http://en.wikipedia.org/wiki/Chicago_Pile-1

Manhattan_Project_US_Canada_Map
http://en.wikipedia.org/wiki/Manhattan_Project

Shortly after the Little Boy was dropped on Hiroshima on August 9, 1945, the Kodak Company observed some spotting/fogging on their film which was, at the time, usually packaged in cardboard containers.

Dr. J.H. Webb, a Kodak employee, studied the matter and concluded that the contamination must have come from a nuclear explosion somewhere in the United States.

He discounted the possibility that Little Boy was responsible due to the timing of the events.

A hot spot of Fallout from the Trinity explosion had contaminated the river water that the paper mill in Indiana used to manufacture the cardboard pulp from corn husks, aware of the gravity of his discovery, Dr. Webb kept this secret until 1949.

The physicist’s knowledge of the secret project was not altogether surprising considering that the Kodak Company ran the Tennessee Eastman uranium processing plant at the Oak Ridge National Laboratory.

http://en.wikipedia.org/wiki/Trinity_%28nuclear_test%29

In 1972 Libby confirmed he had “guessed” [during 1945] that nuclear fallout [which includes Carbon 14] is mixed in the lower atmosphere.

We know now (although we only guessed it in 1945) that the stratospheric air mixes downward with the lower air–the troposphere–only in a matter of years.

This information has been gained from studies of the radioactive debris of nuclear explosions introduced into the stratosphere by the high rising fireballs.

At the present time we still are detecting such fallout from explosions in 1962.

Radiocarbon Dating, Memories and Hopes – 1972 – W. F. Libby
Department of Chemistry and Institute of Geophysics and Planetary Physics,
University of California, Los Angeles
http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0338&numPages=17

However, Libby’s 1945 “guess” quickly turned into a racing certainty because [after all] his theory of Radiocarbon Dating is based upon Carbon 14 mixing in the lower atmosphere.

The cosmic ray production of radiocarbon in matter is the basis of radiocarbon dating.

It is made from the most abundant atom in air: nitrogen of mass fourteen.

Radiocarbon –carbon-l4 or 14C– lasts 8300 years on the average (see note on radioactive decay for explanation on “half life” and “average life”) before reverting by radioactive decay to nitrogen-l4.

During this time it enters all living things as well as sea water and air.

Chemically, carbon dioxide is the food of life and presumably the freshly produced 14C atom is oxidized sooner or later (probably in a few days, although this time is not at all well known) to 14CO2 which is mixed with the ordinary carbon dioxide (0.03% in air) by the winds.

Radiocarbon Dating, Memories and Hopes – 1972 – W. F. Libby
Department of Chemistry and Institute of Geophysics and Planetary Physics,
University of California, Los Angeles
http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0338&numPages=17

Therefore, when Libby initiated his quest to establish a baseline for “natural” Carbon 14 radiation [extracted from Baltimore sewage] he was well aware that Baltimore [and its residents] would be mildly contaminated by the nuclear fallout from the atmospheric explosions of 1945 and 1946.

However, our major objective was to search for natural radiocarbon and thus to test whether the whole theoretical fabric was false in some way.

The theoretical structure was in a sense simple – the cosmic rays make radiocarbon atoms at a steady rate of about 2 per square centimetre of area of the Earth per second and have been doing so for tens of millenia.

Thus at present, there should be an equilibrium inventory in which about 2 radiocarbons revert to nitrogen every second for each square centimetre of area.

Therefore, we should find about 2 disintegrations per second for every 8 g of carbon in living beings, or dissolved in sea water, or in the atmospheric CO2, for the total carbon in these three categories adds to 8 [7.5 in the oceans, l/8 in the air, 1/4 in life forms and perhaps l/8 in humus. Some of these figures are not accurately proven but since the ocean is the largest and is best known (5% error or better) the total is known to about 10%].

Thus we expected to find this concentration of radiocarbon in living matter and the job was to test for it.

Unfortunately at that time no instrument was sufficiently sensitive, so my colleague, Dr E. G. Anderson and I were stumped for the time, until we recalled that an old friend from World War II days had a carbon isotope separator with which he was making concentrated 13C for isotope tracer work in cancer research.

This expensive machine was operating at Marcus Hook near Philadelphia and we enlisted Dr A.V. Grosse’s aid to enrich the natural 14C by some hundredfold in concentration so we then could detect the radioactive rays it gives in reverting to 14N in our Geiger or methane-filled proportional counters.

Dr Grosse’s equipment operated on methane (CH4).

Therefore we needed to find a source of “live” methane, i.e., methane of recent origin.

We found it in the gaseous effluent of the sewage disposal plant of the city of Baltimore.
Methane (in natural gas) from oil wells would be completely devoid of C because its age is so great, but the sewage gas methane should, of course, have its full complement of 14C.

Dr Grosse after obtaining the sewage methane proceeded to enrich it to varying degrees (as measured by the 13C enrichment) and Dr Anderson and I excitedly put the enriched methane in our proportional counter and recorded the counting rate.

Strangely enough this whole thing worked and we did find about the anticipated 14C concentration as a small additional counting rate for the enriched methane, compared with the rate for unenriched methane or for petroleum natural gas methane.

Radiocarbon Dating, Memories and Hopes – 1972 – W. F. Libby
Department of Chemistry and Institute of Geophysics and Planetary Physics,
University of California, Los Angeles
http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0338&numPages=17

Very fortunately, a friend, A. V. Grosse, was in the business of concentrating carbon isotopes, using methane as a process gas in a thermal diffusion column, and he was asked to join in the search for natural radiocarbon.

The next task then was to find methane which was alive, in the sense of not having been too long out of the biosphere.

Methane from an oil well would obviously contain no radiocarbon, since it would be far too old.

This was accomplished by Grosse by asking Joseph Pew, of the Sun Oil Company, to persuade the mayor of the city of Baltimore to permit sewage methane from the Baltimore City sewage disposal plant to be used.

It was this methane which Grosse concentrated in his thermal diffusion column at Marcus Hook, Penn., and shipped to Chicago, where it was measured in the author’s counters.

Grosse’s concentrates were measured for 13C enrichment, and from observed 13C enrichment the expected 14C enrichment was readily calculated.

The enriched methane gas was placed directly in an ordinary cylindrical Geiger counter, rather than making carbon of it and using the screen wall, because the enrichments calculated were somewhat larger than the bare minimum.

Unenriched methane was used for the background measurement.

A plot was made of the difference in count-rates from the enriched and unenriched methane, using thick shielding (a foot or so of iron and lead in all directions) to eliminate the background from radioactivity in the laboratory and leave only the meson level.

Biomethane Radioactivity

In this way a rise with enrichment, that fitted the theoretical curve well, corresponding to about the concentration predicted was observed.

The good fortune in many stages of this research was most miraculous.

As a fourth, no one in Baltimore had used synthetic radiocarbon from the Atomic Energy Commission for research at the time of the study, so it was quite certain that the radiocarbon found in the sewage was natural.

History of Radiocarbon Dating – 1967 – Willard Libby
http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0336&numPages=23&fp=N

The task was to take this living methane and concentrate it in the isotope separation column to see whether the heavy enriched product was radioactive.

Happily for our research, it was found to be so and in about the expected amount.

The material used was methane gas from the sewage disposal plant of the City of Baltimore.

Radiocarbon Dating – Willard Libby
Nobel Lecture, December 12, 1960
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1960/libby-lecture.pdf

Evidently Libby didn’t push his luck in his search for “natural” radiocarbon because there are only three point plotted on his graph.

Additionally, the intriguing vertical axis [labelled “Excess count rate from biomethane over petromethane”] suggests Libby may have held an ace up his sleeve because his results could have shown that “methane from an oil well” wasn’t really “too old” to contain radiocarbon.

However, the really important result for Libby was that he had established an elevated baseline for “natural” Carbon 14 radiation that made it a racing certainty that he would be able to demonstrate reduced levels of Carbon 14 radiation in material that truly pre-dated the atomic age.

The elevated baseline [where d14C = zero] is evident in the atmospheric monitoring performed in New Zealand because actual d14C values only managed to rise above the zero baseline in 1955.

d14C

Source: I. Levin, B. Kromer, H. Schoch-Fischer, M. Bruns, M. Munnich, D. Berdau, J.C. Vogel, K.O. Munnich – University of Heidelberg
http://cdiac.esd.ornl.gov/trends/co2/cent-verm.html
http://cdiac.esd.ornl.gov/trends/co2/welling.html

This elevated baseline [where d14C = zero] is also underlined by current projections that show atmospheric d14C values will be below zero be the end of the century.

The Future of Atmospheric Radiocarbon

Atmospheric d14C
2009 Radiocarbon in Ecology and Earth System Science
University of California, Irvine

https://webfiles.uci.edu/setrumbo/public/2009_14C_class/2009_Atmosphere_Randerson.ppt

Unsurprisingly, Libby then proceeded to establish that reduced levels of Carbon 14 radiation could be measured using material that truly pre-dated the atomic age.

The plan was to measure living materials from various places on earth and to see whether they had the same radiocarbon content per gram of carbon.

These data on the natural abundance of radiocarbon in the earth were presented by E. C. Anderson for his doctoral thesis at the University of Chicago.

They show no appreciable differences even though they come from places varying in latitude from near the South Pole to near the North Pole.

Radiocarbon Dating – Willard Libby
Nobel Lecture, December 12, 1960
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1960/libby-lecture.pdf

Having acquired a sufficiently sensitive and practical technique, we went to work to test the main assumption on which radiocarbon dating was based.

This problem, the natural distribution and concentration of radiocarbon, actually was Dr Anderson’s doctoral thesis project.

He took wood samples collected about the turn of the century from widely dispersed places, as well as seal meat and oil from Antarctica (the source was Admiral Byrd’s last expedition).

All gave the same result (cf. Table 1).

This result still stands.

At the Nobel Symposium XII on Radiocarbon Dating held m Uppsala, 1970, several papers once again reaffirmed Dr Anderson’s conclusions.

The mixing is excellent.

ACTIVITY OF TERRESTRIAL BIOSPHERE SAMPLES

Radiocarbon Dating, Memories and Hopes – 1972 – W. F. Libby
Department of Chemistry and Institute of Geophysics and Planetary Physics,
University of California, Los Angeles
http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0338&numPages=17

Thus, forearmed with the results from E. C. Anderson’s doctoral thesis Libby was ready to confront The Four Just Men

One of the great achievements of Post-Normal Science after the Second World War was the establishment of Radiocarbon Dating as academically acceptable Settled Science.

This accomplishment was strategically initiated by Willard Libby when he asked for mainstream assistance with the validation of his pioneering Radiocarbon Dating technique.

The mainstream response was to form a formidable committee of Four Just Men [“three archaeologists and one geologist”] to assist Willard Libby.

https://malagabay.wordpress.com/2014/05/16/carbon-14-libbys-ring/

Footnote

The Anaerobic Digesters

The Back River Wastewater Treatment Plant (BRWWTP) began construction in 1907 and was opened in 1911. It is owned and operated by the City of Baltimore. It is situated on the west shore of the Back River; a tributary of the Chesapeake Bay. The plant occupies a 466-acre site and has a 35-foot elevation difference from influent to outfall, allowing wastewater to flow through the plant entirely by gravity. An estimated 1.3 million residents in a 140 square mile area of Baltimore City and County are served by this plant.

http://publicworks.baltimorecity.gov/Bureaus/WaterWastewater/Wastewater/BackRiverWastewaterTreatmentPlant.aspx

At the BRWWTP, sludge stabilization is currently achieved by the use of six, 1.3 million gallon conventional and two, 3 million gallon, egg-shaped anaerobic sludge digesters. The egg-shaped digesters were started in December of 1992. They are slightly over eighty feet in diameter and one hundred and fifty feet high. They were selected because of their life-cycle cost, operating efficiencies (never require cleaning) and large volume/small footprint aspect.

Anaerobic digestion is a biological treatment where anaerobic bacteria decompose and stabilize the organics in the thickened sludge. Consequently, this sludge stabilization process reduces the volume of the sludge by destruction of volatile compounds while producing combustible gas as a by-product. Digester gas typically consists of about 65% methane and 35% carbon dioxide and is used for heating the digestion process, which operates between 96 and 98 degrees Fahrenheit. The gas is also used to heat various plant buildings and facilities. Digestion generally destroys about 45% of the volatile solids while producing an average 1.5 million cubic feet of gas per day. Reduction of sludge volume greatly reduces our costs for disposing of plant sludge,

http://publicworks.baltimorecity.gov/Bureaus/WaterWastewater/Wastewater/BackRiverWastewaterTreatmentPlant/SolidsTreatmentProcess.aspx

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3 Responses to Carbon 14 – Libby’s Luck

  1. Pingback: Carbon 14 – Willard’s World | MalagaBay

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