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  • This timeline lets you see aspects of Athol's life and work, and how these fit into a wider science picture of radiocarbon dating. A full transcript is underneath.

    Athol Rafter – nuclear chemist

    • Changing scientific ideas
    • Advances in science and technology
    • Biography


    Changing scientific ideas

    Each specialised field of science has key ideas and ways of doing things. Over time, these ideas and techniques can be revised or replaced in the light of new research. Most changes to key science ideas are only accepted gradually, tested through research by many people.

    Advances in science and technology

    All scientists build their research and theories on the knowledge of earlier scientists, and their work will inform other scientists in the future. A scientist may publish hundreds of scientific reports, but only a few are mentioned here.


    This part of the timeline outlines just a few events in the personal life of the featured person, some of which influenced their work as a scientist.


    Rutherford and radioactivity – 1902

    Ernest Rutherford and Frederick Soddy (pictured) suggest that radioactivity might be used to date minerals and rocks.
    Acknowledgement: Public domain.

    Carbon-14 discovered – 1940

    Sam Kamen and Martin Ruben discover C-14, a radioactive isotope of carbon, at University of California, Berkeley.
    Acknowledgement: The University of Waikato.

    Prediction proved – 1947

    Willard Libby (pictured) and Ernie Anderson make first detection of C-14 in biological material.
    Acknowledgement: Public domain.

    1st radiocarbon revolution – 1949

    Radiocarbon dating becomes one of the most important dating methods in archaeology.

    Atom bomb effect – 1957

    In the 50s, there is a growing realisation that the proportion of C-14 to C-12 and C-13 in the atmosphere is not uniform over time or space or in its uptake by different types of organic matter. For example, between 1955 and 1963, the use of atomic bombs doubled the amount of C-14 in our atmosphere. With Fergusson, Rafter links a measured increase in radiocarbon in the atmosphere with nuclear weapons testing.
    Acknowledgement: Public domain.

    Increased accuracy – 1958

    Calibration curves allow radiocarbon dates to be converted to calendar dates. Across the late 50s and 60s scientists, recognise that C-14 in the atmosphere varies through time and from place to place – for example, the atom bomb testing that skewed C-14 levels in the 50s and 60s.
    Acknowledgement: Public domain.

    Cambridge half-life – 1969

    It is discovered early on that Libby’s original estimate of the half-life of C-14 – 5,568 years – is out by 162 years. Improved estimates available by the late 1960s set it at 5,730 years. This updated value is known as the ‘Cambridge half-life’.

    This means that many calculated dates in papers published prior to this are incorrect. For consistency with these early papers and to avoid the risk of a double correction for the incorrect half-life, radiocarbon ages are still calculated using the incorrect half-life value of 5,568 years.

    Bayesian statistical method – 2006

    A shift to using the Bayesian statistical method means that radiocarbon dates are even more accurate.

    Present day and into the future – 2017

    Radiocarbon dating was expected to establish an empirical foundation for absolute chronologies. However, refining of sample processing and calibration curves, the anomalies in some replicability of results and differing cultural inferences around dates are highlighting that scientists and archaeologists must continue to use multiple lines of evidence and robust networks when interpreting radiocarbon data and drawing subsequent conclusions.


    Carbon-14 in living things? – 1946

    Willard Libby in America predicts that C-14 exists in living matter.

    Radiocarbon dating – 1949

    Willard Libby and colleagues develop radiocarbon dating using radioactive decay of isotopes in solid carbon.

    Improving radiocarbon dating – 1953

    Rafter improves method of radiocarbon dating, making it more accurate than Libby’s original method.
    Acknowledgement: The University of Waikato.

    First New Zealand dates – 1953

    Rafter and Gordon Fergusson obtain first radiocarbon dates for moa bones and Taupo ash layers.

    Atmospheric radiocarbon – 1954

    The measurement of C-14 in atmospheric CO2 started at Makara, Wellington.

    2nd radiocarbon revolution – 1958

    Accuracy greatly improved using a calibration curve based on tree ring dating.

    New dating facility – 1959

    Department of Science and Industrial Research (DSIR) Institute of Nuclear Science is set up in Lower Hutt.

    Libby Nobel Prize – 1960

    Libby receives the Nobel Prize in chemistry for his radiocarbon dating work.

    Second lab for NZ – 1974

    Waikato Radiocarbon Dating Laboratory is set up at University of Waikato.
    Acknowledgement: The University of Waikato.

    3rd radiocarbon revolution – 1977

    Accelerator mass spectrometry (AMS) counts isotope atoms directly, making radiocarbon dating more accurate and using much smaller samples.

    A southern hemisphere first – 1987

    An accelerator mass spectrometer at the Institute of Nuclear Science, Lower Hutt, is the first for radiocarbon dating in southern hemisphere.
    Acknowledgement: Lloyd Homer, GNS Science.

    New organisation – 1991

    Institute of Geological and Nuclear Sciences (GNS), a new Crown Research Institute, is formed.
    Acknowledgement: GNS Science.

    Another increase in accuracy – 2006

    Bayesian statistics and modern computers allow radiocarbon date ranges to be narrowed.

    Atmospheric C-14 measurement continues – 2010

    The C-14 measurements started by Rafter in 1954 continue. Longest such record in the world.

    New accelerator mass spectrometer opens – 2010

    19 May, Rafter Radiocarbon Laboratory gets new accelerator mass spectrometer, the only facility of its kind in the southern hemisphere. View the Rafter Laboratory AMS facility at GNS Science in this video.
    Acknowledgement: GNS Science Limited

    Resetting the carbon clock – 2012

    The sediment of Lake Suigetsu in Japan has preserved a time capsule of radioactive carbon dating back to 52,800 years ago.
    Present calibration of radioactive curves for C-14 are based on only 12,550 years of terrestrial data, leaving approximately three-quarters of the timescale calibrated via less-secure marine records. Cores from this lake are expected to provide more precise terrestrial data that will make the process of carbon dating more accurate, refining estimates by hundreds of years.
    The recalibrated clock won’t force archaeologists to abandon old measurements wholesale, but it could help to narrow the window of key events in human history.
    Acknowledgement: National Land Image Information (Color Aerial Photographs), Ministry of Land, Infrastructure, Transport and Tourism, Japan.

    Refining radiocarbon dating – 2014

    Professor Thomas Higham lead a team who re-tested a number of Upper Palaeolithic bone samples from across Europe. Higham used improved ultrafiltration to pre-treat the samples in order to refine the radiocarbon dating. The results, published in August 2014 showed a number of the past dates were inaccurate or wrong. This has provided new insights into Neanderthal distribution and extinction and has implications for other radiocarbon dates for ancient bone samples.


    Born in Wellington – 1913

    Full name Thomas Athol Rafter, but becomes known as Athol.

    University – 1935

    Obtains BSc at Victoria University College, Wellington.

    More studies – 1938

    Chemistry MSc at Victoria University College, Wellington. Becomes school teacher.

    Marriage – 1939

    Marries Ruby Valerie Organ, known as Val.

    Beginning research – 1940

    Becomes research scientist at Dominion Laboratory, analysing coal ash and uranium-bearing minerals.

    Training in radioactivity – 1948

    Is sent to America to learn about radioactivity.
    Acknowledgement: GNS Science.

    Radiocarbon dating – 1949

    Begins working on new technique of radiocarbon dating.

    Treating cancer – 1951

    Starts encouraging hospitals to use radioactive isotopes to treat cancer and supplies them with the isotopes.

    Publication of ‘The Atom Bomb Effect’ – 1957

    Rafter and colleague Gordon Fergusson publish their paper ‘The Atom Bomb Effect' in the New Zealand Journal of Science and Technology. The paper summarises their findings from measurements of C-14 levels in the environment, particularly in the atmosphere and surface ocean. The atmospheric data is collected from Makara.

    The results are announced to the wider scientific community when published in Science (USA) Volume 126 on 20 September 1957.

    Receives OBE – 1958

    Receives OBE (Officer of the Most Excellent Order of the British Empire) for services to science and education.

    Institute of Nuclear Science – 1959

    Becomes first director of Department of Science and Industrial Research (DSIR) Institute of Nuclear Science in Lower Hutt.
    Acknowledgement: GNS Science.

    Awarded DSc – 1968

    Awarded DSc (Honorary doctorate in science) by Victoria University of Wellington for his radiocarbon work and geothermal studies using oxygen isotopes

    International conference – 1972

    The 8th International Radiocarbon Conference is held in Lower Hutt, a sign of the important role played by Rafter and colleagues.

    Athol retires – 1978

    Although retired, Athol continues to be active on science committees. Plays bowls when time allows.
    Acknowledgement: GNS Science.

    Athol’s wife, Val dies – 1992

    Val had been Athol’s wife for 53 years.

    Rafter Laboratory – 1993

    To mark Rafter’s 80th birthday, the Institute of Geological and Nuclear Sciences names their dating facility the Rafter Radiocarbon Laboratory.
    Acknowledgement: GNS Science.

    Athol dies – 1996

    Athol dies aged 83.
    Acknowledgement: GNS Science.

    Useful links

    Learn more about the sediments of Lake Suigetsu and how it is helping in refining radiocarbon dating and resetting the carbon dating clock.

    Rights: University of Waikato Published 10 June 2010, Updated 31 August 2017 Referencing Hub media
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