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Blasts from the past It does not matter if they were published 10 years ago or 100 years ago, old scientific papers may be more important than you think, as Werner Marx and Manuel Cardona explain
In this article we look at papers from the time of Newton right up to the present day. We will concentrate on the pre-1900 and pre-1930s eras, but we will also explore some more recent trends. Most citation data come originally from the Science Citation Index (SCI) published by Thomson ISI in Philadelphia. The results in this article were obtained using SCISEARCH, the version of the SCI offered by STN International. Although SCISEARCH only covers papers published since 1974, the references in these papers obviously stretch back much further than that date. Since 1974 only about 0.5% of the references in papers in all fields of science have been to articles published before 1900, whereas about 4% have been to papers that were published before 1950. When the "age distribution" of the references in all the papers that have been published in a particular year is plotted, it tends to peak three years previously. For example, papers published in 1999 dominate the reference lists of articles published in 2002. We can also use this plot to calculate the "half-life" of papers, a concept introduced by the crystallographer John Desmond (JD) Bernal in the late 1950s. For a given year the citing half-life is defined as the number of years that one has to go back in time to account for 50% of the total references given in that year. We are not convinced that the increase in the citing half-life that we have found - from 9.3 years in 1975 to 10.5 years in 2002 - is significant, although a similar increase has been found in a recent, more extensive analysis by Kevin Boyack and Alex Bäcker (see further reading). The fact that papers can still have an impact several decades after they were originally published is noteworthy because it contradicts the growing belief among some information scientists and others that the lifetime of scientific publications is rapidly decreasing. The data also show that there is considerable variation between subjects. The references in physics papers tend to be older than the average for all fields of science. For example, the share of papers with pre-1900 references is about 1%, and this increases to 6% for the pre-1930 era and 17% for the pre-1950 era. Engineers tend to cite fewer old papers (only 3% for pre-1930), whereas geoscientists tend to cite more (12%). The impact one century after publication
Einstein's three most-cited pre-1930 papers (with a total of about 2600 citations) are based on his PhD thesis and show how measurements of Brownian motion can be used to determine the size of molecules. In comparison, his famous 1905 paper on special relativity has been cited "only" 450 times since 1974, making it his fifth most-cited pre-1930 paper. However, Einstein's most-cited article of all time is his 1935 paper with Boris Podolsky and Nathan Rosen, which has over 2000 citations. This paper - which suggests that quantum mechanics cannot offer a complete description of "physical reality" - introduced what is now known as the EPR paradox. In second place behind Einstein in the pre-1930 list is Peter Debye, who published two influential papers on the theory of electrolytes in 1923. The other names in the top 10 are Max Born, Irving Langmuir (the only industrial physicist in either list), Lord Rayleigh, Marian Ritter von Smoluchowski, Peter Paul Ewald, James Clerk Maxwell, Hermann Weyl and Paul Dirac. Born published highly cited papers on the hydration of ions (1920) and the quantum theory of molecules (1927). Langmuir, who spent most of his career at General Electric, is best known for his 1918 paper on the adsorption of gases by solid surfaces. Von Smoluchowski's most-cited article put forward a new theory for the coagulation of colloids in 1917. When we look at individual papers we find that the most-cited pre-1900 article was published by the Dutch applied mathematicians Diederik Johannes Korteweg and Gustav de Vries in Philosophical Magazine in 1895. This paper, which introduced the concept of solitons, received about 600 citations in all journals (not just physics journals). In the most-cited paper for the pre-1930 era, Ewald showed how to calculate the sums of functions of the type 1/rn: such calculations are central to understanding the electric and magnetic properties of solids. This paper, which was published in Annalen der Physik in 1921, has received about 1600 citations since 1974. Sleeping beauties and other papers
Citations of influential papers in theoretical physics and chemistry often do not reach their maximum until decades after publication, and it is not unknown for some of these articles to be virtually ignored for many years or even decades. This is not unexpected: it is not easy to incorporate revolutionary ideas into established scientific concepts. Moreover, some theories and predictions cannot be fully tested when they are originally proposed due to lack of suitable equipment or data. One could say that these papers are "premature". The history of science also contains many examples of the scientific community being resistant to new discoveries. Hermann von Helmholtz, for instance, commiserated with Faraday about "the fact that the greatest benefactors of mankind usually do not obtain a full reward during their lifetime, and that the more time new ideas need for gaining general assent the more really original they are". And Max Planck once famously said, "a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents die and a new generation grows up that is familiar with it". Finally, we should note some of the limitations of our analysis. For instance, Gustav de Vries does not appear in table 1 because he was the second author on the paper with Korteweg. However, the majority of papers before 1930 only had a single author. Also, the actual numbers in the tables are underestimates because they only include citations from physics journals. The overall citation counts are somewhat higher because papers are often cited outside their own discipline. This is particularly true for early papers, because science was more interdisciplinary then than it is now. Final thoughts Author Further reading
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