Knut Lundmark and the Prehistory of Dark Matter

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Look in your standard cosmology textbook (in my case, the closest one at hand is Barbara Ryden’s Introduction to Cosmology) and go to the section which describes experimental discovery of dark matter. Two of the things you will likely find in there are the following pieces of information:

  • The virial theorem applied to the Coma cluster by Fritz Zwicky in 1933. In the paper “Die Rotverschiebung von extragalaktischen Nebeln”, Helvetica Physica Acta 6: 110–127 (1933), Zwicky studied the motion of galaxies in the Coma cluster and concluded that they were moving too fast to be bound together unless there was a large amount of unseen matter in the cluster adding to its gravitational strength. Zwicky named this matter “Dunkle Materie” or, literally translated, “Dark Matter”.
  • Zwicky’s work on dark matter did not have a very large scientific impact until 1970 when Vera Rubin studied the rotational curve of the Andromeda galaxy, “Rotation of the Andromeda Nebula from a Spectroscopic Survey of Emission Regions”, Astrophys.J. 159: 379 (1970), that the dark matter story really began. Just like Zwicky had discovered that the Coma cluster would need a significant amount of invisible matter to hold together, Rubin found that the stars in the Andromeda galaxy were moving too fast to be gravitationally bound unless there was a large amount of dark matter.
Knut Lundmark

Knut Lundmark as a student in 1908.

The history of the discovery of dark matter therefore seems rather set in stone, Zwicky was the first to discover it in 1933 and it gained traction after the work of Rubin in 1970. However, there is one person who has been forgotten in this storyline, professor Knut Lundmark. Apart from discovering the expansion of the Universe before Edwin Hubble (Nature 490, 176 (2012)), it turns out that Lundmark also had a thing or two to say about dark matter, something which would be forgotten, left to collect dust in a drawer, rediscovered by someone else, and only 85 years later found again.

In a conference celebrating the 40-year anniversary of the German Astronomical Society in 1930, Lundmark presented his findings about the velocities of stars within galaxies. Sounds familiar? It should. What Lundmark had done was essentially to measure the galaxy rotation curves of several different galaxies and compared the mass required to the luminous mass of the galaxies. His conclusion was the same as that of Rubin 40 years later, a large part of the mass of a galaxy is in the form which is not visible to us. Like Zwicky would do three years later, Lundmark spoke about this additional mass as “Dunkle Materie” although he never went as far as suggesting that it would be a new form of matter, only that it was matter which we could not see. Lundmark’s findings were published in Lund Medd. 125, 1 (1930) and subsequently seems to have been largely forgotten.

The rest, as they say, is history. With Zwicky’s and Rubin’s results becoming highly popular and the essential foundation for our modern understanding of dark matter, Lundmark’s work was not rediscovered until 2015. On april 17 of that year, Lars Bergström, professor in theoretical physics at Stockholm University, gave a presentation at a conference in Trieste, Italy, where he told the story of how he had stumbled upon the reference to Lundmark’s work.

As to the sensmoral of the story, dark matter was eventually discovered, but it is not always the first person to discover something who history will credit.

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  1. Alex Klotz
    Alex Klotz says:

    In another example of prescient early-20th century Scandinavian physics, Gunnar Nordstrom wrote down the first "spacetime curvature" theory of gravity a few years before Einstein. Unfortunately for him, his theory was wrong, but it was still conceptually important.

  2. QuantumQuest
    QuantumQuest says:

    Great insight indeed. Unfortunately, history does not always give credits in a fair manner. I don’t know all the details about Lundmark – I’ll definitely dig it deeper, but as far as I know, he deserves the credit. I think, it is in many cases a fairly complex thing, to give credit for a discovery, to the right person. Particular time, person profile and fair knowledge of the importance of a discovery in many respects, are some critical factors.

  3. Chronos
    Chronos says:

    An AAS article was released earlier this month [Lost in the Dark: A proto-history of dark matter, [URL]http://adsabs.harvard.edu/abs/2016AAS…22711406][/URL] unfortunately, only the abstract appears to be freely available at present. Another good historical discussion of dark matter can be found here: [URL]http://www.kiss.caltech.edu/workshops/darkmatter2009/presentations/primack.pdf;[/URL] A Brief History of Dark Matter.

  4. Orodruin
    Orodruin says:

    As far as science or knowledge is concerned, it doesn’t matter who find out what first.

    From a hard scientific point of view, no. For how we look at the achievement of historical figures, in particular in connection with science, it plays a very important role. Certainly someone would have discovered relativity even if Einstein had never existed, yet here we are a hundred years later making T-shirts with his face on them.

    Not that it is important.
    There is an ‘n’ missing in “Zwicky named this matter “Dukle Materie”” → Zwicky named this matter “Dunkle Materie”.


  5. atyy
    atyy says:

    I had to look up “sensmoral” :)

    So should we still consider Rubin deserving of a Nobel, now that she is the second (third?) person to discover dark matter?

    What is the status of Zwicky as an early discoverer? Did he do things correctly enough that his claims of dark matter were valid?

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