Why Was Lise Meitner Left Out of the Fission Nobel Prize?

Lise Meitner is one of the clearest cases in our explainer Who Really Discovered It?. She helped make one of the most consequential discoveries of the 20th century, explained it, and was left off the Nobel Prize for it. Our Lise Meitner “Split Happens” sticker is our tribute. Here is what happened, kept to what the documents show.

What did Meitner discover?

The Berlin chemists Otto Hahn and Fritz Strassmann bombarded uranium with neutrons and reported barium among the products (Hahn & Strassmann 1939^[1]). NobelPrize.org summarises the puzzle: barium was “far too light an element to be a decay product of uranium”. Hahn’s “long-time colleague, Lise Meitner, and her nephew, Otto Frisch, tackled the problem from a theoretical standpoint and proved that the uranium nucleus had been split” (NobelPrize.org, Otto Hahn facts^[2]).

Their explanation appeared in Nature on 11 February 1939, “Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction”, signed by Meitner from the Physical Institute of the Academy of Sciences in Stockholm and Frisch from the Institute of Theoretical Physics in Copenhagen (Meitner & Frisch 1939^[3]). A week later Frisch reported physical evidence of the split, describing it as “a ‘fission’ of the uranium nucleus, similar to the division of a droplet into two” (Frisch 1939^[4]).

The physics: why a nucleus can split

A heavy nucleus behaves somewhat like a liquid drop. OpenStax explains that when a neutron is absorbed, the nucleus deforms; “acting like a struck liquid drop, the nucleus deforms and begins to narrow in the middle”, until the electric repulsion between protons “is able to break the nucleus into two parts” (OpenStax College Physics, §32.6^[5]). A typical reaction is

n + ²³⁵U → ¹⁴²Ba + ⁹¹Kr + 3n

Charge is conserved (92 = 56 + 36) and so is the number of nucleons (1 + 235 = 142 + 91 + 3). The energy is huge. Frisch wrote that the energy liberated “was estimated to be about 200 Mev., both from mass defect considerations and from the repulsion of the two nuclei” (Frisch 1939^[4]). The mass-defect route is simply E = Δm c², where Δm is the mass lost when the nucleus splits and c is the speed of light.

A worked number

OpenStax works through the fission of 1.00 kg of uranium-235 at 200 MeV per fission. The number of nuclei is N = (1000 g ÷ 235 g/mol) × 6.02 × 10²³ mol⁻¹ ≈ 2.56 × 10²⁴, so

E = N × 200 MeV × 1.60 × 10⁻¹³ J/MeV ≈ 8.21 × 10¹³ J

That is about 82 terajoules from one kilogram (OpenStax^[5]). Why the nucleus holds together at all is the subject of What Holds the Nucleus Together?. More nuclear-physics characters are in our Particle & Nuclear Physics collection.

Who got the Nobel Prize, and when?

The Nobel Prize in Chemistry 1944 was awarded to Otto Hahn alone, “for his discovery of the fission of heavy nuclei” (NobelPrize.org^[6]). The timing was unusual: during the 1944 selection, the chemistry committee decided that none of that year’s nominations met the criteria, so under the Nobel Foundation’s statutes the prize was reserved, and Hahn “received his Nobel Prize for 1944 one year later, in 1945” (NobelPrize.org^[6]).

Meitner was not short of support. The Nobel Prize nomination archive lists her as a “nominee in 49 nominations” (Nobel Nomination Archive^[7]): 19 for chemistry, between 1924 and 1948, and 30 for physics, between 1937 and 1967, the year before she died. She never won.

Why was she left out?

For decades the reasons could only be guessed at. Then, using what they describe as “recently released Swedish documents”, the historians Elisabeth Crawford, Ruth Lewin Sime and Mark Walker studied them. In a 1997 Physics Today article titled “A Nobel Tale of Postwar Injustice” they wrote that, in November 1945, “a narrow majority” of the Royal Swedish Academy of Sciences voted to give the 1944 chemistry prize to Hahn. They argued that Meitner’s exclusion points to flaws in the decision process and “to four factors in particular” (Crawford, Sime & Walker 1997^[8]):

1. “the difficulty of evaluating an interdisciplinary discovery”;
2. “a lack of expertise in theoretical physics”;
3. “Sweden’s scientific and political isolation during the war”; and
4. “a general failure of the evaluation committees to appreciate the extent to which German persecution of Jews skewed the published scientific record”.

The same article explains, from Swedish documents, why Meitner did not receive the 1946 physics prize for her theoretical interpretation either. On Strassmann, who was also left out, the authors wrote: “Probably, Strassmann was ignored because he was not a senior scientist.”

This is the historians’ interpretation of the archive, and it is the most detailed one published. We present it as their argument, quoted in their words, rather than as a settled verdict on every individual’s motives.

How was Meitner recognised?

In 1966 Meitner received the U.S. Enrico Fermi Award. Her citation reads: “For pioneering research in the naturally occurring radioactivities and extensive experimental studies leading to the discovery of fission” (U.S. DOE Office of Science^[9]). Meet more under-credited scientists in our Physicist Stickers collection, and read about another, the astronomer in Cecilia Payne: What Stars Are Made Of.

FAQ

Did Meitner work with Hahn?

Yes. NobelPrize.org calls her Hahn’s “long-time colleague”. The fission explanation itself was written with her nephew, Otto Frisch.

Who coined the word “fission”?

The term appears in Frisch’s February 1939 Nature paper, borrowed from the division of a droplet. NobelPrize.org says the phenomenon was “later called ‘fission’”.

Was fission discovered by chemistry or physics?

Both, which is part of the problem. Hahn and Strassmann’s chemistry found the barium; Meitner and Frisch’s physics explained it. Crawford, Sime and Walker list the difficulty of judging such an interdisciplinary discovery as the first of their four factors.

References

1. O. Hahn & F. Strassmann (1939), “Über den Nachweis und das Verhalten der bei der Bestrahlung des Urans mittels Neutronen entstehenden Erdalkalimetalle,” Die Naturwissenschaften 27, 11–15 (DOI 10.1007/BF01488241; metadata verified via Crossref). https://doi.org/10.1007/BF01488241
2. NobelPrize.org, Otto Hahn – Facts (Nobel Prize in Chemistry 1944). https://www.nobelprize.org/prizes/chemistry/1944/hahn/facts/
3. L. Meitner & O. R. Frisch (1939), “Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction,” Nature 143, 239–240. https://www.nature.com/articles/143239a0
4. O. R. Frisch (1939), “Physical Evidence for the Division of Heavy Nuclei under Neutron Bombardment,” Nature 143, 276. https://www.nature.com/articles/143276a0
5. P. P. Urone & R. Hinrichs, College Physics 2e (OpenStax, Rice University), §32.6 “Fission”. https://openstax.org/books/college-physics-2e/pages/32-6-fission
6. NobelPrize.org, The Nobel Prize in Chemistry 1944 (Otto Hahn). https://www.nobelprize.org/prizes/chemistry/1944/summary/
7. NobelPrize.org Nomination Archive, “Lise Meitner” (nominee record). https://www.nobelprize.org/nomination/archive/show_people.php?id=6097
8. E. Crawford, R. L. Sime & M. Walker (1997), “A Nobel Tale of Postwar Injustice,” Physics Today 50(9), 26–32 (DOI 10.1063/1.881933). https://physicstoday.aip.org/features/a-nobel-tale-of-postwar-injustice
9. U.S. Department of Energy Office of Science, Enrico Fermi Presidential Award, “Lise Meitner, 1966”. https://science.osti.gov/fermi/Award-Laureates/1960s/meitner

Written by Pixelated Physics. Every factual claim is linked to the source we checked; points that are still debated are labelled open.