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Stjepan Mohorovicic

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Stjepan Mohorovicic
Born(1890-08-20)August 20, 1890
Bakar, Croatia
DiedFebruary 13, 1980(1980-02-13) (aged 89)
Zagreb, Croatia
ResidenceZagreb, Croatia
NationalityCroatian
Alma materUniversity of Zagreb; University of Göttingen
Known forPositronium, Relativity criticism, seismology, aviation meteorology
Scientific career
FieldsPhysicist, geophysicist, meteorologist

Stjepan Mohorovičić (20 August 1890 – 13 February 1980) was a Croatian physicist, geophysicist, astronomer and meteorologist, and one of the very few critics of Einstein's relativity whose independent scientific work is unambiguously part of the mainstream canon. In 1934 he predicted the existence of positronium — the bound state of an electron and a positron, and the lightest atom — which he named electrum. It was found experimentally by Martin Deutsch in 1951, seventeen years later, and Mohorovičić is now routinely described as the "father of positronium".

He was the son of Andrija Mohorovičić, discoverer of the crust–mantle boundary that bears the family name, and made substantial contributions of his own to seismology, lunar geophysics and aviation meteorology. He also predicted, in the 1920s, that the Moon has a crust and a Mohorovičić discontinuity of its own — confirmed by the Apollo seismic experiments in 1969.

Alongside this, from 1922 until the 1960s, Mohorovičić was a persistent and technically informed opponent of the theory of relativity. He published a book-length critique in Berlin in 1923 with a foreword by Ernst Gehrcke, advanced an alternative theory of his own, and in old age assembled what was probably the largest bibliography of relativity-critical literature then in existence — 744 references across two volumes. His case is frequently cited on this wiki because the professional cost is so clearly documented: despite a body of confirmed predictions that would ordinarily have secured a chair, he remained a secondary-school teacher for his entire career, and his work was largely ignored in his own country.

Biography

Family and education

Mohorovičić was born in Bakar, on the Croatian coast, the son of the geophysicist Andrija Mohorovičić (1857-1936), who in 1909 identified the discontinuity between the Earth's crust and mantle now known as the Moho. He completed gymnasium in Zagreb in 1908 and studied mathematics and physics at the University of Zagreb from 1908 to 1912, where his teachers included the physicist Vinko Dvořák and his own father.

From April to December 1912 he continued at Göttingen, then the strongest mathematical-physical centre in the world, where his professors included Arnold Sommerfeld, Woldemar Voigt and David Hilbert. This is worth emphasizing in view of what followed: Mohorovičić learned his physics from the people who built the framework he would later contest, and he was not an outsider to it.

Career

From 1913 he taught at the Great Gymnasium in Bjelovar, and subsequently at gymnasia in Koprivnica and Osijek; in December 1917 he transferred to the Commercial Academy in Zagreb, and he later became a gymnasium professor in Zagreb. During the First World War he directed Austro-Hungarian military meteorological stations. In 1918 he received his doctorate in philosophy from the University of Zagreb.

He never held a university post. Croatian encyclopedic sources are unusually direct about the reason: his long-standing rejection of Einstein's theory of relativity, together with what are variously described as political indiscretions and his pre-war German connections, prevented his academic advancement and left his work largely unrecognized at home. He nonetheless published more than fifty scientific papers over a career spanning six decades, and remained scientifically active into his eighties.

He died in Zagreb on 13 February 1980, aged 89.

Scientific work

Positronium

Mohorovičić's best-known result appeared in "Möglichkeit neuer Elemente und ihre Bedeutung für die Astrophysik" ("The possibility of new elements and their significance for astrophysics"), Astronomische Nachrichten 253, No. 4, pp. 93-108 (1934).

In it he argued that an electron and a positive electron could form a bound, hydrogen-like system — a genuine "atom" with no nucleus, the lightest possible. He called it electrum. Crucially, he did not stop at the qualitative proposal: he calculated the spectrum of the system, and he predicted that it should occur in stars, which is why the paper appeared in an astronomical journal rather than a physics one.

Every part of this was subsequently borne out. Martin Deutsch produced positronium in the laboratory at MIT in 1951. The spectral lines Mohorovičić had computed were first identified in the laboratory in 1975. In 1984 positronium was detected in space, in the Crab Nebula — the astrophysical prediction confirmed fifty years after it was made. Proleksis and other Croatian sources go further and credit him with anticipating the positive electron itself in 1923, ahead of Dirac's theory and Anderson's 1932 detection; this claim is less widely reported outside Croatia and should be treated as attributed rather than established.

Seismology and lunar geophysics

Working in his father's field, Mohorovičić developed a new method for determining the focal depth of earthquakes (1913) which provided an independent confirmation of the Mohorovičić discontinuity — a matter of some delicacy, since the discontinuity was his father's discovery and independent verification by a family member required a genuinely different method. In 1916 he proposed a further, weaker discontinuity within the Earth's crust, and later argued for additional weak discontinuities at greater depth.

In papers of 1924 and 1927 he put forward a theory of the Moon's origin and internal composition, arguing that the Moon must possess a crust and a discontinuity of its own. The Apollo 11 seismometers left on the lunar surface in 1969 confirmed a lunar crust and a crust–mantle boundary, vindicating a prediction made more than forty years earlier with no prospect at the time of ever testing it.

Astrophysics and meteorology

He developed a theory accounting for the redshift of spectral lines through the gravitational fields of stars — a topic of obvious relevance to his relativity criticism, since it offered an alternative route to an effect commonly presented as a confirmation of general relativity.

From 1915 he carried out early aerological measurements using pilot balloons, analysing the circulation of the upper atmosphere, and in 1943 he published Oblaci ("Clouds"), the first manual of aviation meteorology. After the Second World War he was a significant figure in linking the emerging Croatian optical industry to optical education, work described in a 2022 study in the journal Cris.

Criticism of relativity

The 1922 lecture and the 1923 book

On 26 February 1922 Mohorovičić delivered a lecture at the University of Zagreb attacking the mathematical, physical and philosophical foundations of relativity. He reworked it into a book published the following year in Berlin by de Gruyter: Die Einsteinsche Relativitätstheorie und ihr mathematischer, physikalischer und philosophischer Charakter (1923, 77 pp.), with a foreword by Ernst Gehrcke and — characteristically for the internationalist mood of the period — a summary in Esperanto. Bibliographers of the critical literature describe it as a comprehensive presentation of all the objections to both the special and the general theory, and it remains one of the standard early critical monographs.

Mohorovičić did not confine himself to criticism. He is listed among the small group of authors — with Guillaume, Willigens and von Raschevsky — who answered the claim that Einstein's assumptions were the only ones possible by constructing alternative, internally consistent relativity theories. This is the more demanding form of dissent, and the one his sympathizers on this wiki regard as the model: not merely showing that a theory has difficulties, but exhibiting a rival that does the same work.

He was also a signatory of the public declaration of German-speaking scientists protesting the promotion of relativity at meetings of the Gesellschaft Deutscher Naturforscher und Ärzte, signing as "Prof. Dr. S. Mohorovicic, Agram" alongside Gehrcke, Lenard, Palágyi, Strehl, Vogtherr and others.

A note for readers. That declaration and the German critical circle around Gehrcke and Lenard cannot be separated from their political context: parts of that movement, and Lenard in particular, went on to pursue the campaign against relativity on explicitly antisemitic grounds under National Socialism. Mohorovičić was a Croatian secondary-school teacher publishing on physics, not a participant in Deutsche Physik, and nothing in his scientific writing turns on that association — but the association is real, is part of why Croatian sources record his "pre-war German connections" as damaging to his standing, and is stated here rather than passed over.

Raum, Zeit und Welt

Mohorovičić's largest critical work is the two-part essay "Raum, Zeit und Welt" ("Space, Time and World"), contributed to Karl Sapper's collection Kritik und Fortbildung der Relativitätstheorie (Akademische Druck- und Verlagsanstalt, Graz): Part 1 in volume 1 (1957; the wiki entry dates it 1958), pp. 168-281, and Part 2 in volume 2 (1962).

Its most remarkable feature is bibliographic. Part 1 carries 409 references; Part 2 continues the sequence with numbers 410 to 744. Taken together, Mohorovičić's 744 citations constitute what is probably the single largest bibliography of relativity-critical writing compiled up to that date — an act of scholarship independent of whether one accepts his conclusions, and one of the principal reasons the essay is still consulted. He was then in his late sixties and seventies, and had been reading the literature continuously since 1922.

He also contributed to the Austrian critical journal Wissen im Werden (from 1958), alongside Gehrcke, Sapper, Vogtherr and others.

Reception

Mohorovičić presents an awkward case for the usual accounts of scientific dissent, in both directions.

For the mainstream, he is a critic of relativity whose independent theoretical work was not merely competent but strikingly prescient: positronium, its spectrum, its presence in stars, the lunar crust and discontinuity, the confirmation of his father's boundary by a new method. These were not lucky guesses but calculated predictions, several confirmed only decades later. It is not possible to file him under incompetence.

For his fellow critics, he is the clearest available demonstration that opposition to relativity carried a professional price independent of the quality of one's other work. A man who had studied under Sommerfeld, Voigt and Hilbert, who held a doctorate, who published more than fifty papers and who correctly predicted the lightest atom in the universe, spent his working life teaching physics to schoolchildren. Croatian sources say plainly that his rejection of Einstein was among the reasons.

The counterweight, which an honest account should record, is that his marginalization was not purely intellectual either: the same sources cite political missteps and his association with the German critical circle, in a country that had just lived through the Second World War, as contributing causes. And his positronium paper — published in a mainstream journal in 1934, at the height of his relativity criticism — was accepted, printed, and eventually vindicated, which suggests the suppression was of the man's career rather than of his ideas.

Today the Croatian scientific community has largely recovered him. He is honoured as the father of positronium, and the standard reference works record both the achievement and the neglect.

Publications

Selected scientific papers and books

  • S. Mohorovičić, "Möglichkeit neuer Elemente und ihre Bedeutung für die Astrophysik", Astronomische Nachrichten 253, N4, pp. 93-108 (1934) — the positronium prediction
  • S. Mohorovičić, Die Einsteinsche Relativitätstheorie und ihr mathematischer, physikalischer und philosophischer Charakter, foreword by Ernst Gehrcke, Walter de Gruyter, Berlin (1923), 77 pp.
  • S. Mohorovičić, Oblaci ("Clouds"), Zagreb (1943) — the first manual of aviation meteorology
  • Papers on the determination of earthquake focal depth (1913), on a further discontinuity within the Earth's crust (1916), and on the origin, crust and discontinuity of the Moon (1924, 1927)

Abstracts

  • 1962 - "Raum, Zeit und Welt" — Part 2, in Kritik und Fortbildung der Relativitätstheorie, vol. 2, ed. Karl Sapper, Graz; references 410-744
  • 1958 - "Raum, Zeit und Welt" — Part 1, in Kritik und Fortbildung der Relativitätstheorie, vol. 1, ed. Karl Sapper, Graz, pp. 168-281; 409 references

See also

References

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