Adrianus de Hoop

As is the case with all other employees, professors retire when they turn 65. But there are exceptions. This week: mathematical physicist and electrical engineer Prof. ir. Adrianus de Hoop (86).

The interview was held in the garden of Aad de Hoop and his wife Annelies. A pile of papers lay on the table: an article being reviewed by De Hoop for an American journal. It was a tough job that had kept De Hoop busy for weeks. ‘If it’s rubbish, it goes faster’, he laughs.

Until last year, De Hoop cycled every day from Bergschenhoek to the EEMCS building in Delft, where he still has an office. When he retired in 1996, he was no longer required to attend meetings, and he enjoyed having more time for colleagues and his last doctoral students. De Hoop was also a regular in the Schlumberger-Doll American research laboratory. When he asked what they expected of him, the answer was, ‘Just sit back and think’.

The daily trips to Delft came to an abrupt end with a stroke, which caused him to lose control of the left side of his body. He considers himself fortunate that his mental ability was not affected, so that he can continue to work on articles written by others, as well as on his own scientific work.

His field is the triple intersection between mathematics, physics and electronics: from seismic research and acoustics to antennas and beyond. His thoughts have recently been taking him even further. He has returned to the mathematical equations of the Lorentz transformation – a system of equations compiled by Hendrik Antoon Lorentz (Nobel prize winner of 1902) that describes the relationship between the space-time coordinates of two observers moving in relation to each other using electromagnetic waves to exchange information. These equations form the foundation of Einstein’s special theory of relativity.

In addition to regarding time as a component of a four-dimensional geometry, as proposed by Einstein, De Hoop sees time as a separate, independent and observer-specific measure of the course of physical phenomena (following Herman Weyl). This arrangement allows space for speculation concerning the relationship with the quantum theory developed by Dirac (Nobel prize winner of 1933). De Hoop regards the article that he recently published on this topic in the journal Wave Motion as a springboard for further research in this direction.

For example, he discovered another set of equations with a related structure, which he now thinks could be used to describe gravity. This could clarify the nature of dark matter, which is currently a persistent problem for physicists.
Aad de Hoop is far from finished. Inexhaustible and enthusiastic, he is taking on the major questions of contemporary physics. He still wants to understand, solve and explain them. ‘I’m currently working on my book on the theory of everything’, states De Hoop in all seriousness. ‘It will be on the internet’. It might take another few years.

Adrianus de Hoop (born Rotterdam, 1927) was appointed Professor of Theoretical Electronics and Applied Mathematics in the Faculty of EEMCS in 1960, where he remained until his retirement in 1996. Thereafter, he retained an honorary appointment as Professor Emeritus. His 21 doctoral students included Jacob Fokkema, who would later become Rector. De Hoop made an impression with his improvements to the method for solving seismic pulse problems (Cagniard-De Hoop method, 1960) and his Handbook (1995). He received two honorary doctorates (Ghent and Växjö). He is a member of the Royal Netherlands Academy of Arts and Sciences (KNAW) and a foreign member of the Royal Flemish Academy of Belgium for Science and the Arts (KVAB). He maintains his own website at:

‘I’m currently working on my book on the Theory of Everything’ (Photo: Sam Rentmeester)

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