How difficult was it to reconstruct the (more personal) details of the Alsos mission? How much information is drawn from Alsos by Sam Goudsmit and The Alsos Mission by Boris T. Pash?

Quite difficult. Like I said, the personal life of Sam has not been very systematically recorded. He kept many of his letters, both incoming and outgoing. But most letters were mainly work-related, although Sam as a person is always present in what he writes and does. Alsos and the book by Pash are really good sources for the general story lines and personal views. For the details, it took a lot of research to find out historic facts.

The hardest part of the story was to assess Sam’s feelings of guilt, because of the death of his parents in Auschwitz. He hardly mentions it to anyone in letters, and Esther says she doesn’t really know, but I became convinced these feelings of guilt have been his main motivation for all his actions and life views after the war. He was a sad man, beneath his happy appearance.

In your opinion, what is the reason why Sam Goudsmit never received the Nobel prize for his discovery of electronic spin?

Sam was nominated many times together with George Uhlenbeck, as can be checked from the Nobel Prize archives. Many good scientists get nominated and never win, so there might be just no particular reason. I do not know if the Nobel prize committee ever actually considered Sam and George. If they did, there might have been the problem that electron spin had been previously proposed (not published), but had never been taken seriously by senior scientists. It took a free spirit like Ehrenfest to go ahead (whatever Lorentz thought at first). Anyway, the discovery might be a bit too muddled for the Nobel Committee.

How much truth, in your opinion, do the Farm Hall transcripts contain, given that the interned German physicists might have known that they are being recorded?

For example, the transcript contains the following: WEIZSÄCKER: I believe the reason we didn’t do it (editor note: build the atomic bomb) was because all the physicists didn’t want to do it, in principle. If we had all wanted Germany to win the war, we would have succeeded. HAHN: I don’t believe that but I am thankful we didn’t succeed.

Hard to tell. I think a lot of historic research has been done on this subject. Most historians agree that the German nuclear programme did exist, but was a mess due to bad management and conflicts between scientific and military groups. The real reason the bomb was not built was that the German sciences had been robbed of many of the finest by race laws.

Based on your research on the book, how much intellectual exchange do you think there was between German theoretical physicists and the physicists based in the US and UK shortly before and during the war? Did they actually publish papers during the war?

There was not much exchange, judging from the efforts it took to understand the nuclear work from the outside.

Do you think that a non-Dutch person could have written this book? It seems like it took a lot of understanding of Dutch culture and local knowledge (and of course, lots of the documents are in Dutch). For example, the story of the child who Goudsmit meets in his parents’ abandoned house, who gives him a piece of orange cloth.

Most archives are in English, but I explicitly tried to keep a Dutch perspective, because the book was written for the Dutch market, providing the first lengthy biography on this forgotten Dutch scientist. This is why a chapter like the one on Kistenkamer is included –  the Dutch physicist who worked for the Germans in Paris for a while, and after the war became the central figure in the Urenco uranium enrichment programme.

Is there anything you ended up not including in the book but would like to share now?

Not really. Mainly, there are some questions left open because I did not find convincing answers. The war stories are quite clear cut with many sources. The personal story is somewhat sketchy here and there, because no sources exist or remain. I would like to have a clearer picture of the young couple, Sam and Jaantje, deciding to go to Michigan just like that. Also my story of his colleague and friend George Uhlenbeck is not very elaborate I think and again, no biography exists of Uhlenbeck, only archives. Perhaps I should pick that up sometime soon. Finally, there has recently been some talk of quite antisemitic tendencies in the Dutch sciences after the war (just like in society in general), making it hard for Sam and George to relate to the Dutch. I would like to find out more about that at some point.