Max Delbrück, Physicist Turned Biologist – 13 Questions

Max Ludwig Henning Delbrück was born on September 4th, 1906 in Berlin, German Empire and died on March 9th, 1981 in Pasadena, California.

Max Delbrück entered the field of physics when it was really ‘booming’. Classical concepts had to be overthrown, and with the arrival of Relativity Theory and Quantum Mechanics, entirely new concepts were introduced into the scientific community.

Yet, at the height of his career, Delbrück chose to pursue the largely descriptive and yet poorly understood field of biology. He worked with giants of physics like Max Born, Niels Bohr, Wolfgang Pauli and Lise Meitner – only to leave them and become nothing less than a giant in his own right, receiving the 1969 Noble Price in Medicine together with Salvador Luria and Alfred Hershey.

Max Delbrück’s work established how viruses replicate; it has thus blown the field ofMolecular Genetics wide open. Without his research, the pharmaceutical industry as we know it would not exist today. We would not have bacteria producing recombinant insulin for us. No genetic testing. We would not even know what DNA really is!

Max Delbrück Portrait

What compels someone to make a radical career change – when he could have just coasted along – with so much power and hunger to help found a completely new discipline in biology?

Delbrück was born into a family of academics and scientists. The German chemist Justus von Liebig – famous in his own right – was his Great-Grandfather, and his father was a well-known history professor in Berlin.

After studying Astrophysics at the University of Göttingen, Delbrück attended a talk about the exciting new field of quantum mechanics. He was so inspired by a comment made by Albert Einstein – which suggested to him that it was possible to have a deep understanding of our world using the newest physical hypotheses – that he switched his major to theoretical physics. He received his Ph.D. in 1929 – at the age of 23 – and subsequently had several research visits – with Niels Bohr and Wolfgang Pauli.

One of the biggest new principles derived from Quantum Mechanics was the notion that any element can be shown to be a particle – or a waveform. Depending on how you measure it. Apparently, matter can exist in two very complementary properties states.

In 1932, Delbrück attended a lecture by Niels Bohr, where he realized that this complementary principle can maybe also be applied to life itself. If a biological cell consists of organic matter, there may be a second aspect to it, one that is independent of its material properties. Spirituality? Life force?

This fascinated Delbrück so much that he – after being a research assistant to Lise Meitner from 1932 to 1937, who later on discovered nuclear fission with Otto Hahn and Fritz Straßmann – left Germany for a fellowship at the California Institute of Technology in Pasadena, where he studied Genetics in the fruit fly Drosophila melanogaster under Thomas Hunt Morgan.

His initial studies were not very successful, and he turned to investigate a different system: bacteriophages – which are basically viruses that use bacteria as host. He pursued the bulk of this work at Vanderbilt University in Tennessee, and received the 1969 Nobel Prize in Medicine for understanding how a virus replicates. Nobody had understood genes and their propagation until Delbrück (together with Salvador Luria and Alfred Hershey) tackled the problem.

How somebody can follow his calling to pursue a completely new field, armed only with the belief that the principles he learnt would be applicable to his new area of study – and excel in that area! – I found tremendously interesting.

#1 – You came from a highly academic and scientific background. Did that influence your decision to become a scientist?

Delbrück had ties to both history and natural science. What prompted him to choose the career path of a physicist? Did he feel beholden to family tradition in a specific way, or was he just curious? Was the scientific environment very prevalent when he grew up?

#2 – Was physics an interesting subject to study because so many new discoveries were made?

The new developments in quantum mechanics and Einstein’s Relativity Theory must have been very exciting. Yet still – those findings were highly counterintuitive. So what draws you towards them? Being part of an exciting new research field, or the search for truth and meaning in a truly revolutionary and partly devastating era that the beginning of the 20th century was?

#3 – What prompted you to make a radical change from physics to biology later on in your career?

After growing up with and being invested in physics, having worked with giants like Niels Bohr, Wolfgang Pauli and Lise Meitner – who was Otto Hahn’s assistant on experiments that would later lead to the development of the Nuclear Bomb – Delbrück was right in the center of some of the biggest scientific discoveries. Yet in 1937, he went to Caltech to learn more about biochemistry and genetics, later on pursuing research about the replication of bacteriophages – essentially viruses – for which he received the 1969 Noble prize in Medicine. Why change disciplines?

#4 – Did the point that Uncertainty had a central part in the laws of physics help you get into biology? 

As mentioned above, elementary particles like photons or electrons can exist as both a particle and a wave. That was one of the central concepts in Quantum Mechanics. It was very attractive to take this concept a bit further – what if you have a similar duality in life itself? Maybe there could be a material “particle” aspect and a more spiritual “wave” aspect in life. Could it be that Delbrück tried to dig deeper into this concept by applying his physical research to the pursuit of biology?

#5 – Did you see the discoveries from physics reflected in other fields during the 20th century?

Everything changed in the beginning of the 20th century. Art, music, literature – and of course political systems were infused with new ideas and reborn in a scale too large to handle by societies. Did these new developments in society had at least some grounding in the revolution of physical laws?

#6 – Is there anyone or any event that inspired you to become a scientist?

Or did Delbrück just “grow into science” because of his family background?

#7 – How do you feel about those of your colleagues that stayed in Nazi Germany while you emigrated?

Furthermore – was it his wish to emigrate to the United States, or did he just receive his fellowship to CalTech as a “lucky break”? I am wondering about this because even though several eminent jewish and non-jewish scientists like Albert Einstein, Niels Bohr, Enrico Fermi, Wolfgang Pauli and others left Europe, scientists like Otto Hahn, Fritz Straßmann and Werner Heisenberg stayed.

#8 – Did you ever have the desire to go back to Germany?

Delbrück became American citizen in 1945. He never returned to Germany, even though he helped set up the new Institute for Genetics in Cologne.

#9 – How did you see those talented scientists that were in your lab and branched out on their own?

When Delbrück came to the US, he first studied genetics in the fruit fly Drosophila melanogaster under Thomas Hunt Morgan. He had to realize that Drosophila is not a good research model to test his ideas about the nature of genes, derived from physics and chemistry; so he switched to bacteriophage genetics instead, very successfully so.

It impressed me how he kept in friendly contact with researchers like George Streisinger and Sidney Brenner, who started their own very successful research careers on multicellular organisms like the zebrafish or Caenorhabditis elegans. This is not always the case; Sir Humphry Davy grew increasingly jealous of his student Faraday when the latter started to surpass his master.

#10 – Did you have any morning routine or habits that helped you through your day?

Was it his passion for research alone that helped him through the day, or did Delbrück put some additional order into his day?

#11 – Science is a demanding and time-intensive field. How did you integrate your lab work with family life?

Delbrück had four children. How did he manage to be both active in family life and science? Or were both aspects deeply entangled with each other?

#12 – In which way do you see your scientific work connected to spirituality?

One of Delbrück’s motivations to get into biology was to search for a model of genes that is similar to the dual particle-wave principle derived from Quantum Mechanics. You can see this as a materialistic “particle” and a non-materialistic “wave” quality to every element. Dd Delbrück think this could apply in any form to the field of Genetics?

#13 – At the end of your life, can you say: I have been correct more often than incorrect in predicting developments?

Did he find a way to reconcile his initial thoughts about the application of quantum mechanical principles to molecular biology with the results he got from doing the corresponding experiments?

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