Marietta Blau
Born: 29 April 1894, Vienna, Austria-Hungary
Died: January 1970, Vienna, Austria
Marietta Blau was born into a middle-class Jewish family in Vienna, Austria. Her father was a court lawyer and music publisher. After graduating high school in 1914 with sufficient distinction to attend university, she studied physics and mathematics at the University of Vienna, receiving a Ph.D. in 1919 on the absorption of gamma rays. She worked as an industrial physicist in Austria before moving to Berlin, Germany, in 1921 to work for a manufacturer of x-ray tubes.
In the early decades of the 20th century, scientists working to understand the newly revealed mysteries of nuclear physics had limited tools with which to probe the structure of the atom. Experimental physicists needed instruments to measure, observe, and record the effects they found in their experiments. They relied on the Geiger counter to detect charged particles and the Wilson cloud chamber to display the particles’ tracks. A physicist could spend hours sitting in a darkened lab, peering into a microscope to spot tiny flashes created by ionizing particles in a phosphorescent material. But these crude devices had little capacity to record data and were somewhat hit-and-miss in reliability. There had to be a better way. It was into this arena that the work of Marietta Blau provided solutions.
A particle, such as a speeding proton, isn’t seen directly but by the evidence of its passing—the track it leaves behind—much like the vapor trail of an unseen jet high in the twilight sky. A particle’s mass, speed, and electrical charge might affect the microscopic grains of a photographic emulsion in various ways, leaving different sorts of tracks in its wake. It was this possibility that caught Blau’s attention.
Blau worked as an unpaid scientist at the Institute for Radium Research of the Austrian Academy of Sciences in Vienna from 1923. It was here that she concentrated her studies on the development of photographic emulsions. These emulsions were not the kind for photographing family pictures or scenic landscapes, they were for the detection of high energy particles. They provided experimentalists with a way of detecting and recording their results. Blau was the first person to detect neutrons using one of her photographic emulsions.
Cosmic rays had been discovered in 1912 but were difficult to study with the equipment available at that time. As interest in cosmic-ray research increased in the 1930s, the advantages of Blau’s nuclear emulsions became even clearer to experimenters. Her interest in this special application led to perhaps her most important scientific contribution.
Since cosmic rays are scattered and attenuated by Earth’s atmosphere, researchers like to get their detecting apparatus as high as possible, which in the 1930s meant high-altitude balloons and mountaintops. Beginning in 1932, Blau and her chief assistant, Hertha Wambacher, placed specially designed emulsion plates about 7,500 feet above sea level on a mountain near Innsbruck, Austria, at Hess’s Hafelekar observatory. When the plates were recovered and developed, they found plenty of cosmic ray tracks, mostly protons, as expected. But in 1937 they found the unexpected. Unlike most particle tracks, which are basically straight or curving lines with a beginning and end, some of the tracks ended in odd starlike patterns, as if tiny fireworks had exploded. In a letter to the journal Nature, Blau called them disintegration stars.
The physics community was electrified. Blau and her nuclear emulsions had found the first hard evidence of something scientists had been trying to confirm for years: the disintegration of the nuclei of a heavy atom, such as silver or bromine, by the impact of another particle, in this case, a cosmic-ray proton.
But just as Blau’s scientific career seemed ready to take off, the growing darkness of Nazism descended on her in direct and personal ways.
Blau had made plans for further experiments on balloon flights and at Hafelekar and other mountaintop observatories, but two major complications stood in her way. One was the perennial lack of funding she faced at the Radium Institute; the other was her inability to secure a permanent academic position—chiefly the result of Nazi-inspired antisemitism already gripping Germany and quickly worsening in Austria. (Apparently there was another factor: when inquiring about promotion, she was reportedly told, “A woman and a Jew, that’s just too much!”)
Several other of Blau’s colleagues at the Radium Institute were ardent Nazis, and even before the 1938 German annexation of Austria they were maneuvering to steal credit for her work and have her removed. As her personal and professional situation rapidly deteriorated along with the political climate, Blau realized it was time to leave.
She fled Austria in 1938. She first went to Norway and later Mexico, where she obtained a university teaching position. Doing her research in Mexico was quite difficult so she seized an opportunity to move to the United States in 1944. She worked in industry until 1948, then at Columbia University and the University of Miami. In 1950 she moved to the Atomic Energy Commission at Brookhaven National Laboratory. At last, she was truly back in the research game, in her own field, and with access to the latest advanced equipment. She proved herself a pioneer again, using her photographic methods in conjunction with the latest cyclotrons and particle accelerators. In 1956 she returned to Austria for an unpaid position at the Institute for Radium Research where she analyzed particle tracks from experiments at CERN.
Throughout her life she received sparse recognition for her work and was often denied paid work. Her fellow Austrian and Nobel Prize–winning physicist Erwin Schrödinger recommended her and Wambacher to the Nobel Committee for the 1950 Nobel Prize in Physics for their cosmic ray work and development of the nuclear emulsion technique. But her long absence from the field and relative obscurity cost her. The physics prize went instead to British scientist Cecil F. Powell, who had built on Blau’s work and perfected the photographic emulsion method, using it to discover pi-mesons (pions) in cosmic rays in 1937.
She died in Vienna from cancer in 1970. Her illness may have been related to her lifetime handling radioactive substances. She was also a smoker. No obituary appeared in any scientific publication after her death.