UNIVERSITY PARK, Pa. — When Peter Heaney, Penn State professor of mineral sciences in the College of Earth and Mineral Sciences and the Materials Research Institute, was preparing for a graduate seminar in crystallography last spring, he searched for a photo of an unsung hero of materials science and engineering, Walter Friedrich. What he found instead was a buried interview from 1963 with Friedrich that Heaney helped to translate, shining some light on the German scientist’s vital yet forgotten role in a Nobel Prize-winning discovery.
According to Heaney, Friedrich has never received his due regarding his contributions to the discovery of X-ray diffraction, which uses the wave-like nature of X-rays to obtain data about crystalline materials. X-ray diffraction and the data it gathers is vital to the development of new materials.
“It is hard to imagine the field of materials science existing without the contribution of Friedrich and his collaborators,” Heaney said. “Walter Friedrich is hardly remembered today, but he was front and center in a discovery that nearly all scientists would include in a top-10 list of 20th century experiments that changed the world. The crystalline state of matter is interrogated today using essentially the same technique that Friedrich innovated — we just have more intense X-ray sources and more sensitive detectors.”
Beginning the path to a Nobel Prize
In the early 1900s, the fact that materials are composed of distinct atoms was considered highly controversial in the scientific community. Even the fact that atoms exist was disputed. However, a German physicist, Max von Laue, had a theory on how to prove atoms were real.
“Von Laue knew that when visible light strikes a grating whose wavelength is of the same order of magnitude as the light, the light waves will interfere constructively and destructively, depending upon the angle and the wavelength of the light,” Heaney said. “Depending on the viewing angle, certain colors or wavelengths are reinforced, and the rest are canceled, like how light creates a rainbow effect on the grooved surface of a CD.”
Therefore, von Laue theorized that if X-rays are wave-like, and if crystals have atoms with the same periodicity as the X-rays, then when X-rays strike a crystal, they should selectively reinforce and cancel each other in a comparable manner. Overcoming major skepticism, von Laue convinced his faculty supervisor at the University of Munich, Arnold Sommerfeld, to allow Friedrich and a doctoral student, Paul Knipping, to conduct experiments during the summer of 1912.
“As Friedrich recounts in the 1963 interview, everyone was a naysayer,” Heaney said. “The common perception was that the natural thermal vibrations of atoms would be so great as to destroy any interference phenomena.”
Proving atoms are real
Von Laue knew that he needed Friedrich’s help.
“Von Laue was a theoretician, not an experimentalist, and he could never have constructed the experimental instrument,” Heaney said.
Friedrich designed the apparatus to run the experiments, and after many false starts stemming from von Laue's imperfect guesses, Friedrich obtained a photographic plate with distinct X-ray interference spots.
“He showed that the atoms in crystals will scatter X-rays in such a way that the X-rays constructively interfere and generate sharp spots on a photographic emulsion,” Heaney said. “That simultaneously demonstrated that there are individual atoms that compose crystals; that these atoms are ordered in space; and that X-rays, like visible light, can be modeled as waves.”
This major discovery led to von Laue receiving the Nobel Prize in physics in 1914, and to this day, X-ray diffraction has played a key role in research. This includes game-changing breakthroughs such as mapping the structures of complex organic macromolecules such as proteins and DNA in the 1950s. At Penn State’s Materials Research Institute (MRI), with which Heaney is affiliated, X-ray diffraction equipment is a vital part of the Materials Characterization Lab and the Nanofabrication lab.
However, Friedrich was not part of the Nobel Prize.
Forgotten by history
Heaney noted that Friedrich’s relative anonymity in the annals of scientific history was part of the reason he found the interview. He was surprised to find that there was no Wikipedia page for Friedrich so he was forced to dig through Internet archives to find an image for his graduate seminar.
“I stumbled upon an interview with Friedrich that was buried in the archives of the American Physical Society (APS),” Heaney said. “It was an image file of a typewritten manuscript in German from 1963.”
Heaney believes that Friedrich is not as famous as von Laue for three reasons. First, he was very modest and deferential to von Laue, and at that time, the experimentalist was considered below the theoretician in stature. This is despite von Laue offering gracious acknowledgement of Friedrich and Knipping’s role.
Second, soon after the ground-breaking diffraction experiments, Friedrich focused his research on the biological effects of X-ray radiation and away from physics. And third, Heaney notes that Friedrich joined the University of Marburg in East Germany after World War II, placing him outside the domain of western scientists.
So, Heaney believed, translating the 1963 interview was his way of increasing Friedrich’s historical fame, but there was a problem.
“I don’t know any German,” Heaney said.
Translating German when you do not speak German
While Heaney does not speak German, he has used Google Translate to figure out sentences in a language other than his own. However, he had never been able to use it to properly translate an entire document, and the Friedrich interview was a 13-page manuscript. With some free time, due to the pandemic, he used Google Translate and other online translation tools to pull together a rough translation.