The history of science is littered with many examples of diverse thinking that found convergence. A 110 years ago, an unknown Indian physicist by the name of Satyendra Nath Bose, then 30, wrote to Albert Einstein saying he had solved a problem in quantum physics. Einstein, who was then at the University of Berlin, realized that Bose had indeed correctly derived the solution to a problem that had stumped him. It concerned a satisfactory derivation of Planck’s Law, which describes the spectrum of radiation from a black body (an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence). First derived by Max Planck in 1900, the law showed that the radiation emitted by a black body does not keep rising at ever shorter wavelengths as suggested by classical physics but instead peaks before falling back.
So what? you may ask. The answer is that Planck’s law has many ramifications in theoretical and practical science. It is fundamental to quantum theory as it describes how energy is transferred in chunks called quanta, and the relationship between the energy of a photon and its frequency. It also forms the basis for many technologies, including computer chips, MRI scans, photovoltaic solar panels, photodetectors, thermal imaging and applications in climate science.
Einstein quickly translated Bose’s short paper (just 4 pages long) into German and had it published in a premier physics journal. He then extended Bose’s theory to show that it applies not only to photons but also to gases like hydrogen or helium. More precisely, Einstein predicted that at sufficiently low temperatures, the wavelike characteristics of gases would be more pronounced, to the point where viscosity would rapidly decrease, and all gas atoms would coalesce into a single new state of matter. Thanks to Bose and Einstein, we now know that this state of matter (BEC) applies to all particles at temperatures near absolute zero.
All this is theory until 1995 when a group of experimental physicists at JILA, a laboratory run by the National Institute of Standards and Technology, the University of Colorado in Boulder, Colorado, and MIT obtained compelling evidence for Bose-Einstein condensation in dilute atomic gases. This confirmation of BEC led to the 2001 Nobel Prize for Physics being awarded to the leading researchers of the group – Eric Cornell, Wolfgang Ketterle and Carl Wieman.
The Bose-Einstein exchange may have been brief, but it is one of the great correspondences in the history of physics. As mentioned, the exchange not only led to a consistent derivation of the Planck constant, one that is based solely on quantum theoretical principles, but also opened the doors to many technological applications. A turning point was the invention, in 1975, of laser cooling in which somewhat counterintuitively, finely-tuned laser light fired at atoms moving in the opposite direction can result in atoms cooled to temperatures approaching absolute zero. The laser-cooled atoms may then be manipulated in applications ranging from quantum clocks to the design of atom-based quantum computing architectures (See footnote 1).
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[1] https://www.nature.com/articles/d41586-023-00323-7
This post is partially based on a writeup by Professor Robert P. Crease published in www.physicsworld.com on 24 Feb 2004.