Satyendra Bose and Albert Einstein published a paper in 1924 which to this day helps to explain the difference between various types of subatomic particles.

One of the most important steps taken to further define Photons during the first decades of the twentieth century in light of the newly-minted quantum theory was that by Indian Physicist Satyendra Bose in 1924.

Without the benefit of living in any sort of scientific “hub” such as England, France, Germany, Italy or the U.S.A., this brilliant thinker from Calcutta was able to beat the odds and truly make his mark on physics.

Bose’s Work with Blackbody Radiation

What Bose did which was truly spectacular was to start from the very beginning and investigate an issue known as “blackbody radiation,” which had been solved in the first years of the century by Max Planck and then Albert Einstein (the result of these solutions had become the founding principles of quantum mechanics – the theory that light itself is “quantized”). Bose, on the other hand, went about the same problem from a “fresh” perspective.

In the end, Bose came up with his own theory, which while wholly original remained perfectly compatible with Planck's theory.

Bose realized that even though photons (particles of light) can be considered to be particles in the new quantum theory, they behave differently than “normal” particles such as electrons or protons (particles with greater than zero mass).

For one thing, they do not obey any known laws of conservation. Where electrons cannot (under normal conditions) be spontaneously either created or destroyed, photons are being both created and destroyed all the time.

Anytime a light bulb comes on, countless little photons of varying energies are being created out of nowhere (well, not exactly – they are a manifestation of the energy put into the bulb), and as they absorb into the molecules which make up the walls and everything else in the room, they are disappearing, being snuffed out of existence as they are absorbed by electrons and transferred into changes of energy levels in atoms (which then contributes minutely to the overall heat of the surface that is being struck).

There is a constant fluctuation of the total number of photons in the universe at any given time, while the amount of energy they possess remains constant. In other words, energy is conserved, but photons certainly are not.

Bose Statistics

In addition to their lack of compliance with the idea of conservation, the particles Bose observed when he viewed light in a statistical sense seemed to be almost “ghostlike,” as they didn't necessarily behave like “normal” particles ought to.

The very fact that they could interact so readily with other particles told Bose that they clearly didn't obey the normal exclusion principles within an atom – where every particle within an atom must be “unique,” with no two exactly alike, and only existing in certain, very well-regulated configurations. Photons seemed to be able to go absolutely anywhere they liked, being absorbed and emitted by both the electrons as well as the nucleus.

This realization led Bose to believe that photons were able to exist in these sorts of “in-between” quantum states, and thus required different rules from those particles which were clearly and strictly quantized within the atom.

So Bose did just what any good physicist would do: He developed his own set of statistical laws which would finally seek to describe the behavior of these photons and, completing his paper, sent it into a German science journal for publication. He never heard back.

Help From Einstein

Fortunately, Bose knew of someone who might be able to help him. So he sent his paper to Albert Einstein, the most famous physicist in the world.

Fortunately for Bose (and for all modern physicists), Einstein did recognize the importance of this paper. So much so, in fact, that he translated it into German himself (Bose had written it in English, for India was still a colony of England at that time) and promptly sent it off to the Zeitschrift fur Physik (“Journal of Physics”, naturally), where it was published on August 24th, 1924.

It is for this reason that the revolutionary statistics Bose invented to deal with the behavior of particles such as photons are today known as Bose-Einstein statistics, rather than simply Bose statistics. While Einstein’s name may have been necessary to lend it some credibility, Bose did probably deserve to have his name stand alone. But science, like life, is rarely fair.

Bosons and Fermions

Those particles which thus conform to the Bose-Einstein statistics (so far only photons have been mentioned, but there are others) are known, naturally, as bosons.

The other types of particles – normal particles – such as electrons, protons, neutrons, and many others, are known as fermions, as they obey the fermi-dirac statistics, named after physicists Enrico Fermi and Paul Dirac, who developed their statistics in 1926 initially to describe the collapse of stars, though the theory was generalized to describe particles themselves in the couple years that followed.

An oft used analogy for the difference between Bosons and Fermions is that of attending a concert: Fermions would be analogous to a concert of classical music where everyone has a ticket with a seat number on it, and everyone must remain in their place and seated.

Bosons, on the other hand, would be like a rock concert where everything is open space and the entire audience is free to move wherever they please, even if it means having to share a very limited amount of space with other concert-goers. What is happening inside atoms would then be a sort of combination of these two, with different particles obeying different sets of rules.

For a much more “scientific” definition of the difference: Fermions are those particles which possess half-integer spin, where bosons are those particles which possess whole-integer spin. So electrons, protons and neutrons, all having a spin of ½ are clearly fermions, where photons, having a spin of 1 are bosons.

Surely the concert analogy is easier.

To learn more about fermions and bosons, click here.

References:

Weinberg, S. (1992). Dreams of a Final Theory: The Scientist's Search for the Ultimate Laws of Nature. New York, NY: Vintage Books.

Oerter, R. (2006). The Theory of Almost Everything. New York, NY: Plume Printing.

Kl-Khalili, J. (2003). Quantum: A Guide for the Perplexed. New York, NY: Weidenfield & Nicolson.