Taking Bearings

Of all my lectures on physics, my favorite to deliver is on wave-particle duality. The Q/A is always fun.

You can tell by the comments below the articles linked below that people have trouble wrapping their head around the concept of duality. That is understandable, especially for people who have not studied quantum physics. The misunderstandings they hold primarily arise from the human need to impose understandable answers and concepts on phenomena that we do not fully understand.

https://www.newscientist.com/article/2367388-light-interacts-with-its-past-self-in-twist-on-double-slit-experiment/?utm_source=facebook&utm_medium=psc&utm_campaign=paidfbnps&utm_content=light&fbclid=IwAR3uaBtabBfvlbIQQUE0MLasRoDlYVYiKSL7i8n7Dq1JFgoxOaPXZ3yFk8o

https://www.iflscience.com/light-interacts-with-itself-when-squeezed-through-slits-in-time-68282

I can tell by the comments below the article (linked in comments) that people have trouble wrapping their head around the concept of duality. That is understandable, especially for people who have not studied quantum physics.

We are often limited by how our brains are neurologically hard-wired in trying to understand. The imposition of constellations on the night sky are ancient testament to this need.

Math helps a bit. Using probability theory, and allowing for a wave-particle duality, quantum mechanics replaced classical mechanics as the method by which to describe interactions between subatomic particles. Quantum mechanics, for example, replaced the electron orbitals of classical atomic models with allowable values for angular momentum (angular velocity multiplied by mass) and depicted the position of electrons in terms of probability clouds and regions.

Both particle and wave treatments of nature have their uses.

By extending the well-known wave properties of light to include a treatment of light as a stream of photons (i.e., treating them a particles), Einstein was able to explain the photoelectric effect.

On the other hand, De Broglie showed that the electron was not merely a particle but also a wave form. This proposal led Schroödinger to publish his wave equation that described electrons as “standing waves” surrounding the nucleus.

Born and Dirac made further advances in characterizing subatomic particles (principally the electron) as waves rather than just particles and in so doing reconciled portions of quantum theory with relativity theory. It was left to Heisenberg, however, using matrix mathematics to formulate the first complete and self-consistent theory of quantum mechanics.

In 1926, Heisenberg put forward his uncertainty principle that states that two complementary properties of a system, such as position and momentum, can never both be known exactly. This proposition helped cement the dual nature of particles (e.g., light can be described as having both wave and a particle characteristics).

When misapplied to larger systems –as in the famous paradox of Schrodinger’s cat — quantum mechanics was often be misinterpreted to make bizarre predictions (i.e., a cat that is simultaneously dead and alive). On the other hand, quantum mechanics made possible important advances in cosmological theory by accepting the duality of light, electrons, and other particles.

It is, however, human limitations that make think in terms of duality, per se. Simply put, our brains are hard-wired by evolution to impose the concepts of particle or wave upon the photon or electron in order to describe them and treat them mathematically. All of this is fine, in our everyday position between the relativistic and quantum worlds, such hard-wiring give us good answers.

Yet it is misleading to think of photons and electrons, for example, as being able to be EITHER wave or particle. They ARE — integrally and simultaneously — BOTH waves and particles.

Yes, via experimental design, we can force photons or electrons to act either as waves or particles, but they are what they are — it is just that we have no concepts, words, or mathematics for what they actually are and so we must use the concepts of particles and waves to define them, measure them, and predict their behavior.

One of the most important attributes of good science — and of good scientists — is the ability to look beyond “common sense” or intuitive answers, for the results of such comfortable thinking often proves too simplistic or errant. Moreover, in our attempt to understand nature, we must also remain mindful of our own cognitive limitations and bias.

Just as some animals see different portions of the electromagnetic spectrum, the cosmos often contains phenomena like wave-particle duality that lies beyond our everyday experience and conceptual ability to characterize without mathematics or experimental models. Phenomena like wave-particle duality force us to accept nature as she reveals herself to us via observation and experiment.

Read  more

https://scholar.harvard.edu/kleelerner/publications/development-quantum-mechanics-2001