I would now like to return to summarizing the major theories and conceptual approaches throughout the history of physics. The next one I would like to discuss is quantum mechanics (QM). So rich a topic is quantum mechanics that I will be writing several entries on different aspects of it over the next few months (I will also intersperse entries on current events, where appropriate).
The Wikipedia's summary of quantum mechanics introduces its many facets. The major scientific contributions promoting the development of QM occurred in the first few decades of the 20th century. To start off, the main idea to grasp about QM is that it applies to phenomena at an extremely small level (atomic and subatomic).
The word quantum itself is defined as, "The smallest unit of something that it is possible to have. Originally used for the quantum of light, now called a photon" (John Gribbin, Quantum Physics: A Beginner's Guide to the Subatomic World, glossary).
To laypersons and professional physicists alike, two features of quantum mechanics are its complexity and weirdness. A recent (July 5) New York Times article alluded to "the bizarre realm of quantum mechanics, where matter is both a particle and a wave and where the predictable stability of Newton gives way to probabilistic uncertainty."
As we'll see in future entries, there is even the idea that an object can be in two places at the same time!
As seen in the quote below from the transcript of the PBS documentary of Brian Greene's The Elegant Universe, even an MIT professor of physics admits he doesn't have a deep intuitive grasp of quantum mechanics:
EDWARD FARHI (Massachusetts Institute of Technology): You have to learn to abandon those assumptions that you have about the world in order to understand quantum mechanics. In my gut, in my belly, do I feel like I have a deep intuitive understanding of quantum mechanics? No.
From my own, non-physicist, perspective, I want to make a point about the complexity of quantum mechanics. Due to the advanced mathematics needed to fully understand seemingly any topic in physics, I would say the discipline of physics as a whole is complex. Once the mathematical aspects are put aside, however, I think several areas of physics (e.g., what happens under special relativity when an object travels extremely fast) can be grasped at a conceptual level by the non-expert. Where I think QM differs is that, even after the mathematics has been stripped away and we're left with just concepts, QM can still be baffling!
As I've read various books and articles on QM over the last several months, I've spent a lot of time scratching my head. At this point, I think I have a decent enough understanding to proceed. Since I am not a physicist, my policy all along with this website has been to stick to the original sources as closely as possible, both through web links and quotations of text passages; in this case of QM, I plan to stick very closely to my source materials. I hope you'll come along for the journey as I write my next several entries on QM.