In This Topic
Exploring the early days of quantum physics Riding a wave of new ideas about light and particles Realizing that some quantities can’t be measured precisely Considering different models of quantum physics Scaling Planck units down (or up) to size
strange as relativity may have seemed to you (see topic 6), it’s a cakewalk compared to understanding quantum physics. In this strange realm of physics — the realm of the extremely small — particles don’t have definite positions or energies. They can exist not only as particles, but also as waves, but only when you don’t look at them. One hope scientists have is that string theory will explain some of the unusual results in quantum physics or, at the least, reconcile it with general relativity. Particle physics, on the other hand, is at the heart of string theory’s origins and is a direct consequence of this early work in quantum physics (see topic 8). Without quantum physics, string theory could not exist.
As in the other topics in this part, the goal of this topic is not to provide a complete overview of all of quantum physics — there are other topics that do a fine job of that, including Quantum Physics For topic by Steven Holzner (Wiley). My goal here is to give you the background you need to know about quantum physics so you can understand certain aspects of string theory. It may not seem that these ideas relate directly to string theory, but being familiar with these concepts will be handy down the road when I explain string theory itself.
In this topic, I give you a brief introduction to the history and principles of quantum physics, just enough so you can understand the later concepts related to string theory. I explain how quantum theory allows objects to act as both particles and waves. You explore the implications of the uncertainty principle and probability in quantum physics (dead cat not required). I list some of the many interpretations of what all of these strange quantum rules may actually mean — though no one really knows (or can know) for sure. Finally, I discuss the idea that special natural units can be used to describe reality.
