Details Added to Monday’s Article

A couple of days ago, I posted an article describing how the size of a quantum object, such as a proton or electron, can be measured. This isn’t obvious. For example, scientists say that an electron spreads out and is wave-like, and yet that it has no size. This apparent contradiction needs resolution. While I addressed this puzzle in the book‘s chapter 17, I didn’t do so in detail, and so I wrote this article to fill in the gaps.

Now, in response to a reader’s question, I’ve added a section to the end of the article, entitled “Estimating the Object’s Size From Its Excited States”. There I explain in more detail how one goes from simple measurements, which confirm that a proton’s size isn’t zero, to an actual estimate of a proton’s size. The discussion is a little more technical than the rest of the article; you will probably need first-year physics to follow it. But I hope that some readers will find it useful!