<story><title>Physicists finally nail the proton’s size, eliminating an anomaly</title><url>https://www.quantamagazine.org/physicists-finally-nail-the-protons-size-and-hope-dies-20190911/</url></story><parent_chain></parent_chain><comment><author>ur-whale</author><text>I wish a physicist could explain here how the very notion of &amp;quot;diameter&amp;quot; has any meaning for an object whose size (IIUC) belong entirely to the quantum realm.&lt;p&gt;Is the hydrogen atom two hard little balls of matter orbiting one another, as we were taught in primary school, or are they a probabilistic soup with various, vaguely localized extrema?&lt;p&gt;If the latter, how do you even define the notion of diameter?</text></comment>
<story><title>Physicists finally nail the proton’s size, eliminating an anomaly</title><url>https://www.quantamagazine.org/physicists-finally-nail-the-protons-size-and-hope-dies-20190911/</url></story><parent_chain></parent_chain><comment><author>conistonwater</author><text>&amp;gt; &lt;i&gt;If the discrepancy was real, meaning protons really shrink in the presence of muons, this would imply unknown physical interactions between protons and muons — a fundamental discovery. Hundreds of papers speculating about the possibility have been written in the near-decade since.&lt;/i&gt;&lt;p&gt;This reminds me of a joke. An experimental physicist walks into a theoretical physicist&amp;#x27;s office with a really cool experimental result, shows the printed out graph to the theoretician. He thinks for a while and says, &amp;quot;this is perfectly in line with theory, let me explain how&amp;quot;. The experimentalist looks at the graph, scratches his head, says &amp;quot;uh, this is upside down&amp;quot;, and rotates the paper 180 degrees. The theoretician thinks a while more and says, &amp;quot;well this can also be explained&amp;quot;.</text></comment>