It's been close to a century since we established how quantum mechanics "works," and we still don't know what it really means — and that, says cosmologist Sean Carroll in the video up top, may make QM the most embarrassing subject in all of modern physics.
What's embarrassing, says Carroll, isn't that there remain unanswered questions about quantum mechanics, or that there's debate within the physics community regarding its significance. In science, uncertainty, skepticism and deliberation participate in a powerfully deductive dialectic that enables us to rework our understanding of nature — to step back from what we think we know, re-assess our preconceived notions, and bring forth newer, more fully formed views of our Universe. This notion — that science advances not in spite of uncertainty, but because of it — is precisely why Stephen Hawking bet against the discovery of the Higgs Boson. In physics (as with pretty much any scientific field), unanswered questions and internal debate are, almost invariably, wellsprings of progress.
Not so with quantum mechanics, says Carroll, who claims that what's truly embarrassing about the physics of the very small is that questions surrounding its significance have gone unanswered for some 80 years, "with very little... immediately demonstrable progress, even though it's such an important question."
"It seems to me that we have not been been trying to answer this question with as much vigor as we should," Carroll continues. "What is quantum mechanics, really? I mean, that's like saying 'what is the Universe?' What more important question is there than that?"
At just shy of 15 minutes, this video's a bit long for anyone with an attention span conditioned by the internet, but we highly recommend watching the whole thing. Carroll's explanations are lucid and intriguing, and the points he levels are compelling without being condescending. All-in-all, it's as good an introduction to QM as it is an exploration of the present state of the field.
For more, check out Carroll's blog entry on the subject of QM-as-embarrassment over at Preposterous Universe.