I'll do a bit of catching up on newish news. After a conversation with our daughter, I posted a video to YouTube,

https://www.youtube.com/watch?v=frSL-BJTh90, that makes a blunt point about quantum mechanics:

##
**Quantum Mechanics: Event Thinking**

**Published on Feb 18, 2017**

To
save time, watch the last five seconds, where I write down the word
that this is in part a polemic against. That word appears in almost
every interpretation of quantum mechanics. In this video, I talk about
how to think about quantum mechanics as about events instead of using
that word. This isn't a full–blown interpretation of quantum mechanics
in 4'26", but it's a way of thinking that I find helpful. Something can
be taken from this way of thinking without knowing anything about
quantum mechanics, but inevitably the more math you know already the
more you'll pick up on nuances (and, doubtless, know why you disagree
with many of them).

Thinking about quantum mechanics as about events helps a little, but thinking of quantum field theory as a formalism for doing signal analysis is better, if you can get to that level of mathematics.

Adding a little more thinking in terms of events, imagine that we have a black box that puts out a continuous zero voltage on an output wire, but occasionally something happens inside the box so that the voltage rises sharply to some non-zero voltage for a very short period of time, then the voltage equally sharply returns to zero. We set up a clock so that whenever the voltage rises the time is sent to a computer's memory.

When we put our event black box into a dark room at 20℃ we see events every now and then; if we change the temperature, the statistics of the events changes a little. Imagine we have a different kind of black box, which has a power cable into it, but no output, however when we introduce this box and turn on its power, the statistics of the events from the first box change, so we call the new kind of box a

*source* of events. If we move the source black box to a different place, the statistics of the events change.

If we have a number of event black boxes, we can do more sophisticated statistics, including correlations between when events happen. Then we can introduce multiple source black boxes and other apparatus, such as lenses, prisms,

waveplates, polarizers, crystals, etc., and see what changes there are in the statistics.

After many decades, we would have a quite comprehensive list of how statistics change as we change many aspects of the geometrical arrangement of source black boxes, event black boxes, and other apparatus. We would find that how the statistics change obey various equations as we move the pieces around. Eventually we would find that there are different kinds of source black boxes, which affect different kinds of event black boxes differently, and we would characterize the different ways that changes of the geometry change the statistics of the events.

One thing that would soon become clear is that event black boxes cause statistics associated with other event black boxes to change. We'd like to have event black boxes that cause other statistics to change as little as possible, but we'd be disconcerted to discover that there's a limit to how much we can reduce the changes that an event black box will cause in the statistics of other black boxes' events.

To return to the real world, which already knew about the electromagnetic field, electrons, atoms, before anyone thought of recording times of events so systematically, there was already a lot of knowledge about different kinds of sources, much of which had to be unlearned when quantum mechanics came along. When we use just light, the equations are provided by quantum optics. There are different equations if we use different types of source black boxes. We know what type of source black box we are using because the statistics change differently as we change the geometry. A lot of the work of quantum mechanical experiment is to characterize newly invented source black boxes using event black boxes we have already characterized with other sources carefully enough that we can use the new source black box to characterize newly invented event black boxes.

The altogether too difficult question is "what is there between the source black boxes and the event black boxes?" The instrumentalist is quite certain that it doesn't matter, all we need to know is how the statistics change. As I said in the last post, there are so many possibilities that it's worth not worrying about what's between too much so we can do other things. Not quite the old-timers "shut up and calculate", more "we can do some fun stuff until such time as there's something it's useful to say for the sake of doing even more fun stuff". There is, inevitably, a lingering thought that if we better

*understood* what is between we could do more fun stuff, but the regularities will be the same whether we understand or not.