> A lot of physics experiments are very indirect, and you're not actually measuring the 'thing' you're looking for.
This is actually true for any experiment. Just at a macro scale the proxy is often less complicated. A simple example of this might be measuring how big a piece of paper is. You get a ruler and measure it, right? Your measurement is an approximation of the ruler's measurement, which is an approximation based on the standard meter. I have a bunch of rulers and I can tell you that none of them measure exactly the same. Usually it doesn't matter though because the difference is much smaller than the level of uncertainty and we're usually measuring with enough accuracy that we don't care.What physicists do is a generalization of this same thing. Usually much more accurately than your paper experiment. But yes, in high energy physics (HEP) you're usually measuring very indirectly and based on theory. This is a big part of the Von Neumann's Elephant thing. Fitting data is easy, explaining it isn't. The casual nature is the critical aspect
The problem with QM isn't that it isn't predictive, but that people in the field often seem incredibly sure of fundamental nuances of reality that have never been experimentally tested.
“A thousand years ago we thought the world was a bowl,” he said. “Five hundred years ago we knew it was a globe. Today we know it is flat and round and carried through space on the back of a turtle.” He turned and gave the High Priest another smile. “Don’t you wonder what shape it will turn out to be tomorrow?”
I am not suggesting parent is right, but who knows what the future holds.
"When people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together."
I think there will be some light Asimov (re)reading in my future; as a kid you focus on different things.
Physicist's definition of time: "it is what is measured by a clock"
Philosopher's definition of time: "it is the thing that passes by when you wait!"
(Or even all the way back to Saint Augustine: when you're living day-to-day, time is as natural and obvious as could be; when you're trying to explain time in words, it's a morass of tautologies and contradictions.)
For non-relativistic classical mechanics these concepts plainly coincide. General relativity leads to unintuitive consequences but doesn't come into friction with "what passes when you wait" since humans are subject to GR. But humans are not meaningfully quantum-mechanical, and the philosopher's definition of time is meaningless for a photon. For QM, all we have is the physicists's definition; the negative time measurement observed in the lab is the only time it makes sense to talk about.
When you say "not able to measure time appropriately" I think you mean more precisely something like "not able to phrase a subatomic theory of time which aligns with our classical intuition" - e.g. a quantum theory of causality itself where classical time "falls out," kind of like how some physicists are looking for information-theoretic approaches to gravitation where mass "falls out." But it's a much bigger problem than measurement of time - if we come up with such a theory the measurements of "second" would be the same up to a minor correction, but supplemented by additional measurements of physical properties we don't understand yet.
> Physicist's definition of time: "it is what is measured by a clock"
I hate this quote, because it makes people think there is something unique about time. There is, but not because of this. We could similarly say "a meter is what a ruler measures" (defined by how far light moves in 1/299792458th of a second; a second is defined as 9192631770 Hz, or the transition of 2 hyperfine levels of a CS-133 atoms).We can do this with any SI unit! What is an Ampere? You gotta define charge and frequency (time). What is a kilogram? You gotta define Planck's constant, the speed of light, and... frequency. Kelvin? Planck's constant, frequency, and kilo. Candela? Also depends on frequency. Mol? Well... actually this one is unique.
Truth is that these are not as "well defined" as one might think. They're kinda made up and arbitrary, and that's perfectly okay. In particle physics you often set hbar = 2pi = c = 1 (or if you're Mills, you include i). If we meet aliens, they would very likely have a different set of units, but their physics would look identical (they'd be isomorphic, i.e. we could translate between them).
So what is time? Distance? Mass? Energy? These are still very open questions at a base fundamental level. We treat them like axioms but even math still questions axioms and would love to remove them (and just like math, axioms are typically developed in hindsight). Someone might give you some definition for these things and you might be satisfied, but that doesn't mean there is a question one level deeper that's unknown. Beware this trick, as you'll fool yourself into thinking you know more than you do (it's quite common, and we all do it. I'm not trying to stand on a pedestal, every human does this and in abundance. Sweep things under the rug, but don't forget that you've done this).
(also, this quote is usually attributed to Einstein, not Feynman)
For info on SI units: https://www.bipm.org/en/si-base-units/mole