short answer -- light isn't a 'thing', it is what it does, i.e. how it behaves. light is an idea, just like 'bitcoin', like 'animal', like 'math'. it is a figment of our imagination. but don't tell me that we don't have consistent definitions.
Sure no definition is perfect, but there is a difference between a perfect definition and one that is simply good enough that it doesn't have to be changed sentence by sentence to fill holes in the theory being presented.
Light is indeed what some
thing does. "To wave" is what some
thing or
things do. Physics is the study of objects and their motion. So what is the object that "lights" or "waves"? These are questions physics has given up on answering. We can call the problem one of dealing in nonsense and inconsistent definitions, or we can call it one of avoiding doing science (rational explanation of phenomena) at all. Really it is both, one fronting for the other.
The grand sweep of what has happened in modern physics is that word games are played to obfuscate the fact that most of the original questions physics was meant to answer are not being addressed at all. In more modern physics, the esoteric math adds a nice heavy blanket of obfuscation on top of that for good measure. Since this relates to the quote below I'll continue down there.
also, a good counter-point to the 'oh it works that's engineering'. it was advances in particle/atomic physics that led directly to the development of the atomic bomb. it was our 'nonsense' models of the workings of an atom, which no one has ever seen, but whose properties we knew well enough to manipulate the system to our ends. if physics were not consistent, we would not have been able to do this.
Note that I never claimed that physicists do not know a lot about the "properties of matter" and such. You can build a motor without knowing the actual mechanism of magnetic attraction or electricity, and you can indeed do so while using highly confused terminology. You can even create useful equations based on incoherent terms and they may help you build your motor or bomb, as long as they are - as you implied - coherent
enough.
But shall we really call making equations "science" or "physics"? Are you, as a physicist, satisfied with simply summarizing the observations into neat mathematically expressed packages? Have you no curiosity about hypothesizing objects and their movements (i.e., phenomena) that have
not been observed/measured?
I don't mean to downplay this cataloging of quantitative relationships as "glorified stamp collecting" as Rutherford might have - it certainly has its uses in technology. But look, what made your eyes glow with wonder when you first saw two magnets being pulled together and pushed apart with no visible mechanism to attract or repel them? Isn't this the kind of thing that sparked your interest in science? It was for me.
Modern physics has nothing to say in the way of
by what invisible mechanism this attraction and repulsion happens between magnets. It talks of field lines (and/or other mathematical entities) doing this or that, not of actual mechanics. It gives you equations that catalog the observed relations of the relevant quantities, such as how strong the magnets are and how far apart they are. This is really useful if you want to engineer something. However, this isn't what most people originally get into science for...is it?
Ptolemy's epicycles were used for many centuries to describe the motion of the planets. Would we say they
explained the mechanism by which planets orbit the Sun? No, they merely cataloged the observations. It was useful, but was it science? Or as a deeper question, it was useful for predicting where planets would be at what times, but was it useful for figuring out how to alter their orbits or build an anti-gravity device? Even for engineering purposes, the Ptolemaic "explanations" of modern physics leave off most of the interesting questions.
I want to build an anti-gravity device! Modern physics is of only a little help here, much less than it would be if it used coherent terminology and actually tried to explain things again.
For instance, suppose you hear a rattling in your car at certain times. After a while, you notice that it gets louder with the square of how long you have had the car running at greater than 40 mph, and gets quieter in a similar way as you maintain lower speeds. You'd like to look under the hood, but for some weird reason it is absolutely impossible to open it or in any way view or measure inside it, and no information is available about its internal design.
Bearing with this improbable premise, a scientist studies the car, recording data on loudness, temperature, running speed, etc. He finally creates some graphs and equations that describe very accurately how these quantities relate.
What use is this? Well, it will indeed let you predict with remarkable accuracy how loud the rattling will get in which situations, and it will also be useful for mitigating the annoyance of the rattling because you'll be able to engineer workarounds, such as avoiding driving at high speeds for very long and maybe putting a block of ice on the hood.
The curious thing about this car scientist is that he seems totally uninterested in what is actually what is going on inside the hood, since it is not observable or measurable. He calls hypothesizing about what is "actually going on" a kind of "philosophy." To him, hard science involves data collection, measurement, and mathematical analysis. Since it is impossible in this case to view what is going on inside the car, all the measurements of heat, vibration, and so on are taken at the surface. The equations are collated into a "theory," perhaps with unique mathematical entities proposed, and that is science to him.
Now what would we say if a second scientist came along and posited that the heat generated by the engine at high speeds was causing Gasket X to expand, loosening some connection and causing the rattling. Suppose he made a 3D diagram of the hypothesized Gasket X and how it deformed under the heat and how it was positioned in relation to other hypothesized parts, and finally made a little video of how its deformation would cause Part Y to unhinge and swing around banging into Part Z, causing the rattling. Is this philosophy? It sure looks like science to me, far more than the other scientist's methodology of purely mathematical data analysis of observables.
The second scientist did something moderns physicists don't do much of, if they do it at all: he posited
unobserved physical entities and used them to explain how the rattling occurred. To be fair, though, he did benefit from the first scientist's explorations and handy equations. These helped limit the possibility space for his mechanical theory of what was going on under the hood.
With this theory, many new possibilities are available. Since various parts of definite shape and size in a definite location under the hood were proposed, more enlightened engineering is possible. Perhaps placing a powerful magnet on the hood to help hold the wayward part in place would be tried successfully thanks to this physical theory. This is way, way more useful.
This is an actual theory, because it actually
theorizes something physical happening, rather than just observing the physical happenings that are observable and cataloging them as a so-called "theory." (The only way the first scientist could be said to be theorizing is in the most mundane way of simply extrapolating his equations. "I theorize that this square law will hold even at 100 mph.")
But really both scientific exploration (collecting observed data, cataloging, summarizing the data into equations) and actual theorizing (hypothesizing unobserved objects and how their motion and mechanical interaction produces the observed phenomena) are necessary. Modern physics simply skirts around the latter, using wordplay to obscure this shirking of responsibilities by dressing up the exploration part in the garb of an actual theory, throwing a heavy blanket of math on top to be extra sure no one will see through the charade.
Now if asked how magnets attract and repel each other, the first scientist would catalog observations and summarize them in equations, perhaps with some mathematical entities like field lines thrown in to give some semblance of physicality to the presentation. If pressed, he'd admit that the field lines aren't physical at all and are just sort of layman metaphors, and if you want the real explanation, "It's in the equations." Give or take a few details, this is the modern scientific method as it is actually practiced and presented. The semantic obfuscation I mentioned is just there to hide the fact that no actual explanation has been given, just a summary of appearances.
The second scientist wouldn't be satisfied with that "explanation" at all. He'd imagine what was going on behind the scenes, where our instruments couldn't yet measure or observe. He'd think about what
as yet undetectable physical objects and what motion of those invisible physical objects could be mediating that attraction and repulsion. He'd try to imagine a movie featuring some of these objects (made visible in the movie of course, for communication purposes) where the objects interacted in such a way that the final net result was a pull or a push between the two magnets.
It may be that there are no such physical objects mediating attraction and repulsion; maybe they "just happen" and all we can ever do is note the pattern of what happens. If so, though, further scientific investigation is limited entirely by the sophistication of our measuring instruments and otherwise just by refinement of the accuracy of our cataloging of the patterns of observations. Does that really seem right? Since there's no way to know that magnetic attraction "just happens," physicists refusing to hypothesize physical mechanisms for that attraction can only be interpreted as giving up.
Also: please don't assume I'm speaking from a position of ignorance just because I appear to disagree with you and your authority figures.
p.s. no such assumptions have been made. most of what we're discussing (high school level physics), i have verified through the scientific process with my own hands. literally. no authority necessary. that being said, it is a safe bet that you are indeed speaking from a position of ignorance of these things, precisely because you needed me to supply to definition for something like a 'wave'. not faulting you at all for this ignorance, but i do fault you for refusing to concede that you are ignorant of the things you're talking about.
Well this should now be moot, but for completeness of argument the whole reason I needed YOU to supply a definition of "wave" is because physicists use it in multiple ways as is convenient for them - sometimes as a verb and sometimes as a noun/object or quasi-object. You've probably heard of a wave packet, for example. I needed to know which definition you thought could be used consistently before I could show that this was not the case. If I had been the one to supply the definition and then later showed that it needed to be modified for the purposes of QM, etc., I would risk being accused of strawmanning. I'm sure you see my dilemma.
Now, though this is also mentioned only for completeness, you obviously cannot have verified with your own hands that the
terms used in physics are not nonsense. What you have verified is a certain set of facts that I am probably not disputing at all. I never said that physics is "wrong," as in
F is not equal to
ma, but that it answers the wrong questions and uses semantic obfuscation to cover up this fact. It's a serious problem, and every scientist should lament it.
