> These are human definitions for classifications, and biologists agree on that.
I'm a biologist, and I don't agree.
> However, if you make a statement that "two groups of animals that can never reproduce successfully with each other are separate species" then nobody will argue that.
You're assuming animals with two sexes, and even there things like ring species throw a wrench into that.
> What I'm saying is that the photons exist only in the model.
and
> See, you made the same mistake as everyone else! Atoms aren't the only things that exist! There are free particles in vacuum chambers, particle accelerators, outer space, etc... that aren't atoms. There's a device called a "free electron laser" that has a continuously adjustable output frequency!
But those particles exist to us only as the results of measurements. We cannot impute a category to them that is definable in terms of familiar categories. They are no more or less real than the photon. I don't personally dislike the term "particle" for them, but "vacuum excitation" or similar just doesn't have the same cachet as "particle," and usually carry other undesirable baggage. Even "vacuum" carries problematic classical baggage.
> The electron is in an orbital though, right? With a defined angular momentum, position in space, and everything. Even if you abandon the concept of point particles, it has a bunch of properties. Now show me all of those properties changing as it absorbs the photon.
No, you can't impute properties like angular momentum to a state outside of measurement. We're used to thinking that we can because of classical systems where we take our sequence of measurements of a phenomenon over time and interpolate them infinitely finely and assume that as we do so the measurements converge to a continuous function. But since that limit doesn't exist for quantum mechanical phenomena, you can only speak in terms of measurement outcomes.
Plus, even if you could impute a property before measurement, you could only impute them to pure states. Almost all quantum states are not pure states.
So we can't show you those properties changing. All we can speak of is the probable outcomes of sets of measurements.
> That's fine if you're designing a laser or something, but that's not what is physically happening with a single electron around a single atom.
Is what you consider "what is physically happening" something theoretically observable?
> Even then it's not entirely clear if all interactions are quantised.
Of course. That's why continuous spectra are a thing.
I picked a bad example. Well, no, actually, a good one, but an example that does not lend well to online debate. And then I failed to make myself clear.
I already know about all of the corner cases, such as ring species, the fuzziness you get during speciation, sub-species, the constant reclassification of taxa, etc..
What I was trying to get at is that "species", like "photon" is a human word. A label for an abstraction that's useful.
No working biologist (sans a few creationist crazies) would disagree about that vast, vast majority of what makes a species a species. The chromosomes, the interbreeding capability, the genetics, DNA, etc... Where they disagree is on the finer points of classifications, such as whether two very similar specimens are a species, sub-species, or just a "trait" within a species. Those are just human labels, like the dewy decimal code. They're not the thing. They don't disagree that the specimens exist, that their DNA is different, etc...
Quantum theorists disagree with each other on things comparable to the existence of species. As in, some will say that there is such a thing as wave function collapse, others will say that this is nonsense and there's no such thing. They're not disagreeing on exactly when wave function occurs in some obscure corner case. No, they disagree on the existence of the concept itself.
This is a crucial distinction.
No two chemists will ever disagree that H2O is water or not. Ever. There's just no such argument, and hasn't been for well over a century.
In theoretical physics, specifically quantum mechanics and its cousins, there still is debate at this level, and shows no signs of resolution.
> But those particles exist to us only as the results of measurements...<snip>... you can only speak in terms of measurement outcomes.
That is a complex debate that's been had in the past: is it meaningful to speak of something existing if it cannot be measured, even in principle?
The issue with that is that sometimes people just state that certain categories of experiments are impossible, and then it turns out that oops.. no, it was possible, just really hard to do. This is my favourite example: https://tf.boulder.nist.gov/general/pdf/2723.pdf
Note the quote at the end: "Some observations can be made on the existence of ‘blinders,’both in theory and in experiment. Some theorists were accustomed to seeing problems in terms of the tools which had previously proven useful for describing experiments with large numbers of atoms, such as the optical Bloch equations. Their intuition seemed to fail for the case of single atoms, and they were unprepared to accept the phenomenon of macroscopic quantum jumps."
This is particularly common in the QM field, especially in relation to single particles or atoms. The tools are optimised for ensembles, so... people seem to forget that single particles exist. The experiments involving single interactions are crazy difficult, so some people will simply state that they're impossible, and it's difficult to argue with that when there are so few experimental results available to counter that.
Note that GR had some similarly "hard" experiments, such as the detection of gravitational waves. That doesn't mean that people seriously said that talking about gravitational waves was meaningless.
> Of course. That's why continuous spectra are a thing.
Okay, so you're on the photons-are-not-always-quantised side. I agree with you, but other people don't.
This is a fundamental disagreement much like Hinduism and Islam, to pick two random religions. Sure, there are silly people saying things like "all religions are equally valid", but.. no, no they are not. Some of them are just local church traditions, some are full on sects, and others aren't even vaguely compatible.
"Quantum theorists disagree with each other on things comparable to the existence of species. As in, some will say that there is such a thing as wave function collapse, others will say that this is nonsense and there's no such thing. They're not disagreeing on exactly when wave function occurs in some obscure corner case. No, they disagree on the existence of the concept itself."
This is an extremely uncharitable analogy. Physics is not a framework to guide your conceptual understanding of the world. It is human nature to try and conceptualize everything but there are limits to this and the interesting areas of physics operate beyond those limits. You can not conceptualize quantum interactions in a way that is meaningful because that process requires forcing our intuition (based on the macroscopic/classical world) into a space where it does not belong. This is why we create mathematical models to "describe" these types of systems and their interactions. To emphasize this, consider how illogical it is to try and "visualize" the fundamental building block that all visualizations are built with? There are visualizations of the corresponding mathematical models but they only provide insight into certain properties, they do not "show" you what a photon interaction looks like because the concept of physical visualization fundamentally doesn't make sense at the quantum level.
I'm a biologist, and I don't agree.
> However, if you make a statement that "two groups of animals that can never reproduce successfully with each other are separate species" then nobody will argue that.
You're assuming animals with two sexes, and even there things like ring species throw a wrench into that.
> What I'm saying is that the photons exist only in the model. and > See, you made the same mistake as everyone else! Atoms aren't the only things that exist! There are free particles in vacuum chambers, particle accelerators, outer space, etc... that aren't atoms. There's a device called a "free electron laser" that has a continuously adjustable output frequency!
But those particles exist to us only as the results of measurements. We cannot impute a category to them that is definable in terms of familiar categories. They are no more or less real than the photon. I don't personally dislike the term "particle" for them, but "vacuum excitation" or similar just doesn't have the same cachet as "particle," and usually carry other undesirable baggage. Even "vacuum" carries problematic classical baggage.
> The electron is in an orbital though, right? With a defined angular momentum, position in space, and everything. Even if you abandon the concept of point particles, it has a bunch of properties. Now show me all of those properties changing as it absorbs the photon.
No, you can't impute properties like angular momentum to a state outside of measurement. We're used to thinking that we can because of classical systems where we take our sequence of measurements of a phenomenon over time and interpolate them infinitely finely and assume that as we do so the measurements converge to a continuous function. But since that limit doesn't exist for quantum mechanical phenomena, you can only speak in terms of measurement outcomes.
Plus, even if you could impute a property before measurement, you could only impute them to pure states. Almost all quantum states are not pure states.
So we can't show you those properties changing. All we can speak of is the probable outcomes of sets of measurements.
> That's fine if you're designing a laser or something, but that's not what is physically happening with a single electron around a single atom.
Is what you consider "what is physically happening" something theoretically observable?
> Even then it's not entirely clear if all interactions are quantised.
Of course. That's why continuous spectra are a thing.