TSR Philosophy Society (TSR PhilSoc)

Actually, the "vast majority" of scientists don't, including such notaries as Einstein. It's been noted that the uncertainty principle helps the maths work, but that doesn't mean that it's right.
Many physicists accept the uncertainty principle as one possible explanation, but only if they also accept Schroedinger and the Copenhagen interpretation.

No, I'm not. I know there's only one photon in transit (it's a light-proof box), so I know where it came from and when. Since I also know the distance it's travelled and the time it took, I know its velocity and direction. Those are 'now' quantities. How are you proposing that you measure velocity? What means of measuring velocity does not include two discrete observations in time? What evidence do you offer for this bald assertion? You can't invoke the uncertainty principle in order to justify itself.

We know where it was and where it is. We also know its velocity (it must be exactly the speed of light, if it's a photon), so we can check that it took the correct time to travel from source to destination (since we know how far apart they are). That rules out the chance that it's not the same photon, or that it took a path other than a straight line from source to detector. You're left to argue that it QM tunnelled to some other location at some point and thus arrived on a different vector. However, you can repeat the experiment many times and QM tunnelling becomes exceptionally unlikely as a possibility (it's blooming unlikely to start with over a distance as large as 1m).

You can't know its the same photon because they pop in and out of existence as part of quantum randomness

This is special pleading. You can repeat the experiment a million times and show that the same results occur. You might have the occasional random event, but I doubt very much that a new photon would continue on the same path, so it would never get detected. Remember, our detector only needs to be a single photon in diameter (or to have a granularity at that level), so it ignores any strays.
There's the problem, you are using a circular definition. You say we can't know anything for certain, including physical dimensions. But you're ignoring what the principle says. it says that I can't know both the momentum and the position of a photon at the same time. It doesn't say that I can't measure a distance exactly, rather the contrary, I can measure a static distance exactly, because it isn't moving (i.e. has no momentum). Oh, I grant that the atoms in the slit and detector are oscillating slightly but we can average those out over a few million experiments. Not in any version of the principle I've seen. Could you give me a reference, please?

It relates to several pairs of observable variables - position and momentum, time and energy, something to do with angular momentum

It's a thought experiment, just like the Einstein/Bohr box. You might as well ask how you emit one photon at a time and detect it. Anyway, the exact distance isn't material to the argument as long as it's greater than any reasonable quantum tunnelling.

Even quantum physicists can't agree on the central tenets of QM. If you want to attack the experiment properly, you need to do so by using physics, not just an appeal to authority.

It is material becaue for the experiment to work you need to know the exact position of your detector

Why? Firstly, it's a thought experiment. All I need is a detector. For its position to be uncertain, you have to say why it's uncertain. You can't invoke the uncertainty principle here - that's simply self-referential. You need a reason why I can't determine the distance which doesn't involve the uncertainty principle. Let's assume I have a number of fixed observation points and determine the position of the detector by triangulation.

Nonsense. You're using your pre-determined conclusions before you've performed the experiment. That is, you're assuming the Copenhagen interpretation. Let's be clear, I do not believe the Copenhagen interpretation. I think it's logical nonsense which happens to fit the maths.

So were phlogiston theory and Newtonian mechanics.

Why do I need to? I have established the position of the photon and its vector at the same time. If you prefer, my detector can also measure the energy of the photon at impact.

What are you trying to argue? Of course I can reference the uncertainty principle.

Bohr didn't in his conversation with Einstein. He argued using principles with which Einstein agreed. You're making this pointless by saying (wrongly) that everything is uncertain.

So it's a waste of time, really. You've already decided that you can appeal to authority (everyone believes it) and to a circular argument (everything's uncertain, so you can never measure anything, ergo everything's uncertain).

Your argument hinges on some notion that we can't know the position of a single body relative to another. Except that that's not something which the uncertainty principle claims. (Wel,, not in anything I've read, but feel free to give me a reference).

QM is a flawed model, it's merely better than the previous ones (which had just as many authorities defending them in the past). It will be overturned and future schoolboys will proudly mock anyone who ever believed in it.

To make this worthwhile, you need to argue in terms that don't involve your invoking the uncertainty principle as some Cartesian denial of all knowledge (and I've already given an example of such an argument). If not, I'm dropping out.

Both of Einstein's famous thought experiments were defeated on the basis of indeterminacy applying to the measurement apparatus.

Only because Bohr showed that the loss of energy would result in movement, which would affect the time measurement under special relativity. He didn't say "You can't measure the mass because it's uncertain".
I can only comment that you were possibly wise to give up philosophy in favour of maths. You postulate a global premise and then produce a conclusion which is completely predicated on that assumption. Yet you think that's somehow convincing. Let me simplify your argument:

P1 - I am a woman.
P2 - If I am a woman, I have a womb.

C1 - I have a womb.

The only problem is that I'm not a woman. Oh, and not all women have wombs.

You've made a false premise that QM necessarily involves the uncertainty principle for all measurements in all dimensions. What about the case where some QM priciples are true, but uncertainty is not? That's what Einstein and others have debated. That's why the Copenhagen interpretation is not universally agreed - there's still room for exploration. Ultimately, I think it will be that most of QM is shown to be a limited subset of a wider theory. Just like Newtonian physics is true only to a limited extent.

I've already pointed out that QM does, in fact, necessarily involve uncertainty

Well of course, that's not what I said, is it? QM does not necessarily involve uncertainty in every measurement. It merely says that there will be uncertainty between pairs of non-commuting values. So you can know the position of a particle or its momentum, but not both at the same time.
<sigh> You haven't proved that there is guaranteed uncertainty in individual measurements either, so I'm not bound to accept it as a premiss. In fact, the thought experiment is entirely consistent with the basic premisses of QM. It only relies on measurements in a single time frame and where none of the objects are moving relative to each other (except the photon, obviously).

You have to know that the detector is not moving relative to the emitter and the slit.

Bohr's objection (as I understand it) was that the loss of mass would cause the box to move on the scale, so the two would not have a consistent time base. I've already said that the loss (and detector's later gain) of the photon ought to cause the apparatus to move apart which would distort the time base under relativity. However, we can figure out exactly how much it will move and therefore, the exact time dilation. After all, we're emitting photons of a single frequency, so they all have the same energy (and thus, relativistic mass). We know the vector, (because we know where the photon landed), so we can exactly allow for the relative movement of the two.

There's nothing in QM that says I can't know that. Anyway, as I keep repeating, the distance is irrelevant. All I have to know is that neither is moving relative to each other.

To set up your experiment, you must first ensure that they are not moving relative to each other - fine. And their relative position does not change as long as they are not moving relative to each other.

Well, I'm actually going to join them together, so that they form one big structure. I'm not having them moving freely in space. So, it's not hard to establish the distance between them and to be sure that it doesn't change (i.e. they are at constant temperature throughout, so there's no expansion or contraction).

I don't think that's quite as hard to achieve as you're making out. Well, as a thought experiment anyway.

I'm not convinced. The only reason that the momentum would stop being zero is if you have a source of energy. You'll have to give an explanation for that change, without resorting to a deus ex machina like vacuum fluctuations.

Remember I only have to reduce uncertainty below the theoretical limit for there to be a problem.