geordief

Not really.I think I have heard this from time to time but can't remember where I did. Not recently ,anyway.

Especially Thanks.(I hope nobody took the use of the word literally ,as in time travel.I just used it as a turn of phrase) Thanks.It doesn't seem that extraordinary to my untrained ears. Would probability equations in QM normally have a time component?(it comes as a surprise to me that they would but I only aspire to a layman status )

I don't "mean" anything.I am asking a question. You seem to be suggesting that the question is trivial and might as well be considered in macro systems. I have no way of knowing if that is right or wrong as I don't have the expertise.

Is it just that there are some interactions where reversing the time signature in the maths doesn't change the outcome?(I am fairly sure I have heard this more than a few times)

I think I have read that there are circumstances where ,at the quantum level the direction of time does not apply. Is this is true ,is it just for limited circumstances or is it across the board? Do perhaps quantum systems evolve in time generally but some do not?

Can a scenario involving only quantum objects be modeled using spacetime diagrams and their frames of reference? Is it ever done? Would there be a need? I understand that special relativity is used in such scenarios.

Well a frame of reference can have its origin tied to a physical point in space (even though ,I think it applies generally and not to one in particular) If ,though the frame of reference with a spatiotemporal origin coinciding with a quantum object is populated with other physical quantum objects then it seems to me that it is not simple to map their positions onto the frame of reference I did have a look at @MigL video and perhaps I begin to see how some circles can be squared. So perhaps frames of reference can apply to physical scenarios where objects' position and momentum are not separately defined? Might one map objects' combined states into a Minkowski like frame of reference chart? (Eg position and momentum combined) As to the parsing of my phrase ,"Does a frame of reference have to be applicable to a potential physical scenario to be physically valid?” .... I had thought first of writing "Does a frame of reference have to be applicable to a potential physical scenario to be valid?” Maybe the second "physically" made it less comprehensible?

Ok.I am a bit of a literalist myself.If someone greets me in the street with a "How are you?" my reflex is to wonder how I am and to communicate my state of being with the person

There could never be two physical objects at rest wrt each other could there? Does a frame of reference have to be applicable to a potential physical scenario to be physically valid?

Which came first ,religions with a soul or religions without a soul? Is there a connection between the two belief systems? Or do we call them both "religions" out of laziness . Is there a better word that would describe all the world's "religions"?

Seriously,or did you just mislay the sarcasm emoji?

The thing I find confusing is that on the one hand it must be clear that Israel has such a back history of truly despicable behaviour against the Jews down the years culminating in the most odious collective stain on our common civilisation that it is incredible to imagine that it can be forced out of its one last refuge. On the other hand its behaviour has more or less united (if they dare speak it) all the countries in the world against them. It seems like the irresistible object meeting the immovable force. Noone has any idea how this car crash develops I hope Netanjahu gets his comeuppance but it would be more than naive to suppose that his removal (and being held to account) will move anything forward. It feels like this drama has its own life force and is pulling us all along with it. Against that Israel has only been in existence for 75 years -a blink in the eye of nothing at at and so there is all the time in the world for things to evolve (at their own pace)

Maybe put on Stray Cat Blues on the car stereo as well

Motion itself is something that would occupy the attention of a cat. Does it see like a big dangerous animal? . This original statement? Perhaps you are right.

Doesn't that change the structure of the brain of the observer?

Which is which? The space time expansion is the one where the clock does co-move with the cosmological fluid? But if we are talking only if space expanding this is not so? First time I have heard mention of "cosmological fluid"...

Since the Big Bang I understand that the distances between galaxies and ,generally regions not bound together gravitationally have been increasing in an accelerating way. I have seen this process described as either space expanding or space-time expanding. Which is the more correct way of describing it? To my mind it should be the former. I see space time as a mathematical model (and don't see how a model can expand) I see space as the distances between objects and can understand how these measurements can be continuously increasing. On the other hand I think I can also see that the space time intervals between the galaxies might also be increasing.....

Coming back to you earlier post (hopefully with a better understanding) So the particle is in a superposition of eigenstates and you measure its momentum.... Are you saying that none of the superimposed eigenstates are changed by the measurement, or that jst the momentum eigenstate is unchanged or that all the other eigenstates (not including the momentum) are unchanged?

How do we know that a particle is in a momentum eigenstate and not in a superposition of states?

What might it be if it was not in a momentum eigenstate? Any one of the other eigenstates it could be in? Can it be in more than one eigenstate at a time ?

So a particle whose momentum is measured does not undergo a change in momentum as a consequence of the measurement? Or is it rather that a particle whose momentum is measured does not undergo a change in position as a consequence of the measurement.? I feel it should be the latter as the position is unknown both before and after the measurement. And ,if that is right ,the same would apply to a measurement of the position of the particle.That should not change its momentum ,for the same reasons.

Would that apply to the position/momentum of a quantum object? (I hope "quantum object "is a meaningful description of something)

Could I ask you for an example?

You say "usually". Does that mean or imply that some measurements do not change the state of a system?

Are there other features of QM that could be described as essential in the way that it differs from Classical Physics?