Since physics is a quantitative science, one would like to quantify thisFra; [ said:Too large an energy density creates a black hole and spoils the measurement.
This is essentially the uncertainty relation applied to the observer,Fra; [ said:one is limited in the amount of energy one can invest in a measurement
Priceless!!an obese observer sitting inside his black hole.
But this is a ridiculously small uncertainty, which can (and should) be ignored for all practical purposes.In formulas, the observer's position and velocity do not commute, but
[q, v] = i hbar/M
I would say sort of but not quite. I definitely see it as much more involved than that.This is essentially the uncertainty relation applied to the observer,
This also relates a little bit to the original construction of QM, by Dirac etc.This is what I associate most closely to undecidable.
The difference here is between say something "undecidably undecidable" or something "decidable undecidable". My view is that we can not find hard universal constraints on the undecidability, instead it's evolving.
I think I fully share this vision. But from various readings on this, I have distinguished at leat a couple of quite different ways to handle observer dependence. I'm curious on Thomas view here:I suspect that QG requires us to take observer dependence to its logical conclusion: that the observer has quantum dynamics and affects the system just as much as the system affects the observer. After all, that is how all physical observers behave. To turn this philosophy into a concrete formalism will of course take a lot of effort.