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I know this is probably a common point of confusion, but I have a specific question about measurements in Quantum Mechanics. I read an explanation on this, but still have a point of confusion.
The explanation of why a measurement somehow affects what occurs in a quantum experiment, for example the double slit experiment, seems to be that by measuring, even just by watching, we interact with the system and cause the "wave function to collapse". But it seems to me, with such a broad definition of "measurement", all particles, everywhere in the universe, would in some small way be measured at any given instance.
This answer explains that light is a form of measurement, but light, after all, is not the only way to perform measurements, as we very often measure things purely with gravity, and would all particles in the universe not be subject to (and the source of) some trace amount of gravity? Or have some interaction with some other particle, in some way shape or form? It seems like the answer would be yes. So it seems like we would never be able to observe an experiment without that collapse.
With "measurements" in quantum mechanics, interactions per se, why are they not always occurring?