I am still confused about the difference between measurement and interaction. I mean when electrons are travelling from source to the screen through the slits, there are air molecules in their way. And even if the electron double slit experiment is carried out in total vacuum in a completely closed box, there will still be infrared photons present in that box's volume due to temperature (Stefan's Law & E=hf gives significantly large number of infrared photons per unit volume inside the box). And further the quantum Foam (Heisenberg's uncertainty principle :-E & t pair) will be there to interact with the electrons. Then why these Interactions mentioned above do not collapse the wave function & why does it collapse when we try to "Measure " electrons position??