Observing the double slit experiment

TheRealTL

In this experiment wave particle duality is shown. Without observation the wave function is used. With observation the particle function is used.

My question is what is the definition of observation? Specifically in the case of an electron gun is the observer a conductive piece of material in and around the electron path?

arkajad

"Observation" is not a very good concept. "Detection" is better (presence of human "observers" is irrelevant for the detection to take place). You have a detection when you have a detector (or several of them) coupled to your quantum system.

TheRealTL

Ok, anyone got some examples of detectors that influence the system?

arkajad

Photographic plate, Geiger counter, cloud chamber, fluorescent screen. Eye of a fly.

arkajad

I should add that in "Bohmian mechanics" the philosophy is different. But I do not think you want to know about Bohmian mechanics - it is a separate subject.

GeorgCantor

How about ear?

arkajad

Ear is not that sensitive to individual quanta. Not a good detector for quantum events.

GeorgCantor

Detection clicks are audiable. But my focus was on the "fly's ear" not just ear, or just 'eye'.

eaglelake

Without observation, what is the wave function used for?? What is the "particle function"??
A quantum experiment must include a measurement result that is obtained when the particle is detected. I think this is what you mean by observation; observation is the measurement result. This result is a necessary part of the experiment. (Bohr) Without a result (observation) there is no experiment to discuss. The wavefunction is used to calculate the probability of obtaining that result. Without observation, there is no wave function.
Neither the theory nor the experiment describe what the particle is doing before it is detected. Quantum mechanics predicts only the possible results of a measurement and the statistical distribution of those results. We have no idea what the particle is doing before detection. (Wheeler)
The particle is always detected as a particle. It is the statistical distribution of the results that we identify as an interference pattern, which is characteristic of classical waves. Thus, we see "a particle" when the individual particle hits a detection screen. We see an "interference pattern" (caused ?? by "a wave") when a large number of particles have hit the screen one at a time.
An observation is a measurement result that gives a value for a specified observable, such as energy, momentum, spin, etc. The particle detector is part of the measuring apparatus, which is the observer. As noted by others, the experiment does not require a human observer.
What are you trying to measure with " a conductive piece of material in and around the electron path?"

arkajad

Ear is not necessary. Irreversible recording of whatever kind is.

arkajad

That depends on which "theory". If your theory does not bother - then it does not describe. If it bothers - then it describes. Some people do not have an idea and do not care, some other people have an idea (right or wrong) and describe. Some theories bother only with the statistics, some with description of individual detection processes.

questions,yes

If there is no "human observer", how does one acquire knowledge of the experimental results?

arkajad

Acquisition of knowledge is a separate branch of science. It is not needed if you want to discuss the behavior of detectors, interference, double slit experiments etc. For this you need physics, dynamics, evolution equation, a little bit of probability theory.

questions,yes

But in order for such a discussion to take place, doesn't there at some point have to be "human observation"?

arkajad

Are you interested in human beings or are you interested in physics. Human beings, their psychology, neurobiology, etc. is a different branch. Of course quantum processes, in particular detection processes take also place in neural activities. But that does not influence the laws physics.

questions,yes

But you agree that "human observation" is required for completion of the exercise?

arkajad

It depends on the exercise. Rats also exercise, frogs do, and birds exercise as well. Perahps the whole Nature exercises, one way or another. Physics is about making the patterns. Recognition of patterns is another thing.