Double-Slit Experiment - Clarification on 'Observation'

In summary, the conversation discusses the role of measurement in classical and quantum physics, specifically in the double-slit experiment. It is unknown what specific type or degree of measurement causes the particle's path to be altered, but there are ideas and theories about it. Some sources suggest looking into 'quantum decoherence' for more information. The conversation also mentions that the concept of measurement in quantum physics is still heavily debated and lacks experimental evidence. However, it is believed that all types and degrees of measurement alter the particle being measured, as extracting information requires energy and energy is conserved.
  • #1
FeDeX_LaTeX
Gold Member
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Hello;

In classical physics, measurement does not play a major role, but in quantum physics measurement plays an active role, correct? In the double-slit experiment, whether or not the path of the particle is measured - a detector finds which slit it passes through. I'm not questioning why this happens (well, I do, but that's not what I'm asking here). I want to know what kind of 'observation' or measurement specifically causes the particle's path to be altered, i.e. at what degree of measurement does this phenomenon (begin to) occur?
 
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  • #2
Bump...
 
  • #3
FeDeX_LaTeX said:
I want to know what kind of 'observation' or measurement specifically causes the particle's path to be altered, i.e. at what degree of measurement does this phenomenon (begin to) occur?

That is unknown.

There are ideas in what direction the answers to such questions are to be sought. For instance, you can look up information about 'quantum decoherence'. The current state, as far as I know, is that all ideas for addressing the measurement problem are interpretations.
 
  • #4
FeDeX_LaTeX said:
I want to know what kind of 'observation' or measurement specifically causes the particle's path to be altered, i.e. at what degree of measurement does this phenomenon (begin to) occur?
If we ever settle that, we'll put a few dozen philosophers out of work, so maybe we shouldn't touch this problem for fear of making unemployment worse.

The amusing thing about quantum measurement is that virtually nobody who discusses it backs up his/her statements with experimental evidence. Greenstein and Zajonc have a nice book, The Quantum Challenge, that discusses experimental evidence regarding measurement that isn't difficult.
 
  • #5
I think the simple answer is all kinds of measurements alter the particle being measured. Also, all degrees of measurements alter the particle being measured. There is no measurement you can make without altering what your measuring.

If I want to measure the length of my finger, I need to interact with it in some way, with a ruler, or with light perhaps.

You can't get something for free, to extract information is to extract energy, energy is conserved.
 

1. What is the double-slit experiment?

The double-slit experiment is a classic physics experiment that demonstrates the wave-particle duality of light and matter. It involves shining a beam of particles, such as photons or electrons, through two parallel slits onto a screen and observing the resulting interference pattern.

2. How does the double-slit experiment demonstrate wave-particle duality?

The interference pattern observed in the double-slit experiment is only possible if the particles are behaving like waves, interfering with each other as they pass through the slits. This suggests that particles, such as photons and electrons, have both wave-like and particle-like properties.

3. What is meant by "observation" in the context of the double-slit experiment?

In the context of the double-slit experiment, "observation" refers to any type of interaction that causes the particles to lose their wave-like behavior and behave as particles. This can include things like measuring the particles' position or velocity, or even just detecting their presence in some way.

4. Why is the concept of "observation" important in the double-slit experiment?

The concept of "observation" is important in the double-slit experiment because it highlights the role of the observer in defining the behavior of particles. This experiment shows that the act of observation can fundamentally change the nature of particles, from behaving like waves to behaving like particles.

5. Can the results of the double-slit experiment be explained without invoking the concept of "observation"?

There are some alternative theories, such as the pilot-wave theory, that attempt to explain the results of the double-slit experiment without invoking the concept of "observation." However, these theories are still controversial and not widely accepted by the scientific community. The majority of scientists still view the concept of "observation" as an essential part of understanding the double-slit experiment and the wave-particle duality of light and matter.

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