Problem with the two-slit experiment

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Discussion Overview

The discussion centers around the two-slit experiment in quantum physics, specifically addressing the impact of air molecules on the results of the experiment. Participants explore the necessity of conducting the experiment in a vacuum and the implications of atmospheric interference on the observed interference patterns.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that conducting the two-slit experiment in a vacuum is essential to eliminate interference from air molecules, which they believe could affect the results.
  • Others question the necessity of a vacuum, suggesting that many variations of the experiment have been successfully conducted on Earth and that air has minimal effect on photons.
  • A participant argues that while air does not significantly affect photons, it does impact larger particles like electrons, which require a vacuum to maintain a clear interference pattern.
  • There is a discussion about the principle of determining which slit a particle passes through, with some asserting that if this information is available, the interference pattern will not appear.
  • One participant emphasizes that the presence of air may slightly reduce interference but is not significant enough to invalidate experimental results.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of a vacuum for the two-slit experiment. While some argue for its importance due to potential interference from air, others contend that the effect is negligible for photons and that experiments can be valid without a perfect vacuum. The discussion remains unresolved regarding the extent of air's impact on the results.

Contextual Notes

There are varying assumptions about the quality and effectiveness of vacuum chambers, and the discussion highlights the complexity of controlling variables in experimental physics. The nuances of quantum mechanics and the specific conditions required for different particles are also acknowledged but not fully resolved.

Pianoasis
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The test should have been done within a vacuum. The interference of air molecules in Earth's atmosphere obviously causes an unwanted result, thus making the test results improbable. I don't know much about Quantum Physics, but I do understand how tests are supposed to be conducted, without any unwanted variables.

Again, I said I don't know much about Quantum Physics, but is it a possibility that photons traveling through air molecules will cause the air molecule to travel along the path of the photon wave and hit the monitor as a particle, yet develop into the pattern of a wave?
 
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Do you have a source that says the two slit experiment is not done in a vacuum?
 
Well it's difficult to find Tanamura's original procedure anywhere, but I'm fairly certain that all variations of the double-slit experiment were done on earth.
 
So, are you refuting the existence of vacuum chambers on Earth, or are you unsatisfied with their quality?
 
Pianoasis said:
The test should have been done within a vacuum. The interference of air molecules in Earth's atmosphere obviously causes an unwanted result, thus making the test results improbable. I don't know much about Quantum Physics, but I do understand how tests are supposed to be conducted, without any unwanted variables.

Again, I said I don't know much about Quantum Physics, but is it a possibility that photons traveling through air molecules will cause the air molecule to travel along the path of the photon wave and hit the monitor as a particle, yet develop into the pattern of a wave?

Air molecules are subject to the laws of Quantum Mechanics.
 
Were there any double-slit experiments done inside of a vacuum chamber?
 
Pinoasis, the effect of the atmosphere is well-understood, and plenty of experiments have been done in vacuum chambers. For photons, air doesn't have much effect at all: after all, the fact that air is transparent is just the fact that photons pass through air without being affected. For double slit experiments with electrons and larger particles, the experiment must be conducted in a vacuum, because electrons do interact with air molecules. In a perfect vacuum, you get a regular interference pattern. As the vacuum becomes less perfect, the interference pattern gradually goes away. You can think of this as a result of air molecules interacting with the electron, and thus "observing" which path the electron took through the slits. And when something observes which path the electron took, there's no interference pattern.

To be clear, air molecules tend to *destroy* the interference pattern, they do not create it.
 
Pianoasis said:
...I don't know much about Quantum Physics, but I do understand how tests are supposed to be conducted, without any unwanted variables.

Again, I said I don't know much about Quantum Physics, but is it a possibility that photons traveling through air molecules will cause the air molecule to travel along the path of the photon wave and hit the monitor as a particle, yet develop into the pattern of a wave?

No, that is not possible. There is a simple rule for determining whether there is interference or not. That rule is whether or not it is possible, in principle, to determine which slit the particle passes through. If you could know, there will be no interference.

There are ways to vary the knowledge we have of the "which slit" info continuously. Keep in mind that the interference pattern can theoretically vary from 0% to 100% (perfect case of course). The easiest example of that is to place polarizers in front of each slit. When they are crossed, there is no interference. When parallel, there is. Angles in between 0 and 90 degrees yield less more or less interference according to the cos^2 rule. So that is the primary factor.

As previously mentioned by The_Duck, the presence of air has an extremely slight tendency to reduce the amount of interference in the pattern. So maybe air reduces it from 95.0% to 94.9% or something like that. Not enough to bother with in an experimental situation. It is NOT required that all variables be eliminated in an experimental situation, it is sufficient that they are controlled or minimized.

Of course, you are free to ignore experiments that do not meet your own standards. However: If you reject the double slit, then you may as well also reject every experiment ever done.
 

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