Electrons change how they act when they're being observed (double slit experiment)

Quantum Physics never ceases to amaze me.

The video seems childish, but I think it does a good job of explaining what is happening.






Can anyone explain how/why this happens?

First of all, the double slit experiment is done with photons, not electrons.

That being said, the final line of the presentation -- "The observer collapsed the wave function simply by observing" -- is incomplete. When the photons are in transit they are amounts of energy, not matter, and exist as waves of potential to do work. So long as they are not absorbed by the slit aparatus they'll continue on their way until they reach the wall.

The measuring device, or "observer", interacts with the photons and thus collapses the wave at the slit(s). In other words: in order to observe photons you must interact with them thus changing them.

The film states that the wave function collapses "simply by observing" it as if the experiment observed the photon in the same way as we might observe the dog across the street -- from a distance. The observation of the photons in the double slit experiment, however, involves manipulation, not simple "observation".

Originally posted by Tuning Spork
First of all, the double slit experiment is done with photons, not electrons.

That being said, the final line of the presentation -- "The observer collapsed the wave function simply by observing" -- is incomplete. When the photons are in transit they are amounts of energy, not matter, and exist as waves of potential to do work. So long as they are not absorbed by the slit aparatus they'll continue on their way until they reach the wall.

The measuring device, or "observer", interacts with the photons and thus collapses the wave at the slit(s). In other words: in order to observe photons you must interact with them thus changing them.

The film states that the wave function collapses "simply by observing" it as if the experiment observed the photon in the same way as we might observe the dog across the street -- from a distance. The observation of the photons in the double slit experiment, however, involves manipulation, not simple "observation".

The double slit experiment can be and often is performed with electrons, though I've personally only done it with light.

Other than that, though, it's important to know that in the context of quantum mechanics, an observer does not imply a conscious entity. It doesn't matter if it's a person looking at something, or some kind of hall effect sensor who's results will never be seen, just that there is something taking measurements.

The meaning of measurements and observation is also debatable here, too. Pretty much any interaction could be called a measurement; it doesn't have to give actual data, much less be passed to a person's brain for review.

The world goes on just fine without people to look at it. The general molecules that make up things serve as capable "observers" for quantum events, collapsing the waveforms.

ETA the word "often"

[edit on 4-6-2008 by mdiinican]

Buddy you got it all wrong. They do not change how they behave when observed.

They don't even exist until they are observed.
There is a world of difference.

They are a probability which has not yet instantiated until observed.

LMFAO Gotta love this subject. Truly fascinating. BUT as Richard Feynman so simply stated, "Nobody understands quantum mechanics." Therefore, you all are right and you all are wrong.

reply to post by Cyberbian


Indeed, that is the Copenhagen Interpretation. There are many others all of which are consistent with the experimental data.

There just doesn't ever seem to be just one correct answer in quantum theory

This is a paragraph from an old set of experiments we performed in the 1970's; it might add perspective to this particular discussion.


"It turned out that the system for monitoring and controlling particle discharge had to be wholly unmanned.

Even in proof of concept experiments, this was the case. It soon became apparent that we could not even have anyone in the same building who was aware of the nature of the experiments taking place. They in fact, had to leave the campus.

This anomaly persisted until we were made aware of the influence that we had over this experiment just by knowing about it and being in the vicinity of the tests.

We weren't even acting as an "observer," we were simply aware of the nature of the experiment.

We then concluded that such a system could only be possible if the "operational" controls were unmanned and the "pilots" completely unaware of the nature of the drive system they were using.

Such systems being highly complex and in need of constant re-adjustment and human attention, forced us to conclude that as a means of space travel, Humans aware of the nature of their engine would have to be at a minimum 1200 meters away from the device itself.

One earth, distances exceeding 400 meters would allow for the experiments to go ahead and the equipment to function as predicted.

This is was all hypothetical to a point, but nonetheless it was one of the conclusions drawn from this series of experiments.

Our hypothesis was not correct, but the observations and results were amazing. However, we considered the whole thing a success.

We merely included the reference to space travel (in our conclusion) as a possible use for such a device, and it wasn't until years later that I began refining the ideas for my own purposes."

fascinating yes but like 50 years old.
but the electron/ atom smashing graphs from Fermi lab in Illinois show electron behavior to behave different under observation than where these elctrons show up before and after the experiments versus what they do and where they go under observation.

Observational biasing of any experiment happens on the atom and sociological level cool but weird.