observation's role in the light duality experiment

[Didymus]

I haven't spent much time reading on this particular one, but the topic came up today. I recall hearing that the particle waves (such as light) behaved differently depending on whether or not it was observed by a camera. What I've always wondered is how they isolated that "observation" was the variable changing how the light behavior as opposed to anything else, such as the electromagnetic fields of the running equipment.

It seems silly, but did they repeat the experiment with the detectors/cameras running, but facing away or with a blacked out lens? I know they ran the experiment with the camera present but on vs. Off... But "observation" seems a less likely variable than a physical effect of running electronics in the area. Was the experiment repeated with people looking in the direction vs. Looking away (with or without a blind covering the experiment)?

It seems that all would be required to isolate the idea that observation was the key variable.

I'm looking for specific facts, not an appeal to the concept that we should trust professionals not to overlook obvious holes.

 

 

Edit to add: I believe it was originally explained to me pertaining to light, but I could very well be mixing up my particle waves.

Edited January 21, 2014 by Didymus

[davidivad]

interestingly enough, you cannot see light unless you interact with it.

 

if you shine a laser at a target, you can see the result but cannot see the light directly.

put it in fog and you have ruined the experiment still only seeing the result of interaction.

even if you use a flashlight, you may see the light coming out at you but not the light in question.

 

your eyes do the same thing a camera does.

in the duality experiment, there was a need to minimize any extranious interactions because it would ruin the experiment.

to say that observing the experiment with a camera changes the results is silly.

it misinterprets the very basis of the experiment.

[Sensei]

I haven't spent much time reading on this particular one, but the topic came up today. I recall hearing that the light behaved differently depending on whether or not it was observed by a camera.

 

You're talking about Young's Double Slit Experiment.

http://en.wikipedia.org/wiki/Double-slit_experiment

 

There is no single reason to not do it at home.

Buy green laser 100 mW (it costs here $16) and set like this one in physics equipment shop (it costs $7):

 

 

 

"Observation" in the case of Young's experiment usually means using polarization filter.

In early XIX century they didn't have any cameras or electronic devices..

 

What I've always wondered is how they isolated that "observation" was the variable changing how the light behavior as opposed to anything else, such as the electromagnetic fields of the running equipment.

 

 

It seems silly, but did they repeat the experiment with the cameras running, but facing away or with a blacked out lens? I know they ran the experiment with the camera present but on vs. Off... But "observation" seems a less likely variable than a physical effect of running electronics in the area. Was the experiment repeated with people looking in the direction vs. Looking away (with or without a blind covering the experiment)?

 

It seems that all would be required to isolate the idea that observation was the key variable.

 

I'm looking for specific facts, not an appeal to the concept that we should trust professionals not to overlook obvious holes.

 

"Observation" means "measuring", not "real eye watching"...

 

First you should learn about photon's polarization, the best with equipment - laser and polarization filter (in physics shop equipment it costs $10)

 

I showed how they work with polarized photons coming from LCD monitor in this thread

http://www.scienceforums.net/topic/80366-particle-location/?p=783255

[Strange]

I recall hearing that the light behaved differently depending on whether or not it was observed by a camera.

 

It is probably more accurate to say that it depends what you measure. If you measure a property that we would normally associate with a wave (such as wavelength) then light will, not surprisingly, appear to be wave-like. If you measure a property that we normally associate with a particle (e.g. quantised energy) then, again not surprisingly, it will appear to be particle-like. (And if you don't measure anything, then you won't know!)

 

Clearly it is not a particle or a wave, and it doesn't switch between them depending whether you are looking or not. It just has a number of properties some of which we relate to waves and some we relate to particles.

[Didymus]

this is similar to the explanation I was given (although this person is specifying atoms rather than packets of light. I've heard the same explanation for other wave-particles such as light, unless I'm just mixing things up):

(it becomes relevant from about 5:30 for the next couple minutes)

Unless this is a misrepresentation, it seems that the -suggestion- is that the observation itself changes the projectile from a wave to a particle. It seems more reasonable to attribute this change during the act of measurement to interference based on the measuring process... rather than what seems to be advertised as though measuring the item (observing it) inherently changes it.

This variable could be isolated by leaving the camera on, but otherwise disabling it (turning it in a different direction) in order to maintain all variables except the act of measuring. Edited January 21, 2014 by Didymus

[swansont]

 

Unless this is a misrepresentation, it seems that the -suggestion- is that the observation itself changes the projectile from a wave to a particle.

 

It's more that the photon (or atom) is neither a wave nor a particle, it's just that these are the most convenient terms for describing them, because that's what we're used to. But, as with all analogies, this fails to perfectly describe all of the behavior. In terms of actual physics, it's never "wave or particle".

 

The bottom line in these experiments is that if the path information is somehow available, you don't get interference.

[Strange]

Unless this is a misrepresentation

 

Beware of popular science descriptions (even from someone as cool as Jim Al-Khalili). They are always simplifications / analogies. Take them with a pinch of salt. And don't try and extend them beyond their range of applicability (many people make the mistake of thinking they can develop a new theory based on these analogies).