I consider myself at least… Minorly able to read a newspaper digest about physics. And I’ve read about the double slit experiment. You have two slits in a piece of paper, fire electrons at them and they form wave patterns. “Observe” them and they act like particles and form particle patterns.
Here’s the the thing. Every single class, teacher, physicist I have known has said the same word. “Observe”. But…. What does that *mean*? If I look at it? If I have a detector? What does the detector do? How do we know that isn’t interfering with the particle? Why does this never seem to be extrapolated on and just that one fucking word pops up everywhere? Is it just a thought experiment? This had been driving me nuts, can someone explain?
In: Physics
When they say “observing,” That’s really what they mean. It doesn’t matter how you do it. In this case you can’t just look at it because that’s not possible the way the experiment is set up (the light source, slits, detection screen are all in an enclosed box or tube because outside light ruins the experiment). But by setting up some way to detect which slit it goes through, the interference pattern will disappear. One way people have tried was to use polarizers before each slit, with their axes 90 degrees apart. That means that at the detector you can measure what polarization the light had, which will tell you which slit it went through. Doing this results in the loss of the interference pattern.
Something interesting about that setup is that if you “erase” the information about which slit it went through – in this case, putting a third polarizer at the detector, 45 degrees between the axes of the two in front of the slits – then the interference pattern comes back.
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