Can someone explain dual slit experiment why is it a big thing ?
In: Physics
The double slit experiment shows that we fundamentally do not understand what light (and for that matter, everything else) actually is. Depending on how we set up the experiment, we can get particles of all kinds (photons, electrons, etc.) to behave like either little balls or like waves of energy. We can do this with every minuscule particle – all the things that make up everything we can feel and see and react to (including all the things that make up each of us). So are these things that make up everything like tiny little balls or are they like waves of energy? The answer is yes – they are BOTH of these things simultaneously. From our everyday perspective of the world around us, this seems impossible. Yet we can experimentally verify that it’s true. Even more than that, the experiment seems to suggest we can change whether these things act like balls or waves based on just “looking” at them? We don’t really look at them, but we can use detectors that are effectively our eyes in these experiments. So now we know that everything is simultaneously both tiny little balls and waves of energy, and we also know that we can change how they interact with us and the entire world by whether we “look” at them. It makes no sense based on our everyday experience, but we know it’s true based on experiments.
The double slit experiment is set up by shooting particles (photons, electrons, etc.) at a small board with two slits cut into it. Initially, a stream of particles was shot at the board, and an interference pattern emerged on receivers on the other side. Waves make interference patterns, so we can conclude these particles are waves, or at least that a collection of particles is a wave (or acts as a wave). So the next step was to shoot the particles at the slit one at a time. If you shoot paintballs one at a time at a wall with two slits, you’ll get splatters on the other side in two lines (basically, whatever is directly behind the slits). So the experimenters expected to see the same thing when shooting particles one at a time through the slits. But that’s not what happened. Instead, the same interference pattern happened, which means that each particle INTERFERES WITH ITSELF, meaning each particle is actually a wave!
Weird, but we’re not done. The experimenters then set up detectors in front of the board to look at each particle as it went through one slit or another. So now they know which slit each one went through. And that knowledge changed the outcome! Instead of an interference pattern, two stipes emerged on the detectors. This means we can change what happens (and whether these things act like little balls or like waves) based on what we know.
And then there’s a version of the experiment called the “quantum eraser” which gets even more bizarre – it seems to change the behavior of the particles in the past. Too much to explain here, but it shows we really don’t understand what all these things are at a fundamental level. We have really good tools for understanding what they do, but we can’t really say what they are.
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