# How do we know if we can’t observe?

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In physics some experiments get different results when we don’t observe? How do we know if we can’t observe? Even surveillance cameras changes the result.

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Contrary to popular belief, The Shroedinger Cat thought experiment highlights this. A cat in a box that would randomly kill the cat, does not create a state in which the cat is both alive and dead. Instead, it creates a state of alive OR dead which can only be confirmed through observation.

Ergo, observing the outcome is how we collect evidence of an event we cannot observe.

You get different results based on which part of the experiment you’re observing.

For example: double slit experiment.

We always observe the end result of the experiment (the distribution of the particles on the final surface.

But if you also have some apparatus detecting (observing) through which slit the particles go through, the result changes.

Also you seem to think “observing” is related to vision in some way. It’s not. Observation is just a specific category of quantum interactions.

You’re asking about a peculiar property of quantum mechanics – that everything appears to exist in “superposition” until an observation occurs. It’s important to understand that observation doesn’t necessarily mean something with consciousness actually saw or felt or heard something. In this case, observation means something more along the lines of “was influenced by it in some way.”

Superposition means existing in multiple states at once – it does not mean “existing in a particular but unknown state.” An example is flip a coin and when it lands on the back of your hand, immediately place your other hand over it so that you (and no one and nothing else) can see whether it’s heads or tails. Classical mechanics says that the coin is either heads or tails and we just don’t know which one it is yet because we haven’t looked. But it’s definitely one or the other even before we check. Quantum mechanics says it’s simultaneously BOTH heads and tails and it remains both (in superposition) until we look, at which point it BECOMES ether heads or tails (this is called the “collapse of the wave function”). It’s technical and detailed and mathematically driven, and there are definite issues with it conceptually, but quantum mechanics is THE most successful predictive theory we’ve ever had – over and over and over it’s wacky postulates prove to predict perfectly outcomes we actually observe. There are issues with the theory and we know it cannot be the ultimate final theory of everything for several key reasons, but we do know that the act of observation (again, the act of being influenced by) is critical to causing something observed to “collapse into” and become in one state or another.

But it gets weirder – we’ve done experiments that seem to show that a “delayed observation” impacts an event that happened in the past. Again, it’s complicated and technical, but that’s actually what happens. Do a simple random beam splitting experiment that sends particles randomly down one path or another and observe which detectors are activated by which particles and you get one result. Add in a device that detects which path each particle was sent down AFTER the particle has already reached the final detector and you get another result. It’s against all intuition to understand how bizarre this is – the mere act of observation of which path was randomly chosen well after the observed particle had already made its way to the final detectors changes which particles were received at which detector.

Even the classic double-slit experiment shows how observation changes results. Send photons one at a time toward a photon detector but place a board with tow narrow slits in front of it, and you’ll end up with a wave pattern on the detector. The only observation made for each photon is after it’s passed through the board with double slits. Now add a detector that shows which slit each photon passed through (i.e., observe which path the photon took) and you’ll end up with a smattering of photons in two spots on the final detector (showing which slit each photon came through) rather than the wave pattern. Nothing changed other than observing which slit each photon travelled through. But because of that each photon went from having some probability of landing somewhere on the final detector to having a 100% probability of landing in a definite position.

Quantum mechanics is weird and unintuitive. No one really understands it (and those that say they do are lying). But it seems to wok really, really well to describe the universe we live in.