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ass_bongos t1_iriunq0 wrote

To add to the good answers already posted, think of how you "observe" something in day-to-day life. When you see an object, you see it because a photon (or many photons) from some light source bounced off of it and went into your eye. In the quantum world, this bounce itself changes the object you're looking at. The electromagnetic interaction between the mystery particle and the photon puts the particle in a different state than it was before. This is generally what we mean when we say that observing a quantum state "changes the outcome".

There is definitely some additional nuance as other posters have remarked, and observation is not always as simple as bouncing a photon. The delayed choice quantum eraser is a fun experiment that shows you can actually wait to "choose" whether or not to "observe" a quantum event until after it happens! Quantum is weird.

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Kered13 t1_irlfube wrote

> The electromagnetic interaction between the mystery particle and the photon puts the particle in a different state than it was before. This is generally what we mean when we say that observing a quantum state "changes the outcome".

This is the observer effect, and while it is also an issue when trying to make very small or very precise measurements, it is unrelated to the quantum physics question of what exactly an "observation" is for the purposes of wavefunction collapse.

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