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Ok, so I understand why an electron would change while being observed. But does it change exponentially when being observed by more than one person? Say having 10 or 100 observers.

Qmechanic
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John Connors
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  • Would you consider changes being reversed by other changes to remain added into the total number of changes, or as cancelling each other out: In other words, would your considerations include an existence of time? – Edouard May 13 '22 at 04:35

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The term observer is an unfortunate one as it has a special meaning in quantum mechanics that is not the same as in everyday life. Over the years this has mislead countless students into believing that there us something special about humans observing a quantum system.

In QM an observation of a system is an interaction of the system with some other system (the observer) that has many degrees of freedom. See the question What is an observer in quantum mechanics? for more on this. The other system could be a human, but could also be any complex system including purely mechanical ones that have no sentience.

In this light a single human, ten humans or a hundred humans are all just complex systems that can interact with the system being observed, and there is no major difference between them. An electron being observed by a hundred humans wouldn't differ in any major way from a system being observed by a single human.

The theory that describes interactions of this sort is quantum decoherence. The complexity of the system does make a difference to the rate at which a quantum system decoheres, and since a hundred humans form a system that is more complex than one human we might expect the decoherence to proceed faster. In practice there would be no measurable difference as even single human is such a complex system that the decoherence is effectively instantaneous.

John Rennie
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  • I've noticed for years that "observers" tended to be inanimate objects in QM verbiage, but I've never seen the reason for that so clearly and concisely described. A good answer makes the question become a good one. – Edouard May 13 '22 at 16:46