I read in the Stanford website on this topic "The Role of Decoherence in Quantum Mechanics"(adsbygoogle = window.adsbygoogle || []).push({});

"Indeed, while it is well-known that localised states of macroscopic objects spread very slowly with time under the free SchrÃ¶dinger evolution (i.e., if there are no interactions), the situation turns out to be different if they are in interaction with the environment. Although the different components that couple to the environment will be individually incredibly localised, collectively they can have a spread that is many orders of magnitude larger. That is, the state of the object and the environment could be a superposition of zillions of very well localised terms, each with slightly different positions, and that are collectively spread over a macroscopic distance, even in the case of everyday objects.13

13 As a numerical example, take a macroscopic particle of radius 1cm (mass 10g) interacting with air under normal conditions. After an hour the overall spread of its state is of the order of 1m. (This estimate uses equations [3.107] and [3.73] in Joos and Zeh (1985).)

The equations of Joos are shared in their website at http://www.decoherence.de/J+Z.pdf

My question is this.

Why don't we see everyday objects spread over macroscopic distance? Is it because we can see experience only one of the branches or is it the case like the wavepacket of a free particle that spreads in time? Is the latter the context of what Joos is saying and not the latter about the branches? If it's the latter, what is the explanation why everyday objects are not spread over macroscopic distance (the is a consequence of decoherence)?

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# Joos Equations

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