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OK am trying to find out the meaning of vacuum since particle do exist everywhere even where all 'matter' has being removed am certain the definition of vacuum doesn't make sense with particles can someone explain this better thanks in advance

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    $\begingroup$ Perfect vacuum would mean no particles at all. Locally, this is possible. On Earth as well as in space. Quantum field theory includes virtual particles though. At this point, the answer is not as clear $\endgroup$ – lmr Apr 4 '19 at 19:44
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    $\begingroup$ How did you conclude that particles are everywhere, even when all matter is removed? $\endgroup$ – JMac Apr 4 '19 at 19:47
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    $\begingroup$ @lmr virtual particles are not "particles" but quick-calculation tools. $\endgroup$ – Avantgarde Apr 4 '19 at 19:56
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    $\begingroup$ @lmr I suppose a better way to state it would be that for a field $\phi$, the commutator $[\phi, \partial_t \phi] \neq 0$ $\endgroup$ – Avantgarde Apr 4 '19 at 20:16
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    $\begingroup$ I love the smell of vacuum in the morning! $\endgroup$ – Ryan Thorngren Apr 4 '19 at 20:35

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