Random musing:
What does "nothing" really mean or imply?
No stuff. Not even empty space. No space at all. Nothing
Such musings invariably leads to confusing the layperson when physicists use terms such as “nothing is not really nothing” and “something coming from nothing”.
The terms have their origins when comparing the classical and modern definitions of a vacuum.
The classical definition of a vacuum is space devoid of atoms, molecules, ions and electrons and is consistent with the intuitive definition of nothing.
The modern definition is much more complicated.
A vacuum is now a quantum field in the lowest energy level.
In fact there are different types of vacuums depending on the field in question (electromagnetic field, Higgs field etc).
Heisenberg’s uncertainty principle in its well known form is expressed by the inequality ∆x.∆p ≥ h/2Π where ∆x and ∆p are the uncertainties in the position and momentum of a particle respectively.
A “controversial” version of the uncertainty principle is the energy-time version defined as ∆E.∆t ≥ h/2Π (controversial as the there is no mathematical
quantum mechanical time operator that measures time let alone an uncertainty in the time measurement).
The energy-time version is interpreted as a fluctuation in the energy of the vacuum ∆E over a time interval ∆t.
The smaller the time interval, the greater the energy fluctuation.
This vacuum energy fluctuation is manifested as virtual “particles” popping into and out of existence over the time interval ∆t.
This takes care of the term “something coming from nothing" as virtual particles pop into existence.
It also takes care of the term “nothing is not really nothing" as it deals with the differences in the classical and modern definitions of a vacuum.
The modern definition would be meaningless word salad unless these virtual particles can be detected.
Virtual particles have been detected in the laboratory using the
Casimir effect where the vacuum exerts a pressure on closely spaced metal plates.
The modern definition of a vacuum is therefore supported by empirical physics and the terms “something coming from nothing" and “nothing is not really nothing" are not confusing pieces of terminology.