Comments by "Lepi Doptera" (@lepidoptera9337) on "What is "Nothing"?" video.

  1. What physicists mean by "nothing" is "no thing". That is perfectly well defined. If the background has Lorentz invariance, then it is, by definition, empty.
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  2. Unless he understood the properties of the Poincare group he is irrelevant today. ;-)
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  3.  @farhadfaisal9410  Rovelli? Kid, the man doesn't even understand quantum mechanics. Not even at the high school level. And his hypotheses about gravity are all not even wrongs. Well, technically they are not even hypotheses since they are not testable. ;-)
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  4. The lowest energy that we can measure in space is the energy that we put in there ourselves by defining physical boundaries and systems. Even temporal boundaries require energy in form of the energy reservoir of the clock measuring the time interval between the beginning and the end of a system or experiment. How little energy we can find in a system is therefor an experimental choice. The universe certainly doesn't seem to be afraid of a bottomless pit. ;-)
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  5. In physics nothing means "no thing" and its consequence is Poincare symmetry. That's a perfectly testable condition for an operational definition of "nothing". The consequences are as trivial as the differences between the acoustic Doppler effect (non-empty background) and the relativistic Doppler effect (empty background).
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  6.  @sjoerd1239  Physics is not philosophy. It doesn't split words for the purpose of splitting words. It describes reality. In reality we are observing macroscopic "things" and their properties. The strategy we use to cope with the significant complexity of the phenomenological richness of the physical world is by using a divide-and-conquer strategy. Physicists divide the world into systems. A system may or may not have material objects in it. Even if it doesn't (i.e. it's a system of "no things"), such a system still retains a few fundamental properties because of symmetry (symmetry is the absence of symmetry breaking physics). That symmetry turns out to be local Poincare symmetry. That's as "simple" as we can make it in modern physics without "falling off the horse" like the philosophers do with their pointless hair splitting. As it turns out these few properties are sufficient to explain ALL of the known phenomena that matter and radiation is capable off. If that is not beautiful, I don't know what is. Throw Poincare symmetry out and you can literally NOT explain anything. Keep it in and "every thing" follows almost seamlessly from the symmetries of "no thing".
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  7. Which god? We invented so many of them. ;-)
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