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<blockquote data-quote="freyar" data-source="post: 6687012" data-attributes="member: 40227">Umbran has already addressed the spherical symmetry issues quite well, so I'll just talk about the quantum field theory issue a bit.One thing I'd like to make clear is that there's not just one &quot;quantum field.&quot;&nbsp; Quantum field theory is the name for a framework in physics.&nbsp; This is like how quantum mechanics isn't a single theory (like the theory of the hydrogen atom is) but rather a set of rules that should apply to theories of physics.&nbsp; So when we say that the Standard Model of particle physics is &quot;a&quot; quantum field theory, we mean that it obeys the rules and framework of quantum field theory with a particular set of fields and interactions --- each field corresponds to a type of particle.&nbsp; In any case, this framework is going along very well, thank you. <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f609.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=";)" title="Wink&nbsp; &nbsp; ;)"&nbsp; data-smilie="2"data-shortname=";)" />&nbsp; I mean that it's a well-developed framework with lots of very precise results and quite a few Nobel prizes.&nbsp; But most of the developments have been for theories where the interactions between fields are weak, so there is a lot of work right now in trying to understand principles that apply to quantum field theories with strong interactions.It is true that, as in quantum mechanics (which quantum field theory is part of), the results of measurements are probabilistic.&nbsp; And, in quantum field theories, that applies even to measurements of empty space.&nbsp; So I don't know if I'd actually use the word &quot;chaotic,&quot; but it is true that there's &quot;quantum activity&quot; even in empty space (virtual particles, etc).&nbsp; And we definitely don't understand it --- there is a quantum contribution to energy, which should show up as the energy of empty space (the vacuum).&nbsp; I've already talked about that in one of the answers here, but the thing is we certainly don't understand the value of that (though there are ideas).Quantum fields (or maybe some quantum gravitational generalization) certainly existed back to the Big Bang (Singularity), except that in the true theory of quantum gravity, we don't expect there is actually a singularity at the Big Bang.If you're interested in this stuff, I recommend the blog <a href="http://profmattstrassler.com/" target="_blank">&quot;Of Particular Significance&quot; by Matthew Strassler</a>.&nbsp; He has a number of articles up on &quot;what is quantum field theory,&quot; including <a href="http://profmattstrassler.com/articles-and-posts/particle-physics-basics/quantum-fluctuations-and-their-energy/" target="_blank">a nice introduction to fields and particles</a>.I think I'll come back to your question on time tomorrow.</blockquote>

[QUOTE="freyar, post: 6687012, member: 40227"] Umbran has already addressed the spherical symmetry issues quite well, so I'll just talk about the quantum field theory issue a bit. One thing I'd like to make clear is that there's not just one "quantum field." Quantum field theory is the name for a framework in physics. This is like how quantum mechanics isn't a single theory (like the theory of the hydrogen atom is) but rather a set of rules that should apply to theories of physics. So when we say that the Standard Model of particle physics is "a" quantum field theory, we mean that it obeys the rules and framework of quantum field theory with a particular set of fields and interactions --- each field corresponds to a type of particle. In any case, this framework is going along very well, thank you. ;) I mean that it's a well-developed framework with lots of very precise results and quite a few Nobel prizes. But most of the developments have been for theories where the interactions between fields are weak, so there is a lot of work right now in trying to understand principles that apply to quantum field theories with strong interactions. It is true that, as in quantum mechanics (which quantum field theory is part of), the results of measurements are probabilistic. And, in quantum field theories, that applies even to measurements of empty space. So I don't know if I'd actually use the word "chaotic," but it is true that there's "quantum activity" even in empty space (virtual particles, etc). And we definitely don't understand it --- there is a quantum contribution to energy, which should show up as the energy of empty space (the vacuum). I've already talked about that in one of the answers here, but the thing is we certainly don't understand the value of that (though there are ideas). Quantum fields (or maybe some quantum gravitational generalization) certainly existed back to the Big Bang (Singularity), except that in the true theory of quantum gravity, we don't expect there is actually a singularity at the Big Bang. If you're interested in this stuff, I recommend the blog [url=http://profmattstrassler.com/]"Of Particular Significance" by Matthew Strassler[/url]. He has a number of articles up on "what is quantum field theory," including [url=http://profmattstrassler.com/articles-and-posts/particle-physics-basics/quantum-fluctuations-and-their-energy/]a nice introduction to fields and particles[/url]. I think I'll come back to your question on time tomorrow. [/QUOTE]

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