If the universe was rewound to an earlier point of time(to the beginning of the universe for example), would events have manifested exactly the same?

That is, would facts such as "[The Sun] formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud" or "Earth formed around 4.54 billion years ago" be true after 13.8 billion years had passed in the newly played out universe?

Would the randomness of stochastic events allow it to be manifestable that the factual history of the newly played out universe be divergent from ours?

I assume that the bare minimum satisfying the factual history of the newly played out universe departing from ours would be that a stochastic event after the point of rewoundment would occur differently than which occured in ours.

Thus, I assume, that the future of the newly played out universe could be vastly different from ours depending on when the first diverging stochastic event occured.

  • In Spinoza's universe, in your thought experiment, any alteration in anything up to this moment would prove a flaw in Deus/Substancia/Natura, which by genetic definition contains no deficiency, by necessity and of completeness. Since nothing can 'be' or 'exist' outside of this substantial necessity and everything flows from it with the force of naturally 'self-caused' creation, everything would remain exactly as it is. See, 'Spinozistic Tao te Ching', at academia.edu. – user37981 Oct 4 '20 at 22:42
  • @CharlesMSaunders Would then everything be wholly deterministic in Spinoza's Universe? That is would all interactions be governed by Causality, and no random events be possible? – TomDot Com Oct 4 '20 at 22:58
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    How is this different from asking whether the universe is deterministic or not? Which, of course, is a perennial question we are not going to resolve here. – Conifold Oct 5 '20 at 9:43
  • @Conifold Ah, I guess it would be the same as asking if the universe was deterministic or not. – TomDot Com Oct 5 '20 at 10:05
  • @TomDot Com- The confusion around the attribution of determinism to Spinoza's system has to do with secondary sources. Spinoza used the term 'determined to act' in a specified manner when discussing 'contingent' being'. His treatise, "On the Improvement of the Understanding" is a 43 page guide to improving human capacity to understand Nature' and our own lives. That does not square with determism in any way. The "Ethics" Part 5 is titled, 'On Human Freedom's, wherein he expands on the notion of becoming free from the debilitating negative emotions. There is no determinism in Spinoza. Read it – user37981 Oct 5 '20 at 17:15

Physicists disagree, never mind metaphysicists.

The current standard understanding of quantum theory is that nature is inherently uncertain and probabilistic, so a second rerun would be almost certain to differ in detail, up to quite large scales inherited from the uncertainties inherent in the Big Bang and still visible across the night sky.

However some physicists believe, or suspect, that this uncertainty reflects our own ignorance of the true state of affairs; if we knew enough about aspects currently hidden to us, called "hidden variables", then the uncertainty would disappear. The universe would be found to be entirely deterministic after all, and any rerun would be expected to be identical.

The problem is that no such comparative rerun is logically possible, so it is in principle impossible to test which prediction is correct and the two positions are regarded as unscientific interpretations of quantum theory, as opposed to the theory itself.

Metaphysicians tend to pick and choose between such interpretations according to how they impact issues such as free will. For example physicist Hugh Everett posited a many-worlds theory in which a deterministic universe splits into multiple new universes every time a choice or an experimental observation is made. Thus, in any given timeline we appear to have free will. The idea appeals to those who seek some sense of free will in a deterministic reality, but it too is an unverifiable interpretation.

  • Metaphysicists are, however, limited by Bell's theorem to a rather restricted set of possible interpretations. For example, if you want to have local hidden variables, you need to adopt a superdeterminism position, which has significant metaphysical implications (eliminates the distinction between possibility and necessity). If you want hidden variables without superdeterminism, then you need something resembling pilot-wave theory, which is nonlocal. And if you want locality and non-superdeterminism, you have to give up on hidden variable theory altogether. – Kevin Oct 6 '20 at 19:11
  • Bell's theorem is a part of the theory, it is one of the underlying things that people interpret. Hidden variable theories have to take it on board and interpret it, just like they do with the rest of the theory. Metaphysicians find themselves stuck with the same theory too, whichever interpretation they turn to. Yes, hidden-variable models changed dramaticaly once nonlocality was elevated from interpretation to theory, but the older stuff is all history now. – Guy Inchbald Oct 7 '20 at 9:07

A question loaded with assumptions.

  1. Your question carries the assumption that we know how variables behave along universe formation, so you ask what if we change one. This should be answered by you, according to the assumptions you are taking.

  2. "the randomness of microscale events in the newly played out universe be non-negligible" assumes a subjective order of magnitude to make the difference: negligible to what degree? three atoms of difference is negligible? the existence of two stars? The results of a poll in USA? [1]

[1] Given that you use the term microscale, which is probably equivalent to thermodynamics microstate, I remember you that macrostates are subjective (e.g. temperature is basically a feeling). You suggest that even microstates change, macrostates might not. So, your measurement would depend essentially of subjective opinions. Think the consequences of such condition.

  • "negligible to what degree?" Apologies, I should have specified the degree. I guess the degree would be the bare minimum (whatever that may be). In essence I was intending to ask whether it is manifestable that a stochastic event subsequent to the point of rewoundment, could play out differently than that which occured in our universe. Thus that event would have caused the newly rewound universe to have departed from the factual history of ours. – TomDot Com Oct 5 '20 at 5:53
  • When you say my "question carries the assumption that we know how variables behave along universe formation" what exactly do you mean? Do you mean that I'm assuming, for example, that the law of Causality is constantly being obeyed during the formation of the universe, or something like it? Also are you defining a variable as an entity such as a proton or a quark? – TomDot Com Oct 5 '20 at 6:08
  • I've edited the question such that I've specified the bare minimum degree that I expressed in my first comment – TomDot Com Oct 5 '20 at 6:12

I tend to believe to the theory of Max Tegmark, that we live in mathematical universe. Which says that some mathematical structures exists, we don't know yet which mathematical structures are "basic", therefore existing, and which are "invented" by us. According to that theory, there is infinite number of possible universes, therefore our universe is, by anthropological principle, one of them, with laws of nature expectedly suitable for intelligent life.

Leopold Kronecker said that god created integer numbers, and everything else is created by man. According to that logic, only (positive?) integers are somehow bult-in into reality, in realm above and beyond "universes", perhaps because non-existence of integer numbers would cause some logical inconstancy.

From that point, we can assume, that any projection of integer set is equally "existent". Every way we look at existing object (integers) is equally "right" or "existent". Our universe, therefore, in its deepest level is mathematical function (projection) of integer numbers, which in turn, as an emergent by some additional projection can be perceived like "Level-3 multiverse" (Max Tegmark), which is multiverse of all Everettian possibilities of quantum interactions.

Note that in this model randomness is human invention, in nature itself there is nothing really random going on, only pseudo-randomness, like indexing problem, or insufficient knowledge / insufficient information.

Tegmark made great point, in my opinion, that function which defines laws of nature in our Level-4 universe is definitely "existant", because we can confirm its existence. But, if similar functions, with little bit different parameters or operators are non-existent, there would have to be some magic substance inside our particular mathematical function. That doesn't sound plausible. Also, we don't know what function define our mathematical universe, we are approaching it from two sides: Schrodinger equation and general relativity, but maybe it contain enormously huge numbers (constants) that we simply cannot ever derive from anything.

Side note: I'm sorry for not being yet allowed to comment/answer on your questions re this and other my posts.

  • So since according to this model, "randomness is a human invention", the factual history of the current universe is unique and could not have been any other way? Essentially Hard Determinism is the case? – TomDot Com Oct 5 '20 at 9:19
  • What exactly are the "Everittian possibilities of quantum interactions"? – TomDot Com Oct 5 '20 at 9:22

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