Forum:Physics question

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Actually two. Sort of more. Sorry if these come across as extremely stupid, but I have basically no understanding of modern physics and I was hoping for some clarification. Thanks in advance.

Firstly, I recall reading that the expansion of the universe is slowing down is because the gravity of objects more towards the relative centre of the universe is pulling at objects/energy at the relative fringes. If this is true (my understanding is probably incredibly incorrect though), then it means eventually the universe will stop expanding, and start contracting. It will continue to contract until the whole of creation is nothing more then a single point of matter containing all of the "stuff" that makes up creation (a singularity of matter, energy, and the four fundamental forces of the universe). So, my question at this point is both is, is it reasonable to then assume that if/when this happens, the inertia of the whole of creation slamming together will act like a spring snapping in on itself, and cause an outward expansion, resulting in another Big Bang.

I suppose an answer of "this is more or less right" raises three interesting questions for the Theologian, Cosmologist, and Metaphysicist* to debate: 1) Is our universe and it's Big Bang the first universe and Big Bang, and if not, how many have their been, and how many more will there be? 2) Where did the single point of matter come from in the first place, and what caused its initial expansion? 3) Is there something akin to friction which will slow down the initial expansion of the snapping of the spring, resulting in smaller/slower expanding universes, and eventually no new universe, simply a naked causality?

• This sounds like the opening to a pretty bad ass joke "a Theologian, Cosmologist, and Metaphysicist walk into a bar..."

The second question I think is pretty much 100% wrong, but here goes. So, Cause and Effect are kind of big things. Nothing can happen without having a cause, which itself had a cause, etc. This leaves no room for free will, and that (in effect) there is a fate to life determined by simple cause and effect, and that if we had the computing power we could predict what a person will do in response to literally anything, and what they will be doing in a decade, simply as a result of cause and effect. However, subatomic particles don't necessarily act on cause and effect, but instead act on a percent chance that they will do something in response to a given stimulus. If this is true at a subatomic level, could the actions of these subatomic particles then impact the actions of atomic-level particles, meaning that there is a percent chance determining the reaction of an atom to a certain stimulus? And could this continue on to a percent chance that macroscopic objects have a percent chance of reacting a certain way to a certain stimulus? This then breaks the fundamental chain of cause and effect (or atleast changes it to a chain of cause-and-effect-as-determined-by-chance), and the brick universe breaks?

Thanks for the patience folks.--Logic and Empricism (talk) 03:48, 4 June 2012 (UTC)

• First off, according to modern knowledge, the expansion of the universe is in fact accelerating, so there's no possibility of a cyclically exploding universe.
• Regardless of that, there is currently no known theoretical framework which can describe events during the Planck epoch (less than the Planck time, 5.4 · 10^-44 s, since the beginning of the universe). There is no way to answer the question about past universes right now.
• Regarding the 'free will' question: it's true that it is impossible to predict behavior at the subatomic level given the state of the system due to inherent randomness of some measurements in quantum mechanics, but free will doesn't follow. There is no way for your consciousness to affect this randomness, so your actions are still just as deterministic as in a hypothetical, purely Newtonian universe, only less predictable - unless you want to claim that every random number generator has free will.
• Whether you have free will (a philosophical proposition) is independent of how precisely the future events in the universe can be predicted (a technical proposition); if it was dependent, then your free will would be contingent upon the level of scientific knowledge and technology available to you, which doesn't seem acceptable.
• It's also questionable to assume that randomness somehow breaks causality.

--Tweenk (talk) 06:47, 11 June 2012 (UTC)