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3

The great simulator idea is piffle, see See http://www.daviddeutsch.org.uk/wp-content/ItFromQubit.pdf. A brief summary of the problem. A set S of computational gates is universal if by composing gates in the set S you can do any computation allowed by the laws of physics. Both the classical and quantum theories of computation say that there are many ...


2

The article you quote is about metaphysics: The idea that we might be living in an artificial reality constructed by something higher than ourselves has been a recurring philosophical hypothesis for centuries. Plato's Allegory of the Cave, and cannot really be discussed in a physics framework because it is searching for a Creator. It never ceases to ...


1

Well, i would say no. Why? Because an absolute center of mass would require a uniform covering (coordinate system) over the whole manifold, which, even if it exists, will probably not be on the manifold itself. An analogy would be the center of mass of a spherical surface/manifold. It would be exactly on the center of the sphere (i.e not on the sphere ...


2

The current entropy in the Universe is all stored in photons. The first reference by Qmechanic gives you the precise value. Since the photons of the CMBR do not at present interact with anything, the entropy of the Universe is very close to being a constant. What evolution there is, is all due to non-reversible processes in baryonic matter, but it amounts to ...


1

If we assume our universe as an isolated system, then its entropy can only increase. It cannot decrease because of the second law of thermodynamics. It cannot stay unchanged because the universe is undergoing all kinds of irreversible processes.


3

Simulation implies an author, so this is another attempt at trying to find a creator for the universe, imo. Thus it is metaphysics and not relevant to the subject of physics. Physics as a discipline starts from observations and fits them with mathematical models that have predictive power, having accepted axioms and postulates. The mathematical forms are ...


2

I am on record of having the opinion that there is no real argument against us being a simulation in a general sense, however we frequently find people jumping to quick into the simulation pool and stating there new what-ever-it-is proves the universe is a simulation. The example given above sounds like one of them. First off, Quantum Error Correcting Code ...


0

Carroll (2004) introducing the standard Friedmann-Lemaitre-Robertson-Walker model, shows that this will become clear in a formula that sheds light on the fate of the cosmos: To determine the dividing line between perpetual expansion and eventual recollapse, note that collapse requires the Hubble parameter to pass through zero as it changes from ...


4

The short answer is yes, the presence of dark matter would act to counter the expansion of the universe. And in fact it does--but not enough to stop the expansion. Dark matter has gravity just like normal matter. In fact, that's pretty much the only reason we know dark mater exists at all: we can observe dark matter's gravitation effects in the rotation ...


5

The acceleration of the expansion is currently observed to be happening. This observation is one of the pieces of data we use to infer the amount of dark matter. It tells us that there can't be more than a certain amount of dark matter, because that would be incompatible with the observed acceleration.


3

The ball, in fact, is always accelerating downward, even though it is moving up for the first part of its trip. A ball that kept accelerating upward would just fly up out of the atmosphere.


2

As Count Iblis pointed out, The Church–Turing–Deutsch principle makes this impossible to decide using the structure of the laws of physics as it will always be compatible with the universe being simulated by a quantum computer. Nevertheless, in this well-known paper the author argues that if we accept some very reasonable assumptions, then is is almost ...


-2

If you were a simulated person inside an emulation, would you ever be able to tell the universe was emulated? the answer is no, not if it is set up correcty.


1

It's certainly possible, though on current evidence it looks unlikely. The past bound isn't really a bound in the usual sense of the word, but instead it's a singularity. If we solve Einstein's equations for the universe with a few apparently plausible assumptions we find that the universe is described by a scale factor, normally written as $a(t)$, and as ...


5

As for the straight line, yes. All objects will continue moving along geodesics (a straight line in curved-space but sometimes a curved line in straight-space) if there are no external forces acting on them. Unless, by different velocity you mean the direction is not entirely radial to us. In that case, the expansion will cause the object's path to appear to ...


-1

As the incredible difficulty to finding solutions to the three dimensional Ising model proves beyond doubt, discrete problems are fundamentally just as hard as continuum problems, in many cases probably even more so. More interestingly, physically relevant solutions of the higher dimensional Ising model correspond to modes of certain continuous equations, ...


1

I am sorry to say that I can not agree with previous answers. We believe, but do not know for sure, that light from some galaxies will never reach us. This has nothing to do with the fact that they are moving away from us at more than the speed of light. Rather, it is assumed that these galaxies, like us, are not moving relative to the special frame in ...


4

I am aware that my answer can sound surprising, too simple to be true, but please take a deep breath before downvoting.The answer has little to do with relativity. In SR it is the moving object that gets shorter , but space is stable. In such a universe, even if a body is receding at 2,3,30 c, its light will reach us sometime, and the time is short as it ...


6

Let me present a slightly different perspective to Luboš, though I'm saying basically the same thing. From our current location we can define an area of space called the future light cone. This is the region of spacetime that is connected to us by motion at less than or equal to the speed of light. If we draw a spacetime diagram then the lightcone looks ...


3

The relative speed between two objects is only restricted within the special theory of relativity. These restrictions are only guaranteed to apply in general relativity – the theory of curved space that you need for the Big Bang theory – if the space surrounding the objects is the flat Minkowski spacetime, or at least can be approximated by the flat ...


0

I didn't watch enough of the video to see the alleged claim, but I'm almost sure he is talking about the idea that the universe has different regions in which the "constants" of nature have different values, and only a few of those regions are hospitable to intelligent life, and we (of necessity) live in one of those, and that's why the constants here seem ...


0

Due to the work of Julian Barbour and others, time is defined (in a closed system) by keeping track of all the changes (of particles and so on). In this respect we would say that in a classical system (macroscopic) that time would be continuous since the motions of such objects are essentially continuous and the way that you parameterize the changes would ...


-2

ever since the big bang,there universe has been expanding.other stars continues to burst and expand when they get hotter.so yes other stars wil disappear in the future and no longee be seen with naked eyes.


3

Alright, here's the skinny. The universe is much much larger than 92 billion light years. But the region we can see is around that number. Also, you have it all wrong for the expansion rate of the universe. The expansion is more like stretching. No matter where you are (that's an approximation), you would see a length x expand by the same amount after a time ...


1

Ok, this is going to be a math-free-ish answer. Let's get something straight right off the bat. Inflation is over. Inflation refers to the first ~$10^{-34}s$ of the universe after the Big Bang. What we have now is accelerated expansion. Second, asking if this accelerated expansion "costs energy" is not particularly meaningful. What you'll find is that most ...


2

One of the Friedmann equations is a "conservation" equation: $$\dot \rho_i= -3\frac{\dot a}{a} (\rho_i + p_i) \tag{1}$$ where $\rho_i, p_i$ describes energy density and pression for a particular "fluid" (dust, relativist particle, dark energy/cosmological constant). For each fluid, there is a relation between $p_i$ and $\rho_i$ (respectively $p_i=0, p_i ...


4

The point is that during the ordinary phase of the Big Bang expansion, the difference $|\Omega-1|$ was rather dramatically increasing with time. Today, we know that $|\Omega-1|\lt 0.01$ or so. If we use the cosmological equations to reconstruct what $|\Omega-1|$ had to be when the Universe was a second old, or very young, we find out that the following ...


0

We can't peek deeper than a certain distance away from our current cosmic position, but we know for sure that the universe extends far beyond that cosmic horizon. In fact, for all we know, although our observable universe is finite, the full universe is infinite in size. If this is indeed true (and there is no single piece of evidence against an infinite ...


-1

There is no edge if you come along with the infinite concept. Update: Harvard complements my answer: http://www.cfa.harvard.edu/seuforum/faq.htm#s1 Galaxies extend as far as we can detect... with no sign of diminishing.There is no evidence that the universe has an edge. The part of the universe we can observe from Earth is filled more or less uniformly ...



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