When I was younger and had most interest in non-useful things (in a boring sense) I came to "the theory" that each time observation or logical induction is performed, the universe splits into many variants ahead of time and these variants that produce "oops" in terms of contradiction simply disappear. Each time you see something weird but real, it is oops that survived, because you didn't see something contrary yet (and now you cannot, because only one thing has to be remaining).
That made me sad, because we could come to hyperdrives and FTL journeys to alien worlds, but some people in 20th century made few observations and conclusions that now prevented fun forever. Magic things were easy before the technology, now they are physics-hard. Our universe is spoiled in a very wrong way.
I feel that assuming that the nature of how the universe is computed matches up with our first intuition feels a bit like the assumption in geocentrism that the universe matches up with our intuition of Earth being the center and the most significant body.
Even if you accept the basic premise of the universe being a simulation, there are still many ways it could work with MWI. The simulator's universe needn't have classical physics; the simulation could be running on quantum computers or something more advanced. Or the simulator's universe could be classical with a classical computer doing the simulation at exponentially-decreasing speeds as it has to simulate the increasing number of branches. It wouldn't make any difference to us how long the simulation takes to compute us, as long as the simulating machine doesn't break down and succumb to entropy. The simulator's universe could be something like Conway's game of life, and the simulation is running on a turing machine pattern which will never decay or break down. (I might be borrowing more than a few ideas from Permutation City here.)
If the universe gets cloned one time every second that would still be a huge claim.
A million times every nanosecond is even a bigger claim.
Now imagine how many states the universe can be in, and how many times a second can be meaningfully divided.
If you can solve the "one clone every second" then I would be satisfied.
https://en.m.wikipedia.org/wiki/Bell%27s_theorem#Bell_inequa...
EDIT: tone.
Not everyone agrees on what is "reasonable". I have no problem giving up locality, but "true" randomness (i.e., information generated without an algorithm) seems like a philosophical cop out.
Note that something can also be globally deterministic but indeterministic from the perspective of a subsystem. In this sense, the universe would appear random as far as we're concerned, but not random to whoever is simulating the universe (this is often called superdeterminism, but I think that's a silly word—the universe is either deterministic or it isn't).
Would you agree that something is determined iff its probability is zero or one? I'm guessing the disagreement is here - what definition would you use?
One concerns a lack of knowledge, like in your cards example. In that case, the probability is an expression of your state of understanding of the deck, and is not a property of the deck itself. The physical details of the deck and the situation it is part of could be entirely deterministic and we could still talk about this kind of probability. In this case your knowledge is independent of whether it is probabalistic or not.
The other is whether the universe contains fundamental randomness, such that you could say it is literally "probabalistic". And in this case whether that is true or not is independent of our knowledge of the probabilities.
http://lesswrong.com/lw/jlb/logical_and_indexical_uncertaint...
I would say, not. There's no actual randomness from an objective point of view, it's just a lacking in your understanding of things.
I think that map/territory confusions are the source of so many problems and should be rigourously avoided. I think it would be a map/territory confusion to consider it a kind of actual randomness.
Even though it makes perfect sense to apply probability theory to it? We found a perfect coin, one that we know that you can't predict in advance even in principle, and you want to avoid considering it a kind of randomness? Why does the mechanism by which the universe implements randomness -- in this case via determinism -- matter?
So, does indexical randomness fit your definition of "fundamental" randomness? And what did you mean when you said "a coin that may well actually be random" if it wasn't the indexical kind of coin?
No, it does not. MW is determinsitic. The fact that you don't know which universe you will observe is a limit on your knowledge. It does not make the things actually random.
There are other interpretations of QM where there is literal randomness, independent of an observers knowledge.
What is the chance that you're shot? Is it 1/6? What about if you open it up and look in the barrel to see if there's a bullet there?
Are you suggesting this example somehow shows that changing knowledge/probabilities determine whether what's going on there is deterministic or not, as is the issue under discussion?
For anything that exists outside of a light-cone around the first electron, a measurement of the second electron will be truly random from the measurer's perspective.
What about the universes in the multiverse where 'multiverse theory' is wrong, and there is no multiverse? Are they islands? Are they like multiverse 'diodes' which may allow only one-way travel into that universe, but from which return to the larger multiverse is impossible?
"outside" is not very rigorous. For example, we seem to be observing objects vanishing behind the comoving horizon. It seems unlikely that the individual cosmic horizons centred on each of our microscopic components is destroying these objects, and it seems unlikely that they will ever reenter the comoving horizon. The metric expansion induces other interesting horizons, too, and each has an "inside" and an "outside". But how many of these horizon-crossings are directly detectable by the objects crossing them? (Reflectively, we are each exiting the horizons of distant observers at slightly different scale factors because we aren't occupying the same point in spacetime).
"More of same" for some distance outside of e.g. the cosmological event horizon is wholly reasonable. We can even put lower bounds on "some distance" depending on how we look at the homogeneity and flatness problems. They're big. IIRC Guth's original cosmic inflation work predicted that the Hubble volume is no more than 10^-26 of the total causually connected volume at the start of inflation. We can also put bounds on any sort of gradient on various apparent constants such as c and G, and the region in which they are virtually certian to have the same values we have experimentally here is also big.
However we currently can't do much better than that. The bits and pieces that were close to us in the hot dense phase of the universe are mostly inaccessible to us now, but there is every probability that they have identical local physics to us. There may be bits and pieces that were insufficiently close to us in that phase that have wildly different physics; and we do not really know anything about the still denser phase of the universe. It is perfectly reasonable to consider observables generated by detailed guesses that e.g. avoid an actual singularity like Carroll & Chen (who propose one or more other universes evolving towards de Sitter space from some arbitrary shared values surface) for instance. But even there, "outside" gets tricky.
Moreover, "inside" vs "outside" is not really the best way to approach the underlying question, "what is the nature of the metric expansion of space?" where the real answer should identify the cosmological frame and its preferred coordinate system in which almost all matter remains at essentially the same spatial coordinates from the big bang to the infinite future, with the scale factor relating to radar distances (and radar beam wavelength changes) between objects at distant spatial coordinates. Then we can admit that there are various ways to interpret the radar observables, with the "easiest" one being a purely local evolution of the vacuum at each point along the radar's path, which in the preferred cosmological frame can be seen as dark energy, but which with other systems of coordinates can be seen as anything from "the local creation of more space" to a Doppler effect to (somewhat less usefully) a change in the vacuum's refractive index.
> what is North of the North pole
Well, a change of coordinates on the Earth gets rid of that particular coordinate singularity, doesn't it? We can get rid of all sorts of oddities by swapping the coordinates we're using, which is probably the greatest strength of general covariance.
What we can't do by changing coordinates (even to accelerated systems of coordinates) is eliminate the Earth's oblateness.
Likewise, we can change from FLRW coordinates to other coordinates on the cosmological frame and get rid of (or introduce) all sorts of oddities. We can't, however, get rid of angle-brightness-redshift relations.
It is a bit silly to introduce all sorts of additional action-at-a-distance forces to explain the Earth's oblateness in an effort to do away with the rotation-oblateness relation for objects close to hydrostatic equilibrium.
Similarly, it could be a bit silly to introduce all sorts of new (and presently broken) symmetries in an effort to do away with away with causally disconnected regions (with possibly different physics) before inflation or whatever mechanisms produced the relic field anisotropies. And I think it's reasonable for physical cosmologists to argue that it's hard to foreclose on that type of multiverse without doing so.
Moreover, "before the big bang" is perfectly reasonable if one starts adding in new symmetries anyway; if quantum gravitation avoids the BB singularity (as practically everyone hopes it will avoid BH singularities), why wouldn't it be meaningful to consider the universe before the classical singularity BB? It's just technically difficult as a theoretical programme and is unlikely to be guided by current data. Well, so what? It's technically difficult to predict early structures or them right after reionization, let alone say anything about or observe anything at slightly higher redshifts, and we don't even expect new physics to be relevant in those regions at all.
Let's imagine a simplified example. I give you two sets of numbers (let's pretend they are atom coordinates). One set is purely random, another one is generated with a very simple formula (example: f(n) = SHA256(N + salt)). I will give you as many of the numbers as you want. Can you determine which set is which (if you don't know the formula ahead of time)?