The Universe Is Not a Computer by Ken Wharton

I don't know -- I'm quite suspicious of attempts to 'start with logic', as that's exactly how anthropocentric mistakes are most likely to sneak into the foundations in the first place. This goes doubly so for efforts built on information theory.

Now, I am a big fan of Einstein's method of building theories from big-idea principles, but at the end of the day it's the comparison of the math with reality that is the only way to determine if those ideas were right in the first place.

And I'm afraid I disagree with your sentiments concerning a derivation of SR from QM in an ordinary causal (NSU) framework. Your essay dismisses Bell's theorem far too cavalierly for my liking. If you really want to tackle Bell inequality violations in a spacetime framework, check out my essay references [6] and [12] to see how an LSU can do the trick.

Thanks, Inger, for the kind words!

Gene,

There certainly may be other anthropocentric biases built into physics, and it also is true that I only experience this one universe, so that might unfairly bias me against your ideas.

That said, as a physicist, I want to explain the particular universe that I observe. Maybe it will turn out that the best explanation will require the use of other places and times outside "my universe", but I can't see myself seriously pursuing that possibility until I've ruled out some simpler options.

Here's a quote I still kind of like from my entry to FQXi's very first contest:

"Looking to quantum theory for answers about spacetime is like looking to a roadmap for answers about geology: it's a tool designed for something else entirely. In general, quantum theory tells us nothing about spacetime except what its formulators put into it in the first place."

Best, Ken

Hi Mark,

Yes, you and Silberstein are further along than any other LSU-style approach that I know of, and it's great to see some new cosmological results coming out of it. For now I hope we can agree to disagree about the continuum/discrete issue, and keep finding points of contact, such as this essay. More to come...

Rich,

Thanks for the kind words -- although I think both you and Jackson may be misreading my main point to some extent. From what I can tell about your essay (and Jackson's, and McEachern's), you're still working in a conceptual framework aligned with the NSU. If there's some LSU approach buried in any of those essays, I must have missed it, but I'm certainly interested in any such efforts.

Best, Ken

Hi Mark,

I'm not sure if by "story" you mean "explanation" or mere "description"... If the former, we're not on the same page: LSU explanations don't make much sense when viewed sequentially in 3+1D -- they require 4D "stories". But I'll assume you're merely using "story" to refer to my hoped-for-3+1D representation of what is happening between measurements.

As for whether giving up NS for LS means that *nothing* can be conserved instant-by-instant... That seems way too strong a conclusion. After all, there are aspects of Noether's theorems that provide conservation-type-rules (from the symmetries of the Lagrangian) even if the Euler-Lagrange equations are not strictly adhered to. There's a nice paper by Harvey Brown to this effect...

If you ask me about ontology, "what is being mediated", my best guess right now is the classical Lagrangian density itself, and the classical fields that comprise it. (Bearing in mind that those fields need not strictly adhere to the Euler-Lagrange equations, just as single-photon experiments obviously don't adhere to Maxwell's equations.)

On your last point, perhaps the problem is what you mean by "story" (see first paragraph above). Otherwise, I think we're on the same page. Also, note that LS approaches can give meaning to *new* instant-by-instant constraints, that don't make any sense in an NS framework -- such as enforcing a zero total Lagrangian density throughout spacetime (to pick a not-so-offhand example... :-).

Cheers, Ken

Phil,

Yes, lots of great philosophical questions at the heart of this stuff. Usually I just point people to Huw Price at this point, but I'll venture a few comments of my own.

Very nice quote about Fermat's principle, but if you'll look closely, the claim that "nature... acts without foreknowledge" is precisely the NSU assumption that the universe is just as limited as us humans.

When you get into words like "predecided", I'll direct you to my discussions concerning the block universe in response to Silberstein, above. The very word "predecided" refers to two different times (its subject and object), and therefore has no physics translation -- the philosophical concept of predecision doesn't make sense in the block universe of modern physics.

As for your excellent question: "The deeper question for me then is to ask how a universe underpinned by predecision can have physical outcomes present as being so seemingly lawless respective to their certainty." I certainly have a few thoughts. At one level, the hidden variables that I'm proposing (and that are necessary in any LSU) answers this to a large extent. Just because it's a block universe doesn't mean that we *know* the block; to the extent it's unknown, it appears probabilistic.

But I've only recently come to realize this isn't the whole story. You can't get all quantum phenomena simply by constraining deterministic fields at two times. And the path I'm going down right now -- departing from deterministic equations of motion, underconstraining the intermediate physics between the LSU constraints -- provides plenty of uncertainty all around. (Although one must also relax the Principle of Sufficient Reason to the point where our universe is just one of many possible solutions to the same ultimate constraints.)

As for that great quote you ended with, you may be surprised to see that we used that very quote to start Ref. [12]. We like the intuition of locality (as defined in that quote), and the LSU allows us to keep it, quantum phenomena notwithstanding.

Best, Ken

Hi Amanda,

Glad you liked it, and thanks for the interesting question. Before your post, I had only read summaries of 'top down cosmology', and it originally struck me as making the time-reverse of the usual mistakes when it came to interpreting the wavefunction. But after your comment, I went back and read some of the original papers. I was pleasantly surprised to find that much of Hawking's original motivation mirrors my own complaints about the NSU -- especially the first 1.5 pages of Hawking's original http://arxiv.org/abs/astro-ph/0305562 . It's effectively a critique of the NSU, and concludes that the way forward is to look to the path integral (LSU).

But that's where things go awry, because no one has ever come up with a realistic interpretation of the path integral -- even in laboratory experiments, let alone the whole universe. The '06 paper with Hertog simply assumes that once one has the "amplitude" (not probability!) of the universe the problem is solved, ignoring the fact that the quantum foundations community can't agree on what the amplitude/wavefunction means in the first place. So the motivation is great, but there's no LSU interpretation for Hawking to tap into -- because it hasn't yet been developed, probably for the reasons I outline in my essay.

As it stands, though, top-down cosmology seems to hold that the *past* is a huge-dimensional configuration space (like I said, the time-reverse of the usual thinking), which is pretty confounding to someone like me, committed to the block universe. In fact, if you look closely, the argument goes like this: 1) We don't know the past, 2) We represent things we don't know in huge-dimensional configuration spaces, so 3) The past *is* a huge-dimensional configuration space. In other words, the time-reverse of the same anthropocentric (not anthropic) reasoning that I'm complaining about here.

Still, thank you very much for drawing this connection; I'll definitely find it useful if I ever nail down this realistic re-interpretation of a (modified) path integral that I'm working on.

Best,

Ken

Hi Tom,

Thanks for the very nice comments! I'm way behind on reading essays, but I've added yours to the list... That's interesting about the connection you see with Joy Christian's work; I haven't yet put in enough effort to wrap my head around it, perhaps because I'm stuck in too much of a classical-spacetime mindset.

Cheers!

Ken

Michael,

Actually, I'm being much more heretical than you suggest. I'm not saying that we can't physically reproduce nature's computations, I'm saying that nature doesn't even *utilize* computations, at least not in the standard past-to-future sense of the word. I'm denying any map between reality and Hilbert space, as well as the premise that you're assuming when you say "used by NATURE as well". (I'm using nature=universe here, although I use only 'universe' in the essay.)

Hope that makes it sound a bit more interesting... :-) And yes, I do propose an alternative path forward; I'm not just pointing out unresolvable problems.

Best,

Ken

Yuri,

You picked out the one group of sentences that I was setting up as straw men, as bad arguments that I don't agree with, to complain about.

I'm happy with a constant speed of light, but that's completely beside the point of my essay.

Ken

No, I'm not; I agree with Huw Price on this issue.