Archive

Posts Tagged ‘digital physics’

Consensus Quantum Reality

January 15, 2013 1 comment

A paper was recently reported on the Arxiv blog that I feel compelled to comment on. It showed the results of a poll of physicists, philosophers and mathematicians about the nature of quantum reality. It makes a for a fascinating read. One message comes through loud and clear, which anyone can pick up on regardless of their level of scientific knowledge, and that’s that scientists are massively undecided.

I can’t say I’m hugely surprised by this, but I find the results of the poll somewhat disappointing. I don’t often resort to rolling my eyes at mainstream physics, because I believe that digital physics researchers, and computer scientists in general, have a huge amount to learn from the physics community. Furthermore, if digital physicists don’t create tools that can pass muster in the eyes of physics professionals, then, at some level, we haven’t done our job. However, on this occasion, I think eye rolling is in order.

Let’s take question one on the list: What is your opinion about the randomness of individual quantum events? A great question. Kudos to Anton Zellinger and his team for asking it. However, the results are as follows:

  • The randomness is only apparent: 9%
  • There is a hidden determinism: 0%
  • The randomness is irreducible: 48%
  • Randomness is a fundamental concept in nature: 64%

Good lord. Really? Let’s take a moment to ask the question: what is randomness? We can start with a pretty basic definition on Wikipedia. It states that randomness commonly means a lack of pattern or predictability in events.

In other words, we define randomness through a negation. This is true up to and including the most formal definitions of randomness that I’m aware of. We say that something is random when we don’t know what’s going to happen next.

But there’s a deep problem here. Randomness, as we’ve defined it, isn’t a thing. It’s the opposite of a thing. And we have defined it based on the notion of predictability. Except, (as I’ve pointed out in previous posts), prediction is always done with some limited amount of computing power. There is no such thing as an infinitely powerful prediction machine. It’s hard to know what this would even mean.

And any system with limited ability to compute can only pick out and identify a finite number of patterns. For instance, I have the ability to surprise my four-month-old son on a regular basis. However, that does not make my behavior quantum mechanical.

The same limitation is true at any scale you want to pick. The combined computing power of the human race is still limited. There are problems that we can’t solve. Which means that there must be patterns in the universe that we cannot predict, but which can be derived from some underlying deterministic process. In fact, we know that this is true. We’ve been studying problems of this sort since the 1880’s, before quantum mechanics was even invented.

So, in order for someone to propose that randomness is a fundamental concept in nature, they have to assert that even though we know unpredictable deterministic patterns exist, quantum mechanics is not like them. And given that there can be no proof either way, this choice is always made in the absence of information. In other words, it is faith.

I do not like faith in my science. It has no place, IMO. And the only approach that is not faith is to continually doubt. In this case, doubting means assuming that the minimal information model is correct until you have evidence otherwise. In other words, proposing that an underlying mechanism exists and trying to look for such a model until you have a concrete, inviolable reason to believe that one could never be found. In other words, doubting equals determinism–the basis on which we founded science in the first place. (The same answer that received a zero percent vote.)

My concern about this mystic belief in randomness is that it suggests that a great number of physicists, while no doubt highly adept in their respective subfields, have not thought independently about the tools that they are using. They have accepted the notion of implicit randomness because it’s baked into the culture of physics and so it seems foolish to disregard. They believe in implicit randomness because ‘of course there is randomness’, or some mathematically dressed up version of the same. Whichever way you cut it, this is a bad reason.

For further evidence that this lamentable state of affairs does indeed exist, one need look no further than question 12: What is your favorite interpretation of quantum mechanics? Forty-two percent of the respondents picked the Copenhagen Interpretation, making it by far the most popular response.

What, you mean the version dreamt up by a bunch of coffee-swilling logical positivists in the 1920s, while Alan Turing was still in middle-school?

Sheesh. Don’t get me started.

Advertisements

Simplicity and Turing Machines

July 9, 2012 6 comments

I have an exciting result that I want to share with you. However, in order to get there, I’m going to have to take this blog in a slightly more abstract direction than it’s been going recently.

‘More abstract?’ I hear you ask. What could be more abstract than discussing whether the fundamental nature of reality is based on simple algorithms? The answer is: discussing the nature of simplicity itself. Is such an abstruse subject still relevant to physics? Undoubtedly. I believe that it holds the key to resolving the long-standing difference in perspective between computer scientists and physicists.

I have been to several painful conference discussions in which physicists at one end, and computer scientists at the other, debate about the nature of reality. The computer scientists proclaim that nature must be discrete, and that Ockham’s razor supports their reasoning. The physicists look at them blankly and tell them that Ockham’s razor is a tool for building models from experimental data, and represents a heuristic to guide reasoning–nothing more. Neither side can apparently fathom the other. Filling the panels with luminaries from the highest levels of science seems to only make the problem worse.

It’s my belief that the study of simplicity can potentially provide a language that can unify everything from group theory up to quantum mechanics, and put this battle to bed forever. I will endeavor show you how.

Discussions in digital physics often revolve around the notion of programs that are ‘simple’, but not much is said about what simplicity actually entails. Computer scientists are very familiar with the notion of complexity, as measured by the way in which the solution to a given problem scales with the size of the problem, but simplicity is something else.

For instance, consider Turing machines. There are idealized models of computation that computer scientists use to model what computers can do. A few years ago, Stephen Wolfram held a competition to prove that a given Turing machine model was capable of universal computation. Why was this model considered interesting? Because it contained fewer components than any other Turing machine for which the same proof had been made.

A Turing machine is a pretty good place to start exploring the idea of simplicity. You have a tape with symbols on it and a machine that can read and write those symbols while sliding the tape forward or backward, based on what it reads. You can build one out of lego.

Though there’s not much to it, but this incredibly simple machine, given enough tape and enough time, can do anything that the most sophisticated computers on Earth can do. And if we ever succeed in building quantum computers, the humble Turing machine will be able to do everything they can do too.

However, when it comes to providing a truly simple model of computation, I propose that the Turing machine doesn’t go far enough. This is because there is hidden information in the Turing machine model that isn’t written in the symbols, or stored in the state of the machine. In fact, for a classic description of a Turing machine, I’m going to propose that there is an infinite amount of information lurking in the machine, even when there are no symbols on the tape and the machine isn’t even running.

The hidden information is hiding in the structure of the tape. In order for a Turing machine to operate, the machine has to be able to slide the tape left or right. Unless we know which piece of tape is connected to which other piece, we have no program to run. This problem, I’d propose, infects the theory of information down to its roots. When we discuss the amount of information in a string of binary bits, we consider the number of bits, but not the fact that the bits need to come in a sequence. A bag of marbles colored white or black which can be drawn in any sequence doesn’t hold much information at all.

Any truly simple model of computation, therefore, needs to contain an explicit description of what’s connected to what. Hence, I’d propose that the simplest unit of machine structure isn’t the bit, but the reference. In other words, a pointer from one thing to another. You can build bits out of references, but you can’t build references out of bits, unless you presume some mechanism for associating bits that’s essentially identical to references.

Once you start representing computation using references, the structures you come up with suddenly start looking a lot more like the programs for replicating physical experiments that I’ve outlined in previous posts. From a digital physics perspective, this is already useful. However, we can go deeper than that. When we compute using references, something strange and wonderful can happen that I’m still figuring out the implications of. In the next post, I’ll show you what I mean.

On Consciousness and Free Will

June 1, 2012 17 comments

On this blog, we’ve recently tackled religion and the nature of existence, but we’ve left out one huge chewy topic that people tend to lump into this philosophical category, and that’s consciousness. You need only look at a site like Closer to Truth in order to see just how tightly coupled these ideas are in the public imagination. It’s also a topic of significance to me, as it was through writing on this subject that I first found myself exploring digital physics many years ago.

One of the great defenders of the specialness of human consciousness in the physical realm has been Roger Penrose, the man who proposed that consciousness was non-computable because it was founded on non-computable processes in nature. A lot of this blog has been about demolishing that idea. So on Penrose’s hypothesis, digital physics is pretty clear.

However, there are plenty of other ways you might integrate consciousness with discrete reality. For instance, take the essays submitted for the 2011 FQXI prize, on the subject ‘Is Reality Digital or Analog‘ (probably the highest profile public discussion forum on this subject in the last five years), and you’ll see the word consciousness showing up within the first four titles. What about these other models? Do they have anything to add? Here’s my answer:

Digital physics has nothing to do with consciousness, because consciousness has nothing to do with physics. 

The notion that consciousness has any bearing on quantum mechanics, and therefore physics at large, is, to my mind, a lamentable side-effect of the times in which QM was first formulated. Poor old Neils Bohr had the unfortunate fate of hanging out with a bunch of logical positivists, who were sort of trendy at the time, and he tracked some of that muck back into physics along with him.

Enthusiasts on the topic of quantum consciousness point to the fact that observation of a QM event affects how it will play out. However, as we’ve seen in previous posts, we can generate identical effects in a simulation by simply asking the question–is information leaving the system or not? If it is, then an observation has taken place, if it isn’t, then an observation hasn’t happened yet.

In other words, particles are non-committal. They’ll hedge their bets and be everywhere until you force them to make up their mind. And forcing them to decide often has the side effect of forcing a bunch of their friends to decide too. In this regard, particles are rather like teenagers trying to decide where to go on a Friday night. They’re no more strange and magical than sixteen year-olds. (Though, admittedly, sixteen-year-olds are pretty strange.) Ask any self-respecting working particle physicist about the role of consciousness in QM, and they will struggle not to roll their eyes at you. This is why.

So if we can rule out consciousness having an impact on quantum mechanical events, and we can rule out its dependence on smooth symmetries of nature, is there anywhere left for the specialness of consciousness to hide? At this point, we invoke the principle of minimal complexity which we used to unpack the idea of god, and we ask ourselves if the universe is more or less complex if we have to carve out some special extra room for sentience in physical law. The answer, I’d argue, is that it’s more complex, and therefore massively unlikely. Nice though it might be to cogitate on, then, consciousness arises naturally out mechanistic physical processes, just like everything else.

But what about free will? Given that quantum mechanical events are completely unpredictable, isn’t there at least enough room left for that? Not in this model of the reality, there ain’t.

To describe the universe completely, we need to treat the rules that run nature and the data that they run on as a single closed system. Otherwise we haven’t finished describing them yet. Thus, if we find that a huge pile of random numbers are necessary for the universe to work, then they belong as part of our model–as a giant list of lottery tickets printed at the beginning of time and slowly spent.

Of course, a huge pile of random numbers that lasts for the length of the universe is a really, really awful implementation. The principle of minimal complexity strongly suggests that reality is better than that.

Free will, does it exist, then (at least in the sense of something special outside of logic)?

Sorry, no luck, as it were, so to speak, if you’ll pardon the pun, etc.

Citizen Scientists

May 28, 2012 Leave a comment

This week, I had a very interesting discussion with someone who I had never met, who had a digital physics idea that they wanted to share. I found myself in the position of giving feedback on work I was not familiar with, and it occurred to me that I should say something about it on this blog. I want to make it clear how I feel about citizen scientists, the concept of ‘crackpots’, and digital physics in general.

First, let us be completely honest. Digital physics is considered a crank topic by many mainstream physics. You need look no further than the blog of Lubos Motl to see just how fervently this is felt, or the level of anger that that can be directed towards the notion of a discrete universe.

For the most part, the reasons for this contempt are down to laziness. Those who don’t care to engage assume that a digital universe must involve a cartesian spatial grid on which some number of cells are turning on and off–the classic CA approach. This picture looks utterly incompatible with either quantum mechanics or general relativity, so they consider the entire notion to be stupid.

Those who do engage attempt to transfer the familiar tools they are used to using, the Minkowski metric, quantum fields, etc, into the discrete domain without modification. When they discover that this approach fails, they consider that they have given the idea a try and that it’s clearly inadequate. Usually, they do not look any deeper.

However, there is another reason why people have contempt for discrete approaches. That’s because they are both intuitively easy to grasp and easy for amateurs to explore with computers. This means that a great many people who are fascinated by science can perform basic simulations and become excited with the suggestive patterns that they find. Feeling that they have something to contribute, these people suddenly become the most vocal, amateur, would-be contributors to physics.

For professionals who have worked hard to carve out a place in an extremely competitive field, suddenly being vigorously courted by people claiming to have new physical theories can be galling. This is particularly true when those doing the courting have no notion of what has been tried already, incomplete grounding in physical mathematics, and an apparently unshakeable conviction that they have discovered something immense.

The simple fear of an encounter with someone who might be like that is enough to send some physicists running. I know because I have seen them run.

What is utterly stupid about this state of affairs is that those members of the public who are most interested in physics and most willing to engage often end up feeling the most shut out. Physics, particularly particle physics, is a field struggling for funding at a time when the cost of running groundbreaking experiments has skyrocketed. To throw away contact with those members of the public most likely to act as cheerleaders for the field doesn’t help anyone. Furthermore, disengagement from a public who want to exercise skepticism means that confidence in abstruse domains of physical theory, such as string theory, becomes ever harder to attain. How are the public to differentiate between M-brane theory and their own concoctions when dialog is expected to be one-way, as if from priests to the masses? The answer is, usually they do not, and frankly, should not.

How do we fix this? Work is needed on both sides. The physics community needs a better attitude towards so-called ‘crackpots’. Often such people are usually not crazy or stupid, just untrained and enthusiastic. Physics needs to find more things for interested members of the public to do, and more explicit ways for amateurs to help out. It needs to swallow its fear of strange people (an irony in itself). Guidelines for public engagement need to be written, to ensure that there is more of it, not less. If there are common misconceptions about physical theory that amateur theorists fall foul of, they need to need to be pooled, and collated as a series of challenges.

Having said this, the bulk of the work lies on the shoulders of aspiring citizen scientists. Professional physicists hold themselves and each other to incredibly high standards. They have little patience for would-be contributors who seemingly do not. This means that anyone from outside the field who wants to join in needs to do their level best to hold themselves to levels of rigor at least as high. Their work needs to be transparent, fully logical, and expressed in terms that makes it as easy as possible for physicists to read. Anything less than that is simply not good enough.

I have been incredibly lucky. My wife is a prize-winning astronomer. My housemate is a cosmologist. I have many dear friends who are physicists and mathematicians. Without exception, they have called me out when I have made statements I cannot substantiate. They have forced me to examine my own work with a critical eye. They have been unrelenting in making me describe what I have actually achieved, not what I would like to imagine I have done.

I believe that all citizen scientists can do this. Furthermore, we can do it for each other. We can, and must, exercise the highest degree of skepticism in our own work that we possibly can. Otherwise, we will never be heard, and the science we love will pay the price.

The eeriest result I’ve seen in years

May 23, 2012 6 comments

Here’s a recent result posted online which, if it’s true, is incredibly eerie.

The upshot of it is that these guys claim to be able to have an experimental quantum entanglement setup that can affect events in the past. Not anywhere in the past, mind you, just specific, isolated events within the same experiment. Still, it’s an amazing result if someone manages to successfully duplicate it.

I rather suspect that they won’t succeed, and that the whole thing will turn out to be dodgy, but here’s the thing: if the result is correct, it probably invalidates the approach that I outlined in the last few weeks of posts. This is because, while the approach I outlined resolves problems with non-locality, it maintains a strict ordering of cause and effect.

I wanted to share with you because in digital physics, we like refutability! There are other discrete approaches in which this kind of result is probably fine, but my favorite model is probably toast.

I’d like to share with you what I think is wrong with this result, but first I should probably summarize the result, for those who don’t want to click around. It works like this:

* Alice and Bob both create pairs of entangled photons.

* One photon from each pair is sent to Victor.

* Alice and Bob make a measurement on their photons.

* Victor makes a decision as to whether to entangle the photons he received or not.

* When we check later, we find that whether Victor decides to entangle or not affects the correlation that Alice and Bob previously saw. Crazy!

So there are multiple reasons to suspect that this research requires more investigation before we know for sure. One is that each experimental pass seems to take place in 14 billionths of a second. That seems to me like a small enough window that experimental error could creep in. Another is that very few particles make it through the whole experimental setup, so the entire result hinges on statistical patterns in the collected data.

However, the thing that I wonder most about relates to the ordering of events. I haven’t gone through the paper yet but I suspect that the catch here is that Alice and Bob’s measurements are compared with Victor’s after Victor makes his decision.

Consider the case where Alice and Bob get to compare results before Victor makes up his mind. In that case, we have information with no quantum ambiguity traveling from the future into the past. My guess is they can’t do that. (If they can, financial trading will never look the same.)

And Victor has to decide first, the whole Alice/Bob/Victor setup only works if we treat it as an entangled system that we can’t touch until the whole trick is over. And that means we have to wonder whether Alice and Bob made a true measurement, if the outcome of it depends on whether we add Victor into the system or not.

In any case, it’s an awesome idea for an experiment. With luck, someone will be out there looking to repeat the result already.

Why is there something rather than nothing?

May 9, 2012 14 comments

A debate recently erupted on the web in physics and philosophy of science circles about some comments made by Lawrence Krauss, author of a new book A Universe from Nothing. I learned about it from a rather good blog article by Sean Carroll.

The net is this: Krauss states that physics can now explain why the universe exists at all, without help from religion or philosophy. He also suggested that philosophers had been less than useful in making this clear. The philosophers were peeved.

As a digital physics person, I feel compelled to chime in. This is because Krauss’s way of explaining the spontaneous appearance of the universe is to define ‘nothing’ as a fluctuating quantum state, and then to show how such a state can give rise to a spontaneous universe.

But there’s a problem here, and I think it’s what some of the philosophers take issue with. A fluctuating quantum state that has conveniently been around for eternity and which is defined by an infinite-dimensional Hilbert space of possibilities is a really specific, and somewhat unusual, way of defining ‘nothing’. It’s the sort of hilarious goal-post moving that physicists do without even noticing that they’re doing it.

I think the philosophers are tempted to ask: ‘But where does the quantum potential come from?’. Me too. I think Krauss’s answer is approximately: ‘That’s the wrong question. It’s just there. You’re behind the times.’

In my opinion, Krauss’s assertions are lame. Invoking a quantum potential is just another way of saying that the universe was always there, just in another form. To say that this answer suffices is to embed your assumptions directly into your explanation. However, some philosophers’ assertion that the question of why the universe exists can never be answered is also lame. I believe that the logic of digital physics gives you an instant way out of all this waffling.

Think of it this way. Let’s say I have the rules for a universe and start following them on a napkin. I use a really big napkin so that simulated people in that universe can ask about their origins. Is the universe I simulate in the napkin real or not?

If we say it’s real, then we’re saying that something simulated is as real as our universe.

If we say that the napkin universe isn’t real, then we have to ask whether we’re in someone else’s napkin simulation. How would we ever know? Does that make us possibly not real either?

There’s no way to tell if you’re in a simulation or not, because everything in the universe can be described in terms of information. If we believe in the existence of logical physical laws, then we also believe in the potential for a simulated universe.

One might say, in response to this, that regardless of how simulated the universe might be, it’s still happening, and therefore there’s some level at which the universe is real. There has to be something at the bottom of things that’s concrete because we’re here.

But that’s wrong.

What is this magic commodity of reality that let’s us know that we’re actually happening? It’s not something that manifests as information because it can’t be simulated.  This means we can’t measure it or even talk about its properties. In fact, presupposing that it exists is a form of mysticism because it can never be proven. If it wasn’t there, and the universe wasn’t ‘happening’, how would you know?

The simple answer often given is: ‘Because otherwise I wouldn’t be here.’

But this is circular and not useful. It’s a form of faith. It’s a bit like saying that Jesus loves you because you’re loved by Jesus. It doesn’t cut it.

But here’s a question that gives us another way to look at the problem:

Does the number three only exist when someone is counting? Regardless of what units it occurs in, there’s an attribute of more-or-lessness that has a consistent effect on the universe. That attribute is so absolute that it’s conserved rigorously in physical law, defines how organisms develop, and determines which stars turn into black holes. It’s abstract enough that human beings all over the world support cultures containing the same exact notion. Quantifiability clearly exists without any of us paying attention to it. And so, therefore, does three.

Many people will tell you that three is a human creation, and something that doesn’t exist without the act of counting. But this is also wrong. Couples of any sexually reproductive species will tell you that having someone else try to muscle in on the act of intercourse is interference. Three is a crowd in any language.

But if three exists, yet isn’t physical, we have another form of existence on our hands. This existence is purely informational, and thus a lot more concrete than our nebulous sense that ‘something is real down there because it is’.

Stating this same idea more broadly, if you have a sequence of expressions that follows a simple rule, it will look the same now matter how the rule is followed. Three is still three, whether it’s measuring cows or planets. Thus we can say that logical sequences have the same kind of existence as three. Indeed, three is an example of a term in such a sequence–the set of integers. And if logical sequences can exist in this informational way, then so can universes.

This makes things tidy and simple. We don’t have to propose two kinds of existence, only one. And all sequences that have a complexity less than our own universe can be said to exist because we know that we do. No god. No magic. No quantum potentials. No mysticism. Just an assertion that certain kinds of mathematical series can be known to be ‘real’ because we occupy an instance of one, and that’s it. In a way, it’s rather like the mystical notion of ‘something is real down there’ that we discussed before, except that this time, the base reality we invoke is informational, and therefore amenable to examination.

The only question we can’t answer in this paradigm is why logical order exists in the first place. But in order to ask this question, you need logical order to frame it. (‘Splange’, for instance, isn’t a very satisfying answer, but it’s fine if you’re not insisting on logic.) So at this point, we’ve pushed as far to the edge of our fishbowl as we can get, which is as far as it makes any sense (literally) to push.

However, while we can’t follow the chain of ‘why’ backwards any further than this, we can push it forwards, and use the same kind of logic to refine our understanding of nature more deeply. We can use the same logic to demonstrate that the laws of the universe will be minimally implemented for the complexity that we see, and explain why physical laws seem regular in the first place. We can also demonstrate very simply why the idea of a god is both irrelevant and ridiculous. The same logic inexorably marches us to the conclusion that the implementation of the universe is discrete. But I’ve probably covered enough ground for now. We can unpick the rest of reality later.