Tuesday, July 04, 2017

Physics doesn't justify that "everything and everyone is connected"

Tetragraviton wrote a nice text about the idea that "everything is connected because of quantum mechanics or string theory etc.", titled The Way You Think Everything Is Connected Isn’t the Way Everything Is Connected, and I completely agree with him.

Science in general, physics, and modern physics in particular is often being "summarized" by the laymen – and especially religious people or people with a good heart – by the slogan that physicists have found evidence that "everything is connected" or "everyone is connected". So the message is that all of us should think as one soul or as limbs of the same God. Everyone should love each other, emulate others in the world, share his assets with others, or have a romantic relationship with everyone else, depending on the precise flavor of the religious or ideological framework.

They're nice conclusions according to many people and the very phrases such as "quantum entanglement" and "string theory" are being used as the scientific justification for the goals listed in the previous sentence. Well, "entanglement" makes it particularly clear. It sounds like a tight emotional relationship between everyone and everything. And strings may probably be the things that connect the dots and connect all the people, too. You must have heard various flavors of the same statement. And if you're a randomly chosen reader of this text, you have "more likely than not" said similar things in the past, too. ;-)




Well, Tetragraviton says that this interpretation isn't so. Strings aren't invented in order to connect things, especially not distant ones. Most of the strings, and especially the important ones, are ultramicroscopically short so they're not enough to connect you with another person. And even if they become cosmic strings that may connect very distant objects, the connection isn't the purpose. The purpose of strings and other concepts in science is to understand the observations, whether or not the observations are connected or aligned with one religious or political definition of the good.




Tetragraviton deserves a special praise for his defense of locality in quantum mechanics. John Bell has invented the delusion that "one may prove nonlocality in physics" that has become widespread among the non-professional fans of physics in recent 50 years – including some philosophers and would-be physicists who think that they have the credentials to write about the foundations of quantum mechanics. Tetragraviton puts it nicely:
If you think about things in terms of wavefunction collapse, then yeah, if you measure one side something instantaneously changes on the other side. Here’s the thing though: you can’t tell whether the wavefunction of the one on your side has “collapsed” without measuring/collapsing it yourself, at which point you still can’t tell if the other person “collapsed it first”. So whatever sort of “instantaneous change” is happening, it’s not something you can do anything with, or measure.
Your humble correspondent likes to say clearly that the wave function encodes the subjective knowledge of an observer. So its collapse is just something that happens in the observer's mind – and it doesn't really matter at all when it happens as long as it happens before the observer is making another observations whose correct prediction depends on the previous adjustment of the wave function.

Some people react emotionally because the dependence of physics on the observer or his subjective perception is something they find insufficiently materialist, something that they simply don't like. And of course, if a physicist wants to avoid controversies, he may shut up and calculate. He may avoid the terms "subjective", "perception", "mind", and perhaps even "observation" and "observer". A physicist may only calculate how the things that "everyone sees or understand" may be correctly calculated and say nothing about the philosophical essence what he's doing.

But there are still implications of the fact that the wave function isn't a classical wave. When the wave function collapses, it's not an implosion that may be "observed by all other external observers", i.e. by other people, and that has some impact on the external world. In other words, as Tetragraviton says, the instantaneous change of the wave function is "useless" – you can't achieve anything with it. For example, whether the wave function collapses in some Lorentz frame or in another Lorentz frame – which also involves "whether the collapse influences the particle A or particle B first" – is something that will have zero effect on the probabilities that some actual event that many other people/observers may see.

In order to be minimally controversial, Tetragraviton's paragraph contains none of the provoking "spiritual" words such as "subjective", "perception", "mind", and perhaps even "observation" and "observer". But what he is saying without using these words is exactly physically equivalent to the story that simply uses them. He is contradicting the misconception that "the wave function should be considered a version of a classical wave", something that objectively exists i.e. something whose changes may always be observed by all observers in principle.

Well, the collapse or its precise timing just cannot be measured. The collapse of a wave function only modifies the predictions for additional measurements by the same observer in the future. But whether the collapse from a generic "dead and alive" superposition to a more well-defined state or not is not a similarly objectively well-defined question as the question "whether a powerful bomb exploded in Hiroshima in 1945". The collapse of the wave function only affects the particular observer's predictions but the changes are changes of his knowledge and the information used to make his predictions, not something that is objectively out there. In particular, the timing of the collapse of the wave function – even if someone feels it's counter-intuitive or dangerous – cannot be used to ignite a nuclear bomb instantaneously or superluminally.

At the end, I think that even though one may want to speak in ways that avoid all the subjective words including the "observer", it doesn't really help to clarify the problem at all. The idea that the "wave function is an objectively real classical wave" is a fundamental misconception that one simply has to get rid of. When you try to teach quantum mechanics to somebody, it is a critical enemy that has to be killed. And Tetragraviton's language is a more pacifist language to deal with the enemy. I still think that clear and targeted nuclear bombs, such as ones in Hiroshima in Nagasaki, are a more effective way to deal with the enemy. One should say that the wave function is a complex and generalized package of numbers encoding the subjective probability distributions i.e. knowledge of an observer because it's both true and relevant and being silent about this point doesn't make it less true.

Science isn't good-vs-evil polarization of concepts

OK, hundreds of blog posts have been dedicated to the interpretation of quantum mechanics and I have already understood that their impact is close to negligible. Most people are just too stupid and too stubborn to understand these matters and the situation is bound to be getting worse because increasingly misleading and vulgar oversimplifications and confusions are being made increasingly tolerated in the society – because they are often deliberately encouraged, funded by powerful players who don't care that they're paying for the promotion of lies, and supported by the people's decreasing intellectual integrity.

But I still think that it's possible to defend a simpler and more general point – that science isn't an enterprise that calls certain structures "good" and others "bad". For a scientist, the learning of the truth is the main "good thing". But the scientific learning of the truth about Nature must be done without prejudices. The scientific research may a priori lead to many different outcomes and none of them should be disfavored too strongly or banned because of some pre-existing prejudices about the good and the evil. Scientists have to follow the evidence wherever it leads them.

In particular, I think that not only every physicist but every scientifically or rationally thinking person knows that there is nothing "globally good" about things' being connected or correlated, relatively to their being disconnected or uncorrelated. Let us ask a question discussed in this text that is a great example: Is everything in physics connected? Should it be connected? Should we be happy when it's connected?

Well, it's not true that everything is connected. First, entanglement is just a description of a general correlation between 2 subsystems of a composite system that may be described by a pure quantum state. So it doesn't imply any ability to remotely communicate. OK, let's assume that the reader understands that the entanglement is just a correlation that has evolved thanks to some interaction or contact or common origin in the past, and that only affects some future observations but only one or a limited number of them. Is this properly understood entanglement a good thing?

It's not a good or bad thing. It's something that exists and that a physicist cannot deny because it's obvious that entangled states are important. In fact, in some uniform measure on a Hilbert space, almost all states of a composite system are entangled. So entanglement is the default situation. It's not some "super weird exception" to something. On the contrary, the lack of quantum entanglement is the measure-zero exception.

At the same moment, one must understand that this "measure-zero" adjective – derived from a smooth measure on the Hilbert space – heavily underestimates the importance of non-entangled states. Non-entangled states i.e. states of composite systems that may be written as simple tensor products\[

\ket{\psi_{AB}} = \ket{\psi_A} \otimes \ket{\psi_B}

\] are very important and relevant in lots of situations. In particular, when we make a measurement of a complete set of observables that describe the subsystem \(A\) (or \(B\), it doesn't matter), then we fully learn the factor \(\ket{\psi_A}\) above and the wave function of \(AB\) is guaranteed to tensor factorize in the way depicted above. So there is a simple way to produce non-entangled state – to collapse any state to a non-entangled state. Just measure the state of one of the subsystems – and all the entanglement goes away!

We have some ability to separate the measurements to pieces and make the objects' properties independent of properties of other, faraway objects. Is this ability an evil thing? Again, science doesn't define what is "good" and "evil" in general. But in this case, we may at least answer that this ability is a good thing from some perspective – it is good and perhaps crucial for the scientific method to work.

In science, we study objects and processes somewhere – e.g. those inside a laboratory – and it is important that we may assume, to one extent of certainty and precision or another – that these objects and processes aren't too strongly affected by some other, faraway, objects and processes. If "everything were really connected", we couldn't make any localized, e.g. laboratory, experiments at all. Any conclusion that we could end up with could have been said to be the result of some distant agents or objects that have manipulated our lab from a distance. Because we can't know everything important about such faraway agents or objects – especially because they may be very powerful and able to hide themselves – we couldn't ever precisely define the initial states that have led to one outcome of the laboratory experiment or another.

Fortunately, these influences of the faraway agents and objects may be minimized, reduced practically to zero, which is why questions in science may often be "disentangled" from each other. So it is "disentanglement" that is really such a good thing for science in this sense.

I think that competent scientists would agree with all the statements above. They may disagree with the following paragraphs in which I would claim that "disentanglement" – or migration-reducing policies or even "apartheid [apart-hood] policies" – are often very good things, too. These policies are analogies to the animals' skin that is needed to protect them from the environment, to make it clear how they are actually separated from the rest of the world. The skin or the objects' isolation or "apartheid" is often needed to be able to create some environment where some special things – different from the generic mess that is taking place outside – may be sustainable at all. And this is a good thing for the evolution of organs (in which cells are specialized), for the evolution of species (for their splitting after some desired properties are being amplified), for the evolution of the human civilization, too.

Well, I find it obvious that even at the political level, these comments are self-evidently true and an intelligent person simply must know that they are true. But some people live in freedom-restricting shackles, e.g. the shackles of left-wing ideologies, and these shackles force them to mindlessly deny certain ideas. So even though they may understand why skin is not only the human's largest organ but also an important one, they will fight against any immigration bans etc. simply because they would be excommunicated or ostracized by their equally shackled soulmates.

At any rate, the scientific passion is really the passion to obtain the important information about Nature that we didn't know in advance. If the information is specified as a sequence of ones and zeroes, e.g. Yes/No answers to some nicely chosen questions, a person with the passion of a scientist doesn't dream about the answers' being Yes or their being No. She wants the true answers, whether they are Yes or No, and she enjoys seeing the evidence and arguments that show that it is the right answer, whether it's Yes or No, too. This mindset – with the passion for the truth at the center – is a very different attitude to the world than any ideology, religion, or philosophy that tries to strengthen certain memes such as the "everything is connected" meme.

It's really the encouraged diversity of the organized Yes as well as No answers that makes the scientific approach so powerful. Even if you are an "everything is connected" New Age religious hippie, and even if the word "powerful" looks like "evil" in your eyes, you should better not ignore science because it's in some sense the powerful things, and not those labeled "good" according to some pre-existing ideology, that are going to win most battles, including and perhaps especially the long-term ones.

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