Flaws in Bohmian mechanics

LuMo rightly trashes Bohm's quantum mechanics:

In the first sentence, Bohmian mechanics is promoted as "one interpretation that manages to skip... all the mysterious ideas". This is, of course, rubbish. The thing that Bohmian mechanics skips is that the world is quantum mechanical, not classical. And this "skipping" is a fundamental and lethal flaw, not a virtue, of Bohmian mechanics because it's the quantum mechanical nature of our theories that is absolutely needed to get an agreement between the reality and the experiment. It's been needed for more than 90 years. It's a long enough period of time for people to notice.

Moreover, while Bohmian mechanics is a classical theory, it in no way "skips" bizarre features. In particular, Bohmian mechanics has to introduce straight non-local influences – which are really voodoo and have been known to be prohibited by the 1905 theory of relativity. Also, it contains new classical waves that spread and their number and dilution is constantly getting out of control. A "janitor" that would clean all this mess – the spreading omnipresent wave functions that are no longer needed for any predictions and won't be observed – would be badly needed.

In spite of this, the theory still has defenders, such as this Quora article:

Physicists today remain largely unaware of the fact that quantum mechanics is perfectly choreographed by the mathematics of the de Broglie-Bohm theory, otherwise known as Bohmian mechanics. Despite the fact that Bohm’s formalism is entirely deterministic, and less vague than the standard interpretation of quantum mechanics, so far it has only been widely recognized and embraced among philosophers of physics. ...

To dive right in, let us note that in addition to the Schrödinger equation, which is shared among all quantum mechanical interpretations, Bohmian mechanics[1] is completed by the specification of actual particle positions, which evolve (in configuration space) according to the guiding equation. This combination elegantly restores determinism into the dynamics of physical reality; accounting for all the phenomena governed by nonrelativistic quantum mechanics—from spectral lines and scattering theory to superconductivity, the quantum hall effect, quantum tunneling, nonlocality, and quantum computing.

On top of this, Bohm’s theory magnificently elucidates state evolution without elevating the role of the observer to something mystical.[2] This reveals that the stochastic property of the orthodox approach of quantum mechanics, which manifests in state vector reduction, is merely a reflection of the incompleteness of that approach.[3] ...

Bohm’s model has been praised as a cure to the conceptual difficulties that have plagued quantum mechanics because it elegantly does away with much of the subjectivity and vagueness found in the standard approach. Despite this, mainstream physicists haven’t embraced this interpretation, or examined it in depth. In fact, the large majority of them haven’t even heard of it. This is embarrassing, surprising and frustrating.[5] If Bohmian mechanics provides a cure to modern quantum mechanical philosophic complacency, then why have there been so few to study the richness of this elegant formalism? ...

Bohm’s model has been praised as a cure to the conceptual difficulties that have plagued quantum mechanics because it elegantly does away with much of the subjectivity and vagueness found in the standard approach. Despite this, mainstream physicists haven’t embraced this interpretation, or examined it in depth. In fact, the large majority of them haven’t even heard of it. This is embarrassing, surprising and frustrating.[5] If Bohmian mechanics provides a cure to modern quantum mechanical philosophic complacency, then why have there been so few to study the richness of this elegant formalism?

David Bohm was a Jewish Communist ex-American with peculiar beliefs and a cult following.

Some ppl claim that Bohmian mechanics is equivalent to quantum mechanics, at least for very simple systems. So you can believe in it if you wish. Where they lose me is when they claim that it is more intuitive, a causal interpretation, and explains the nonlocality of nature.

These claims are all absurd. Conventional physics, including quantum mechanics, is local and causal. Believing in Bohm's theory is like ghosts and magic, with electrons have weird nonlocal effects with no causal explanation.

Science has always been able to give causal explanations for events. Bohm abandons this for silly philosophical reasons, not because of any observations or weaknesses in theory.

No climate science evidence needed

Here is the current Rationally Speaking podcast:

Over the last two decades, the Evidence-Based Medicine (EBM) movement has transformed medical science, pushing doctors to rely less on intuition or "common wisdom" in choosing treatments, and more on evidence from studies. Sounds great -- but has EBM become a victim of its own success? This episode features John Ioannidis, Stanford professor of medicine, health and policy, and statistics, and author of the famous paper, "Why Most Published Research Findings are False." John and Julia discuss how EBM has been "hijacked," by whom, and what do do about it.

Ioannidis makes a lot of great points about the fallibility of research papers in medicine and social sciences, but he loses me with this:

There's some things in science that we're very, very close to 100% certain about them. It's like 99.999% — like climate change and the fact that humans are making a difference in that regard, or smoking is killing people. It will kill a billion people in the next century unless we do something.

It's 99.999%. I think that it makes a huge difference, compared to pseudoscience claims that are “100% correct” and there's no way that you can reach a different conclusion, in that we're always open to evidence, and open to understanding what that evidence means.

I don't think we need more evidence about smoking and about climate change. I think that we've had enough.

Really? No need for more evidence?

I get worried when our most extreme skeptics refuse to be skeptical about some things. Even assuming that humans are making a difference in the climate (which is probably correct), we need a lot more evidence before we can adopt reasonable policies. We need more smoking evidence also. This opinion is strange.

Purpose versus scientific worldview

Robert Wright writes in the NY Times philosophy column:

You could call these the “Three Great Myths About Evolution and Purpose.”

Myth number one: To say that there’s in some sense a “higher purpose” means there are “spooky forces” at work.

When I ask scientifically minded people if they think life on earth may have some larger purpose, they typically say no. If I ask them to explain their view, it often turns out that they think that answering yes would mean departing from a scientific worldview — embracing the possibility of supernatural beings or, at the very least, of immaterial factors that lie beyond scientific measurement. ...

Myth number two: To say that evolution has a purpose is to say that it is driven by something other than natural selection.

The correction of this misconception is in some ways just a corollary of the correction of the first misconception, but it’s worth spelling out: Evolution can have a purpose even if it is a wholly mechanical, material process — that is, even if its sole engine is natural selection. After all, clocks have purposes — to keep time, a purpose imparted by clockmakers — and they’re wholly mechanical. Of course, to suggest that evolution involves the unfolding of some purpose is to suggest that evolution has in some sense been heading somewhere — namely, toward the realization of its purpose. Which leads to:

Myth number three: Evolution couldn’t have a purpose, because it doesn’t have a direction.

The idea that evolution is fundamentally directionless is widespread, in part because one great popularizer of evolution, Stephen Jay Gould, worked hard to leave that impression.

This is heresy to modern evolutionists and philosophers of science.

Aristotle and Darwin talked about purposes as central to scientific study, but modern scientific dogma is that nothing has a purpose. Furthermore, any talk of purpose is just a sneaky way to infect Science with God, and thus must be resisted as unconstitutional and contrary to the Scientific Revolution.

Here are Aristotles four causes:

Aristotle held that there were four kinds of answers to "why" questions (in Physics II, 3, and Metaphysics V, 2):[2][4][5]

Matter: a change or movement's material "cause", is the aspect of the change or movement which is determined by the material that composes the moving or changing things. For a table, that might be wood; for a statue, that might be bronze or marble.

Form: a change or movement's formal "cause", is a change or movement caused by the arrangement, shape or appearance of the thing changing or moving. Aristotle says for example that the ratio 2:1, and number in general, is the cause of the octave.

Agent: a change or movement's efficient or moving "cause", consists of things apart from the thing being changed or moved, which interact so as to be an agency of the change or movement. For example, the efficient cause of a table is a carpenter, or a person working as one, and according to Aristotle the efficient cause of a boy is a father.

End or purpose: a change or movement's final "cause", is that for the sake of which a thing is what it is. For a seed, it might be an adult plant. For a sailboat, it might be sailing. For a ball at the top of a ramp, it might be coming to rest at the bottom. ...

Explanations in terms of final causes remain common in evolutionary biology.[23][24] It has been claimed that teleology is indispensable to biology since the concept of adaptation is inherently teleological.[24] In an appreciation of Charles Darwin published in Nature in 1874, Asa Gray noted "Darwin's great service to Natural Science" lies in bringing back Teleology "so that, instead of Morphology versus Teleology, we shall have Morphology wedded to Teleology".

Sure, I don't mind saying that the purpose of a clock is to keep time, or that sailing is the purpose of a sailboat.

Maybe that is just unimportant semantics. But what about ppl who act with purpose? That view seem essential to understanding humans, but there are many big-shot professors who claim that this is wrong, and that we are all mindless automatons.

Update: Massimo Pigliucci offers his own rebuttal, and adds:

Regardless, I think Wright makes a very good point when he writes: “When an argument for higher purpose is put this way — that is, when it doesn’t involve the phrase ‘higher purpose’ and, further, is cast more as a technological scenario than a metaphysical one — it is considered intellectually respectable. … Yet the simulation hypothesis is a God hypothesis … Theology has entered ‘secular’ discourse under another name.”

QC progresses, except for market and qubits

AAAS Science mag has an article (2 DECEMBER 2016 • VOL 354 ISSUE 6316 p 1091) about the many companies pour 100s of millions of dollars into quantum computer research, promising results real soon now:

One thing is certain: Building a quantum computer has gone from a far-off dream of a few university scientists to an immediate goal for some of the world’s biggest companies.

Here is the explanation of QC, which Scott Aaronson would hate:

QUBITS OUTMUSCLE classical computer bits thanks to two uniquely quantum effects: superposition and entanglement. Superposition allows a qubit to have a value of not just 0 or 1, but both states at the same time, enabling simultaneous computation.

Entanglement enables one qubit to share its state with others separated in space, creating a sort of super-superposition, whereby processing capability doubles with every qubit. An algorithm using, say, five entangled qubits can effectively do 2⁵, or 32, computations at once, whereas a classical computer would have to do those 32 computations in succession. As few as 300 fully entangled qubits could, theoretically, sustain more parallel computations than there are atoms in the universe.

This is the way most ppl explain, but Aaronson complains that it is wrong. He says that it leads ppl to overestimate what quantum computers can do.

Buried in all the hype is a couple of admissions:

They say they have a mutual interest in publicizing their advances, not least so that potential customers can think about how they could use a quantum computer. “We all need a market,” Monroe says.

What’s more, nobody knows enough about quantum computing yet to go it alone with a single qubit type. Every approach needs refining before quantum computers can be scaled up.

In other words, there is no market for quantum computers, and the researchers have not even created one scalable qubit.

Update: I was also amused to see the article claim that 50 qubits may be needed to demonstrate quantum supremacy, and Google is claiming that it will soon get 49 qubits. My guess is that Google secretly realizes that it is not getting quantum supremacy.

Comic about quantum computing misconception

Scott Aaronson announces an SMBC cartoon about quantum computing.

Scott tries to explain quantum computing as not really a matter of qubits being 0 and 1 at the same time, but rather probabilities being negative or complex, and interfering.

There is some merit to what he says. Schroedinger's cat is not really alive and dead at the same time. If qubits could be 0 and 1 simultaneously, then we would expect exponential speedup in certain search algorithms, and we do not.

Probabilities are not really negative, so he is careful to say "probability amplitudes", but he wants you to think of them as analogous to classical probabilities.

No, this is just nonsense.

It is a little more accurate to say that the qubit is a superposition of 0 and 1. And that measuring the qubit can give 0 or 1. But to the layman, that is just like being 0 and 1 at the same time.

Many physicists explain quantum computing as using superpositions to do simultaneous computations.

Sequentially operating on bits having 0 or 1 values gives us Turing machines, like all known computers. Operating on qubits that are superpositions of 0 and 1 is supposed to give us quantum supremacy, and faster computers for certain types of computations.

Scott says the core of the quantum voodoo is amplitude interference. But all sorts of classical phenomena have interfering waves, and that is not particularly mysterious. It only becomes mysterious when you think of those amplitudes as probabilities or generalized probabilities.

Saying that they are probabilities is just a sneaky way of pretending that the qubit really is a 0 or 1 (or both). The qubit is not a 0 or 1 or a probability. A measurement gives a 0 or 1, and we can give a probability based on our knowledge of how the system was set up, but that is not what the qubit is. It is not an amplitude either. The amplitude is just a way of codifying prior knowledge.

We have no numerical equivalent for the state of a qubit.

Scott concedes that quantum supremacy has never been demonstrated and we do not know whether or not it is possible. He sure is opinionated about something that may not exist.

LuMo likes the comic, altho he cannot resist some cheap shots. He agrees that complex numbers are fundamental to quantum mechanics, because [x,p] = xp-px is anti-symmetric, and hence has imaginary eigenvalues.

This argument is unpersuasive. Lots of real matrices have that property, such as the 2x2 matrix [(0,1),(-1,0)]. (Sorry I am not using mathjax.) [x,p] is not directly observable, so the imaginary eigenvalues pose no problems. It implies the uncertainty principle, whether using real or complex numbers.

LuMo buys into Scott's line almost verbatim:

The wave functions are closer to probabilities but they're not quite the usual probabilities. Instead, they're probability amplitudes which are complex and also have the ability to constructively or destructively interfere. When one is observing anything, the amplitudes are converted to the usual probabilities only. But when no one is looking, the probability amplitudes evolve as a new entity according to new rules that have no counterparts in classical physics.

Sorry, but this is just not helpful. If you are doing classical mechanics, such as predicting the location of the Moon in 1000 years, you compute probabilities. The Moon's position has probabilities that evolve with time. Observations tell us where it really is (to within measurement error). All this talk of probabilities as being unique to quantum mechanics is misleading.

So is talk of probability amplitudes interfering. Classical waves interfere also. Probabilities do not really interfere in either classical or quantum mechanics.

There's no "splitting of the worlds" during a quantum computation. On the contrary, the splitting of the worlds may only make sense after a measurement which can only occur after decoherence – but the quantum computation depends on the absence of any decoherence (I will make the same observation again later). So a key necessary condition for the quantum computer to work – and do some things that are practically impossible on classical computers – is that there's no decoherence and no splitting of the world during the calculation.

LuMo is right for the wrong reason. I say that there is never any splitting of the worlds, and never any quantum computation.

If a quantum supremacy computation did exist, it would have to somehow take advantage of a qubit staying in a superposition, and not decohering. In the lingo of many-worlds, the qubit has to straddle different worlds. Supposedly quantum supremacy is possible because qubits can leave this world and do some of its computation in a parallel world. I am not buying it, but that is the theory.

Essays: Wandering Towards a Goal

FQXi announces:

the next $40,000 FQXi essay contest,...

This year’s theme is: Wandering Towards a Goal – How can mindless mathematical laws give rise to aims and intentions?

One way to think of physics is as a set of mathematical laws of dynamics. These laws provide predictions by carrying conditions at one moment of time inexorably into the future. But many phenomena admit another description – sometimes a vastly more useful one – in terms of long-term, large-scale goals, aims, and intentions. ...

Relevant essays might address questions such as:

* How did physical systems that pursue the goal of reproduction arise from an a-biological world?

* What general features — like information processing, computation, learning, complexity thresholds, and/or departures from equilibrium — allow (or proscribe) agency?

* How are goals (versus accomplishments) linked to “arrows of time”?

* What separates systems that are intelligent from those that are not? Can we measure this separation objectively and without requiring reference to humans?

* What is the relationship between causality – the explanation of events in terms of causes – and teleology – the explanation of events in terms of purposes?

* Is goal-oriented behavior a physical or cosmic trend, an accident or an imperative?

We are accepting entries from now until March 3, 2017, with winners announced in June.

I submitted some essays to previous contests.

Trump picks Perry for Energy

The NY Times reports:

President-elect Donald J. Trump plans to name Rick Perry, the former governor of Texas, to lead the Energy Department, ...

“Oops,” Mr. Perry said in 2011 as he racked his brain during a nationally televised Republican primary debate, trying to remember the three departments he wanted to dismantle. He mentioned the Commerce and Education Departments but could not recall the third: the Energy Department.

This makes Perry a funny choice, as Trump had to realize that Perry has been endlessly mocked for this gaffe.

Trump does not take orders from his enemies, and so the Left hates him.

I am wondering about this dopey explanation:

Despite its name, the department plays the leading role in designing nuclear weapons, thwarting their proliferation, and ensuring the safety and reliability of the nation’s aging nuclear arsenal through a constellation of laboratories considered the crown jewels of government science.

Why does the paper say "Despite its name"? Does it somehow think that energy and nuclear weapons are unrelated?

Nuclear weapons are the most dramatic releases of energy known to man. The whole subject is a study of energy.

This is like saying, "Despite its name, the Astronomy Department has a telescope for studying the night sky." Or "despite its name, the National Institute of Mental Health studies treatments for crazy people."

If Perry said something this stupid, then I would be worried about his competence.

Physicist and leftist science popularizer Lawrence M. Krauss has an op-ed attacking Perry in the same paper.

In terms of qualifications, Mr. Perry, a former governor of Texas, doesn’t come close to his immediate predecessors. He would follow President Obama’s two energy secretaries: first, Steven Chu, a Nobel laureate physicist, and then Ernest J. Moniz, a distinguished nuclear physicist from M.I.T. ...

I met Governor Perry once, at the World Economic Forum. He seemed like a genuinely nice guy. After finding out I was a physicist, he singled me out in the audience while he was onstage, saying, “As Professor Krauss knows, you can violate the laws of physics, but only for a while.” My answer was, “Well, actually you can’t,” which was followed by a bit of nervous laughter from the crowd. ...

In the present climate, when nuclear tensions are higher than they have been since the height of the Cold War, ...

Actually, Trump's election has dramatically lowered nuclear tensions. Hillary Clinton was the biggest warmonger presidential candidate we have seen in a long time, and was particularly hostile to Russia. So were some of the other Republican candidates. Trump stood out as someone who does not want a war with Russia. And now he has appointed a Secretary of State who believes in doing business with Russia.

Russia has the biggest nuclear arsenal outside the USA, by far, and now it is a lot less likely to use it. Russia should be our friend, not our enemy.

Krauss is entitled to his opinions, but Trump won the election, and he needs a cabinet consistent with his mandate. Are there any distinguished physicists who supported him? From what I can see, the physics establishment is dominated by leftist groupthink. A cabinet secretary is a political position, not a research position.

I am sure Krauss has a much higher IQ than Perry, but it does not show in his political opinions.

Update: Here is another Krauss rant against Trump.

Arguing science is against free will

A new paper details the case Against free will in the contemporary natural sciences

The claim of the freedom of the will (understood as an individual who is transcendent to Nature) in the name of XXth century scientific knowledge, against the perspective of XVIIIth-XIXth century scientific materialism, is analysed and refuted in the present paper. The hypothesis of reductionism finds no obstacle within contemporary natural sciences. ... A fatalistic or materialist view, which denies the possibility of a free will, makes much more sense in scientific terms.

The paper gives a good account of the anti-free-will position, with attention to modern science. I have attacked that position many times on this blog.

It makes a big deal about classical mechanics being deterministic, and quantum mechanics being random.

After giving all the arguments, it adds:

All the preceding argumentation would be unnecessary if we were to admit what seems to me and others seems utterly trivial: science, dealing as it does with what is objective, cannot defend the idea of freedom, which requires autonomous recognition of the subjective. The development of the argument given here is in a sense a tautology regarding the simple fact of the determination of some scientists and thinkers to deny it.

Science – past, present, and future — can never defend the hypothesis of the freedom of man. It is no longer a question of enter into a detailed discussion of quantum mechanics; neither is it a question of waiting for a new theory to provide a suitable defence. It is simply that science and freedom cannot fit into the same holdall. Libertarianism must follow a path that carries it far from science.

In other words, all of the analysis of classical and quantum mechanics was a big smokescreen. Freedom and science are such fundamental opposites that no scientific theory could ever accommodate free will.

As stupid as this sounds, I think that he is partially correct.

The paper goes into a detailed discussion of how some physical theories are deterministic and some not, but either way it reaches an anti-free-will position. So what difference does it make whether the theory is deterministic? Why do any of the properties make any difference?

Free will is rejected for metaphysical reasons that have almost nothing to do with science. Science and freedom have been defined to be incompatible.

Maybe some ppl have free will, and others are preprogrammed automatons. If you tell me that you have no sense of free will, I may choose to believe you.

Suppose it is intuitively obvious to you that you have free will, but someone tries to make a scientific argument that you don't. The details of that argument will be unimportant. The gist of the argument is that science is premised on you not having free will, and so you don't if you believe in science.

If science is defined to exclude free will, then something is wrong with science.

Listening for a black hole interior

Nature mag reports:

It was hailed as an elegant confirmation of Einstein’s general theory of relativity — but ironically the discovery of gravitational waves earlier this year could herald the first evidence that the theory breaks down at the edge of black holes. Physicists have analysed the publicly released data from the Laser Interferometer Gravitational-Wave Observatory (LIGO), and claim to have found “echoes” of the waves that seem to contradict general relativity’s predictions1.

The echoes could yet disappear with more data. If they persist, the finding would be extraordinary. Physicists have predicted that Einstein’s hugely successful theory could break down in extreme scenarios, such as at the centre of black holes. The echoes would indicate the even more dramatic possibility that relativity fails at the black hole’s edge, far from its core.

This is badly confused. If they are really black holes, then we can only observe what is outside the edge (aka Schwarzschild radius or horizon). No LIGO data can possibly distinguish what is just inside the edge with what is at the center.

Lubos Motl just got finished praising one of the coauthors for winning a big prize, but stops short of saying that he is actually right about something:

That controversial Polchinski et al. paper on the firewalls (AMPS) shows that they are experts in quantum gravity and quantum information but because the assumptions and conclusions are wrong, it's obvious that such a paper can't be said to have a million or multimillion-dollar value from a physics viewpoint. You simply shouldn't be getting physics awards for physically incorrect claims. The whole point of science and physics is to find correct insights about Nature, not just to show that you have mastered some tools and you can design clever, but ultimately irrelevant, arguments that derive incorrect conclusions from invalid assumptions.

This is funny. LuMo is very impressed with the string theorists like Polchinski who do a lot of fancy theorizing about extra dimensions or Planck lengths or black hole interior entropy, but if they apply it to real-world data, then he is honest enuf to call BS.

Physicists surveyed about quantum mechanics

I criticize physicists who subscribe to goofy interpretations of quantum mechanics, or who complain that the theory is nonsensical and needs a new interpretation. There are many high-profile and big-shot physicists who say such things.

A Danish student did a master's thesis survey and reports:

A survey was sent out to 1234 physicists affiliated to 8 different universities. 149 responded to the questions, which both concerned foundational issues related to quantum mechanics, ...

More and more work is done concerning quantum foundations; investigating basic properties of quantum mechanics, such as Bell’s inequality, or developing new interpretations of quantum mechanics, such as QBism. However, when one regards the results of the survey, it shows that the resurgence the topic has been undergoing in recent times still has not had an impact on the participants being familiar with foundational concepts.

The "resurgence" has not had an impact because the overwhelming majority of respondents rejected the goofy ideas.

Only 25% said that they liked some non-Copenhagen interpretation. (And some of those preferred reasonable variations of Copenhagen. Only 6% preferred many-worlds.) Only 11% believe that physical objects have their properties well defined prior to and independent of measurement. Only 3% believe that Bell's theorem implies action-at-a-distance.

The author has a different spin on this, saying his survey is "quite a validation of the whole research area concerning quantum foundations". I don't know why he says this, as very few of the answers give any credence to any work done in the last 80 years.

I am not saying that the subject of quantum foundations is completely worthless, but it has mostly just affirmed the Copenhagen consensus of 1930. The ideas that depart significantly have been either proved wrong (eg, hidden variables) or are just conceptually stupid (eg, many-worlds).

Big money prizes for phony breakthrus

Mathematical physicist Peter Woit details the 2017 Breakthrough Prizes

These prizes are often awarded for ideas about the black hole information paradox, independent of whether these ideas work. Maldacena’s citation from 2012 tells us that he got the award partly for “resolving the black hole information paradox”, and the Strominger citation tells us that “His work hints at a solution to the famous ‘black hole information paradox’”. Polchinski is rewarded for ... show[ing] that the solution to the paradox supposedly given by Maldacena actually doesn’t work (not surprising, since it was never more than a speculation). If you’re a string theorist, you don’t actually need to solve a problem to get a prize

There is no black hole information paradox. And if there were, there would be no scientific way to resolve it.

It is the modern of equivalent of the supposed medieval debate over how many angels could dance on the head of a pin. (I think that it is myth about medieval monks.)

Some clever physicists figured out that they could keep writing papers taking sides on this subject, and win prizes, even if other prize-winning papers take contrary views.

Hawking's vision of the future

Physicist Stephen Hawking writes:

This is the most dangerous time for our planet

As a theoretical physicist based in Cambridge, I have lived my life in an extraordinarily privileged bubble. ...

So the recent apparent rejection of the elites in both America and Britain is surely aimed at me, as much as anyone. ...

The automation of factories has already decimated jobs in traditional manufacturing, and the rise of artificial intelligence is likely to extend this job destruction deep into the middle classes, ...

These migrants in turn place new demands on the infrastructures and economies of the countries in which they arrive, undermining tolerance and further fuelling political populism.

For me, the really concerning aspect of this is that now, more than at any time in our history, our species needs to work together. ...

We now have the technology to destroy the planet on which we live, but have not yet developed the ability to escape it. ...

To do that, we need to break down, not build up, barriers within and between nations.

Yes, he has lived in a bubble. He wants to flood First World countries with Third World migrants until we can all escape to another planet.

He is entitled to his opinion, of course, but aren't there any physicists who voted for BREXIT and Trump? Who want to preserve the middle class? Who are not clinging to crazy sci-fi fantasies?

Update: LuMo piles on:

But if you look at the majority of the political questions, Stephen Hawking is just another rank-and-file leftist. And he is perhaps more radical or fanatical than the average obnoxious leftist – especially when it comes to the global fearmongering and the need for a global government and global redistribution. ...

Hawking's essay is interesting, he is a good writer, and references to his very special life always bring some added value. But ideologically, the text is full of nonsense that is basically identical to the nonsense that ideologues were offering at crazy interdisiplinary conferences more than half a century ago.

He quotes R.P. Feyman as rejecting these egalitarian fantasies:

...There was a special dinner at some point, and the head of the theology place, a very nice, very Jewish man, gave a speech. It was a good speech, and he was a very good speaker, so while it sounds crazy now, when I’m telling about it, at that time his main idea sounded completely obvious and true. He talked about the big differences in the welfare of various countries, which cause jealousy, which leads to conflict, and now that we have atomic weapons, any war and we’re doomed, so therefore the right way out is to strive for peace by making sure there are no great differences from place to place, and since we have so much in the United States, we should give up nearly everything to the other countries until we’re all even. Everybody was listening to this, and we were all full of sacrificial feeling, and all thinking we ought to do this. But I came back to my senses on the way home.

The next day one of the guys in our group said, “I think that speech last night was so good that we should all endorse it, and it should be the summary of our conference.”

I miss Feynman. He would expose crap as crap.

Quantum satellites will not change the world

The current Scientific American has "10 ideas that will change the world", and here is No. 3:

Quantum Satellites Are a Big Step toward the Unhackable Internet

Space-based transmission of quantum cryptographic keys could make the “unhackable” Internet a reality

It is theoretically possible for a space satellite to send and receive entangled photons, and that may even be feasible soon.

Maybe someday there will even be a quantum computer router in space that can re-transmit entangled photons without collapsing the wave function.

But even if that is all achieved, it will do nothing to make the internet less hackable. The quantum key distribution is an attempt to solve a problem that is much more efficiently and securely solved by existing technologies. There is just no legitimate reason for a quantum satellite, except to show off some technology.