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12 October 2017

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FkDahl

In my opinion the cost calculations for hyperloop are sheer fantasy, under estimating the cost of production and running by an order of magnitude. From my career in physics and semiconductors I have plenty of experience of high-vacuum systems (Hyperloop predicted pressure is 1/1000 atm) ; they fail and require a steady supply of spare parts. Maintenance is much simplified if parts of the system can be shut off and isolated; pump down time is strongly dependent on the amount of moisture that enters during room pressure maintenance work. Highly reliable and large valves would be needed to isolate parts of the tube - valves would need to be the size of hobbit-doors here, not the usual 2-8 inch size. Leak likelihood scales with the circumference: getting the o-rings to sit just right is an art. OK you say, we don't need no egg-head high-vacuum system with turbo pumps, just low vacuum, still, a certain amount of pumps are needed per length of tube.
In case of a bullet sized leak the incoming gas will move with near the speed of sound and the impact on an oncoming train will be catastrophic. In case of survivors they will have to figure out how to survive in a steel tube at a pressure at best comparable to Mt Everest.
Add to this the climate : a 10C temperature swing will make the San Francisco-Los Angeles tube of ~560km expand 72m. How to deal with that? You could anchor it down and bear the stress for X number of sun-cycles, or let the station positions float.. Of course you could insulate it, but then that bears against the un-realistic construction costs Mr Musk proposed. And that is the constant temperature change: in a place like California one can easily have a 40C temperature delta between top and bottom : in a high vacuum vessel with some kind of joints every tens of meters.
Hyperloop makes Mr Mush appear like a snake oil doctor.

Simpleton

A key aspect of QM is entanglement. Read about EPR (Einstein, Podolski, Rosen thought experiment) and John Bell's Inequality to (fail to) understand the strange world of QM. This
issue gets to the heart of the fundamental difference between classical and quantum mechanics.

https://en.wikipedia.org/wiki/Bell%27s_theorem

turcopolier

Simpleton

entanglement seems to have been incomprehensible to Einstein especially since he could not disprove its existence. pl

Mel

I wouldn't think the tube would just explode or implode on its own. I would fear a train going Mach 1 hitting air that wasn't supposed to be there. Shock waves, etc. Trans-sonic behavior was a disaster for some of the first airplanes that got there.

turcopolier

All

I mentioned QM to learn how many here would actually know anything of such a subject. Interesting result. pl

FourthAndLong

It's remarkable how the concept of fields has proliferated in physics since its inception. There's now a field for everything under the sun. Higgs may be the latest. But when Maxwell introduced the concept at Cambridge for his doctorate, regarding his electromagnetic theory, it was not accepted, he had to do something else. And his supervisors were the leading physicists of the day -- real all time major leaguers. But they simply could not get their heads around the concept of a field. Maxwell himself struggled with it, positing all sorts of mechanistic constructs, but to no avail. So since he apparently was able to accept the abstraction it posed, we now have field theory.

Interesting how in our day we get freshman and HS students to learn these things that James Jeans and his colleagues couldn't understand.

Jagger

The contradictions between the quantum world and our experienced world made me question simple, basic assumptions of reality. Questioning basic assumptions is important because many fallacies arise from those assumptions. The same type of questioning leads to a clarification of the strengths and weaknesses of science. It is vital to comprehend the limitations of science. Finally, those contradictions leads us to examine the subjective manner in which we primarily experience existence. A subjective existence which lies outside the bounds of science.

One little example: is time fundamental to existence? Of course...until you think about it a bit. The quantum world will make you think about it as you attempt to explain contradictions. Personally, I now have serious doubts about the fundamental nature of time to existence.

As for science, science is a great tool but a limited tool. The scientific process is very effective when dealing with the physical/material world-what we can measure and observe. Yet by the very nature of the process, it completely breaks down when dealing with the subjective world which is a majority of our experience of existence. It is necessary to realize the limitations of science before we comprehend the value of other methods of understanding.

The desire for understanding often leads to speculative reason, metaphysics, as our only hope when attempting to come to grips with the oddities of the quantum world. I think it is interesting because the questions naturally lead to theories about existence and then, whether there is any meaning or purpose to existence. For some, it is a fascinating subject and for some, it is a complete a waste of time because even if answers are found, the answers really change nothing.

FourthAndLong

Einstein also rejected the idea of black holes when they were first discussed. And initially modified his general relativity theory because it predicted an expanding cosmos, and he was sure the universe had to be steady state -- same always and forever. Then Hubble made his discovery and Einstein became delighted that he was, er, um, right the first time. He wanted a Mozart universe. I'll never understand how a man of his awesome intelligence could so doggedly stick to theories which depended on differential equations, which depend on matter and the world being infinitely divisible, and furthermore extending infinitesimal theories all over space. How can that work ??

He was famous for saying "God does not play dice with the universe" in response to the probabilistic formulations of QM. I wish I could have been there to say: "Hey Al ! Do you really think the Lord God Almighty actually writes down Lagrangians ??"

Allen Thomson

I aced the graduate QM course at American U back in 1974. (And even got the gummint to pay for it, though the relation of QM to my official duties was not obvious.)

However, I would not equate that to actually knowing anything about it.

The Twisted Genius

ISL,

I checked out the Hyperloop One FAQ and they did address this question. They plan on a medium vacuum that can tolerate leaks. The maglev train could still run in an Earth atmosphere tube, but it would be horribly inefficient. I now see the difference between this and the pneumatic train... two totally different concepts.

https://hyperloop-one.com/facts-frequently-asked-questions

FourthAndLong

I'm 65, and it appears many here are my near contemporaries. We who are Americans were raised in the Space race era. After Sputnik lets just say that the youth of the USA were rather strongly urged to study science and engineering. And if a lad showed promise on aptitude tests many of my teachers considered it their patriotic duty to steer us such wise. And my goodness me, that was one patriotic era. Try not standing for the National Anthem in many parts of the US, and you were lower than a child molester. Jehovah's witnesses were lynched at times during the second world war in the United States, as they claimed the conscientious objector draft status.

Try to imagine smartphones existing in 1955 and a Russian hacking scandal making the news. Or LGBT rights and gay marriage. This America truly is the most awesome noble experiment ever devised despite everything.

bks

All this adoration of SpaceX is misplaced. NASA was reusing the shuttle over thirty years ago. SpaceX is dependent on NASA science, engineering, launch facilities tracking and funding. JFK proposed a manned mission to the moon on 25 May 1961. Neil Armstrong took a step onto the moon 20 July 1969, just over eight years later. SpaceX was founded in 2002. That's fifteen years ago and they have yet to even recapitulate the Mercury missions (1958-1963). Yes, NASA had more resouces than SpaceX, but they didn't have the 50 years of research and expertise in electronics and material science that accumulated in the interim.

Babak Makkinejad

I agree with you in regards to the Exclusion Principle; it is a non-classical additional force that evidently encompasses weak, electromagnetic, and strong force - it is like a common aspect of all forces at Quantum level.

In Quantum Theory of Magnetism, the "Exchange Integral" is sometimes referred to as such.

Babak Makkinejad

IN regards to Black Holes, their existence is inconsistent with Quantum Mechanics.

Babak Makkinejad

In regards to Black Holes, their existence is inconsistent with Quantum Mechanics.

Einstein was a monist. I am too. And I do not know how particularity can emerge from the universal. Even Spinoza did not outline a quadrature for doin so, but that does not mean it is impossible even in principle.

All of contemporary cosmology is based on differential equations and continuity of space-time as well as distribution of matter.

different clue

FourthAndLong,

I remember reading somewhere that when Einstein said to Neils Bohr " God does not play dice!" that Neils Bohr replied " Don't tell God what to do!"

outthere

Yes I remember those days well, walking up the hill to honors physics class, sputnik beeping overhead, and watching an incredible new Saarinen building being constructed. Transistors were a new thing, and IBM was working to manufacture them in a new/different way - a vital step towards manned space flight.
And I remember when LBJ's top advisor was arrested in a mens' room, and hastily secretly fired.
So yes, there has been progress.
But there has also been a downside, just ask almost any wild creature. Here's a good start on that subject:

The Fate of Earth
Humanity’s survival on this planet seems more uncertain than ever. But what happens when we look at ourselves through other creatures’ eyes?

By Elizabeth Kolbert

October 12, 2017

https://www.newyorker.com/tech/elements/the-fate-of-earth

FourthAndLong

Yes. Spin is fascinating. Lasers do their thing being essentially a Bose --Einstein condensate phenomenon. Any number of photons can exist in the exact same quantum state, being as they have integral, as opposed to half integral integral spin. Seperation of matter, that it takes up space at all -- because electrons are fermions, spin one half.

One idea intrigued me long ago, that matter was "on the average" Bosonic. And that gravity, so fundamentally attractive is a " residual" manifestation of Bosonic matter's tendency to flood into one state, as with the lasing photons. After all, most aggregates of atomic matter do have integral spin most of the time. Thus gravity, profoundly weak, is what's left over in the collosal ongoing tendency to become a B E condensate. But I couldn't manage a quantitative estimate. Lack the mathematical talent.

Ivan

..and presented by Stephen Hawking...

English Outsider


Colonel - Quantum theory? As remote for most of us as the far side of the moon though not, unsurprisingly, so remote for some of your readers. Shall we ever end up with whatever they might call that theory of everything they're hoping to reach? And if so, will these investigations into the innermost properties of matter itself reinforce our current view that matter is all there is? That once we understand all things to do with matter we understand all things to do with Man?

That materialist view of us humans has been gathering steam since before the Enlightenment. Darwin wrestled with the implications of it for decades. Painstaking to the point of genius but somehow timid, or maybe just plain scared of those implications, it took him a while to come out with it. Maybe he'd have waited even longer, if a gifted amateur hadn't happened to put it all together in an afternoon and nearly forestalled him. It wouldn't have mattered. It was there already, in the air waiting to be noticed; but when Darwin did come out with his Origin of Species - the clue's in the very name itself so bye bye God or anything metaphysical - they took the ball and ran with it.

Didn't they run with it, and for such a distance. Primitive Darwinism, a way of thinking about evolution that took little account of feedback or ecological systems but focused mainly on the misunderstanding that the strongest tiger wins, ran all the way to the Third Reich - and well beyond. For let's not pretend that that way of devil take the hindmost thinking isn't still enormously powerful amongst those far removed from the study or the pulpit.

More significantly for us, the materialist view that we're nothing else but a collection of atoms, and that there are no secrets about us that can't be discovered and understood and predicted once we've put in enough time in the lab, took off like an explosion in an ammunition dump and apart from a few cranks or diehards it's the view that rules our world.

Pity, because both takes are bullshit. On the scientific level or any other. On the most simplistic level we've now fully grasped the fact that the strongest tiger doesn't win in anything but the short term. The super-tiger eats all the prey and dies out. The tiger can only exist in balance with everything around him including the grass he treads on. Wish the cronies would grasp that, poor suckers, but that's by the way. As for understanding and prediction, the climate scientists and the mathematicians are grappling with the world of complex systems. I think we're starting to realise that, given the fact that measurement disturbs the thing measured, and given that everything to the furthest point of space affects everything else, we may be able to discover everything about the world, including us, but we're never going to be able to predict it fully. As Mrs Pelosi said - didn't she? - we're going to have to get to the future before we can see what's in it. There are no short cuts.

But that's by the way too, essentially, because make no mistake such thinkers as Dawkins, that fearsome materialist, are quite correctly insisting that there is no real physical difference between us humans and a chunk of rock. No difference at all except that we're formed out of more bits and pieces. We're both arrangements of matter and that's the end of it. Materialism rules!

Does it hell. When did you ever see a chunk of rock looking at another chunk of rock and saying "that's a chunk of rock. I must be a chunk of rock too"? No, we have to go all the way with Dawkins, every damned inch and more. We have to accept materialism as the basis of any sensible thinking about ourselves. And then we have to go further. We have to accept the implications of consciousness.

Dawkins, bless him, reckons we can crack consciousness. Sooner or later we're going to discover the exact combinations of matter that give rise to the phenomenon, or the illusion even, that we know as "consciousness". 'Course we will, Mr Dawkins, it's only a question of time. We both know that. We'll crack it soon enough.

But when we've done that we're still going to be conscious. We're still going to be humans with our own specific type of consciousness. And when we accept that, we're going to have to take a closer look at our own specific type of consciousness. I wouldn't be surprised if the theologians and the metaphysicians, even if they use antique concepts and definitions long since lost to most of us, didn't come in handy there.

Last night I was reading that most unexpected of theologians, Oscar Wilde. All theatrics and paradox, Wilde, with that poser's "We must fail gracefully, darlings, since fail we must" fatalism that reconciles so many to defeat. But underneath that false determinism there must have been a very sharp brain and an almost preternatural intuition. He was in the thick of that first great surge of materialism that was in short order to flood our entire world. Suddenly he flashes out, not just an acceptance of Dawkins' fearsome materialism, but an insight into what we must find beyond it:-

"Life is a question of nerves, and fibres, and slowly built-up cells in which thought hides itself and passion has its dreams."

Babak Makkinejad

Can you please elaborate regarding gravity as a Bose condensate?

David

I absolutely agree that one should avoid books that just talk about Schrodinger's cat or the Uncertainty principle. There are four, but equivalent mathematical approaches to doing quantum mechanics. Historically the first was Heisenberg's use of matrices and this approach is used in "Quantum Mechanics in Simple Matrix Form" by T.F. Jordan which is now a Dover paperback.

This is a really nice book and requires the least mathematical background of any serious quantum mechanics book that I know of, yet it teaches one to do actual calculations whose results would require much more advanced mathematics if done using any of the other three approaches. If you know simple algebra, then you know enough to learn about complex numbers and matrices which takes up the first part of the book. The book has been used to teach quantum mechanics to high school students.

I also agree with the other people here that Feynman's book "QED:The Strange Theory of Light and Matter" is superb. Get the edition which has Anthony Zee's introduction where he explains how Feynman was able to make the physics simple, but with out simplifying it.

As was also mentioned, Leonard Susskind's book on Quantum Mechanics is also excellent, but it requires one to know calculus and to have either read his previous book on classical mechanics or to already know that subject.

David

I don't think this has been proven at all. We already have a semi-classical approximation which predicts Hawking radiation
and some string theorists have made claims that it is also present in a fully quantised theory of gravity.

A colleague said to me that "The black hole will be to 21th century physics what the harmonic oscillator was to 20th century physics".

LeaNder

positivism (prior to WWII), mysticism (after WWII), fantasy (The Many-World's Interpenetration)

Babak, that's pretty curious, at least considering mysticism. Even if we differentiate between religious and secular mysticism over the centuries.

But I am aware of your organizational frameworks needs, which for one reason or another I assume are outside your general field concerning your central theses.

LeaNder

Great joke, QSOH, from my as always limited grasp of matters.

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