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12 October 2017

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egl

Re studying quantum mechanics:

Kenneth Ford, 101 Quantum Questions, is a good orientation if you've never heard of the two-slit experiment or aren't quite sure why neutrinos are interesting. The table of contents gives an idea of what to expect.

Leonard Susskind, Quantum Mechanics: The Theoretical Minimum, goes one step beyond the gee-whiz-quantum-effects-are-weird with a nice combination of phenomena and easy calculation. You will have to study this carefully. Susskind also has a lecture series on YouTube.

Babak Makkinejad

In regards to QM:

To my knowledge, there is no sensible non-technical presentation of QM. All such presentations that I have seen aim to shock-and-awe the reader into a state of intellectual paralysis. No attempt is made to connect it to prior physical theories and scientific ideas.

Even many of the technical treatments, depending on when they were composed, reek of the prevalent intellectual fad of their epoch; positivism (prior to WWII), mysticism (after WWII), fantasy (The Many-World's Interpenetration).

The quest ought to be the discovery of Physical Truth which, however central it might be to the development empirical sciences, does not make money at the popular level nor advances one's professional career.

I will be concrete:

The two technical presentations that I have liked - for reasons of taste, consistency, coherence of ideas, and other such qualitative prejudices - are:

The Statistical Interpretation of Quantum Mechanics: https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.42.358

and

Schrodinger's Mechanics:
https://www.amazon.com/Schrodingers-Mechanics-Scientific-Lecture-Physics/dp/9971507609

There is a 3rd approach, by the formerly black-listed Bohm, that I am studying - it is a very interesting and creative approach, like the Action-at-a-Distance approach of Narlikar and Hoyle to Cosmology - "Wonderful, but is it right?". Please see:
https://www.amazon.com/Undivided-Universe-Ontological-Interpretation-Quantum/dp/041512185X/ref=asap_bc?ie=UTF8

All of the interpretations of QM are metaphysical statements on the nature of Reality - they are guesses and cannot be decided on basis of experimentation; I do not find other interpretations useful.

ChuckO

I'm not qualified to judge the credibility of the following info, but I offer it up for commentary by others who are more knowledgeable. I read an article by a physicist who questioned the practicality of such a system. The problem comes from the fact that the hyperloop tube must contain a vacuum. Any breach in that tube, even a very small one, would lead to catastrophic failure. According to the article I read, a rifle bullet could penetrate the tube, and cause such a failure. If that is true, the hyperloop is not practical. Not only would it be ripe for a terrorist attack, but a relatively minor earthquake might lead to a breach where the tubes are joined.

DianaLC

These posts are the ones that make me wish I were younger. I will most likely not live to see the time when this sort of travel is commonplace.

My first child was born in 1975, and I remember hoping that by the time he reached adulthood, he could take his mother on a ride into space.

When he was thirteen, he spent a few weeks in Japan with the family of the boy who had been our exchange student here. His most exciting experience cane from riding the bullet train all around Japan with his friend, needing no adult supervision.

But, sadly, he's probably not going to be able to take his mother on that sort of trip here in the US or on a rocket to outer space.

Thanks for the report!

mike

Space-X founder, Elon Musk, also wants to rebuild Puerto Rico's power grid with solar and his PowerWall batteries. He has already started something similar but on a smaller scale on Hawaii's Kauai. I'm a fan of Musk and a fan of solar, but I think these huge centralized solar facilities are not as beneficial to homeowners as rooftop installations. My son has rooftop solar. He only needs some offset power from the grid in July and August with the AC going full blast. Many homeowners here in coastal WA state are installing solar systems even though our sunny and partly sunny days are few and far between.

Old Gun Pilot

Colonel,
Richard Feynman's lectures are a good place to start. He makes a complex subject easy to follow and he's enjoyable to watch. Many are are available on youtube.
Here's one where he discusses quantum electrodynamics (QED), the subject which won him the Nobel Prize. https://www.youtube.com/watch?v=xdZMXWmlp9g
OGP

The Twisted Genius

ChuckO,

I don't see how a leak would cause a catastrophic failure. Small leaks could certainly cause a failure or at least a degradation in efficiency, but I don't see how it would cause a catastrophic implosion or explosion. A similar system was envisioned by an inventor in the mid-1800s. He secretly built a small pneumatic subway under NYC in 1869.

https://gizmodo.com/how-one-inventor-secretly-built-a-pneumatic-subway-unde-1123695775

Croesus

"terrorist attack."

How sad.

Col Lang encourages the Committee to pursue challenging scientific discipline and to peer into the future, but some remain moored on the sand of a concocted fear-based past.

One lives in the hope that minds that have disciplined themselves to the extent of mastering quantum mechanics will be sufficiently keen to deal construct relations with other peoples and nations in a way that is less likely to require fear mongering.

In an earlier comment I mentioned Jake Sullivan's testimony before a US House of Reps Foreign Affairs committee. Sullivan is about 41 years old, educated in public high school in Minneapolis, Minnesota, then Yale & Yale Law. He was sharp and clear and unruffled, even when Representatives behaved like baying coyotes (or C-grade prosecutors).
Bad things will always happen in a complex world, but they are less likely to devolve to "terrorist attacks"
when well-disciplined minds evaluate the problems cooly and clearly.
If our society can produce more Jake Sullivans, maybe we can move beyond "terrorism" as a societal meme, and concentrate more on Hyperloop.

(Come to think of it -- was the Japanese sarin gas attack on one of Japan's MagLev trains? They're still running.)

Bill Herschel

Please take a look at Richard Feynman's QED. You'll love it.

The Twisted Genius

Last weekend my younger son and I took in the Caps home opener. We went early so we could stop by the Smithsonian Air and Space Museum. After our recent discussion about the proposed lunar space station/base, I had a strong desire to see the Apollo-Soyuz Test Project exhibit. Just seeing it again fortified my hope for the future of mankind. Among the other exhibits, we saw the Mercury and Gemini capsules. I am amazed by the smallness of these craft, far smaller than my old VW bug. The space walk from that Gemini capsule was quite an adventure. The spacewalker's suit ballooned up from the pressure differential and his visor fogged over. His partner had to pull him back in the capsule and seal the hatch behind him before the capsule could be sealed and repressurized. I imagine it had to be like pulling somebody with a rucksack and snowshoes into that VW bug. What an adventure. SpaceX, by making these launches routine and cheaper, is paving the way for far grander adventures in space.

Quartered Safe Out Here

Agree. Colonel, if you spend a few hours with Schoedinger's cat thought experiment and Heisenberg's uncertainty principle, you may feel like you've wandered off into Douglas Adams territory. Fortunately what goes on at the nano-level has little impact on the Newtonian world we live in. But you get to share in obtuse jokes such as: A cop pulls Prof Heisenberg over and asks him "Do you know how fast you were going?" and Heisenberg said "No, but I know where I am." Sorry about that.

outthere

what's the hurry?
plant some seeds
watch them grow
a miracle right before your eyes!
and you did not even burn any hydrocarbons!

Jimmy W

COL and all, freight rail traffic has always prized low-cost way over speed. The proven alternative of air freight has cornered the market of high-speed priority freight. Therefore, freight rail competes with other surface freight on the basis of cost only. Passenger rail, due to speed requirements, displaces/replaces freight rail. For example, Acela hardly takes any freight, its revenue all comes from passenger.

So Hyperloop can either compete on cost against freight rail, or on speed/cost against freight air. This is why Hyperloop is unlikely to succeed on the basis of freight. It can only succeed if it can demolish the competing passenger air.

Babak Makkinejad

I think US has a very deep bench but those sitting on the bench are kept out of the arena because they are empiricists.

Whenever idealists gain dominance, they drive the empiricists out; regardless of the political or religious orientation of such idealists (who wish to make the world Righteous.)

SR Wood

I had some good college coarse(s) in physics but this Forbes article does a good job of summing up quantum mechanics. Wish they had it 40 years ago when I studied physics.
https://www.forbes.com/sites/chadorzel/2015/07/08/six-things-everyone-should-know-about-quantum-physics/#2e20bd9d7d46

FourthAndLong

Colonel,

Don't miss Feynman's treatment of the double slit experiments. Available in his Cal Tech lectures but also in one or two of his more popular books. Many professional physicists consider it the finest introduction to the entire subject. And if that doesn't get through to you, there is essentially not much point in proceeding further. It attempts to show precisely how different QM is from classical. Nothing fancy, no exotic anything, but really fundamental. And essentially no math.

That lecture is reproduced, somewhat updated, in his ‘Six Easy Pieces’ by Feynman and Leighton, as chapter six.

And yes his QED: The Strange Theory of Light and Matter, is marvelous as can be.

His attempt to give a layman’s presentation of why antimatter has to exist is a fascinating sidelight, tho technically a failure, as he acknowledges. His failure in doing so partly convinced him that no one truly understands the subject yet. It was part of his attempt to explain in every day terms the bizarre connection between spin and statistics. But he couldn’t. Einstein, in his nomination of Wolfgang Pauli to the Nobel academy for the physics prize, seemed resigned to accepting it as an experimental fact. Various people, Pauli included, thought they derived it mathematically from special relativity plus standard QM, but no one was too impressed by those attempts. George Sudarshan claims a derivation wo using special relativity. I couldn’t understand it though.

It’s the idea behind the exclusion principle of chemistry. Why can’t more than two electrons share an atomic orbital ? More or less an independent force of nature, in a par with gravity and electromagnetism? No one wants to accept that. Geniuses like Schwinger, Pauli and Sudarshan thought they ‘derived’ it. Feynman wasn’t buying it though. He was famous for saying “don’t let anyone tell you they understand quantum mechanics, because they don’t.’ But he also said that literally everything there is to understand about QM is right there in the double slit experiment, entanglement too (he gave a justification of that last somewhere. Murray Gelman seemed to agree.)

ISL

TTG,

High pressure (pneumatic) versus vacuum. At the speeds desired, the tube must maintain a high vacuum or the vehicle will tear itself apart (due to compressional heating). Keeping flanges of a hyper loop perfectly leak free despite thermal cycles (in the desert of all places) is beyond any current or near term technology, so it would need to be backed up with massive vacuum pumps (and redundant backup pumps) at every flange, pushing costs into the stratosphere plus cancelling the energy savings.

Its a great idea for humanity in a century or so when star trek technology is available.

Now its a great idea to lighten the wallets of various VCs.

FourthAndLong

It’s worth trying to work it out anyway. May have other applications.

Will.2718

Even after earning a BS in Physics, I truly didn't understand Quantum Mechanics ("QM") until entering the Masters program in Electrical Engineering. Then it was like a light bulb turning on in my head. I've seen my key insight later in print, but I came up with it all by my lonesome.

For example the uncertainty principle, the more you know about a particle's position, then the less you know about its momentum and vice versa. Just a consequence of wave mechanics and the superposition principle. In electronics, one goes back and forth between the time domain and frequency domain. Imagine a trumpet blowing a pure C note with no beginning and no end. Its frequency is perfectly established but its time position is all over the place. Likewise, imagine a single infinitely sharp drumbeat. It is perfectly known in time, but its frequency is all over the place- best approximated by a fourier infinite series of sine waves. So there you go, the more you know of one domain, then the less you know of the other.

I met my hero Paul Adrien Maurice Dirac in his 90's when he was giving a talk at the Morehead Planetarium. Got him to autograph my copy of his "Principles of QM-" the book where he predicted the existence of the positron, found shortly thereafter, and speculated about the magnetic monopole, still lurking out there.

My Electromagnetics Physics Professor, Dr Palmatier, was a close friend of DeWitt, who collaborated with Wheeler on some work. Always been fascinated by the Many Worlds Interpretation of QM and the multiverse concept.
https://en.wikipedia.org/wiki/Many-worlds_interpretation

r whitman

One of my undergraduate physics professors 65 years ago was fond of saying that a century from now much of new physics theory will be considered witchcraft.

Quantum mechanics, Big Bang Theory and Relativity are likely candidates.

Ishmael Zechariah

TTG,
Here is a repeat from one of your posts. IMO it cannot be repeated enough:
"But we were born of risen apes, not fallen angels, and the apes were armed killers besides. And so what shall we wonder at? Our murders and massacres and missiles, and our irreconcilable regiments? Or our treaties whatever they may be worth; our symphonies however seldom they may be played; our peaceful acres, however frequently they may be converted into battlefields; our dreams however rarely they may be accomplished. The miracle of man is not how far he has sunk but how magnificently he has risen. We are known among the stars by our poems, not our corpses.” (Robert Ardrey, African Genesis)

Perhaps there is still a future for mankind-perhaps not. Here is a more appropriate Ardrey quote for our times: "The dog barking at you from behind his master’s fence acts for a motive indistinguishable from that of his master when the fence was built" (The Territorial Imperative)

Diplomacy and governance du jour seem to be the purview of barking dogs

Ishmael Zechariah

mongo

Hello Sir,

To say that you are studying quantum mechanics is a little vague -- I could say in response that you are studying everything in physics that doesn't relate to gravity. Other learned members of the group have suggested some good resources to look at, but I'll refrain from joining in unless you have something in particular that interests you.

The quantum world can be thought of in terms of three domains: quantum mechanics, which is essentially Newtonian mechanics with probability theory added in, quantum electrodynamics (QED), which mainly deals with the family of particles that largely persist and are directly observable in nature (protons, electrons, neutrinos, etc.), and quantum chromodynamics (QCD), which deals with the (so far) most basic particles that combine to form those that QED deals with (quarks, the Higgs, etc.).

It's important to keep in mind that all of this stuff is mental constructs that people have put together to help them visualize what our instruments detect. An electron may or may not be a little spherical thing whose position and momentum are known to a finite accuracy. We know that they exist, but only indirectly. We can talk about them as having the properties of both a particle and a wave, but that's not something that our senses report -- we come to those conclusions be observing the behavior of large numbers of these things in aggregate through experiments like Young's double slit diffraction.

Happy Hunting,

mongo

mongo

Hi TTG,

It depends on how close to a true vacuum they need to have in the tube. Adding air to a tube like this would add friction and possibly turbulence, which could make the transport wobble to the point where it bumps into things. Depending on the speed, this could result in annoying dents or it could mean it bashes into something hard enough to destroy itself.

Regards,

mongo

b

What happens to a (pressurized) vehicle that rides at several hundred miles per hour in a vacuum when that vacuum suddenly turns into a comparatively "solid" gas at atmospheric pressure?

Try to breach a concrete bunker with a Porsche 911. The experience will be similar.

Ivan

The only advice I would like to give Col Lang, is never, ever read a book which mentions Schrodinger's Cat or Heisenberg Uncertainty, that does not also contain some mathematics. I say this as a person who wasted many years reading such books as 'The Dancing Wu Li Masters'. The mathematics to understand QM is not that difficult, being largely a more abstract version of the vector and matrix mathematics that one sees in say for example game programming books. But it is also possible to acquire sufficient understanding through the study of the Schroedinger partial differential Equation. There are many ways to acquire such knowledge, and a visit to a well stocked library, or better still taking some extra-mural courses would save an incredible amount of time and mental effort. I am afraid that most of the popular books are not worth the paper they are printed on.

Therefore while it is no shame not study QM, it would be very saddening if anyone tries to acquire such knowledge through the mass of popular books. I would recommend 'The Dreams that Stuff is made of'. A volume of original papers and articles edited and presented by Steven Hawking. Depending on one's background, one may find the mathematical papers heavy going, but there is sufficient knowledge to be gleaned even in the the non-mathematical articles, which together form a connected whole.

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