RE: The Tao of Physics (Full Version)

Foro Flamenco: http://www.foroflamenco.com/
- Discussions: http://www.foroflamenco.com/default.asp?catApp=0
- - Off Topic: http://www.foroflamenco.com/in_forum.asp?forumid=23
- - - RE: The Tao of Physics: http://www.foroflamenco.com/fb.asp?m=274555



Message

Richard Jernigan -> [Deleted] (Apr. 8 2015 21:08:50)

Post has been moved to the Recycle Bin at Apr. 8 2015 21:11:02



Ricardo -> RE: The Tao of Physics (Apr. 9 2015 16:58:18)

quote:

Ricardo: I like that Susskind and others are challenging Hawking. Although Hawking is a brilliant mind, sometimes it is too easy to follow someone just because they are a great mind, not because their ideas are exceptional. What if this were to turn out to be true. Then the metaphysical question would be: "What is responsible for the hologram?"


If it turns out you can actually observe that no info is lost by examining an event horizon at a fine scale (meaning the ghost of all the info/material is permanently left behind at the surface before being wrenched off from existence)...one answer (I read somewhere and it makes some sense) to your metaphysical question is that we, and our observable universe, reside INSIDE the event horizon of a black hole.



Brendan -> RE: The Tao of Physics (Apr. 9 2015 18:28:27)

Richard, thanks for sending me your characteristically detailed and thoughtful reflections on Hersh & John-Steiner on Moore. Since this tack seems to be just we two, I'll reply by e-mail.

BL



reynold -> RE: The Tao of Physics (Sep. 22 2015 14:57:51)

Is this over? What a fun thread. There were brief episodes of personality conflicts
and bits of condescension, but in main this was a good spirited and generous
discussion. I am impressed with the width and depth of knowledge and interests
on display here. I love my ignorance, because it is such a pleasure to displace it with knowledge or understanding. Latcho Drom!

Reynaldo



Beni2 -> RE: The Tao of Physics (Apr. 16 2019 1:28:54)

https://arxiv.org/abs/1902.05080

https://mitpress.mit.edu/books/objectivity

Is objectivity possible?
What can anyone in the foro agree on, if anything?



Ricardo -> RE: The Tao of Physics (Apr. 18 2019 17:59:50)

quote:

ORIGINAL: Beni2

https://arxiv.org/abs/1902.05080

https://mitpress.mit.edu/books/objectivity

Is objectivity possible?
What can anyone in the foro agree on, if anything?

The key is “in the quantum world”.... the answer can be “no”. So once we can define the boundaries between the quantum world and the macro world, we can allow objectivity I think. And since we actually observed that something like the event horizon actually exists thanks to objective observations last week, I am hopeful that one day we will discover the dividing line and learn how to cross it and have some sort of objective truth of the quantum world that currently eludes us.



Beni2 -> RE: The Tao of Physics (Apr. 18 2019 19:54:17)

quote:

Modulo the potential loopholes and accepting the photons’ status as observers, the violation of inequality (2)
implies that at least one of the three assumptions of free
choice, locality, and observer-independent facts must fail.
Since abandoning free choice and locality might not resolve the contradiction [5], one way to accommodate our
result is by proclaiming that “facts of the world” can
only be established by a privileged observer—e.g., one
that would have access to the “global wavefunction” in
the many worlds interpretation [17] or Bohmian mechanics [18]. Another option is to give up observer independence completely by considering facts only relative to
observers [19], or by adopting an interpretation such as
QBism, where quantum mechanics is just a a tool that
captures an agent’s subjective prediction of future measurement outcomes [20]. This choice, however, requires
us to embrace the possibility that different observers irreconcilably disagree about what happened in an experiment.


Head over to: http://www.foroflamenco.com/tm.asp?m=318114&appid=&p=&mpage=1&key=&tmode=&smode=&s=#318146



kitarist -> RE: The Tao of Physics (Apr. 25 2019 20:16:27)

quote:

ORIGINAL: Ricardo

quote:

ORIGINAL: Beni2

https://arxiv.org/abs/1902.05080

https://mitpress.mit.edu/books/objectivity

Is objectivity possible?
What can anyone in the foro agree on, if anything?

The key is “in the quantum world”.... the answer can be “no”. So once we can define the boundaries between the quantum world and the macro world, we can allow objectivity I think.


Speaking of boundaries and objectivity, enter something called the Leggett-Garg Inequalities. These are a class of inequalities that would have to be true for all macrorealistic physical theories. Here, macrorealism (macroscopic realism) is a classical worldview defined by the following three principles:

(1) Macrorealism per se: "A macroscopic system/object, which has available to it two or more macroscopically distinct states, is at any given time in a definite one of those states."

(2) Noninvasive measurability: "It is possible in principle to determine which of these states the system is in without any effect on the state itself, or on the subsequent system dynamics.", and

(3) Induction: The outcome of a measurement on the system cannot be affected by what will or will not be measured on it later.

There is a review paper from 2014 on Leggett-Garg Inequalities (LGIs), experimental attempts (and their pitfalls) at violating them and LGI's possible applications, here: https://arxiv.org/abs/1304.5133

From it: "Whilst classical mechanics conforms with [..] these assumptions, quantum mechanics certainly does not — the existence of a macroscopic superposition would violate the first, and its quantum-mechanical collapse under measurement, the second."

So the inequalities can be used as test to see how far the quantum world's coherences can penetrate before collapsing into definite states in the macro world.

From the conclusion section: "Thus, it is clear that we are only at the outset of the journey in testing the penetration of quantum coherence into the macroscopic world with LGIs. Further progress involves not only moving up in scale to address ever-more macroscopic entities, but also in confronting the challenges posed by the clumsiness loophole."

What is the "clumsiness loophole"? It means when experimental tests of LGIs show apparent LGI violations, however that turns out to be a result of the unwitting invasivity of the measurements, rather that the absence of a macroscopic-real description of the system. Heh.



JasonM -> RE: The Tao of Physics (Apr. 26 2019 20:48:33)

Where does the quantum world end and the macro world start? We sent Buckyballs ( 60 atom carbon soccer balls) through the double slits and still produced an interference pattern.



Ricardo -> RE: The Tao of Physics (Apr. 27 2019 15:53:16)

quote:

ORIGINAL: JasonM

Where does the quantum world end and the macro world start? We sent Buckyballs ( 60 atom carbon soccer balls) through the double slits and still produced an interference pattern.


I remember Roger Penrose talking about wanting to study the quantum gravity effects of “a mote of dust”. So probably much larger than buckyballs...probably some large molecules.



kitarist -> RE: The Tao of Physics (Apr. 28 2019 4:44:28)

quote:

ORIGINAL: Ricardo

quote:

ORIGINAL: JasonM

Where does the quantum world end and the macro world start? We sent Buckyballs ( 60 atom carbon soccer balls) through the double slits and still produced an interference pattern.


I remember Roger Penrose talking about wanting to study the quantum gravity effects of “a mote of dust”. So probably much larger than buckyballs...probably some large molecules.


The largest they have done so far that still produce an interference pattern is with 810 atoms, about 10,000 atomic mass units. (for reference the buckyball is 720 amu - 60*12).



Ricardo -> RE: The Tao of Physics (Apr. 28 2019 7:08:56)

So... 811 atoms it is then. Objectivity and gravity appear at 811 or more atoms in size.... where is my Nobel prize?



BarkellWH -> RE: The Tao of Physics (Apr. 28 2019 14:35:58)

An interesting side-note. The double-slit experiment was first performed with light by the British polymath Thomas Young in 1801. Thomas Young is generally considered to have been the last man to know everything there was to know during his lifetime.

Bill



Paul Magnussen -> RE: The Tao of Physics (Apr. 28 2019 16:10:43)

quote:

I remember Roger Penrose talking about wanting to study the quantum gravity effects of “a mote of dust”


Penrose, for my money, is one of the few authors of popular books that writes clearly about quantum physics. Speculation about the rôle of consciousness seems especially fuddled. Penrose is of the few who goes into what actually constitutes an observation.

So if we place a a detector at one slit, we don’t get an interference pattern. But what if we arrange that we don’t know whether it’s turned on or off? Or, we don’t look at the print-out, and destroy it before anyone else can do so?

What if the result is seen only by the laboratory cat, or just a passing spider?

If the Universe doesn’t exist when we’re not observing it (as some hypothesise), then how can we be here at all (since the Universe is considerably older than we are)?

These are some of the questions that bugged me when I first started reading such stuff. I’m not saying these topics can’t be addressed, but they seldom are, in my experience.

I’ve just started Einstein’s Unfinished Revolution (2019), by Lee Smolin, which looks promising.



Ruphus -> RE: The Tao of Physics (Apr. 28 2019 16:18:45)

On a side note from a documentary:
Theory according to which entry into blackhole was dismantling might be wrong. Could be a slip into a kind of bubble behind it.

The bubble again could be entry to parallel universe / multiverse.

Similarly possible wormholes and 'macro connections' (for lack of better word) with the latter presenting options for a kind of "beaming" oneself to anywhere geographically.
Further, possibly not only geographically but also in time towards future.

-Needless to say, that such should render impossible any kind of gambling, as bets could not be on fair ground anymore.

Rather useful in view of projects, though.

Oh, and -don´t know how this was taken from there, as it was in a language that I don´t fully manage- one´s deads, so it was said, would never be gone / could accordingly be with you all the time.

For my part, I would embrace the idea.



Piwin -> RE: The Tao of Physics (Apr. 28 2019 17:09:02)

Is Bohmian mechanics considered a viable possibility by contemporary physicists or has it been done away with entirely? It had the advantage of solving the measurement problem IIRC.



kitarist -> RE: The Tao of Physics (Apr. 28 2019 21:50:27)

quote:

ORIGINAL: Ricardo

So... 811 atoms it is then. Objectivity and gravity appear at 811 or more atoms in size.... where is my Nobel prize?


Yes [:D] [from here on not in response to what you said]

But in general, it is more complicated. There is so much confusion sowed even with the various explanations - or is it mostly with the misinterpretations of the scientific theories when journalists try to convey them to the public.

Example 1: Schrodinger's cat. Shrodinger brought that up as a reductio ad absurdum argument - in other words, he was mocking the Copenhagen interpretation (or perhaps its popular extensions) with what he thought was an obvious absurdity - to posit that a macro object such a as cat can be dead and alive at the same time until its "wave-function" collapses upon measurement.

However, these days you can find as many if not more people bringing it up as a straight argument FOR that interpretation, as if Shrodinger was its supporter. I blame journalists.

Example 2: Double-slit experiment. The interference pattern at some distance from the slits is not produced by the same "particle" going through both slits at once as if it is actually a wave; that's not what the paradox is. All these micro objects, from single particles to 800+atom molecules, definitely go through either one slit or the other. The apparent interference pattern is produced only over time as you send thousands of these objects over and over, each only hitting at one definite point on the screen. The puzzle is, how do these different objects "know" to mostly hit the areas where the constructive interference would be IF what was sent through was some sort of wave? But that's different than imagining a multi-atom molecule ghostly splitting itself and going through both slits, isn't it?

Example 3: Quantum coherence. Coherence effects do exist in the macroworld, but that does not necessarily mean anything about determinism or objectivity - it seems to depend on what the phenomenon is. Laser is a quantum coherence phenomenon on macro scales, for example; so are superconductivity and superfluidity. BTW macroscopic or macroscale for these purposes is understood to have at least an Avogadro's number's worth ( 6.022 x 10^23) of particles; or extend to macro distances.



kitarist -> RE: The Tao of Physics (Apr. 28 2019 22:08:11)

quote:

ORIGINAL: Piwin

Is Bohmian mechanics considered a viable possibility by contemporary physicists or has it been done away with entirely? It had the advantage of solving the measurement problem IIRC.


It has had a recent revival, for example see this:

https://www.newscientist.com/article/2078251-quantum-weirdness-may-hide-an-orderly-reality-after-all/



kitarist -> RE: The Tao of Physics (Apr. 28 2019 22:12:32)

And here is a curious paper from October last year:

"Local model of a qudit: Single particle in optical circuits", by Blasiak, showing that quantum behavior can be explained with classical physics for a single particle, but not for multiple particles.

Abstract:



The full article is available here.

Images are resized automatically to a maximum width of 800px



Paul Magnussen -> RE: The Tao of Physics (Apr. 28 2019 23:44:31)

quote:

Is Bohmian mechanics considered a viable possibility by contemporary physicists […]?


The answer appears to be Yes. There’s a considerable amount about Bohm et al. in the book by Smolin I mentioned, which I recommend (now being about half-way through).

Smolin seems (so far) to be of the Realist persuasion.



JasonM -> RE: The Tao of Physics (Apr. 29 2019 1:12:16)

I think a spec of dust is similar to the plank mass. Prob why Pensrose was interested.

Ahh Lee Smolin ... I read his The Problem With Physics book. It’s was pretty good, and nice to hear from a point of view from an anti string theorist. Good to hear both sides of the arguments I’m a fan of Leonard Susskind and Penrose though. Not so much into the whole philosophical stuff though



Piwin -> RE: The Tao of Physics (Apr. 29 2019 4:38:24)

Thanks for the article kitarist. That was an interesting read. Oddly I was introduced to Bohm not through physics but through linguistics. His "rheomode" bears some connection to the idea of linguistic relativity.
Thanks for the recommendation Paul. I'll have to add it to my list of upcoming purchases.

One book that might be tangentially pertinent to this discussion is "Lost in math: how beauty leads physics astray" by physicist Sabine Hossenfelder. It's a fairly light read but raises some interesting questions. In a nutshell (spoilers ^^), she notes that, in areas where the data are not yet in, physicists often go by "mathematical beauty" as a standard to separate viable theories from unviable theories. And she goes looking for an answer to whether and why that assumption might be justified or not. After having read her book, I started noticing how often this reference to beauty comes up in science communication. Even during the press conference on the "shadow of a black hole", one of the researchers answered a question by saying "in my experience, nature wants to be beautiful". This doesn't say anything about objectivity per se, but it does point to possibly unjustified expectations we have about what reality should look like.

Another aspect of this that could be considered is the effects of evolution on our own perceptual strategies. A common assumption is that a more accurate perception of reality equals more evolutionary fitness. However, that idea has slowly started to be challenged, some going as far as arguing that the two may have an inverse relationship. Such a prospect wouldn't call into question that there is an objective reality out there, but it would call into question our ability to ever perceive it, suggesting that we are in fact "designed" not to perceive it.



Paul Magnussen -> RE: The Tao of Physics (Apr. 29 2019 15:53:28)

quote:

https://www.newscientist.com/article/2078251-quantum-weirdness-may-hide-an-orderly-reality-after-all/


Thanks Konstantin, good article, well written (apart from the use of alternate to mean alternative)



Paul Magnussen -> RE: The Tao of Physics (Apr. 29 2019 16:28:06)

quote:

Of course the analogy of Theseus's ship applies precisely to Sugar the cat


Sorry to be so late replying to this. Just wanted to say that as far as I can see this is not a problem of philosophy at all, merely a (mostly) trivial one of language: we say “Sugar” simply because it’s easier than “the assemblage of molecules derived from, and largely similar too, yesterday’s Sugar.”

(The nontrivial part comes in when someone is tried for a murder they supposedly committed forty years ago.)

Or am I wrong?



kitarist -> RE: The Tao of Physics (Apr. 29 2019 17:03:40)

quote:

ORIGINAL: Paul Magnussen

quote:

https://www.newscientist.com/article/2078251-quantum-weirdness-may-hide-an-orderly-reality-after-all/


Thanks Konstantin, good article, well written (apart from the use of alternate to mean alternative)


Wow, good catch! I think for some reason physical scientists have started to use 'alternate' as if a close synonym, an alternative [:D], for 'alternative' when they actually mean another option which does not replace the first - i.e. they definitely mean 'alternative'.



Paul Magnussen -> RE: The Tao of Physics (Apr. 29 2019 22:02:46)

quote:

I think for some reason physical scientists have started to use 'alternate' as if a close synonym


It’s not just scientists: it’s very common (sometime, looking at Wikipedia, I think universal) among Americans generally, like convince to mean persuade.

I notice, too, that this is New Scientist, which is British [:'(].



Ruphus -> RE: The Tao of Physics (Apr. 30 2019 3:41:46)

Our physics teacher and headmaster once told us that "alternative" was meaning a single second choice / that there was no plural to it.

I always kept that in mind, but didn´t find anything about it in dictionary, encyclopedia or later on in internet.



Paul Magnussen -> RE: The Tao of Physics (Apr. 30 2019 16:53:23)

quote:

Our physics teacher and headmaster once told us that "alternative" was meaning a single second choice / that there was no plural to it.


The 1983 edition of Fowler’s Modern English Usage (which in my view is the last one that doesn’t endorse sloppiness) says:

quote:

The notion that because it is derived from Latin alter (one or the other of two) alternative cannot properly be used of a choice between more than two possibilities is a FETISH


where FETISH is defined as:

“our current literary rules and conventions misapplied or unduly revered.”



Ruphus -> RE: The Tao of Physics (Apr. 30 2019 17:07:45)

Thanks for checking that one out for me!

So, if I understand that right, my teacher was etymologically right; only not in terms of contemporary use?

PS:
quote:

(which in my view is the last one that doesn’t endorse sloppiness)


So refreshing to see that note!
I am pissed at how any slang, trend, grammatically wrong and BS is being taken into orthography these days!

Images are resized automatically to a maximum width of 800px



Paul Magnussen -> RE: The Tao of Physics (Apr. 30 2019 17:51:34)

quote:

So, if I understand that right, my teacher was etymologically right; only not in terms of contemporary use?


10/10.

(Incidentally, should you be interested, you can pick up a second-hand copy of that edition (ISBN 0-19-281389-7) for one cent, plus postage.)

https://www.amazon.de/Dictionary-Modern-English-Oxford-Library/dp/0192813897/ref=sr_1_1?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&keywords=0192813897&qid=1556646531&s=books-intl-de&sr=1-1



Page: <<   <   1 2 [3] 4    >   >>

Valid CSS!




Forum Software powered by ASP Playground Advanced Edition 2.0.5
Copyright © 2000 - 2003 ASPPlayground.NET