Live data from Hacker News

Lost Causes of Theoretical Physics (2003)

web.archive.org

21–30 of 55 posts

Re: Lost Causes of Theoretical Physics (2003)

#21
post #18

Earlier quoted context omitted.

> nature has no obligation to us This is an excellent point indeed, but what if it also applies to the disagreement between QM and GR? That is, does Nature have an obligation that QM and GR, both being mere reflections, in the human mind, of its particular aspects, should ever become in agreement with each other? What if mathematics (the human logic) can in principle only provide models that are local approximations…

It’s possible, but maybe not likely. I’ll tell you though, if reality is that unpredictable, thst unfriendly to rules, expect a rash of suicides in the physics community the day it’s confirmed.

These discussions are always composed of people who don't know very much laying down philosophical assertions (that they very rarely realize are philosophical), and innocent bystanders posing reasonable what-if questions that really can't be answered with (present) empirical knowledge. Like politics, the content of what is said is dominated by the dynamics of the discussion, with English skills "winning" arguments more often than anything else.

Physics is already approximate; experiments don't have access to infinity significant figures. If you'd prefer a more complicated example then ask anyone who has ever calculated a QED problem to less than infinity terms.

Re: Lost Causes of Theoretical Physics (2003)

#22
I'm not a physicist but as far as I know the key concept of the Everett interpretation is that you can think of universe states as of vectors and perform mathematical operations on them. IMHO giving up the ability to think this way would be a tragic loss. Many other parts of the list would make a huge pity to forget too.

Re: Lost Causes of Theoretical Physics (2003)

#23
post #3

Earlier quoted context omitted.

After skimming the whole thing, I was relieved to see that the argument against Many Worlds was the only one I considered invalid. It took the form of "It's not even a testable theory", rather than "it has mathematical deficiencies". Well, of course, no one's saying it's testable necessarily, but for various aesthetic and intuitive reasons it still seems valid. Just don't expect predictions from it and you'll be fine…

Valid and true are two very different things - and we've seen from history that the human brain can be lead into believing that essentially anything is intuitive or aesthetic.

Sure, hence the reason physicists tend to say MWI is valid and good, rather than 'true'.

Re: Lost Causes of Theoretical Physics (2003)

#24

Earlier quoted context omitted.

It’s possible, but maybe not likely. I’ll tell you though, if reality is that unpredictable, thst unfriendly to rules, expect a rash of suicides in the physics community the day it’s confirmed.

These discussions are always composed of people who don't know very much laying down philosophical assertions (that they very rarely realize are philosophical), and innocent bystanders posing reasonable what-if questions that really can't be answered with (present) empirical knowledge. Like politics, the content of what is said is dominated by the dynamics of the discussion, with English skills "winning" arguments mo…

These discussions are always composed of people who don't know very much laying down philosophical assertions (that they very rarely realize are philosophical)

That seems needlessly judgmental.

...and innocent bystanders posing reasonable what-if questions...

They’re rarely reasonable. You get a lot of questions which are philosophical in nature, but which people believe are scientific. “What is time like for a photon?” “What was there before the Big Bang?” “What is spacetime expanding into?” “What’s inside of the event horizon of a black hole?” “Why are the physical constants what they are?”

When you give the scientific answer, “Bad question, like asking what’s North of The North Pole?” People are unhappy. Plus you’re a dick, because you can figure out what they’re asking and try to give a complete and accessible answer, complete with warnings as to the philosophical/metaphysical nature of both question and answer.

...that really can't be answered with (present) empirical knowledge.

Often the questions themselves are essentially unanswerable in principle. It’s not easy to ask good, relevant, scientific questions about QM or STR/GTR. The lack of knowledge is more of a factor when the questions are insightful.

Like politics, the content of what is said is dominated by the dynamics of the discussion, with English skills "winning" arguments more often than anything else.

Depends on the audience... try that in a rigorous environment and be crucified, but on HN the rigor is absent. It’s a good thing too, because it’s Hacker News, not PhysicsForums.

Physics is already approximate; experiments don't have access to infinity significant figures. If you'd prefer a more complicated example then ask anyone who has ever calculated a QED problem to less than infinity terms.

And? You seem to be complaining that on a site full of non-physicists, people don’t act like physicists. Besides, ontologies of QM are philosophical, not scientific, and hardly limited to laypeople.

Re: Lost Causes of Theoretical Physics (2003)

#25

Earlier quoted context omitted.

From other sections it seems clear that the author is a devout adherent of The Copenhagen Interpretation, aka objective wavefunction collapse; this is a close relative of the baseline non-Interpretation “Shut Up And Calculate.” People like that are generally utterly unmoved by anything short of a rigorous mathematical formulation, which works for them in QM where “rigorous mathematical formulation” is pretty much all…

I am not a physicist, but this seems backwards to me. If anything, it is the Copenhagen interpretation that comes with the largest amount of extra-mathematical baggage while many-worlds interpretation came out of effort to add the least amount of additional assumptions on top of the math.

The price that MWI pays for this minimalism is that it loses some contact with reality, i.e. physical experiments. Basic physical observations like "some measurements are non-deterministic" are quite difficult to explain in the MWI. Reality is inconvenient.

Re: Lost Causes of Theoretical Physics (2003)

#26

Earlier quoted context omitted.

His argument is that it's useless as a research topic because you cannot perform experiments about it. You can still believe it if you like, but its slightly less useful than trying to convince everyone to replace pi with tau..

QM is a mathematical model. Many worlds is an intuition to understand that model. There is a pedagogical question on if many worlds is a useful mental model to have. There is also a philosophical question of if many worlds better captures the essence of the model relative to Copenhagen. We can also flip it around. Why should we think of QM in terms of the Copenhagen when it makes to testable predictions.

Wouldn't you consider the Born rule to be a testable prediction (though in an admittedly weak sense of simply being postulated)?

If the Born rule were found to be violated, it would invalidate Copenhagen but not MWI, which IMO means Copenhagen is more falsifiable.

Re: Lost Causes of Theoretical Physics (2003)

#27
post #2

The many worlds interpretation is just that, and INTERPRETATION, not a predictive theory. The article seems really upset by that, but is it any reason to label it a lost cause? I guess you can’t really study it or preform experiments on it but that shouldn’t be any suprise for any interpretation of quantum mechanics. I might be missing something here...

> The many worlds interpretation is just that, and INTERPRETATION, not a predictive theory.

How does the many worlds interpretation INTERPRET the Born rule? Shouldn't that be a key feature of any QM interpretation?

Re: Lost Causes of Theoretical Physics (2003)

#28

Earlier quoted context omitted.

These discussions are always composed of people who don't know very much laying down philosophical assertions (that they very rarely realize are philosophical), and innocent bystanders posing reasonable what-if questions that really can't be answered with (present) empirical knowledge. Like politics, the content of what is said is dominated by the dynamics of the discussion, with English skills "winning" arguments mo…

These discussions are always composed of people who don't know very much laying down philosophical assertions (that they very rarely realize are philosophical) That seems needlessly judgmental. ...and innocent bystanders posing reasonable what-if questions... They’re rarely reasonable. You get a lot of questions which are philosophical in nature, but which people believe are scientific. “What is time like for a photo…

">That seems needlessly judgmental.

There's a practical takeaway from my statement - that physics explanations should always be taken with lots of salt (even ones written by physicists, who are prone to throwing out the star baby with the mathwater.) Judgmental, maybe, but not needlessly.

>They’re rarely reasonable.

They're reasonable because they have an answer: it's the one you suggested. People would accept your "north of the north pole" response in a universe where there was no false but well-written alternative. The problem is, outside of very limited audiences and forums mixtures of misunderstood philosophy and science are a lot easier to come by than the truth. (This extends to science journalism, and even to the rare bad press release.)

By the way, if you want to tell people that they're asking the wrong question in a way that keeps them happy, try responding with the knowledge that would make them realize their question was misguided. For example, whenever anything involving moving at the speed of light comes up, my go-to responses are:

- Discussing hyperbolic geometry until it's clear that what looked like a question about pi/4 was actually a question about infinity.

- Mention that most of the equations have a singularity there, and then give some more down-to-earth examples of equations that have singularities.

- Say that we've never seen it happen, and as a result the physics we write down doesn't include it. (This is sometimes the best answer, even though it's the least satisfying to give or hear. If science fiction effect X happened, we'd have to account for it, no matter how badly it would break everything.)

>And?

Physics is all about approximations with known error bounds. (That is, X plus or minus Y, and the equivalent of that but with equations instead of numbers.) That's what's going on at the boundary between physics and metaphysics, and it's the ultimate answer to most "unanswerable" questions.

Re: Lost Causes of Theoretical Physics (2003)

#29
There has been an enormous resurrection of the analytic bootstrap. Grep, for example, https://www.icts.res.in/program/NUMSTRINGS2018/talks for bootstrap. The difference is the realization that the bootstrap equations can be solved numerically and can be thought of as a way to test whether certain conformal theories exist at all, rather than as a way to take you from hardly-any-input-at-all to a complete description of the theory.

Re: Lost Causes of Theoretical Physics (2003)

#30
post #2

The many worlds interpretation is just that, and INTERPRETATION, not a predictive theory. The article seems really upset by that, but is it any reason to label it a lost cause? I guess you can’t really study it or preform experiments on it but that shouldn’t be any suprise for any interpretation of quantum mechanics. I might be missing something here...

If a theory isn't predictive, it isn't falsifiable. If it isn't falsifiable, then the theory isn't truly scientific. This is a major issue/concern in advanced theoretical physics. Is it really physics if you can't experiment or is it just mathematics? The foundation of science is falsiability within the scientific method. It's the core tenet.

But what if, after spending more time working on and thinking about it, someone does find a way to make predictions based on it or on an extension/modification of it?

If that's a possibility (I can't say, I'm not a physicist) then I'd be a mistake to discard it on the basis that it's just not predictive now.

Post reply on HN