Not intending to mock anyone and I don't know nearly enough physics to have a credible opinion either way. Thanks for your explanation.
Don’t worry, I didn’t think you were :) you’re welcome!
Readit Newszachf commented on Fundamental physics is dying? [video] youtube.com/watch?v=cBIvS... · Posted by u/nabla9
zachf commented on Fundamental physics is dying? [video] youtube.com/watch?v=cBIvS... · Posted by u/nabla9
No you couldn’t. And it’s been 80 years now!!
All of those things you name came directly out of attempts to create testable hypotheses from experimental observations, and all of them were tested as soon as anyone could build an experiment apparatus or gather the data to do it. Which didn’t take that long considering the extreme engineering difficulties in actually building the apparatus for some of them.
String theory has avoided testability it’s entire existence, nearly a century now, and no one that I’ve seen is even attempting to make an experiment to try to test it - because at this point it’s clear that no one on the theory side is interested in making a testable hypothesis. That isn’t luck, that’s talent and hard work.
It’s one of the most absurd grifts I’ve personally seen play out so far.
80 years? I would date its birth as 1968-9 (Veneziano), it’s hard for me to imagine calling prior work than that as “string theory”. But never mind that—the bigger problem with this (quite common) argument is that everything about quantum gravity, not just string theory, has avoided testability because our other theories are too good, and because we’re limited to doing experiments on Earth with equipment built on human scales with human budgets, and that’s just not where quantum gravity would naturally make itself known. So really this argument just suggests we shouldn’t study quantum gravity at all. Maybe that’s your actual opinion—it’s a waste of time if we can’t access the Planck scale, we should table it all and sit on our hands until we can. But string theory really is quite interesting to study, stuff like AdS/CFT is just really surprising and magical when you get what it’s about, and it would be a real pity to not pay the meager salaries of theoretical physics just because of pessimism. String theory is so far from fully understood! It’s actually…really hard!
BtW I think you got this 80 years number from looking at the earliest date on the Wikipedia page. You might want to read it more carefully. Not everything leading up to string theory is string theory.
zachf commented on Fundamental physics is dying? [video] youtube.com/watch?v=cBIvS... · Posted by u/nabla9
It predicted supersymmetry, which has been experimentally disproved.
The kind of supersymmetry you’re referring to (global spacetime supersymmetry) is not required by string theory; this is a common misconception. Looking for super partners in a collider is actually only telling you about global supersymmetry, which unlike local supersymmetry is not a universal feature of string theory at low energy, in fact the opposite, it is probably non-generic. It so happens that a class of appealingly simple vacua do have this property, which led to some inappropriate optimism among string theorists that has entirely abated with more experiments. Unfortunately this has been widely misunderstood to rule out the whole enterprise of string theory, which is unreasonable for the reason stated above, it is much more likely to not see SUSY below the Planck scale. [0] (Unless you just like to mock string theorists for hoping that the universe would be kind to them.)
Also global supersymmetry has not been experimentally disproved (how would you do this, even?) but it is true that current or even near-term experiments are not nearly sensitive enough to get close enough to answering this definitively, which is obviously upsetting.
[0] https://ncatlab.org/nlab/show/string+theory+FAQ#DoesSTPredic...
By 'America', do you mean the landmass controlled by some administrative entity that calls itself the US government, or do you mean some group of people?
> It’s a pity some people can’t think of politics as possibly more than zero sum. A good policy should actually lift all boats.
That there are such policies doesn't mean one can ignore the zero-sum ones, or the downright hostile ones, as the Uyghurs could tell you.
I mean the people and land area governed by the United States Constitution, a document that provides explicit protections against the kind of ethnostate policies you are so worried about.
And that's why the US is such a terrible place right now; more than 150 million people voted in the 2020 presidential election, a stark decline from the days of 1776 when the entire country had about 2.5 million people in total, many of whom were ineligible to vote, as God intended.
Right, of course, extending the franchise of voting to women and non-white, non-landholding men devalued the franchise, lol.
You're asking the wrong question. Conflicts arise not just from differing views on general questions about governance, but from competing groups each fighting for their own self-interest. "Agreeing with views", for one fleeting moment in time, means little for the long-term cohesion of a country, or the prosperity and sovereignty of a people.
See for example Kashmir [1] - whether the coming immigrants agree with the natives on e.g. the tax rate, term limits for politicians, or environmental laws, don't even come up as concerns. Nor did Czechoslovakia split over gay marriage, or Yugoslavia over differing views on abortion.
This focus on "views" to the exclusion of all else is a purely American phenomenon, and a recent one at that - only six decades old.
[1] https://www.washingtonpost.com/world/2019/08/08/kashmirs-new...
America has a long history of successful integration of racial groups. Once upon a time, the Irish were extremely unwelcome in Boston, simply for being Catholics. Dozens of examples like this abound in American history. America is stronger than the countries you’ve listed because of the melting pot, not in spite of it. That’s because the selfishness you alluded to is contrary to a core American value: that a person is not defined by their ancestors’ virtues or sins, but by the content of their character. All the immigrants I know are fierce defenders of this principle.
It’s a pity some people can’t think of politics as possibly more than zero sum. A good policy should actually lift all boats. Middle America simply will not survive without more people and more economic activity, period. If native born children choose to move to the coasts, and no immigrants fill in the gaps, you’re not going to have the long-term prosperity you’re imagining.
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Unlike marriage, voting is a zero-sum game.
So you would support naturalization of immigrants who agree with your views, then?
zachf commented on Physics is unreasonably good at creating new math nautil.us/why-physics-is-... · Posted by u/Brajeshwar
> Because that would obviously be an untenable position, and the whole point is that quantum gravity AdS (basically) is CFT (it’s an equality! It goes both ways), just in different variables. You can actually study non-gravitational physics with it, using a gravitational language. That’s awesome stuff!
Which makes it an interesting mathematical construct, but in what way does that actually help physics? I included a link to one critique of Ads/CFT in another post, and others have critiqued its applications to QCD and other alleged "successes" because the important properties to do meaningful work in those domains just aren't there.
The versions of this correspondence that are easy to work with also depend on supersymmetry, for which every experiment has failed to find any evidence in the expected regimes. In the old days we'd call this "refuted", but these days it just means reworking it (adding a new epicycle?) to get "new bounds".
Ads/CFT is a mildly interesting mathematical derivation, but its actual utility for physics is questionable.
> He gets funding from string grants. Nobody is angry about that. Anybody can do this.
Maybe anybody can do this now, and I think that's because, as I said, string theory's stranglehold has weakened because of well-motivated criticisms over the past 15 years or so. The evidence of string theory's former dominance is right in what you said: string theory grants.
> but the entire community has always supported and listened.
I think some physicists are open minded, and some are not. You need only look at how physicists who work MOND are treated to see how not open minded some physicists are. MOND is not a final theory, but it and the people who work on it are scorned despite it's unreasonably good predictive success over the last 40 years.
Okay, I’ll tell you about my own research. From studying the way that geometric surfaces work in AdS, we conjectured a relationship between the stress tensor of QFT and entanglement entropy. This is because those quantities translate into geometrical analogs in the quantum gravity theory. We then proved this same relationship holds in some simple field theories and then other physicists proved it in the general case. So we learned something about non gravitational physics from gravitational physics. We study a specific, tractable case (AdS, mapping onto CFT) and then use it to learn about the general case (every QFT). That’s how physics works! You study the spherical cows. Eventually you learn something universal. All this is because I started with an open mind, and pursued the full consequences of AdS/CFT.
Your complaint about supersymmetry is like saying that Newtonian physics can’t work because objects are not rigid, continuous solid bodies. And yeah, that’s true, there are none of those in nature. Does that mean Newtonian physics is not useful? NO! It’s a model that’s useful. Is it wrong? Kinda. And the models that have unbroken SUSY are “wrong” too, in the same way. But the point is—-it’s obviously useful!
Please try to be open minded about string theory, especially if you wish to lecture about small-mindedness around MOND. Diminishing the real accomplishments of physicists doesn’t make other fields more likely to get funded—it makes it more likely that bureaucrats defund everyone. That’s the lesson of the SSC.