I think Relativity is a pretty clear couter-example to the idea that the discovery of new physical laws will always expand the limits of engineering. Whereas under Newtonian physics, you could make objects go arbitrarily fast by pumping in quadratically more energy, there is now an absolute speed limit and you need asymptotically more energy just to get close to it. You didn’t need convoluted, highly speculative schemes like Alcubierre drives to go FTL under Newtonian physics—and that’s putting it mildly. The requirement of negative matter makes it more like wishful thinking, like saying “we have found a way to transmute lead into gold, now we just need to find some Philosopher’s stones”. And no, quantum tunneling most certainly does not allow for FTL.
Also, the idea that “mass and energy interconvert” is a terrible interpretation of special relativity, not just in a smart-ass nit-picky way. It has mislead countless students and teachers alike to think that E=mc2 somehow unlocked nuclear technology. Mass very much is conserved under Relativity, and it certainly doesn’t discriminate between chemical and nuclear reactions. The way in which Relativity interacts with nuclear physics is primarily by making its inventor very famous who then prompted the Manhattan Project by co-authoring a letter to Roosevelt.
I only thought of this after hitting enter, but in one sense, maybe our theoretical limits progress faster than our practical engineering ones. Even though each new theory may take 50 years, each new theory could significantly expand the possibilities-space of things we can in theory do and the configurations we could theoretically get the universe to enter. Engineering progress on the set of things we can easily and reliably do expands every year, but it also expands much less than the expansion caused by theoretical jumps. More specifically, if I mark two frontiers in possibilities-space, a practical fronteir for current engineering prowess and one for known theoretical limit, the theoretical frontier may be expanding faster than the practical frontier. Naively extrapolating this we should assume the practical frontier will never hit the theoretical one. Which seems like an acceptable belief to me, acknowledging high unknown unknows.
I think this line of thinking is another instance of LessWrong being too infatuated with trends and trendlines than specifics. Did, for instance, thermodynamics expand or shrink the possibility space? It thwarted the dream of perpetual motion machines, but it also gave us efficient steam and combustion engines. Electrodynamics gave us telecommunication, but its corollary—special relativity—thwarted the dream of an interconnected galactic civilization.
Different theoretical discoveries also had vastly different usefulness in practice. Quantum physics paved the way for the entire semiconductor industry, whereas general relativity, discovered around the same time period, hasn’t had any practical applications thus far (no, I will not accept GPS as an example, I expect engineers to not just give up a billion dollar project for what can be fixed with a constant factor; more likely in a timeline where Einstein never existed, GPS would have prompted the discovery of general relativity and not the other way round). I could imagine QCD leading to a possibility space based on nuclear matter as vast as our atom-based world. But then again, it might not. These things depend on specifics and can’t be read from extrapolated trends.
The fact that we were discovering new paradigm-shifting physical laws on a 50-year timescale in the past (not even sure about that—what ground-breaking theoretical discovery has happened between 1970 and now? The Standard Model?) does not mean it will continue indefinitely, or even in the near term. For a discovery to be made, there must first exist something to be discovered, and even then it could turn out to be extraordinarily difficult. I could well imagine a long drought after the completion of the Standard model due to the insane energies required to probe quantum gravity.
I am however hopeful in one aspect: the fact that our universe started out in a low-entropy state seems like a deep mystery with far-reaching implications for the ultimate fate of the universe. But there is still a huge inferential distance from “there is a gap in our understanding” to “we’ll be able to stop the heat death of the universe”. From falsehood, anything follows. If you assume the laws of physics don’t hold, you can predict anything and therefore nothing.
I think Relativity is a pretty clear couter-example to the idea that the discovery of new physical laws will always expand the limits of engineering. Whereas under Newtonian physics, you could make objects go arbitrarily fast by pumping in quadratically more energy, there is now an absolute speed limit and you need asymptotically more energy just to get close to it. You didn’t need convoluted, highly speculative schemes like Alcubierre drives to go FTL under Newtonian physics—and that’s putting it mildly. The requirement of negative matter makes it more like wishful thinking, like saying “we have found a way to transmute lead into gold, now we just need to find some Philosopher’s stones”. And no, quantum tunneling most certainly does not allow for FTL.
Also, the idea that “mass and energy interconvert” is a terrible interpretation of special relativity, not just in a smart-ass nit-picky way. It has mislead countless students and teachers alike to think that E=mc2 somehow unlocked nuclear technology. Mass very much is conserved under Relativity, and it certainly doesn’t discriminate between chemical and nuclear reactions. The way in which Relativity interacts with nuclear physics is primarily by making its inventor very famous who then prompted the Manhattan Project by co-authoring a letter to Roosevelt.
I think this line of thinking is another instance of LessWrong being too infatuated with trends and trendlines than specifics. Did, for instance, thermodynamics expand or shrink the possibility space? It thwarted the dream of perpetual motion machines, but it also gave us efficient steam and combustion engines. Electrodynamics gave us telecommunication, but its corollary—special relativity—thwarted the dream of an interconnected galactic civilization.
Different theoretical discoveries also had vastly different usefulness in practice. Quantum physics paved the way for the entire semiconductor industry, whereas general relativity, discovered around the same time period, hasn’t had any practical applications thus far (no, I will not accept GPS as an example, I expect engineers to not just give up a billion dollar project for what can be fixed with a constant factor; more likely in a timeline where Einstein never existed, GPS would have prompted the discovery of general relativity and not the other way round). I could imagine QCD leading to a possibility space based on nuclear matter as vast as our atom-based world. But then again, it might not. These things depend on specifics and can’t be read from extrapolated trends.
The fact that we were discovering new paradigm-shifting physical laws on a 50-year timescale in the past (not even sure about that—what ground-breaking theoretical discovery has happened between 1970 and now? The Standard Model?) does not mean it will continue indefinitely, or even in the near term. For a discovery to be made, there must first exist something to be discovered, and even then it could turn out to be extraordinarily difficult. I could well imagine a long drought after the completion of the Standard model due to the insane energies required to probe quantum gravity.
I am however hopeful in one aspect: the fact that our universe started out in a low-entropy state seems like a deep mystery with far-reaching implications for the ultimate fate of the universe. But there is still a huge inferential distance from “there is a gap in our understanding” to “we’ll be able to stop the heat death of the universe”. From falsehood, anything follows. If you assume the laws of physics don’t hold, you can predict anything and therefore nothing.
I’d give it a 60% chance that quantum mechanics was the last fundamental physics discovery that has any practical implications.