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There Are No Laws of Physics, There’s Only the Landscape

89 points by digital55 8y ago

tw1010 8y ago
There's a quote, in I believe one of Greg Egans books, about the idea that the probable end state of physics will be just a bunch of isomorphic theories, which I wish I could find right now.
- westoncb 8y ago
  For understanding why that might be, I find this to be an elegant little example: take a pattern of black and white stripes; is it white with black stripes, or is it black with white stripes? The two formulations are identical in consequence of what they describe, even though they frame things inversely. (Of course this is just a metaphor to hint toward something in the nature of language, and is not really a deep scenario if you dig into it.) It seems likely that the descriptions we formulate in physical theories work because they create a pattern which is isomorphic to patterns we extract in physical measurements—but there's something in the nature of the universe and/or language so that there tends to be many ways to create some linguistic thing which produces exactly the same pattern.
  - whatshisface 8y ago
    That's actually one of the main ideas of positivism: that if two theories lead to the same physical predictions, they are the same theory. When positivism is presented as "every true thing is empirically knowable" it sounds kind of shaky, but if you instead go for, "you can't tell the difference between two internally-consistent claims unless you compare them with the world," then it sounds a lot more likely to be true.
    - goatlover 8y ago
      > "you can't tell the difference between two internally-consistent claims unless you compare them with the world," then it sounds a lot more likely to be true. But only if it's the case that we end up with more than one theory which explains the phenomena equally well. That doesn't seem to be what ends up happening. We don't have an equivalent to GR, QM, Evolution, or any other well established, large scale theory. Positivism sounds closer to math than it does science. And that's because nature is a certain way, which means you probably can't have equivalent theories at sufficiently granular levels.
      - westoncb 8y ago
        My understanding is that there are multiple precisely equivalent formulations of classical mechanics (Newtonian mechanics being one of them, but then there's e.g. Lagrangian mechanics[0] and other more exotic things). Perhaps that doesn't cross your threshold for 'sufficient granularity'—but it took quite a bit of time to find the alternate formulations in classical mechanics (after Newton I mean), so just because we don't yet have them for certain more modern theories doesn't mean they aren't forthcoming. Also, I'm pretty sure there are at least very nearly equivalent formulations of QM, e.g. the de broglie pilot wave stuff (often termed as an alternate 'interpretation', but my understanding is that the differences extend even to the level of mathematical formulation, and are not just some detached reflections on the 'meaning' of the theory or whatever. [0] https://en.wikipedia.org/wiki/Lagrangian_mechanics https://en.wikipedia.org/wiki/Lagrangian_mechanics
        whatshisface 8y ago
        >so just because we don't yet have them I think the strongest argument for positivism is that you can generate arbitrarily many trivial "different but the predictions are the same" theories from any parent theory just by doing algebra. You can also generate arbitrarily many "the predictions are slightly different but our present experiments can't resolve it" theories from a parent theory by littering it with new, small constants and tiny interactions. Occam's razor will lead you astray about that, too: most of modern physics was at one time a small constant or a tiny interaction.
      - deleted 8y ago
        [deleted]
- Florin_Andrei 8y ago
  Well, Egan was just repeating things that others were saying before. This is M-theory basically, and Stephen Hawking, among others, has mentioned it as a possible "theory of everything".
- gowld 8y ago
  What else could be? The universe is outside our language(s) to describe it, so there's no reason to have only one isomorphic theory. The only alternative is to have two (or more) incomplete theories, but then combining them makes one "unified" theory. Even in pure math, outside of physics, the same applies. The only other possible alternative would be , what, one tiny theory that is essentially simple and minimal in every possible way, yet somehow models everything, in the spirit of ANKOS?
stcredzero 8y ago
The Map is Not the Territory! https://wiki.lesswrong.com/wiki/The_map_is_not_the_territory https://wiki.lesswrong.com/wiki/The_map_is_not_the_territory Another piece of widespread ignorance I've seen here on HN, is the treatment of conservation laws as if they're baked into the fabric of reality. This results in programmers making philosophical/cosmological arguments in ignorance. As far as we know, conservation laws are not baked into reality. Instead, they are very useful analysis tools which can take advantage of symmetries. (Or near-symmetries.) Any given conservation law can disappear if a given symmetry doesn't apply, but Noether's Theorem still remains. https://www.youtube.com/watch?v=04ERSb06dOg https://www.youtube.com/watch?v=04ERSb06dOg If you want to see an example of how social media "bubbles" can impede the dissemination of knowledge, note that I've actually been flagged on HN for trying to explain this, apparently because someone misread this as advocacy for perpetual motion machines. It is not! (Also, because I used <facepalm> -- but when you're wrong, you're wrong, and when you're wrong and you think it's clever, it feels worse.) (That title, "The Map is Not the Territory" acts as a pointer to a series of literary references. https://en.wikipedia.org/wiki/The_Map_and_the_Territory https://en.wikipedia.org/wiki/The_Map_and_the_Territory )
- thanatropism 8y ago
  It's hard to make time symmetry (and thus conservation of energy) "disappear", though.
  - myWindoonn 8y ago
    There probably isn't a plain time symmetry, but maybe there is CPT symmetry. Lucky 10000: https://en.wikipedia.org/wiki/CPT_symmetry https://en.wikipedia.org/wiki/CPT_symmetry
    - wnoise 8y ago
      He's talking about time-translation symmetry, not time-reversal symmetry, which is the T in CPT.
      - 8y ago
ghkbrew 8y ago
The article says that one of the attractive qualities if string theory is that it has no free parameters. But then says that the particles a forces of the standard model are determined by the number and size of extra dimensions. Those sound an awful lot like free parameters. Can someone with more than a passing familiarity with the field explain?
- AnimalMuppet 8y ago
  One might say, given the fundamental particles, there is a unique set of number and sizes of extra dimensions. That is, there are no free parameters if it's going to fit this universe. The same thing happened in relativity. c is not a free parameter; it has to be the speed of light in this universe. You could argue that it could have some other value and relativity would still work correctly. That might be true in some sense, but it wouldn't work as a correct description of this universe. Note well: I do not have more than a passing familiarity with the field. What I am saying here may not be a correct description of the actual state of string theory. Also note that I find "there are no free parameters" and "but it gives rise to this landscape, where there's nothing nailed down in terms of actual physics" to be somewhat difficult to reconcile.
- auntienomen 8y ago
  Normally in a physical theory, you have some equations describing the dynamics and you go looking for solutions to these equations. The dynamical equations may have some parameters (such as the constant G in Newtonian/Einsteinian gravity), and then there are usually additional parameters required to describe the solutions (such as the mass M of the gravitational field source). String theory has the unusual property that its dynamical equations don't have free parameters. The dynamics is apparently unique. But there are many many solutions to these equations, and so there's a huge space of parameters from that. In particular, if you go looking for ways of embedding the Standard Model in string theory, all of its dynamical parameters (like the electron mass and Newton's constant) are realized as solution parameters.
  - kolpa 8y ago
    Can I make Newtonian mechanics into a dyanically 0-free-parameter theory by stating that F == gMm/r^2 , where g is a solution parameter ("the gravity of the universal landscape" ?
FailMore 8y ago
This feels off to me. Einstein’s process did not come from the mathematics, but from an idea of what was happening. This enabled a great number of odd predictions which were verified (the Sun would bend the visible pathway of a star, there would be gravitational waves, etc...). String Theory feels like a theory which is starting at the wrong place. Not an idea of what process is happening and then seeing if the results fit, but an attempt to connect all the results into a theory. Pas bien por moi!
- WaxProlix 8y ago
  > String Theory feels like a theory which is starting at the wrong place. Not an idea of what process is happening and then seeing if the results fit, but an attempt to connect all the results into a theory. Are you saying that it doesn't make any predictions (and is therefore unfalsifiable)?
  - maxxxxx 8y ago
    As far as I know that's the case. At least we can't verify any predictions with the energies we can reach right now and long into the future.
    - manyoso 8y ago
      There are no predictions even in principle. It has nothing to do with the predictions being at a sufficiently high enough energy level that we can't verify...
      - maxxxxx 8y ago
        I remember reading something about a galaxy sized particle accelerator that could detect the extra dimensions of string theory.
  - AnimalMuppet 8y ago
    Well, let's say that string theory has far fewer testable predictions per unit of theorem[1] than other physics theories have. [1] However measured (cubic meter of paper, maybe?)
monktastic1 8y ago
I'm reminded of this beautiful quote from Chris Fuchs, regarding his advisor, the great John Archibald Wheeler: > [Wheeler] would say things like, “In the end, the only law is that there is no law.” There’s no ultimate law of physics. All the laws of physics are mutable and that mutability itself is a principle of physics. He’d say, there’s no law of physics that hasn't been transcended. I saw this, and I remembered my joke about how the laws of physics must be wrong, and I was immensely attracted to this idea that maybe ultimately there actually are no laws of physics. What there is in place of laws, I didn't know. But if the laws weren't 100 percent trustworthy, maybe there was a back door to the stars.
- maskedSlacker 8y ago
  This sounds like semantic befuddlement (though, not on Wheeler's part; he was just engaging in wordplay). Physical laws are not 'laws' in the sense that nature is required to abide by them. They are simply features of natural behavior that have been so overwhelmingly observed that we treat them as axioms. An example of this is the 'law' of conservation of mass. Strictly speaking, nature does not follow this law. Nuclear reactions and subatomic interactions do not conserve mass. They conserve other quantities, but not mass in and of itself. The idea that there is no ultimate law of physics is not novel or interesting. It's obvious on its face, unless you do not properly understand what 'law' means in the context of physics.
  - goatlover 8y ago
    Law of physics implies a casual relationship in nature. Saying there are no laws of physics is saying nature is acausal. B always follows A for no reason other than it just happens to do so in our universe. This is the Humean view of causation, which is constant conjunction instead of there being a reason that A results in B. The plus side is that you don't have to deal with causality, which is a tricky concept. Hume persuasively argued that causality is neither empirical nor a result of logic. The downside is that all necessity is totally arbitrary. It just so happens ... As such, there is no reason for anything we observe. Just descriptions.
ifdefdebug 8y ago
For those like me who are not too happy with this kind of "science" (for one, the title is worded in a way that makes this highly controversial view of reality sound like state of art in physics), "Not Even Wrong" [1] by Peter Woit is a great read for multiverse skepticism (mostly centered on "string multiverse", not quantum "many worlds"). [1] https://www.math.columbia.edu/~woit/wordpress/ https://www.math.columbia.edu/~woit/wordpress/
- kbutler 8y ago
  All models are wrong, but some are useful. -- George Box And some are not useful except as a mental exercise. Maybe they will become useful at some point, maybe not.
lossolo 8y ago
There's a great quote from the X-Files by Scully on this topic. "Nothing happens in contradiction to nature, only in contradiction to what we know of it. And that's a place to start. That's where the hope is."
johnvega 8y ago
This is fake news. Jump off a 10 story building balcony into a cement and see if "There Are No Laws of Physics" or the title can be changed.
danbruc 8y ago
Off-topic question that seems to trivial to take to Stack Exchange but I am struggling to find an answer to, maybe a physicist comes by and can provide an answer or relevant reference. Let's take a spin 1/2 in the superposition state |0> + |1> ignoring normalization and then add the rest of the universe including a measuring device, an observer, and all the other bits and pieces of the environment. This state then undergoes unitary time evolution past the point where we measured the spin and the observer had a look at the measuring device. It now seems to me that if the final state is a definite |0> or a definite |1>, then this measurement outcome must already have been present in the initial state, not necessarily as hidden variables of the spin but somewhere, for example in the micro states of the measuring device. If the final state could indeed be either |0> or |1> independent of the initial state, time evolution would not be unitary, it would not even be a function of the initial state. The only other option seems to be that the final state is still a superposition and we have to reach for something like the multiverse interpretation to reconcile the fact that we indeed observe a definite final state. So what is the correct or at least common way to think about this? Time evolution is only approximately or sometimes unitary? The measurement outcome is, similar to decoherence, determined by the environment? The final state is still a superposition? Non of those seems to be a particularly attractive choice. Or did I somewhere make a stupid mistake?
- maskedSlacker 8y ago
  It's been a long time since my QM course, but, assuming by unitary you mean deterministic, then the answer is that time evolution of a particle's state is NOT deterministic. It is probabilistic. For large collections of particles, the probabilities come to overwhelmingly favor a single average state, but the state of any single particle remains non-deterministic. This is in contrast to, for example, classical statistical mechanics where individual particles are considered to behave deterministically, but we simply lack the ability to measure their behavior. In (the Copenhagen interpretation of) QM there is no underlying determinism at all. You might not like this idea (it's certainly non-intuitive), but decades of experiments have shown that the alternatives are all, most likely, wrong.
  - danbruc 8y ago
tabtab 8y ago
Is it just me, or does string theory seem like epicycles all over again: if you throw enough center-intersecting circles into the engine, it can emulate just about any observed movement of objects in the sky; a sort of "circular regression" in the same way that piling up polynomials gives us Polynomial Regression. String theory is like "dimensional regression". Regression is a powerful tool, but is NOT designed to directly "explain" phenomena, only emulate them. Newton et. al. came along and gave us a much simpler model of gravity and the solar system such that we could toss out the messy nested circle models. (We still can't say that Newton's model is fully "right", but it's certainly simpler.)
- ivankolev 8y ago
  I thought it was actually Kepler that figured it out...
- jcranmer 8y ago
  Well, string theory is kind of the anti-epicycle. The epicycles in Ptolemaic astronomy were added to make the math conform to reality, but people didn't believe that the planets actually moved in epicyclic motion. Superstring theory started from the opposite standpoint: the Standard Model is math that works out, but the theory is messy, so superstring theory sought to make an "elegant" theory that checked out with the math... and ended up with a theory that is so general it can't really be disproven. The end result is the same, but the paths to get there are completely different.
  - whatshisface 8y ago
    String theory was originally exciting because it had a graviton that worked, and to my knowledge it is really the only theory that contains both the standard model and gravity. LQG is not yet at the point of reproducing 3+1 space as far as I know. So, here's my proposal: saying that the earth orbits the sun in a universe where QED also is true isn't proof of string theory, but it does falsify the standard model and so far to my knowledge most of string competition.
    - 8y ago
skissane 8y ago
Multiverse theories like string landscape, eternal inflation, or many-worlds generally have this property: Almost anything that possibly could happen will happen in some universe. But, it is said, that some universes are more frequent than others. From local observations we infer the global laws of physics, which tell us the relative distribution of different types of universes. But, surely there will be some "deceptive" universes, in which (purely by chance) observers are always mislead as to what the actual laws of physics are. Experimental error always goes in the same direction, such that the true laws of physics are never known, and those observers rationally believe in false laws of physics instead. Now, an observer in such a universe will rationally infer a given probability distribution of universes based on their local observations, but the distribution they infer will be completely wrong. My question is: how do we know we are not in such a universe? To say such universes must be exceedingly rare (even though existent) is sort of circular, because our conclusion they are rare is based on our idea of the global probability distribution, but in order to validly make the inference from local observation to global distribution we have to assume we are not in such a universe. But, if we can't know we are not in such a universe, then we can't know that some universes are "more likely" than others, which is a central claim of these theories, and what distinguishes them from David Lewis' modal realism. This is why I think all such "multiverse" theories should be rejected.
superqd 8y ago
This is the one major reason I lost most of my desire to continue grad school (I was studying astrophysics). I chose physics specifically because I wanted to understand the universe. The way I thought of it was that I wanted to lift the hood of reality and see how things "really" worked. As a kid, I'd read a number of books on science and had heard of a quest for a Theory of Everything. I'd decided this was a quest I wanted to go on. I thought of it as the most worthy singular hidden treasure and I was willing to devote my life to digging for it. But over the course of my undergrad, and hours debating with friends, and reading even more, I started to get an uneasy feeling. I decided to go to grad school, partly, because I still held on to the belief that there really was treasure at the end of that rainbow, and that we really could, if we were clever enough, "figure out" how things "really" worked. But, in grad school, it just continued to dawn on me how impossible it was for there to be only One True Theory. One way I thought about it was to regard physics as a program. Even if there were separate theories for different scales, or domains, it didn't matter, you could still regard the whole knowledge base as a single program and the scale and domain, along with physical observables, as inputs to the Physics Program. The output would be predictions for the state of the universe (or some subset, it didn't matter) at some later time, i.e., it would predict later observables' values. The thing was, I had a hard time finding any logical justification for why there had to be only one program that could take in the known inputs and produce the known outputs. That is, there was no way to logically prove that there could not be multiple equivalent programs that could produce the same output given the same input. I.e., there was no way to logically justify the notion that there could only be One True Physics. That is, the treasure I believed I'd be digging for, didn't not exist, it was just that there was more than one treasure, and anyone could find their own. This thought diminished some of the romance, so to speak, of the Quest for Truth, so I lost interest, for a time. Enough to stop taking grad school classes and just start working (coding). Maybe one day I'll create a program of my own.
- lioeters 8y ago
  Your comment stayed in my mind, about the (maybe futile) quest for the "one true theory". Today I was reading an article [1], and a passage reminded me of what you were talking about: Schrödinger’s theory proved easier to use than Heisenberg’s, in part because it is more intuitive. Furthermore, first Schrödinger and then Paul Dirac proved that the two theories are equivalent. In physics any two theories that make precisely the same observable predictions are observably equivalent. And one of the predominant philosophical views of the age — logical positivism — held that any two observably equivalent theories are really one and the same theory. ... Einstein demanded a clear and comprehensible account of what is going on in the physical world — at all scales — in space and time. Bohr thought that the key to quantum mechanics was the realization that no such thing could be had. [1] http://bostonreview.net/science-nature-philosophy-religion/tim-maudlin-defeat-reason http://bostonreview.net/science-nature-philosophy-religion/t...
yedawg 8y ago
Physical theories imply physical laws and consistent variables which require consistent math and hard scientific research; There is no escaping that. To say that physics is like a "landscape" is like comparing scribble of a stick man to a Picasso. There is a lot we don't know about the universe, I think its time for writers and physicists to get on board with that and analyze the shit out of their vague and opaque understandings before hitting the enter key.
warmfuzzykitten 8y ago
But... http://bostonreview.net/science-nature-philosophy-religion/tim-maudlin-defeat-reason http://bostonreview.net/science-nature-philosophy-religion/t...

89 points by digital55 8y ago

There's a quote, in I believe one of Greg Egans books, about the idea that the probable end state of physics will be just a bunch of isomorphic theories, which I wish I could find right now.

westoncb 8y ago
For understanding why that might be, I find this to be an elegant little example: take a pattern of black and white stripes; is it white with black stripes, or is it black with white stripes? The two formulations are identical in consequence of what they describe, even though they frame things inversely. (Of course this is just a metaphor to hint toward something in the nature of language, and is not really a deep scenario if you dig into it.) It seems likely that the descriptions we formulate in physical theories work because they create a pattern which is isomorphic to patterns we extract in physical measurements—but there's something in the nature of the universe and/or language so that there tends to be many ways to create some linguistic thing which produces exactly the same pattern.
- whatshisface 8y ago
  That's actually one of the main ideas of positivism: that if two theories lead to the same physical predictions, they are the same theory. When positivism is presented as "every true thing is empirically knowable" it sounds kind of shaky, but if you instead go for, "you can't tell the difference between two internally-consistent claims unless you compare them with the world," then it sounds a lot more likely to be true.
  - goatlover 8y ago
    > "you can't tell the difference between two internally-consistent claims unless you compare them with the world," then it sounds a lot more likely to be true. But only if it's the case that we end up with more than one theory which explains the phenomena equally well. That doesn't seem to be what ends up happening. We don't have an equivalent to GR, QM, Evolution, or any other well established, large scale theory. Positivism sounds closer to math than it does science. And that's because nature is a certain way, which means you probably can't have equivalent theories at sufficiently granular levels.
    - westoncb 8y ago
      My understanding is that there are multiple precisely equivalent formulations of classical mechanics (Newtonian mechanics being one of them, but then there's e.g. Lagrangian mechanics[0] and other more exotic things). Perhaps that doesn't cross your threshold for 'sufficient granularity'—but it took quite a bit of time to find the alternate formulations in classical mechanics (after Newton I mean), so just because we don't yet have them for certain more modern theories doesn't mean they aren't forthcoming. Also, I'm pretty sure there are at least very nearly equivalent formulations of QM, e.g. the de broglie pilot wave stuff (often termed as an alternate 'interpretation', but my understanding is that the differences extend even to the level of mathematical formulation, and are not just some detached reflections on the 'meaning' of the theory or whatever. [0] https://en.wikipedia.org/wiki/Lagrangian_mechanics https://en.wikipedia.org/wiki/Lagrangian_mechanics
      - whatshisface 8y ago
        >so just because we don't yet have them I think the strongest argument for positivism is that you can generate arbitrarily many trivial "different but the predictions are the same" theories from any parent theory just by doing algebra. You can also generate arbitrarily many "the predictions are slightly different but our present experiments can't resolve it" theories from a parent theory by littering it with new, small constants and tiny interactions. Occam's razor will lead you astray about that, too: most of modern physics was at one time a small constant or a tiny interaction.
    - deleted 8y ago
      [deleted]
Florin_Andrei 8y ago
Well, Egan was just repeating things that others were saying before. This is M-theory basically, and Stephen Hawking, among others, has mentioned it as a possible "theory of everything".
gowld 8y ago
What else could be? The universe is outside our language(s) to describe it, so there's no reason to have only one isomorphic theory. The only alternative is to have two (or more) incomplete theories, but then combining them makes one "unified" theory. Even in pure math, outside of physics, the same applies. The only other possible alternative would be , what, one tiny theory that is essentially simple and minimal in every possible way, yet somehow models everything, in the spirit of ANKOS?

stcredzero 8y ago

The Map is Not the Territory! https://wiki.lesswrong.com/wiki/The_map_is_not_the_territory https://wiki.lesswrong.com/wiki/The_map_is_not_the_territory Another piece of widespread ignorance I've seen here on HN, is the treatment of conservation laws as if they're baked into the fabric of reality. This results in programmers making philosophical/cosmological arguments in ignorance. As far as we know, conservation laws are not baked into reality. Instead, they are very useful analysis tools which can take advantage of symmetries. (Or near-symmetries.) Any given conservation law can disappear if a given symmetry doesn't apply, but Noether's Theorem still remains. https://www.youtube.com/watch?v=04ERSb06dOg https://www.youtube.com/watch?v=04ERSb06dOg If you want to see an example of how social media "bubbles" can impede the dissemination of knowledge, note that I've actually been flagged on HN for trying to explain this, apparently because someone misread this as advocacy for perpetual motion machines. It is not! (Also, because I used <facepalm> -- but when you're wrong, you're wrong, and when you're wrong and you think it's clever, it feels worse.) (That title, "The Map is Not the Territory" acts as a pointer to a series of literary references. https://en.wikipedia.org/wiki/The_Map_and_the_Territory https://en.wikipedia.org/wiki/The_Map_and_the_Territory )

thanatropism 8y ago
It's hard to make time symmetry (and thus conservation of energy) "disappear", though.
- myWindoonn 8y ago
  There probably isn't a plain time symmetry, but maybe there is CPT symmetry. Lucky 10000: https://en.wikipedia.org/wiki/CPT_symmetry https://en.wikipedia.org/wiki/CPT_symmetry
  - wnoise 8y ago
    He's talking about time-translation symmetry, not time-reversal symmetry, which is the T in CPT.
    - 8y ago

ghkbrew 8y ago

The article says that one of the attractive qualities if string theory is that it has no free parameters. But then says that the particles a forces of the standard model are determined by the number and size of extra dimensions. Those sound an awful lot like free parameters. Can someone with more than a passing familiarity with the field explain?

AnimalMuppet 8y ago
One might say, given the fundamental particles, there is a unique set of number and sizes of extra dimensions. That is, there are no free parameters if it's going to fit this universe. The same thing happened in relativity. c is not a free parameter; it has to be the speed of light in this universe. You could argue that it could have some other value and relativity would still work correctly. That might be true in some sense, but it wouldn't work as a correct description of this universe. Note well: I do not have more than a passing familiarity with the field. What I am saying here may not be a correct description of the actual state of string theory. Also note that I find "there are no free parameters" and "but it gives rise to this landscape, where there's nothing nailed down in terms of actual physics" to be somewhat difficult to reconcile.
auntienomen 8y ago
Normally in a physical theory, you have some equations describing the dynamics and you go looking for solutions to these equations. The dynamical equations may have some parameters (such as the constant G in Newtonian/Einsteinian gravity), and then there are usually additional parameters required to describe the solutions (such as the mass M of the gravitational field source). String theory has the unusual property that its dynamical equations don't have free parameters. The dynamics is apparently unique. But there are many many solutions to these equations, and so there's a huge space of parameters from that. In particular, if you go looking for ways of embedding the Standard Model in string theory, all of its dynamical parameters (like the electron mass and Newton's constant) are realized as solution parameters.
- kolpa 8y ago
  Can I make Newtonian mechanics into a dyanically 0-free-parameter theory by stating that F == gMm/r^2 , where g is a solution parameter ("the gravity of the universal landscape" ?

FailMore 8y ago

This feels off to me. Einstein’s process did not come from the mathematics, but from an idea of what was happening. This enabled a great number of odd predictions which were verified (the Sun would bend the visible pathway of a star, there would be gravitational waves, etc...). String Theory feels like a theory which is starting at the wrong place. Not an idea of what process is happening and then seeing if the results fit, but an attempt to connect all the results into a theory. Pas bien por moi!

WaxProlix 8y ago
> String Theory feels like a theory which is starting at the wrong place. Not an idea of what process is happening and then seeing if the results fit, but an attempt to connect all the results into a theory. Are you saying that it doesn't make any predictions (and is therefore unfalsifiable)?
- maxxxxx 8y ago
  As far as I know that's the case. At least we can't verify any predictions with the energies we can reach right now and long into the future.
  - manyoso 8y ago
    There are no predictions even in principle. It has nothing to do with the predictions being at a sufficiently high enough energy level that we can't verify...
    - maxxxxx 8y ago
      I remember reading something about a galaxy sized particle accelerator that could detect the extra dimensions of string theory.
- AnimalMuppet 8y ago
  Well, let's say that string theory has far fewer testable predictions per unit of theorem[1] than other physics theories have. [1] However measured (cubic meter of paper, maybe?)

monktastic1 8y ago

I'm reminded of this beautiful quote from Chris Fuchs, regarding his advisor, the great John Archibald Wheeler: > [Wheeler] would say things like, “In the end, the only law is that there is no law.” There’s no ultimate law of physics. All the laws of physics are mutable and that mutability itself is a principle of physics. He’d say, there’s no law of physics that hasn't been transcended. I saw this, and I remembered my joke about how the laws of physics must be wrong, and I was immensely attracted to this idea that maybe ultimately there actually are no laws of physics. What there is in place of laws, I didn't know. But if the laws weren't 100 percent trustworthy, maybe there was a back door to the stars.

maskedSlacker 8y ago
This sounds like semantic befuddlement (though, not on Wheeler's part; he was just engaging in wordplay). Physical laws are not 'laws' in the sense that nature is required to abide by them. They are simply features of natural behavior that have been so overwhelmingly observed that we treat them as axioms. An example of this is the 'law' of conservation of mass. Strictly speaking, nature does not follow this law. Nuclear reactions and subatomic interactions do not conserve mass. They conserve other quantities, but not mass in and of itself. The idea that there is no ultimate law of physics is not novel or interesting. It's obvious on its face, unless you do not properly understand what 'law' means in the context of physics.
- goatlover 8y ago
  Law of physics implies a casual relationship in nature. Saying there are no laws of physics is saying nature is acausal. B always follows A for no reason other than it just happens to do so in our universe. This is the Humean view of causation, which is constant conjunction instead of there being a reason that A results in B. The plus side is that you don't have to deal with causality, which is a tricky concept. Hume persuasively argued that causality is neither empirical nor a result of logic. The downside is that all necessity is totally arbitrary. It just so happens ... As such, there is no reason for anything we observe. Just descriptions.

ifdefdebug 8y ago

For those like me who are not too happy with this kind of "science" (for one, the title is worded in a way that makes this highly controversial view of reality sound like state of art in physics), "Not Even Wrong" [1] by Peter Woit is a great read for multiverse skepticism (mostly centered on "string multiverse", not quantum "many worlds"). [1] https://www.math.columbia.edu/~woit/wordpress/ https://www.math.columbia.edu/~woit/wordpress/

kbutler 8y ago
All models are wrong, but some are useful. -- George Box And some are not useful except as a mental exercise. Maybe they will become useful at some point, maybe not.

lossolo 8y ago

There's a great quote from the X-Files by Scully on this topic. "Nothing happens in contradiction to nature, only in contradiction to what we know of it. And that's a place to start. That's where the hope is."

johnvega 8y ago

This is fake news. Jump off a 10 story building balcony into a cement and see if "There Are No Laws of Physics" or the title can be changed.

danbruc 8y ago

Off-topic question that seems to trivial to take to Stack Exchange but I am struggling to find an answer to, maybe a physicist comes by and can provide an answer or relevant reference. Let's take a spin 1/2 in the superposition state |0> + |1> ignoring normalization and then add the rest of the universe including a measuring device, an observer, and all the other bits and pieces of the environment. This state then undergoes unitary time evolution past the point where we measured the spin and the observer had a look at the measuring device. It now seems to me that if the final state is a definite |0> or a definite |1>, then this measurement outcome must already have been present in the initial state, not necessarily as hidden variables of the spin but somewhere, for example in the micro states of the measuring device. If the final state could indeed be either |0> or |1> independent of the initial state, time evolution would not be unitary, it would not even be a function of the initial state. The only other option seems to be that the final state is still a superposition and we have to reach for something like the multiverse interpretation to reconcile the fact that we indeed observe a definite final state. So what is the correct or at least common way to think about this? Time evolution is only approximately or sometimes unitary? The measurement outcome is, similar to decoherence, determined by the environment? The final state is still a superposition? Non of those seems to be a particularly attractive choice. Or did I somewhere make a stupid mistake?

maskedSlacker 8y ago
It's been a long time since my QM course, but, assuming by unitary you mean deterministic, then the answer is that time evolution of a particle's state is NOT deterministic. It is probabilistic. For large collections of particles, the probabilities come to overwhelmingly favor a single average state, but the state of any single particle remains non-deterministic. This is in contrast to, for example, classical statistical mechanics where individual particles are considered to behave deterministically, but we simply lack the ability to measure their behavior. In (the Copenhagen interpretation of) QM there is no underlying determinism at all. You might not like this idea (it's certainly non-intuitive), but decades of experiments have shown that the alternatives are all, most likely, wrong.
- danbruc 8y ago

tabtab 8y ago

Is it just me, or does string theory seem like epicycles all over again: if you throw enough center-intersecting circles into the engine, it can emulate just about any observed movement of objects in the sky; a sort of "circular regression" in the same way that piling up polynomials gives us Polynomial Regression. String theory is like "dimensional regression". Regression is a powerful tool, but is NOT designed to directly "explain" phenomena, only emulate them. Newton et. al. came along and gave us a much simpler model of gravity and the solar system such that we could toss out the messy nested circle models. (We still can't say that Newton's model is fully "right", but it's certainly simpler.)

ivankolev 8y ago
I thought it was actually Kepler that figured it out...
jcranmer 8y ago
Well, string theory is kind of the anti-epicycle. The epicycles in Ptolemaic astronomy were added to make the math conform to reality, but people didn't believe that the planets actually moved in epicyclic motion. Superstring theory started from the opposite standpoint: the Standard Model is math that works out, but the theory is messy, so superstring theory sought to make an "elegant" theory that checked out with the math... and ended up with a theory that is so general it can't really be disproven. The end result is the same, but the paths to get there are completely different.
- whatshisface 8y ago
  String theory was originally exciting because it had a graviton that worked, and to my knowledge it is really the only theory that contains both the standard model and gravity. LQG is not yet at the point of reproducing 3+1 space as far as I know. So, here's my proposal: saying that the earth orbits the sun in a universe where QED also is true isn't proof of string theory, but it does falsify the standard model and so far to my knowledge most of string competition.
  - 8y ago

skissane 8y ago

Multiverse theories like string landscape, eternal inflation, or many-worlds generally have this property: Almost anything that possibly could happen will happen in some universe. But, it is said, that some universes are more frequent than others. From local observations we infer the global laws of physics, which tell us the relative distribution of different types of universes. But, surely there will be some "deceptive" universes, in which (purely by chance) observers are always mislead as to what the actual laws of physics are. Experimental error always goes in the same direction, such that the true laws of physics are never known, and those observers rationally believe in false laws of physics instead. Now, an observer in such a universe will rationally infer a given probability distribution of universes based on their local observations, but the distribution they infer will be completely wrong. My question is: how do we know we are not in such a universe? To say such universes must be exceedingly rare (even though existent) is sort of circular, because our conclusion they are rare is based on our idea of the global probability distribution, but in order to validly make the inference from local observation to global distribution we have to assume we are not in such a universe. But, if we can't know we are not in such a universe, then we can't know that some universes are "more likely" than others, which is a central claim of these theories, and what distinguishes them from David Lewis' modal realism. This is why I think all such "multiverse" theories should be rejected.

superqd 8y ago

This is the one major reason I lost most of my desire to continue grad school (I was studying astrophysics). I chose physics specifically because I wanted to understand the universe. The way I thought of it was that I wanted to lift the hood of reality and see how things "really" worked. As a kid, I'd read a number of books on science and had heard of a quest for a Theory of Everything. I'd decided this was a quest I wanted to go on. I thought of it as the most worthy singular hidden treasure and I was willing to devote my life to digging for it. But over the course of my undergrad, and hours debating with friends, and reading even more, I started to get an uneasy feeling. I decided to go to grad school, partly, because I still held on to the belief that there really was treasure at the end of that rainbow, and that we really could, if we were clever enough, "figure out" how things "really" worked. But, in grad school, it just continued to dawn on me how impossible it was for there to be only One True Theory. One way I thought about it was to regard physics as a program. Even if there were separate theories for different scales, or domains, it didn't matter, you could still regard the whole knowledge base as a single program and the scale and domain, along with physical observables, as inputs to the Physics Program. The output would be predictions for the state of the universe (or some subset, it didn't matter) at some later time, i.e., it would predict later observables' values. The thing was, I had a hard time finding any logical justification for why there had to be only one program that could take in the known inputs and produce the known outputs. That is, there was no way to logically prove that there could not be multiple equivalent programs that could produce the same output given the same input. I.e., there was no way to logically justify the notion that there could only be One True Physics. That is, the treasure I believed I'd be digging for, didn't not exist, it was just that there was more than one treasure, and anyone could find their own. This thought diminished some of the romance, so to speak, of the Quest for Truth, so I lost interest, for a time. Enough to stop taking grad school classes and just start working (coding). Maybe one day I'll create a program of my own.

lioeters 8y ago
Your comment stayed in my mind, about the (maybe futile) quest for the "one true theory". Today I was reading an article [1], and a passage reminded me of what you were talking about: Schrödinger’s theory proved easier to use than Heisenberg’s, in part because it is more intuitive. Furthermore, first Schrödinger and then Paul Dirac proved that the two theories are equivalent. In physics any two theories that make precisely the same observable predictions are observably equivalent. And one of the predominant philosophical views of the age — logical positivism — held that any two observably equivalent theories are really one and the same theory. ... Einstein demanded a clear and comprehensible account of what is going on in the physical world — at all scales — in space and time. Bohr thought that the key to quantum mechanics was the realization that no such thing could be had. [1] http://bostonreview.net/science-nature-philosophy-religion/tim-maudlin-defeat-reason http://bostonreview.net/science-nature-philosophy-religion/t...

yedawg 8y ago

Physical theories imply physical laws and consistent variables which require consistent math and hard scientific research; There is no escaping that. To say that physics is like a "landscape" is like comparing scribble of a stick man to a Picasso. There is a lot we don't know about the universe, I think its time for writers and physicists to get on board with that and analyze the shit out of their vague and opaque understandings before hitting the enter key.

warmfuzzykitten 8y ago

But... http://bostonreview.net/science-nature-philosophy-religion/tim-maudlin-defeat-reason http://bostonreview.net/science-nature-philosophy-religion/t...