Has Physics Gotten Something Really Important Really Wrong?
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Smolin also doesn't like many-worlds, because it talks about unreachable regions. This he considers too speculative. There's a basic problem in quantum mechanics, which leads to Schroedinger's Cat, the Copenhagen Interpretation, and, in the end, many-worlds.[1]
Physics has been stuck on this problem for almost a century now. Philosophy won't help.
It sure seems to be an epistemology problem which puts it squarely in the realm of philosophy, not physics.
What "philosophers" are we talking about here? Lakatos? Chomsky? Newton? Logicians? Or do we have some composite postmodern blowhard in mind? (Like any industry's products, philosophy's product quality varies with factors like producer. So specifics are important.)
There's a bias in physics culture against philosophy. (It's no doubt elsewhere too, but very apparent in physics.) But fortunately, there's many exceptions who like to take a step back and think about what they're doing.
Why?
"The world would be better served" carries a lot of cultural baggage.
Alchemy. But that's no reason to still respect alchemists.
It turned out to not be the case, time after time.
There's no inherent meaning in how substances interact. There are laws, they're consistent but devoid of any meaning, on human level.
That's why I'm deeply scetical towards any New Age-style ideas.
Astronomy and medicine are two very obvious examples. Primitive cultures didn't need philosophical underpinnings to notice and record the patterns in the sky or to figure out which plants helped with fevers or how to set broken bones. Philosophy might have helped science in places with structural issues, but it's reaching too far to say that nothing would be around without philosophy.
The philosophy of information is a great example of where it's incredibly important [1]. I seriously, seriously doubt that information theory would have come about without many of the philosophical underpinnings that came before it. It's not just about structure.
[1] http://plato.stanford.edu/entries/information/
edit: interestingly enough, some of the posts in your blog would be considered "philosophy". ;)
PS: The two most widely used and useful parts of math where completely unknown to the anchent Greeks. Aribic numerals are the first example of useful information theory after writing.
When I talk about information theory, I'm talking more about the more generalized forms of it (Shannon, etc), not necessarily something that could generally be described as 'information' in a more classical definition. Specifically, https://en.wikipedia.org/wiki/A_Mathematical_Theory_of_Commu....
(this is a subject I'm actively learning over time, so please correct me if I'm wrong!)
Shannon was more an outgrowth of having already abstracted information and looking for ways to encode that for transmission. I don't want to downplay the value, but in historical context it's very different from how you learn about such things after the fact.
That doesn't make it any less worthy of study of course.
It is, and as I said sometimes doing that is _good_ despite the derogatory connotations of calling it as such.
There's a point I'm trying to make which is not coming across, and I'm not sure I'll be able to.
So what's left in philosophy is the stuff that no one has gotten very far in solving in 3K years. Why is life worth living? What is a good life? What is the best beer?
Also, any particular field you study has philosophical assumptions, like about the reliability of sense data. The reason modern science is so fabulously successful is the philosophers who established it got rid of the supernaturalist assumptions of previous science, and added the assumption that reality is mathematically describable.
What Smolin and Unger are saying is that the particular philosophical assumptions behind string theory and a lot of related physics are mistaken. This would seem to be at least possible.
Indeed, or the practice of asking questions about the nature of questions, ie. what questions are meaningful, well-formed, yield knowledge, etc. in any given subject.
When you understand the nature of the questions in a particular subject, then you're no longer practicing philosophy, you're gathering knowledge of that subject, ie. math, physics, chemistry, etc.
> Boltzmann's kinetic theory of gases seemed to presuppose the reality of atoms and molecules, but almost all German philosophers and many scientists like Ernst Mach and the physical chemist Wilhelm Ostwald disbelieved their existence. During the 1890s Boltzmann attempted to formulate a compromise position which would allow both atomists and anti-atomists to do physics without arguing over atoms. His solution was to use Hertz's theory that atoms were Bilder, that is, models or pictures. Atomists could think the pictures were the real atoms while the anti-atomists could think of the pictures as representing a useful but unreal model, but this did not fully satisfy either group. Furthermore, Ostwald and many defenders of "pure thermodynamics" were trying hard to refute the kinetic theory of gases and statistical mechanics because of Boltzmann's assumptions about atoms and molecules and especially statistical interpretation of the second law of thermodynamics.
> Around the turn of the century, Boltzmann's science was being threatened by another philosophical objection. Some physicists, including Mach's student, Gustav Jaumann, interpreted Hertz to mean that all electromagnetic behavior is continuous, as if there were no atoms and molecules, and likewise as if all physical behavior were ultimately electromagnetic. This movement around 1900 deeply depressed Boltzmann since it could mean the end of his kinetic theory and statistical interpretation of the second law of thermodynamics.
> After Mach's resignation in Vienna in 1901, Boltzmann returned there and decided to become a philosopher himself to refute philosophical objections to his physics, but he soon became discouraged again. In 1904 at a physics conference in St. Louis most physicists seemed to reject atoms and he was not even invited to the physics section. Rather, he was stuck in a section called "applied mathematics", he violently attacked philosophy, especially on allegedly Darwinian grounds but actually in terms of Lamarck's theory of the inheritance of acquired characteristics that people inherited bad philosophy from the past and that it was hard for scientists to overcome such inheritance.
> In 1905 Boltzmann corresponded extensively with the Austro-German philosopher Franz Brentano with the hope of gaining a better mastery of philosophy, apparently, so that he could better refute its relevancy in science, but he became discouraged about this approach as well.
Once we get a better grip on an area, then, finding more proper definitions for its concepts, we branch it off as a subject of its own.
> And since his work became the map used by generations of future explorers, he sent them off in the wrong direction as well.
Aristotle was highly specific and highly empirical. His ethics, for instance, is an elaborate study of the various ways individual go right or wrong in their decisions. His politics was based on extensive studies of the constitutions and political histories of nearly a hundred Greek states. And of course there was his biology, based on empirical studies of over a hundred different animal species.
And as for his physics, according to this astounding article by Carlo Rovelli (yes, that Carlo Rovelli), his physics is accurate for the phenomena he was studying. Rovelli even converts his ideas into equations.
That is a good example. I was trying to think of others since then. That was 500 years ago or so. What are some more recent ones for physics?
I imagine if logic is considered part of philosophy, perhaps boolean and propositional logic had a hand in helping computing...
Then if ecology or sociology is considered I can see how philosophical ideas about class, society, environment would be incorporated into practical fields or be used to start societal transformations (Marxism perhaps?).
But I can't think much for physics recently? I have read and seen known physicists dable in and use philosphy to explain what they accomplished or observed. Bohr, for example, was fond of Kierkegaard. It would be good to have examples of philosophers who changed the course of physics.
https://en.wikipedia.org/wiki/History_of_scientific_method#P...
The word "scientist" was only invented in 1834. The scientist who coined it, William Whewell, also thought up "phycisist" and a whole bunch of other modern terms. [1] Interestingly enough, "naturalist" still survives as a legit term, as does "natural history".
[1] http://etymonline.com/index.php?allowed_in_frame=0&search=Wh...
They are both human endeavors to better get at and understand the truth about ourselves, the universe, reality, etc. Philosophy often extends further into realms such as art, morality & ethics, dignity, aesthetics, the role of society, and human nature. Philosophy even takes a meta-view of science, asking how we are justified to even claim to know something to be true at all (epistemology). And for the most part, these questions are answered in terms of and in concert with our scientific understanding.
Moreover, evidence-based science itself is to some degree an outgrowth of Descartes' "method of doubt" and rationalism, then the empiricist philosophical movement, and on and on. It's no wonder that throughout history often the leading scientists/mathematicians and the leading philosophers were the same people.
Concepts such as natural rights, liberty, free will, social justice, etc. all originated in philosophical works, and have indeed "solved problems" by influencing people who are say, in the process of forming secular governments after a political revolution. You can draw a fairly straight line from Plato to Descartes to Hobbes to Locke to the Constitution. When we talk about a "bill of rights" -- where is this concept of a natural human "right" even from? Philosophical theories such as utilitarianism, the meaning of good vs. evil, are used every day in our legal system, economics, politics, and foreign policy.
Moreover, often a breakthrough in science or development in society may have very practical consequences which FORCE people to face unavoidable philosophical questions. Should scientists be legally permitted to clone humans? Should a Tesla kill its own driver to avoid plowing through kids crossing the street? Should there be a minimum wage? Should pharmaceutical companies make life-saving drugs free? When should abortion or infanticide be permitted?
These questions must be answered reasonably-- I'd much rather have them discussed through the lens of rational philosophical discussion rather than religious or purely emotional "go with the gut".
So philosophy has served as an on-ramp to science. But among its benefits, it also helps us move from the descriptive study of the universe to the prescriptive-- to paraphrase the great philosopher Dr. Ian Malcolm-- there's a benefit to moving from the scientific question of if we could to consider the philosophical one of if we should.
Just like there's a "God of the gap"-- a notion that a need for God pushed back as our scientific knowledge expands, so it seems there is a "philosophy of the gap"-- some people seem to redefine "philosophy" to mean useless mental spaghetti that goes nowhere. Do you judge science by the same criteria? Does every "failed" experiment constitute a failure of science?
Given its usefulness, especially as an alternative to religious methods where "science" doesn't offer a clear answer about how people and societies "should" behave, I think damning philosophy too hard is kind of unfair.
It's true that science and philosophy did come from a common discipline (my undergrad uni originally had a Natural Philosophy dept that only became a physics department somewhere between 100-150 yrs ago).
Though I thought one of the physics professors when I was in grad school said it best : "Physics is philosophy with integrals".
These brilliant men argued for a decade and could not resolve it so they decided to bury the questions. It was not unreasonable in that context to accept that they did not know the answers but the theories work so let's use it and see where it leads. I am sure the hope was that the answers to the philosophic questions would become clear as our understanding of the new physics grew. There was a lot of work to do aside from the philosophic questions. Fast forward 100 years and here we are, the philosophic questions are still unanswered, and the Copenhagen interpretation has hardened into dogma banning any discussion of fundamental questions in physics. I have respect for Smolin for at least trying to re-raise these important questions.
[1] I am of the view that philosophy is distinct from physics in that it studies the nature of reality and knowledge, thus it applies to ALL fields not just physics. WHAT do we know and HOW we know is the more (or the most) fundamental science. The physicists are throwing out the baby with the bath water when they reject philosophy en masse instead of rejecting bad philosophy.
A philosophical assertion about what should be valued, if ever there was one.
That's a quintessential philosophical question.
The quote was by Zlatko Tesanovic, a brilliant and witty theorist who sadly passed away a few years ago. Here's a link to a page of some of his other quotes, as recorded by his students. IIRC he said the integrals quote when I was the TA for his statistical mechanics and thermodynamics class.
> It sure seems to be an epistemology problem which puts it
> squarely in the realm of philosophy, not physics.
Sounds like a good idea and would like to see, for example, a philosophy professor from some university one day publish a paper in arxiv and turn the world of physics upside down with it. It would be like "... because of these logical inconsistencies ... x, y, z quantum mechanics is actually governed by hidden variables, q.e.d"
I just don't see it in practice though. I think it only seems as if philosophy is deeply entwined with and ready to be exploited to help physics, but it is only because physicists were marginally interested in it and offered some philosophical explanations after the equations and experiments have been proven. I think most of those were mostly for curiosity's sake and were rather secondary to their main achievements.
They already do this. Many philosophers of science pursue realist interpretations of QM though, like de Broglie-Bohm, and so they aren't published very widely. The measurement problem is the serious stumbling block for anti-realist interpretations, and why many such philosophers are realists. The measurement problem just doesn't trouble practicing physicists.
So yes, it is really unattainable.
Cosmic rays bombarding the atmosphere do attain such energies, but they are not controllable in a fashion that would permit most collider experiments.
If we were to be able to come up with the technology to manipulate the strong force, would that open up possibilities for alternative colliders?
One problem that I can see is that the strong force might be stronger (strength of 1 vs 1/137 of the electromagnetic force) but the acting range of the force is much smaller (diameter of a medium sized nucleus). The electromagnetic force has a far superior range (technically infinite, but the power drops off depending on the distance)
Arm chair physicist here... I would love your knowledge on the general idea.
If you wanted to scale up the LHC by an energy factor 10^14, you would have to deal with the energy loss caused by synchrotron radiation (charged particles going around a ring are constantly accelerating, so constantly emitting electromagnetic radiation) which is ~E^4/R per turn [2]. To keep the same energy loss as at the LHC and pay an electricity bill which is only 10^14 times larger, you would therefore need to grow the radius R by a factor ~ 10^14^4 = 10^56.
The LHC radius is 4.5 km, so let's go with R = 10^56 km. That's 10^43 light years. For comparison, the radius of the observable universe is ~10^10 light years.
[1] http://www.physics.princeton.edu/~mcdonald/examples/lep.pdf
The problem with physics today is rationalism - constructing theories with only partial reference to experimental data. Some fields, like psychology, have the opposite problem - empiricism - where they accumulate countless statistical correlations but fail to integrate them into consistent theories.
I suggest anyone who's seriously interested in a solution to these issues to listen to the following, then look up Leonard Peikoff and David Harriman's other writings on the subject.
https://campus.aynrand.org/campus-courses/understanding-obje...
Care to tell us what they are?
I have no idea what this is supposed to mean or imply in this context, but it seems to be a classic HN response asking people to judge a book by it's cover instead of its contents/arguments, which is even less helpful.
Ultimately you have to read Rand rather than read about her, as so many of her critics enjoy a somewhat loose relationship with reality. For example, the comment in this thread about "randian evangelism" on HN. I've encountered two other Objectivists on HN, whereas every week we have multiple hundred-comment threads on how fantastic an idea universal basic income is. That's pretty ineffective evangelism.
"Rationalism" is still serving us very well in pretty much every other field of physics except unification theories. We're still coming up with great new theoretical models based on working with the laws we have, sometimes driven by the need to explain existing experimental results and sometimes to look for new places to do fruitful experiments. There's a much better balance between the two for physics as a whole than you're making it out to be.
I'm not sure how wrapping in Ayn Rand's theories with all their politics is going to streamline physics.
What we understand so far is:
* the measurement process can be described as an entanglement of a quantum system with a large external system, followed by a dephasing of the wave function that is caused by the huge number of degrees of freedom in the external system.
* this dephasing decouples the individual terms of the wave function of the system that is being measured, thereby effectively suppressing any further quantum effects in those measured states. This is what we call a transition from a quantum state to a "classical" state.
* the measurement process itself is not a discrete event: We can perform continuous weak measurements on a system's state, which will only partially collapse the wave function (there have been many experiments done on this e.g. by Serge Haroche's group and more recently with superconducting systems as well).
* this whole process is completely reversible and can be described by the Schrödinger equation.
Now, if we want to introduce irreversibility into this picture (which is required for the Copenhagen interpretation), we need a mechanism for it to arise. To my knowledge, no one has come up with a good theory for this, as it would require to modify the Schrödinger equation in a way that subtly depends on the characteristics of the system being measured and the measurement system. This mechanism would need to contain a variable A that would account for the size of the measurement system, as we need to preserve reversibility when the measurement system is small (i.e. has a small number of degrees of freedom), while destroying it when the measurement system is macroscopic.
I'm honestly a bit surprised that no one makes this argument in favor of the many-worlds interpretation of quantum mechanics, as it's the only theory which accounts for all experimental evidence while not forcing us to invent a mechanism that "eliminates" the many realities that we don't want to accept, while in fact they arise naturally out of the theory. I think that many people just don't want to accept that the universe could work this way, even if it's the simplest and most straightforward explanation.
I think you're projecting the existence of these worlds. Certainly you could view the equations that way, or you could view the particles as fundamentally real and obeying a non-classical law of motion, as in de Broglie-Bohm, which was actually the first the interpretation to correctly account for measurement.
That's a very odd way of going about things. We can't actually observe galaxies over long enough timescales to be sure that gravity applies to them but their appearance is consistent with the existence of gravity so we don't even both to consider the possibility that there might be some separate force causing them to look that way.
I didn't. I said math doesn't always predict reality, sometimes it's just interesting math. Some maths are also physics, some maths are just maths and have no bearing on physics.
Conjecture. It seems self-evident that our reality reflects the structure of basic discrete mathematics, ie. if there are two apples, eating one leaves 1 apple. No amount of rationalization will refute this fact. The fact is, the basic structure of our world is mathematical in some way.
> The fact is, the basic structure of our world is mathematical in some way.
Yes, but that doesn't imply the inverse, that all maths are reflections of reality. Reality can be described by maths, but not all maths describe reality. Or to further simplify, physics is the subset of maths that describe reality, which necessarily implies that not all maths do.
Even if you wanted to subscribe to some form of mathematical naturalism, that still doesn't support your point that math that doesn't appear to have a natural analogue, doesn't physically exist. We thought this of many prior mathematical abstractions, like complex numbers and non-euclidean geometry, and they are both now indispendensible tools for describing reality as we know it.
> hat still doesn't support your point that math that doesn't appear to have a natural analogue,
I never made that point, and if you think I have, you've failed to understand the point actually being made.
What is the physical analog of the square root of -1? If all math is physics, then what physics does that predict? Maths are a language invented by humans, some of those language describe physics, some don't, that's not a conjecture, that's a fact.
You didn't make any points, you merely repeated the dogma that there exist maths that have no physical analogue, which I already addressed in my first post. I merely provided more context on the philosophy of mathematics so you can read up on why your position is problematic at best.
> You are effectively claiming that all maths are physics
No I didn't. I pointed out the least problematic and most accepted position on that question, which refutes your claim that your position on mathematics is obviously the only valid position.
Your question about the sqrt(-1) is perfectly exemplary of the elementary misunderstanding of what your position entails. Abstractions don't exist a vacuum. I can just as easily ask you of the physical analogue of the number 1.
It's a meaningless question. Mathematics is an abstraction describing structure, and many things share the structure of the number 1. The structure of the sqrt(-1) appears in many places, like in wave mechanics.
The fact that you conflate maths with the particular syntax we use is another elementary misunderstanding. A grammar also has a structure, and we use that to represent the structure of mathematical objects, but math is not about syntax.
Finally, on the matter of absurdity, I suggest you reread my previous post. While you amazingly seem to think it's devoid of content, I can assure you that I point to two primary philosophies of mathematics, one which disagrees and one which sort of agrees with you, but still doesn't support your claims. It's up to you if you actually want to learn what mathematical truth is really about.
> No I didn't.
Great, then you agree with me, all math isn't physics, and there's nothing more to talk about.
Here's what you don't seem to grok.. from your own original rebuttal...
> The fact is, the basic structure of our world is mathematical in some way.
I agree, I've never once disagreed with that position, you simply failed to understand the point being made and that you're continuing to try and argue it is just... boring now.
No I don't. I'm disagreeing that your position is self-evident as you've claimed, and you've still failed to recognize that.
[0]https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory [1]https://en.wikipedia.org/wiki/Pilot_wave
There's a lot of really strange stuff going on with QM and ST, even tho Brian Greene works primarily on ST he did somewhat coined the concept of the "giant leap" that to some extent theoretical physics has run off way too far from anything that can be proven using experimentation.
>Physics has been stuck on this problem for almost a century now. Philosophy won't help.
Philosophy does help, infact it might be the only thing that would help in it's essence philosophy is about how you approach and solve problems, and more importantly how you think about them. It might need be that we do need a major philosophical change in the world of theoretical physics and start thinking about QM and the universe in general in completely different matter.
There is a lot of natural bias that pushes your thinking into a very predictable path and this plagues theoretical physics just like any other field if not more. The bleeding edge of theoretical physics, especially in the past 60-70 years has really shifted towards almost the metaphysical regardless of how much elegant math there is behind it.
I'm genuinely curious to know how you think any post Frege philosophy helps. At best philosophy can help prevent research/effort being expended in plausible non-sense; but certainly not in the sense of providing a positive result or foundation for one (which is to my understanding what those doing ST are ultimately seeking).
I'll also take the time here to gripe about post-wittgenstein philosophy which went willy-nilly with formal constructions and basically managed to ignore PI entirely (or otherwise remain mum about it) as well as the his remarks on the foundations of mathematics which set up a lot of problematic for the later.
Trudging down those paths prior to experimental evidence is of very real value and is not disconnected from the physics itself.
It's impossible for someone to teach something that they don't know, have never learned, or learned from someone who doesn't really know.
The "good" parts of philosophy are the mushy parts. And when you've created a formal system that's self-consistent yet offers no value, you're going to have to step outside formal systems for a while.
That's gotta be a painful leap for a lot of folks who believe that math is the ultimate reality.
I don't think philosophy strives to provide positive results. That is left to science. But philosophical ideas can help direct science, and that is a great contribution.
> post Frege philosophy
Post Frege? Even if you only value analytic philosophers, and mostly for their contributions to mathematical logic, I think you should at least acknowledge Russel, Kripke, Putnam and possibly others, if only for their immense contributions to computer science.
This. This is what helps.
> how you think any post Frege philosophy helps
If it doesn't then that explains precisely why we need more new philosophy to make the breakthrough.
Physics can never be about a specific philosophy until it works. Without a working philosophy, we're stuck, which is pretty much where we are right now. We need to keep thinking, and we are, so it's really only a matter of time.
If the initial work were not peer reviewed, you would not be holding it up as an example of something successful.
Therefore, it's NASA's sponsorship of the peer review which is a necessary and direct cause of you calling it successful here.
So my initial assessment of what you said stands. You're saying the physics community is receptive because NASA sponsored an attempts to verify it. That proves nothing about the receptivity of the physics community nor of even NASA. But I don't expect this to be something you can easily agree with. After all, you're proving my point.
Which is what exactly?
A fairly outlandish invention was developed outside the mainstream physics community. The community saw it and made the effort to test it. This is good, right?
If not, then what should happen?
It's not like they've given it their stamp of approval. Eagleworks is NASA, but as I understand it, they are on a pretty loose leash, and it's their business to investigate somewhat-crackpot ideas.
- Two time dimensions [1]
- Reality is actually a discrete, combinatorial graph [2]
- We live in a Euclidean space virtual machine on a
general relativistic virtual machine on a Euclidean actual machine [3]
- Reality is a souped up version of liquid helium,
and of course dark energy is just surface tension [4]
[1]: http://physics.usc.edu/~bars/twoTph.htm [2]: https://en.wikipedia.org/wiki/Loop_quantum_gravity [3]: https://en.wikipedia.org/wiki/Euclidean_quantum_gravity [4]: https://en.wikipedia.org/wiki/Superfluid_vacuum_theory
Which is a major problem, given the truism that theory is under-determined by experimental evidence! If given any simple theory of physics I can construct a more complicated theory that makes the same predictions, then we desperately need to confine ourselves to theories that do make unique predictions, lest we be generating ever-more-complicated versions of theories we already had.
For instance, many-worlds is actually conceptually and formally simpler than Copenhagen.
All of our math is an attempt to represent things or ideas. The most important thing I learned in my physics education was how to read math as a metaphor for putting together things I understand into a picture of a thing I don't understand. But I don't think anyone serious thinks that their math is "true", such an assertion just makes no sense. The point of it is to find new ways to approach the evidence to see if it gives some different metaphor that wasn't obvious before.
I don't know enough modern physics to have an opinion on whether this is the case for cosmology or string theory, but I do know that in recent history just formulating a problem slightly differently can suddenly make the solution fit in the same framework as a known simpler problem. Not unlike things I read all the time about algorithm research at all, right?
Teaching and understanding models is predicated highly on metaphor, it's much easier to explain for instance that MRI works via a quantum effect that has the same math as a harmonic oscillator than it is to just... dive in. The model isn't the universe, but humans live by metaphor and so the model is important.
Which is perhaps not the point you were trying to make; I don't know enough modern physics to know whether a critique of these new areas as purely fantastical is justified, but it's also pretty fantastical to think of a particle in a box as if it were like a weight on a spring. Who am I to say that something about this approach can't make a currently intractable, approximate, or computational impossible problem solvable with time?
In my opinion, physics is and has always been about answering the big questions, the how's, the why's of our existence. That new technology sometimes comes out of it is a bonus, not the ultimate goal.
We are never "done", that's kind of the point I was trying to convey. I completely agree that we should use science to help us deal with our current problems. Once we understand more about our world and ourselves, we will automatically get better at solving them. I'm just against the whole short-term, instant results way of thinking.
The overall point was which I might not have expressed fully is that there is in my opinion too much bias in the field of theoretical physics, and to paraphrase Brian Greene again we took a giant leap and probably skipped a few steps and no one seems to want to look back and see if we missed something.
I think one of my favorite quotes that somewhat describes this view is by Rudolf Peierls: “In recent years the debate on these ideas has reopened, and there are some who question what they call ‘the Copenhagen interpretation’ of quantum mechanics’ - as if there existed more than one possible interpretation of quantum mechanics.”
And I think that this view is antithetical to the advancement of current physics, and sadly this bias is instituted even unintentionally in most new physics students especially those who take physics as part of their degree in CompSci/Engineering.
But I'd also expect that people making new theories be intimately familiar with the current ones, right? It would be silly to expect someone to come up with hamiltonian mechanics for the first time without having ever been exposed to newtonian mechanics, even though both give the same answers to every problem. Yeah, thinking outside the box is always super hard, but you have to at least deeply understand the box before you can know enough to replace it. I definitely don't understand this particular box, but I feel it's reasonable to assume that those that do are trying their darndest to escape it -- if for no other reason than fame if successful.
Actually, there's a theorem about that ;) Godel's Incompleteness theorem.
I would describe the problem more like: The new model matches the old model in almost everything (because we've observed a lot). But the math works out quite nicely if itty bitty particles behave this way when exploded at super high temperatures. We have a hard time watching those particles explode, so it's not really tested. Either way it works out, it's not really going to matter for anyone who doesn't explode tiny particles.
I worry that it is the pop sci presentation of physics that non-physicists look at and think wrongly that the actual people carrying out the work are blinded by training bias (which is true for anyone, but I think far less true for experts in the field than otherwise) when in fact it's just the authors of pop sci articles and books who are ignorant of the difference between metaphor and reality. These are people who are paid to figure out how to think differently about their questions, they're not just following conventions and calculating pi to more decimal points.
Is an encryption algorithm "real"? Is the process used in proving a theorem "real"? Is the way that we model an atom "real"? No, of course not; they're all ways to represent an idea/observation through metaphor by breaking down a problem to make it look more like problems we already know how to solve. And if you just decide to approach the metaphor for understanding that idea differently, you can get massively more tractable problems.
As an example, a friend of mine in undergrad was studying crystalline domains in metals and wanted to find a way to understand better the relative misorientations of neighboring crystals in three dimensions. The metaphor as written strongly suggests that the right approach is some manner of statistical approach with a random variable representing orientation that can then be statistically analyzed to provide a misorientation distribution, but the problem is generally intractable in 3 dimensions whereas in 2 dimensions it's fairly straightforward math that way.
He instead decided to represent the crystallites in four or maybe five dimensions, which by so doing he was able to show that the math looks the same as that used for adding angular momentum using Clebsch-Gordon coefficients derived from quantum mechanical spin coupling. And found that by so doing he could turn a statistical problem into one with a closed-form solution that was quicker and easier to calculate in more sophisticated cases. With apologies if I'm explaining it wrong, this one never was quite comprehensible for me, he was far better at math.
Does he then think that crystallite orientation is literally quantum mechanical spin? Of course not. Does the math produce a testably distinguishable result? No, of course not; it should be the same result. But is it likely some future scientist with greater understanding of quantum spin coupling might be able to conceptualize the system more deeply? Definitely! This example is hardly unique.
So my point is that representation and metaphor matters, even if it's not a testably different result. To say that it doesn't matter to me seems to be saying that the current model itself is real, when it's not either! There's no fundamental reason to favor one over the other if the results predicted are the same, other than personal preference, ease of manipulation, or ease of conveying the model/metaphor to future students.
By encouraging different metaphors for the same system, you enable future scientists to be taught those alternative approaches so that they have a bigger toolbox to approaching some yet unknown future problem. We're just humans, and everyone looks at things a bit differently; none of us with a clear picture of what's really "real". Much like how there are a half dozen different approaches for quickly sorting a list, some are more intuitive or powerful or quick to execute than others.
Im not criticizing hard working mathematicians and physicists like your friend- the solution he found sounds rather elegant, and the results are testable. And you are right about having no dogmas when it comes to approaching the riddles of tomorrow- and yet, if all work you do is untestable- you are not a scientist.
Why do you describe many-worlds as 'crazy'?
Edit: to whoever down-voted me, this was a serious question.
If you don't really have independent universe forks but something physically continous, what mechanism makes us seem to only observe a single independent branch at all times?
Given the assumption of quantum foam (from the uncertainty principle) at the Planck length + relativity (the Planck length isn't constant like the speed of light, every observer measures it differently relative to others), how many universe branches are really created every picosecond in every Planck length (volume) across the visible universe?
At least, that's what I took away from this:
http://www.askamathematician.com/2010/10/q-copenhagen-or-man...
and this:
http://www.askamathematician.com/2011/11/q-according-to-the-...
Seriously, to my also-completely-laymen mind this seems adding epicycles to me.
But if at every moment you literally have an infinite amount of worlds branching off, then that's vastly bigger than one world in which interactions can be nonlocal. It violates everything from Occam's Razor to practicality.
The question of why time is non reversible can be answered by saying that entropy of a system grows with time, which is a consequence of simple statistics. But with many-worlds you have branching in the forward time direction? Can you explain anything about it?
As I said in my reply to Natanael_L, I was given to understood that the idea of worlds branching off was a misapprehension of the many-worlds interpretation. But I'm prepared to be corrected.
P.S. If anyone is interested in PWT one of the best materials I've seen is a series of lectures by Mike Towler of Cambridge University[2]. It's probably one of the better constructed lectures I've seen of QM in general, it hits the very rare sweet spot of being actually informative without falling into the realm of popular science while not requiring PHD level physics to follow (infact depending on the country you went to high school if you did cover QM in year 10-12 it's almost everything you need).
[0]https://www.quantamagazine.org/20160517-pilot-wave-theory-ga...
[1]https://en.wikipedia.org/wiki/Von_Neumann%E2%80%93Wigner_int...
[2]http://www.tcm.phy.cam.ac.uk/~mdt26/PWT/lectures/bohm1.pdf (change the url from bohm1 to bohm8 to get all the slides)
Of course, the PWT viewpoint may suggest new ideas and understandings; it is, after all, what led Bell to his inequality and thus spawned all of the entanglement uses including quantum cryptography. But it gets reincorporated into standard quantum mechanics.
None of that really matters. People reject PWT because they want to reject it. There have never been any good reasons. It is an extremely simple theory that answers the questions.
If it gets accepted in the future, it will only be because of a new generation being more willing to embrace it.
At first the physicists said it was impossible and then when it was obvious that it was possible, they said it was too trivial. This is a hallmark of reason being used to justify an already decided on outcome.
It is also not in conflict with string theory. One could imagine string theory actually having strings that evolve. This would be the spirit of PWT applied to that realm.
Yes in it's essence PWT doesn't conflict with the concept of strings (nothing really does), I'm not so sure that I doesn't conflict with the leading "complete" string theories out there today.
But most interpretations have the same statistical predictions as standard QM. The standard Copenhagen setup can be argued to not actually be a theory (the split between quantum and classical in a fundamental theory is an absurdity since the classical is made up of quantum ), but assuming that an interpretation is clear enough to be called a theory and has the same statistical framework as standard quantum mechanics, then experiments will not distinguish them.
The different interpretations, however, may lead to different insights for extending the theory. And in that game, one may pull ahead of the other. For example PWT inspired Bell's results. PWT can also explain the impact of the topology of configuration space convincingly since the configuration is a fundamental part of the theory. It leads to many insights that the others just have to assume.
GRW with a flash ontology has a relativistic version with no foliations. So that's cool.
PS.
To clarify, if double slit will be put in a medium where speed of light is much slower, then there will be a speed, when electron with that speed will stop behaving like wave. This point will be depended on speed of electron, speed of light in medium, and distance between slits.
IMHO, it still possible to adjust slit experiment in such way, that slight increase in speed will break interference, i.e. at speed X electron will behave like wave, but at speed X+1 electron will behave like normal particle.
Which is a shame, because John Bell of Bell's theorem was already a fan back in the 60s. He correctly labelled non-locality as the fundamental problem of QM, where other interpretations just let them gloss over this difficulty by labeling such questions "non-physical".
But realistically, I think information-theoretic formalizations of QM will simply gain more popularity in rather than something like de Broglie-Bohm. There's simply too much anti-realism sentiment in the physics community for it to gain much traction.
The main issue is that QFT does not generate a mathematically well-defined evolution of the wave function, but there are promising directions on that front as well: http://arxiv.org/abs/1506.00497
Basically, they treat the Hamiltonian as a whole instead of a perturbation and use a domain for it that has the probabilities flowing from one area to another appropriately to the different particle sectors.
There is also work on dealing with relativity which is a separate issue. While there are solutions, mainly centering on finding a natural foliation, the tension with relativity has not really been resolved, a tension which exists regardless of interpretation.
Exactly, John Bell had it right 50 years ago: non-locality is the problem of QM that needs to be solved, and other interpretations let you simply gloss over the problem without really addressing it. The recent work for finding a natural foliation present in any formalism with a wave function, including Bohmian mechanics, proves every QM shares this problem (or if you think one doesn't, then none of them do for the exact same reasons).
Uhmm, he’s working on quantum gravity too. Just a different approach. The same applies to loop quantum gravity.
> A practical implication is that it doesn't lead to any technology.
Who cares? It’s science not engineering.
> Smolin also doesn't like many-worlds, because it talks about unreachable regions. This he considers too speculative. There's a basic problem in quantum mechanics, which leads to Schroedinger's Cat, the Copenhagen Interpretation, and, in the end, many-worlds.
The string landscape [1] and the many-worlds interpretation [2] are two completely different things. The string landscape indicates that string theory may never be able to make any predictions. Some physicist try to use many universe in combination with the antropic principle to “solve” this problem. But I’m pretty sure this is a very small minority.
The many-worlds interpretation of quantum mechanics is just that, an interpretation. It doesn’t make any measurable difference from any other interpretation. And the Copenhagen interpretation doesn’t lead to many-worlds, they are just two different interpretations of the same theory.
> Physics has been stuck on this problem for almost a century now.
At this time I wouldn’t call it a “problem” of physics. If all predictions are the same it’s just a matter of taste which interpretation you prefer. To bring it into the realm of physics you would need to come up with some kind of theory of the measurement process that actually makes testable predictions.
[1] https://en.wikipedia.org/wiki/String_theory_landscape
[2] https://en.wikipedia.org/wiki/Many-worlds_interpretation
More specifically, it's about what kind of questions are considered worth asking. You can track the changes through history, and philosophy often leads politics and art as much as it does science.
Philosophy looks like the most abstract and possibly trivial pastime, but in fact it's incredibly powerful and influential, because it literally makes some world views thinkable and others unthinkable.
The different interpretations of QM are trying to ask different questions about reality. The fact that they're empirically indistinguishable suggests that either they're literally irrelevant - because they all give the same answer - or that no one knows how to ask a more insightful question yet.
If a more insightful question exists, it may come from some completely unexpected direction.
Physics has had a century to think about the problem, and hasn't gotten any closer to a definitive solution.
That suggests either more time is needed and we just haven't got there yet. Or perhaps the real explanation is literally unthinkable within the world view we have today.
String theory isn't a quantum theory of gravity in the same way that loop quantum gravity (LQG) is, LQG is background independent. String theory assumes there is a flat background spacetime already present and perturbatively builds off of that. LQG doesn't make this assumption and tries to create spacetime from scratch.
LQG did make some testable predictions, as has string theory in recent years. One was regarding the smallest units of area and volume that might have been seen in light scattering in cosmic ray or gamma-ray burst experiments[1]. Another suggesting evaporating black holes could be used to probe LQG [2]. String theory proposed supersymmetry, where each fundamental particle had a supersymmetric partner. Electron => selectron, quark => squark, etc. But none of these proposals have panned out as yet. Thus far supersymmetry has not been found and LQG has not been able to recover general relativity in a classical limit.
> The many-worlds interpretation of quantum mechanics is just that, an interpretation. It doesn’t make any measurable difference from any other interpretation.
In the last couple years, many-worlds researchers have come up with some potentially measurable consequences [3].
[1] https://www.edge.org/conversation/lee_smolin-loop-quantum-gr...
[2] http://dx.doi.org/10.1103/PhysRevLett.107.251301
[3] http://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.0410...
The issue wasn't that there was no evidence but that there weren't any predictions that would be testable in our lifetimes.
Superstring theory did make a testable prediction though: Supersymmetry. But the LHC didn't find any evidence. [1]
[1] http://arstechnica.com/science/2015/12/first-high-energy-lhc...
If string theory shows 10^500 possible universes, then what if tomorrow we come up with a way to identify which universe we're in? Would we still discard string theory just because it wasn't developed with an empirical footing and start over, or would we begin to examine its other consequences?
That string theory is pretty much just a theory at this point is, I think, not a strong enough argument to not pursue its mathematics. Especially since the theoretical effort has apparently yielded interesting mathematical tools for other areas. If that contribution is discounted, then it pretty much becomes an argument about funding.
Secondly, I'm not sure why time needs to be any less 'real' if it happens to be emergent. The expression "it all adds up to normality" has some power to it. If you think about our current notion of time which holds that a photon crosses all points along its path "at the same time", but that isn't true of the electron or proton, what could we even mean by "time is real"?
This "problem" is exactly a metaphysical one, so only philosophy can help. And there are plenty of interpretations that don't suffer from these problems too, like de Broglie-Bohm.
Multiverse theories in general may say that the universes interact. They may have differing coupling constants. You know you might try to come up with some new physics but your new physics hinges on these things existing... and that's fine... that's how new things are discovered, but we're at a point where SUSY is taken as a given and multiverses are taken as a given and theorists have this really much more convenient model of the universe that they're starting from and making unmeasurable conclusions and it just seems so removed from reality! That's the issue.
String theory isn't pseudoscience, because it does make testable, falsifiable predictions. In fact, it makes the same predictions that quantum field theory does for the phenomena that we are currently capable of testing (and arguably using a more elegant framework than QFT provides). The problem is that the predictions that string theory makes beyond QFT are currently way outside the realm of experimental assessment. This doesn't make the predictions false — if that's the way the universe really is, we just may be incapable of knowing that for a long time. There are a few hints that at least some of the predictions of string theory may be incorrect — we have yet to find any evidence of supersymmetry, and many physicists thought the LHC would turn up at least some evidence of this if it existed.
Regardless, I think people get too hung up on buzz-phrases like "is time real?" or "are we in a multiverse?". A lot of these are what I consider irrelevant to science, as the goal of science is to make accurate predictions about the future. If there is another universe out there, it is by definition unreachable from our current universe, so it makes no difference to science whatsoever. Likewise, what is or isn't "real" has no bearing on how accurately one can compute the evolution of some system's state through time.
If by people you mean science vbloggers like VSauce or Veritasium or even NDT's new Cosmos, then I'd say their goals are not to do or teach science but to inspire the next generation. Pop-sci is not for today's scientists. It is for the next generation of scientists and I think these philosophical questions are a fantastic way to get people interested in pursuing a career that doesn't have much glamor but can be very promising and fulfilling.
We can't know that yet, universes if parallel may interact at small scales in such a way that they can't be detected and reachable. To say they're unreachable by definition is hubris.
edit: Also Xcelerate has confirmed thats what they meant: https://news.ycombinator.com/item?id=12083025
> If there is another universe out there, it is by definition unreachable from our current universe
As this quote by definition accepts the distinction of multiple universes as it makes zero sense otherwise. To take him at his word means he believes it's possible that there is another universe, but that it cannot be reachable from our own; no where does this statement imply he believes there's only one possible universe and it directly implies otherwise.
His correction merely makes it clear he can't express himself clearly because what I just quoted above does not and can not make sense from the position of there being only one universe.
I'll even say props to you for parsing that nonsense because what he said in no way matches what he claims to believe.
Wow, harsh. Sorry to have aggrieved you so much.
I feel like it's also worth pointing out that string theory is also a possible solution to an extremely difficult mathematical problem. You don't fully get an appreciation for this when reading popular accounts. You don't realize that string theory is not just mumbo-jumbo about strings that someone made up but rather that the extraordinarily sophisticated math behind it actually works out, something that can't be said for the vast, vast majority of attempts at resolving the issues that string theory does resolve.
The difficulty of this problem is such that even coming up with possible solutions is itself a Herculean feat (witness the fact that Edward Witten, who proposed M theory, was awarded a Fields medal). This is ultimately why string theory has ever been taken seriously. None of this means string theory is correct, of course.
Is there a list of such issues somewhere?
And then there's the question of why time doesn't flow backwards (aka the arrow of time), which is genuinely interesting. Only a few fields have answers for this, e.g. thermodynamics with entropy. I hope answering this question will give us a much better framework to define time. I'd love it if it was shown in my lifetime that time is quantised.
And how do you know that time doesn't flow backwards? On quantum scale, how do you tell past from future?
Gravity is one directional too, but somehow everyone are mystified by time. I think it's because it's far too easy to let the imagination run wild on the possibilities of reversing time, but much less intuitive to imagine "reverse: gravitation or reverse entropy.
E.g. you don't observe a glass un-smashing. But as you probably also know, the question if/how a quantum arrow of time relates thermodynamics is currently unsolved and probably Nobel Prize territory. Not sure how much progress we'll make on Hacker News.
> Gravity is one directional too
I assume you mean it's purely attractive? It isn't too difficult to imagine a sphere with negative mass repelling another (like magnets), even if you've never seen negative mass :)
How do you picture reversing time? If you imagine it like reversing a video, it's obvious how this breaks down, again from the glass un-smashing. Entropy can be very visceral.
Time is not some parameter you can adjust. Time is just a word we have to express amount of quantum interactions that happen to an object.
That's why I don't imagine reversing time. It makes no sense. You can't reverse effects of interactions even if you reversed the laws of nature. And you can't record reality and play it backwards too.
I understand that dark matter is used to explain gravitational irregularities when observing galaxies. However, saying 'there is x amount of unobservable stuff there' in order to make our calculations correct seems like lazy science.
Are there any theories that don't include dark matter or energy? Can gravity function differently depending on its location (space or time) in the universe?
Yes. Hardly anyone takes them seriously, though, for a variety of reasons.
That's not how this works.
Dark matter and energy are placeholders for anything that can explain the discrepancy. The most likely explanation for dark matter is just undiscovered particles, but changing the physics of it to make the calculations come out right is also something that people do.
There's not really a difference between the two either. Post-QFT the concept of a particle is much blurrier than before, and "changing the physics" might just involve introducing a new background field that behaves differently in different places based on its concentration. In essence, you have introduced a new particle.
Please note that while it feels like lazy science, coming up with alternate theories that have the same success and rigor as QFT is very hard. Its not that they are hanging up their pencils and declaring premature victory. It is that literally the best description of physics out there to date doesn't explain this, and within that description yet-to-be-observed particles is its best bet. They are working on better explanations, but Rome wasn't built in a day.
The gravitational waves we're detecting come from black holes, but the readings we have from LIGO suggest that they most likely come from 'primordial' black holes formed at the birth of the universe.
If many of these black holes were formed they would be distributed much as MACHO theory predicts. 'Normal' black holes have very specific mass profiles so were generally ruled out as MACHOs, although obviously 'dark matter = black holes' has had a lot of consideration.
Just a nit.
There's not even a consensus on how to fit it into GR; the simplest and original solution is the cosmological constant, but there's also the approach of treating it as a field that is dynamic (can vary in space and time) in principle but just happens to be too uniform for us to tell. That doesn't even take into account the fact that this could be a sign that GR is simply missing something when it comes to the large scale structure of the cosmos. We've ruled out some proposed alternate theories experimentally but not all, and that's just the proposed ones.
The Casimir effect and Lamb shift are strong experimental evidence of vacuum energy, which is mathematically equivalent to Einstein's "cosmological constant".
Considering that the cosmological constant is nothing more than a magnitude as far as we can tell, a theory about a link that gives the wrong magnitude is completely useless. You can draw a parallel between them conceptually, but that connection is about as solid as the connection between the cosmological constant and any other isotropic scalar field like the Higgs. This is another speculative explanation, but again there is no theory that actually manages to explain the value.
Yes, I admitted that earlier. This is the tricky part, not that dark energy exists. There are a number of plausible theories as to why the magnitude of dark energy is much lower than expected, but nothing hard and fast yet.
What verified, novel predictions do any of the plausible theories make that makes them the defacto solution? I'd be really curious to know because it doesn't appear that many physicists are aware of this defacto solution.
PBS Space Time has a set of short videos[1] that do a very good job of explaining dark {matter,energy}. It starts with Einstein's field equations and GR, then walks through what the Friedmann equations say about the expansion of the universe.
[1] https://www.youtube.com/watch?v=xZTb6sfHEX8 (and the next few videos: https://www.youtube.com/pbsspacetime/videos )
I'm now hooked on the series, and feel like I am more informed about our latest understanding of physics and the universe.
"Dark matter" and "dark energy" don't refer to unobservable things, just to things whose existence we suspect but which we have not yet been able to observe. The planet Neptune was once in that category, as was the neutrino, and both of them were predicted "backwards" from a discrepancy between theory and observation (the observed orbit of Uranus didn't match what theory predicted, and it turned out the gravity of as-yet-unobserved Neptune was the cause; beta decay appeared to violate conservation laws, and it turned out the as-yet-undetected neutrino accounted for the "missing" energy and angular momentum).
So, lets look at the galaxy rotational curve data[1]. (Go look at the picture in the top right.) Galaxies don't spin like a record, because they aren't stiff. Instead, the stuff spins at different speeds. Also, galaxies are not like the sun and planets, where almost all the mass is at the centre, but rather it's spread out over the disk.
Now, we can try and predict how the mass is spread out, based on the size and colour of the stars we can see, and use that to get one prediction of how the galaxy should rotate.
We can also measure red/blue shift from stars, and use that to try and actually measure how the galaxy is rotating.
The problem is that these two don't match up. Which is a problem. So, we're trying to find ways to explain why they don't match up.
Now, one way to do this would be to note that if there was X amount of matter that we didn't account for when we only looked at the stars, then the curve would in fact match up.
Since this matter isn't stars, and doesn't give off light, it was called dark matter. And it seems more likely that there's a bunch of mass we can't see than that gravity works weird.
As far as I know, it's considered that multiverse is highly-theoretical (potentially non-falsifiable). String theory, a dozen dimensions, etc are still speculative and treated as unproven. Nobody said any of that was proven.
Perhaps when we have some alternative theory that survives that basic hurdle, we can discuss whether we're wasting time pursuing string theory rather than some other idea.
Yeah, not enough people are aware of this in my opinion.
So is the theory "A god did it".
One of the complaints on string theory, as I understand it, is that it ends up being too general: it sort of implies that just about any phenomenon could be plausible, which makes it really hard to falsify. It's not so much that it's made predictions that turned out to be true, but rather that it can be accommodated to fit prior experiments. From a Bayesian perspective, we haven't received any evidence of its truth, only evidence of nontruth of other theories.
You can design arbitrary systems to fit observations without identifying the underlying mechanisms, especially if said arbitrary systems are complex (which symmetry arguments are).
If these models are only predictive after the fact, then what good are they? The vindication for Einstein is that his various predictions are still being proven out a century later. Hawking found evidence that ran contrary to our theoretical understanding and has spent his life trying to explain the divergence.
String theories aren't in contention outside of the fringes, they're interesting mathematical models but they are on a par with our study of the ether in the late 19th century, something that will be looked back upon as a diversion away from the truth of our universe.
To refresh my memory I ran through this paper [1] briefly. My understanding is that multiverse arguments based on the Born rule are circular. One possible interpretation of the Born rule is the existence of a multiverse but it is not the only interpretation and it requires one to make some pretty big assumptions that the existing Quantum mechanics models being perfect representations of reality (which we know it is not).
Some arguments deriving the Born rule may be circular; I don't know - I don't see how that matters - because others are not.
There are some critics but they mostly start from philosophical considerations: that a multiverse is untestable outside the quantum scale, imposes a high cognitive burden or requires us to redefine probability. Those objections are only valid if you consider a multiverse a priori unlikely; the evidence and math is clearly in it's favour.
If you want better answers I would look through that forum, or consult a recent review of the literature around decoherence.
I have some modest undergraduate work in modern Physics, I think you may be taking the dominant voice on the physicsforums.com at face value when there's a high potential for self-selection bias in online forums. Going back to the experiment evidence and underlying mathematics there just hasn't been a breakthrough of any sorts.
I'm not sure what your argument is, but nobody is proving a multiverse, it's just an observation.
It seems like there's some lack of imagination here, like physics is "done", there's nothing more to answer, it's all just up to other sciences to answer the rest of the (many) questions about why the world is what it is and how it works. A reset of approaches is interesting, but it still needs to be in service of something, doesn't it?
(disclaimer: I am not a physicist, etc.)
Between GR and QM, we can explain most observable phenomena, but it's intuitively obvious that both are emergent properties of some deeper law.
I don't suspect frontier physics is ever really studied with an eye to application. Those tend to follow, but the bleeding edge of physics is usually advanced just out of intellectual curiosity, to try to understand the universe.
In this sense, String Theory is just an attempt the unify General Relativity with Quantum Mechanics. The fact that it's not apparently testable is unfortunate,
We can have pedantic arguments about whether that's "Real Science", since science by definition requires testable hypotheses, but at the end of the day, I don't think it's crazy to pursue a model to encompass QM and GR, even if it can't be called "Science".
Previously they did have experimental results they were trying to understand. There might be follow up experiments to confirm, but there were already experimental tensions.
> I don't think it's crazy to pursue a model to encompass QM and GR, even if it can't be called "Science".
I'm not so concerned about whether something is science, it just seems like vanity to pursue unification that provides no insight into the complex world around us.
It's obvious to everyone involved that GM and QM, both the best physically verified theories at their respective energies, are deeply incompatible with one another.
Unfortunately, physical situations where we can see them disagreeing are outside of our reach at the moment. You're suggesting the entire physics community just give up theorizing until we can plausibly reach unification energies, even if that's a thousand years from now?
> it just seems like vanity to pursue unification that provides no insight into the complex world around us
Pure theory has a funny habit of finding applications in the most unexpected places.
Anyway, if it's an interesting problem, and people want to spend their time thinking about it, who are we to tell them to stop?
In my opinion string theory is a very complex case of interpolation. Yes, it "explains" our current knowledge, but it goes way off just after the last point to which it is interpolated. I like that it exists, as it will surely make history in science a grandiose attempt to unify GR with QM, and it is real science in a sense that the methods used in it might be transferred to other fields, but I don't expect for it to give any insight into our universe.
Treat it like a theoretical physicist toy, and when you look at it that way, it isn't that bad at all.
It's a better framework for some problems as a model of other (comparatively mundane) quantum phenomena. But yes, generally you're far better off sticking with QFT or GR separately for observable physics.
In theory, future technology will be able to observe some of the regimes string theory (and other attempts at unification) throw at us. But this of course requires experimenting in places where quantum and specifically general relativistic effects (QFT already incorporates special relativity) are both strong. We don't really have any places where we can observe distinctly GR effects that aren't on some sort of literally astronomical scale (the closest we can go is Earth's orbit with timing for satellites). Since QM likes to stick with the small, this puts us in a real bind until we can do something crazy energy-wise.
> It seems like there's some lack of imagination here, like physics is "done", there's nothing more to answer
Physics isn't more done than any of the other sciences: there's an incredible breadth of active research that makes up most of the fields of physics (condensed matter, quantum information, atomic/molecular/optic). We might have a formulation of most of the fundamental ground rules, but then so do biologists and chemists by the same token. I think the unofficial motto of condensed matter physics sums up the opportunity for exploration pretty clearly: "More is different".
As for Mathematics being selectively real, I agree with that totally. Mathematics is just a language we use to describe models and their properties in a most rigorous way. That's all. Can we find a model of the universe from which we can derive all its properties? Unlikely (see Gödel), if so the model would have to be pretty "primitive" and thus too large for comprehension. But so what, we can find great models for certain aspects of reality, and I don't see a limit for how far this can be taken to get better and better models for more and more areas of reality.
But those models are correct only in what they describe, they don't completely describe nature. They are just that, models. Every time science has progressed, it's either an "exception to the rule", or a re-understanding of an incomplete theory.
I'm not a scientist, but I vividly remember how a physics professor warned us about the laws he was teaching. Those laws work well, use them, but never pretend that they're universal and that they will be for the next 20 or 100 years.
You can see this problem in quantum mechanics. Quantum mechanics is being very hard on philosophy and certainty in general. Up to a point, using models might be a limit to physics.
A great example would be with something like density functional theory (DFT), where we make extremely crude approximations for exchange and correlation functionals. By understanding the limits of our model we can use this information to improve the results; as Feynman said: "The first job of a theoretical physicist is to prove yourself wrong as fast as possible".
I'm not sure I agree with your last statement:
>Up to a point, using models might be a limit to physics.
I argue that this is the most important thing to physics. The moment you start to leave a model, you allow for subjective speculation. I argue that this has no place in physics and is the prime reason that physics has broken away from philosophy.
Don't you need to speculate at one moment or another to improves physics?
Of course you can only do that once you studied physics a lot, but if you want to be creative in physics, don't you have to "speculate" that work with the data?
This "science" is as bad pile of nonsense as Hegelian "philosophy".
From my limited understanding, time is merely the measurement of change. A comet goes from point A to B, and like a screen flickering, it is in a discrete point in space every step along the way. It is time that is introduced when asking ourselves, "how long did it take?" or "when was it at X?" but how can it be woven into the fabric of the universe? If we take reality to be right here, right now, it doesn't seem to exist but rather is a human invention to help us map change.
Quoted from the book in the article:
"Our mathematical inventions offer us no shortcut to timeless truth... They never replace the work of scientific discovery and of imagination. The effectiveness of mathematics in natural science is reasonable because it is limited and relative."
I'm not sure what the authors mean by this. Are we to ultimately abandon our attempts at a consistent, logical explanation of what we see? If so, that's when we revert to un-scientific and, essentially, religious ways of thinking. I'd argue that the pursuit of a mathematical explanation of observations is the work of scientific imagination. Mathematics is merely the most reliable way we've devised of communicating what we imagine to other people. And sometimes the math, itself, sings to you and that drives advances in understanding that are totally valid.
My take - the only way the universe could have got here from nothing as it were is if it's basically maths and seems real to us. I mean what does basic particle behavior look like - a bunch of maths and not much else, and what exist without needing creating - mathematical patterns and relations and nothing else. Hence from observation it's probably all maths.
Hence:
1) There is only one universe. - Nah probably all mathematically possible universes seem real to their occupants.
2) Time is real. - Sorta but more like how time exists in a DVD of a movie. Or as some guy wrote "...for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one."
3) Mathematics is selectively real. - Nah it's real.
The way I see it:
- Consciousness (perceptions, feelings, thought) is the only thing that really exists.
- There are patterns in what we perceive, for example, when we drop a rock, we see it falls and hear the impact.
- So we develop models to describe patterns in our consciousness. Physics is just a description of those patterns. So the physical world doesn't really exist, it's just an idea in our minds.
Definitely not self evident, vast majority of people don't see things this way. It doesn't have to explain anything, it's something akin to observation. Just a description of how things are, not an explanation.
> Saying that consciousness is the only thing that exists is like saying God created the universe.
I don't get this, how is this remotely similar, what does God have to do with this? The way I see it, history is just mental concept / idea. We take our physical model and similate the current state of the universe backwards - and call this history.
> I personally don't believe this to be the case - I think everything exists and consciousness is only one way too perceive that everything, but that's another debate I guess
Well, you only have perceptions (what you see, hear, feel, ...). It's the only thing you can be sure of. The "real world" is in its essence a thought, idea, mental model. Think about what does the statement "Eiffel tower exists" mean. It's a probabilistic statement about future perceptions - if you go to Paris, you will probably see it.
In my opinion it definitely is an explanation. There's a difference between a world where only consciousness exists, to one where the real world exists and consciousness is one aspect of it.
> I don't get this, how is this remotely similar, what does God have to do with this?
Saying only consciousness exists doesn't explain what consciousness is. Same as saying that God created the universe doesn't explain what created God. If it happens to be that the physical world exists and consciousness is a phenomena of the brain, as we see it today through our perceptions, then consciousness is NOT the only thing that exists, and we can start to probe what the role of it is in the bigger picture.
> It's the only thing you can be sure of. The "real world" is in its essence a thought, idea, mental model.
But what if it isn't? What if the real world is tightly coupled to the physics that we perceive, and that our concept of it in consciousness actually comes from physics and not from our mental model. There is definitely a chance that all our perceptions are false / an illusion of some kind, but since as you say, they are all we have, we have to presume some level of reality outside our mind and then go from there, and then if some day it's proven to be totally false we can evaluate our options then.
If we switch off all consciousness by giving strong sleeping pills to all humans (animals too? - or is it just you who matters (solipsism)?), will the moon change its position while we are sleeping?
So will your/the consciousness move the world while you/we are unconscious - using some simple and higly regular rules (called physics)?
But if you/we are unconscious, then why on earth should we call that unconscious mover of the world consciousness?
Basically yes (depending on the definition of solipsism). From your point of view, all that really exists is your current consciousness. Other people's minds are just a part of your mental model of the world.
It's hard to get tenure these days if you ever mention solipsism, the direct conclusion of Descartes' cogito (which he never seemed to quite get to himself) or solipsism seriously. Individually or in some creative combo move. I don't know if that's because people think that Kant has been beat up enough that they don't want to be seen standing near his stinking corpse, or thinking about it just makes some people feel 'icky' or what.
Which is too bad, because I find that Johnson's (to Berkeley) "I refute it thus!" to be more of a hissy fit than a satisfying response. IDK. Maybe I'd just like someone to use more words? :-)
Stop being impatient!
You can infer the mass that is interior to an orbit by measuring the speed at which an object is orbiting. By measuring the redshift and blueshift, we can get speeds of different parts of the galaxy. It turns out that we can account for more-or-less all of the mass near the centre of galaxies, but as we get further out, orbital velocities seem to be higher than they should be implying more mass is there than we can actually see.
In other words, we can tell that the missing mass is not at the centre of the galaxy, but rather spread throughout it.
If it can happen in physics, it can happen anywhere -- maybe even your neighborhood.
http://science.nasa.gov/missions/cobe/
This took the predictions from the big bang theory about a small hot dense universe, and measured the cosmic background radiation, and it matched perfectly.
The idea is that when the universe was young, it was so hot that all the matter was in a plasma cloud, and that photons (and other EM radiation) couldn't travel very far at all before being absorbed and re-emitted in a random direction. Then, the universe expanded and cooled enough that the cloud became transparent. But there were still those photons (etc) that now just kept going in all directions. Some of them happen to be arriving from all directions no matter where you are (unless you're on the rim of the universe or something). That's the cosmic background radiation.
And we measured it, and it matched so well with the predicted numbers it was astounding.
This is also the graph that shows up on the "Science, it works bitches!" xkcd shirt.
What? How is this helping?
"Any headline that ends in a question mark can be answered by the word no."
Has the Hacker News upvote system gotten something really important really wrong?
Yessss, keep feeding me more of those delicious downvotes.
ok, except what else just has 1 of them
ask a photon thatI'm pretty sure it isn't ; ever since quantum mechanics physicists have been very good at separating the two. Popsci, not so much, but the actual physics is very clear about it being a model.
But this is not what a lot of physicists seem to do.
It's not like this lack of context-sensitive speech is specific to physicists either. Programmers do it all the time too.