We often debate on topics related to theories in physics, without realizing, they are all based on certain observations, restricted to our own capabilities.
There are some strongly related comments (a few from me ;)) on another question: "Are there any aspects of physics that are inviolate and absolutely immutable?" to the theme of this question.
As I have argued there, our knowledge of Physics is necessarily incomplete (or at best not provably complete), but the key factor is that the scientific method allows our knowledge to asymptote towards the complete knowledge of physics.
To say that we use our 'five sense organs' is quite limited. Not only do humans have far more than 5 senses, most of our most sensitive measurement devices use sensing modalities that far exceed our human restrictions, for example X-ray telescopes, Atomic force microscopes and neutrino detectors. So we really have far greater capabilities than our biology would seem to allow.
But the fact that our inferences are in some sense limited by our space-time location is also well highlighted by Lawrence Krauss, who points out that because the universe is expanding, at some time in the future, astronomers in the Milky Way will be unable to observe any other galaxies, and hence are likely to infer that the universe comprises just the Milky Way. He asks: what other physics is inaccessible to observation due to the accident of where (again in 4-space) we have evolved?
There are some strongly related comments (a few from me ;)) on another question: "Are there any aspects of physics that are inviolate and absolutely immutable?" to the theme of this question.
As I have argued there, our knowledge of Physics is necessarily incomplete (or at best not provably complete), but the key factor is that the scientific method allows our knowledge to asymptote towards the complete knowledge of physics.
To say that we use our 'five sense organs' is quite limited. Not only do humans have far more than 5 senses, most of our most sensitive measurement devices use sensing modalities that far exceed our human restrictions, for example X-ray telescopes, Atomic force microscopes and neutrino detectors. So we really have far greater capabilities than our biology would seem to allow.
But the fact that our inferences are in some sense limited by our space-time location is also well highlighted by Lawrence Krauss, who points out that because the universe is expanding, at some time in the future, astronomers in the Milky Way will be unable to observe any other galaxies, and hence are likely to infer that the universe comprises just the Milky Way. He asks: what other physics is inaccessible to observation due to the accident of where (again in 4-space) we have evolved?
Think of an imaginary situation. One of our sense organs, Vision, undergoes biological changes due to some genetic reasons. So, we start to see things illuminated by very high or low energy electromagnetic radiation (not detected by presently available tools), instead of visible light. Do we expect the same physics to hold its ground without undergoing any modifications?
what we experience by five sense organs is not what is nature. senses may be decisive often, we can get more insightful results by experiments. the right method of doing science or understanding nature is goes like this:
1. Observation: make observations around you, do as much observation as much you can do.
2. Hypothesis: Based upon observation make a hypothesis. The hypothesis should be explaining every observation you've made.
3. Experimentation: now its time to test your hypothesis, do experiments to test your hypothesis. If every experiment satisfy your hypothesis, bingo.... you are ready to go for a new theory.
any theory is valid until there is no exception. even a single exception and the theory is demolished. scientists are bound to work with the technology of their time, as we as a civilization progress we acquire new technology to test more theories. some theories survive while other are demolished or refined. so no theory of truth is the final or comprehensive in true sense. one last thing i want to add is that, what we observe through our experiments is not nature itself. it is nature exposed to our method of questioning it i.e. methodology of experiment.
Dear Anuj Bhatnagar,
What you describe has in fact been done to an extent, in experiments where colour blind squirrel monkeys were provided with gene therapy to give them the full range of colour vision experienced by females (trichromats) (Mancuso, K., W. W. Hauswirth, et al. (2009). "Gene therapy for red‚ and green colour blindness in adult primates." Nature 461(7265): 784-787.)
Undoubtedly this would have been a huge shift in the perception of these creatures and would challenge their understanding of their environment (and by inference perhaps also their understanding of physics). But just as every new tool we have access to gives us new insights and deepens our understanding of physics, it will not affect 'physics' itself.
Today, progress in Physics (valid for science in general) is heavily dependent on the outcome of our observations, which in turn rely on modern technological tools (equipments). This is leading to advances in physics at very slow pace. To add further, we are not sure how long it will be valid and not replaced by something better, depending upon what set of tools will be available for scientific observations tomorrow.
Dear Anuj,
I am not sure I understand what you mean by 'advances in physics at very slow pace'. Physics as a discipline is expanding at a phenomenal rate, with new concepts and breakthroughs happening routinely. Very clear examples of this including graphene, cooling of cantilevers to the quantum mechanical ground state, verification of the accelerating universe, giant magneto-resistance, and the leap from Bose-Einstein Condensates to ultracold molecules. Many of these breakthroughs are most definitely enhanced by technology, not only new ways of probing systems, but also parallel semiconductor fabrication. Indeed, glancing at opto-mechanical systems, what is really exciting there is how so many different technologies are combined to create working devices (nanofabrication, superconductivity, laser cooling and opto-mechanics) in ways that would have been prohibitively complicated (ie technologically unfeasible) even 10 years ago (in my opinion).
You are absolutely correct, however, that we are getting new tools and hence new insights regularly, but this should be a source of optimism and excitement, as these new tools give us new vistas to explore.
Dear Andrew,
I agree with you that technologically we are making good progress. We are creating more advanced tools to investigate fundamentals of physics (sciences in general). However, our progress is asymptotic towards complete understanding of laws of nature. We are yet to fully understand QM. Good progress in Physics would mean breakthroughs of the kind Special Relativity, QM brought by replacing Newtonian mechanics.
I was just trying to understand the basic nature of time and its origin. Plese see my another question "What is more fundamental: Motion or time".
Our understanding of Physics is grounded on our experiences, but not on our raw experiences: we use data, and from those data we make reasonable generalizations, some of which we elevate to the category of physical laws or principles. In this process we introduce some axioms---like Euclid's common notions---, the rules to combine numbers, for example.
If we keep ourselves within the realm of arithmetic, we know, because of Goedel's theorem that we cannot have a complete system of axioms from which we could prove each and every statement on natural numbers that is true.
The calculus of real numbers, which is the most used in Physics can be explained in terms of the calculus of natural numbers. Therefore, some of those theorems that cannot be proved about naturals might be logically equivalent to theorems about real numbers, and those theorems on real numbers might have an interpretation in one or more of our physical theories.
Dear Anuj,
I see your point, and it is certainly the case that we have a major (at least) conceptual problem with the unification of relativity and quantum mechanics. Mind you, I find it unlikely that such a unification will provide massive changes to our society in the way that both relativity and quantum mechanics have, although I find it very likely that the technologies required to elucidate the correct framework will.
And I still reiterate the fact that although many of the recent breakthroughs have not caused the same upheavals to the scientific fundamentals at relativity and quantum mechanics, they are nonetheless extreme changes in the space of what is called physics. Quantum information science is good example for me (and indeed is one of the major aspects of my research): this is a field that really didn't exists seriously until the 90s. It is arguable whether there is any new physics here, but it is a powerful new conception of physics: what it means and what can be done with it.
Progress in physics has never been faster than it is today, and physics as a discipline reaches into more aspects of science and technology than ever before: these are great successes. However, although we should continue to search for them, we shouldn't just the success of failure of physics simply because we haven't found a new paradigm like thermodynamics, relativity or quantum mechanics recently. It is as well to remember that all of these breakthroughs and paradigm shifts originated in real practical problems where conceptual problems had been found and new physics was demonstrably required (thermodynamics was driven by the steam engine; relativity by the unification of electricity and magnetism, and the problem of the distribution of time; and quantum mechanics by the ultraviolet catastrophe). Human society has many problems at the moment, but apart from the unification of gravity with quantum mechanics, I am hard pressed to find problems in the physical sciences for which the conceptual framework is lacking, and hence it is hard to see where the next great paradigm is going to come from.
Dear Andrew,
I fully agree with your world view regarding the state of technological advancement based on present understanding of physics. However, I feel, the conceptual problems with fundamental laws need to be resolved first. Otherwise, the complex web of technology based world may face major problems in future. You may notice that a lot of innovations do take place everyday. Do we see all reaching market or the end application. Only a select few which can beat other competing technologies on economic front as well as specifications, survive. Even the survival period is determined by what next is better than the previous one.
Under such circumstances, a sudden change of paradigm shift, equivalent to shaking the foundations of physics may disturb the web of technological developments as well. In Physics, the paradigm shift in terms of new knowledge may just create a bigger knowledge domain where our present understanding will be a subset (finding its rightful place). This may not cause a major impact on society immediately, but definitely will have lasting effect. However, on the technology front, the presents gadgets may suddenly give way to the new ones, and this change will be rapid.
As a scientist myself, I feel, the foundation of physics should be so strong that it is not dependent on technology for its advancement in an asymptotic manner. instead, the technology should be used only to accept or reject it.
The idea that physics is grounded on our experiences is a philosophy of science known as empiricism, and it is simply false.
Physics is based on theories. These theories are always only hypothetical. But these theories allow to make predictions. And these predictions can be used to test these theories, by comparison of these predictions with observations. If there is disagreement, the theory is falsified and, therefore, rejected, it cannot be true.
One has to invent a better theory. But this better theory has to be invented, it cannot be derived from the observations alone. One needs something else, ideas. Therefore, observations are only a tool to test theories, and reject some of them. They are not a base for derivation of the theories.
For more about modern philosophy of science, read Karl Popper.
Ilja
THeories are there to explain and guide OBSERVATIONS; and thus without observations there is no physics
Harry,
I thought, theories cover a much wider domain of what all is happening, all the time, around us. A good theory must explain all that we observe with our limited tools (both our senses as well as scientific equipments) and, should continue to do in near future also. If the theory can withstand, let what may come in far-far future, it will be a perfect theory.
In contrast, theories based on pure observations may not survive over time. As an example, we may claim to have understood electromagnetism. But, do we have tool (human and man made) to cover the full band of its spectrum (very low to very-very high frequency). Until that is done, our theories based on limited tools will only throw up theories which may at best be incomplete.
Anuj
That sounds very abstract. what theories are you referring to? Electromagnetism is only aspect of physics and the theories/equations must first of all describe what has been observed so far. However a general formula does not describe a particular observation or an experiment; there one needs auxiliary formulae and constraints. The idea of one general theory is not working in the practice of every day.
Dear Constantin,
I agree with your explanation. In particular the five points. I must add, the fourth point regarding theory or explanation should be simple, is very important. But some how, the current developments in physics are taking the other route. Is there a need somewhere to look for simple theories or solutions to existing problems in physics?
Regarding electromagnetism, We do have state-of-art equipments to cover a wide spectrum. But look at the complaxity, there is no single equipment to cover the whole band: for transmission and detection.
The interplay between theory and experiments is vital. But interplay should be both ways and equally dominating. What we see today is the dominance of technology and new theories are often driven by that.
I don't see it this way. Of course, there are new experiments, but in fundamental physics all they do is to confirm the standard model which is already quite old and has been only slightly modified (massive neutrinos, more accurate parameters, all three generations, Higgs) since then. New theories driven by these confirmations? Nothing serious. String theory is driven by theoretical speculation, not by observation.
Anuj
what new theories do you need for EM? There are different instruments to cover a range of frequencies / wavelength from km's to (what) attometers; how would you think you could do that with a single instrument and why?
Dear Constantin,
Nice information. It is easy to understand now as to why physics is driven by experiments these days. It looks, researchers do what they are paid for. This situation is different from the progress of physics during 20th century or earlier. The likes of SRT, QM, EPR or other similar path breaking ideas or theories are rarely to be seen.
Graphene is probably one such example which will have long term scientific and technological implications. But see, it was the work of few individuals working on very simple idea.
Anuj
EPR is a very small minor part of QM (rather QED) and can be explained within it. Then, every era has its own issues and sometimes observations are ahead of theory and vice versa. We are not in the previous century when your ground breaking experiments and models were the work of an individual: that also typifies the work: it was still quite simple. Nowadays there are often teams of hundreds of scientists involved in the accelerator studies, by necessity because so many different disciplines are required
Dear Harry,
I agree, EPR is a very small or minor part of QM. But, it is seriously related to the foundations of QM and that is why it is very important. On one side, it has serious theoretical implications while on the other, technological applications.
Bigger (International) teams of scientists working on mega projects is certainly need of the hour as no single individual has the kind of expertise required to perform mega projects, in isolation. Just as we need a basket full of multiple equipments to transmit or detect EM fields (full band), we need group of experts in mega projects. But, do we really need OPERA (Faster-Than-Light Neutrinos) kind experiments.
Neglecting the foundations of Physics because applied physics is rewarding is not a win-win situation. Today the technology has advanced so much that even the slightest change at the root of it might cause tectonic changes in technology itself.
My original question was aimed towards bringing out these very core issues.
Ajur
Matter of fact (also in the literal sense, because physics is about matter even more so than EM) at the foundations nothing has changed in the last half century, while at the applied side many new inventions have paved the way for new observations, which up to now can still be explained or are in line with what exists as theory. That is the status (quo) of physics
Andrew
Finally my answer on your reply to me; your original answers in parantheses.
“….. The act of measurement is demonstrably performed by instruments that are not created by humans (e.g. photosynthesis, ion tracks in rocks etc.)”
I agree that not all measuring devices are manmade, and here it took me some time to think and get my thoughts together.
My comment here is that also such data need human perception and interpretation even though they are imprinted in “nature”
“So from this point of view, what I or others actually thinks is not so important, and as you will see from what I am about to say, the existence of neutrinos must be considered absolutely resolved in the positive because we have neutrino detectors/observatories. Note also discussions around pointer states and superselection rules.”
While I am also of the school that conceives neutrinos etc as realities there are others who do not think they are real entities but belonging to theories that are abstract. They consider anything that is not macroscopic as not “real”. I cannot come up with a good argument to make the point that even electrons exist as real entities.
“… what is meant by reality. Probably the most important contribution of the EPR paper was to clarify what was meant by reality. So using EPR as our basis we are led to believe that there should be an objective reality, and that reality
encompasses all of the elements of reality above. It should also not incorporate any items that are not elements of reality (as they are by definition unmeasurable and have no observable consequences). I believe that such an objective reality exists. I believe that that reality exists independent of human consciousness. I am happy to agree that our description of that reality is incomplete and that we are not in a position to state definitively what all of the elements of reality are, or all of the laws that describe their evolution, but I do believe that there are some governing laws, and that these laws constitute elements of reality in their own right.”
The EPR idea does not appeal to me, because the recent outcome of the real experiments do not support it.
And moreover I do not believe that we as humans describe reality with our thoughts or formulae; rather that the theories we establish in mathematical wording, but with further human ideas on the interaction terms, are our own inventions and work as long as there is no other theory that does the same job, plus “explaining” phenomena in other areas.
In metaphysical terms I believe in the miracle idea and am thus not a Realist: that means that we as humans are obviously able to describe and correlate phenomena in nature but actually in QM in the very limited environment of a laboratory, which means well-planned experiments. This in my view is done, in an “objective” way, meaning that all physicists accept the description of the experiment and the (QM) theory. For me that is not reality but a common concept.
I cannot understand how one can prefer to give up realism if all one needs to save realism in the light of the violation of Bell's inequalities is to accept that there are real causal effects with velocities greater than one particular velocity - that of light.
Ilja
What do you mean to give up "realism". What is his realism for you?
For my definition see http://ilja-schmelzer.de/realism/definition.php , essentially it is what we need, in combination with Einstein causality, to prove Bell's inequalities.
If one thinks about this definition and its meaning in detail, it appears to be a very weak notion, but a very important one: Roughly, an observable correlation needs a realistic, causal explanation. The meaning of "realistic causal explanation" is quite simple in formulas, there is not much to weaken. But if we give up to search for realistic causal explanations of observable correlations, what remains from science, what is the difference with astrology?
Ilja
I read the page you mentioned, but I basically see the expression of the wish that causality would exist, like in your comment above. The reality is that millions of scientists successfully apply this astrological science (QM).
There is nothing to object against QM itself. It allows for a realistic explanations. And, if we give up to search for new explanations, the explanations we have already found remain accepted and usable. What is prevented is only further progress toward a subquantum theory. So, of course, my remark about astrology was a polemical exaggeration.
Dear Harry,
Sorry to have taken so long to reply to your response to me. They are thoughtful comments, although I disagree with several of them. Let me explain why.
THe initial point regarding whether human perception is required to interpret and understand results is one that I think that we are always going to disagree on. I'm not at all convinced that the 'understanding' of interactions is in any way important to their dynamics, and most pertinently, that understanding should not effect measurement outcomes, nor the process of a measurement occurring. If understanding did have such an impact, I would worry that measurement results would not be objective (i.e. two observers observing the same process from the same frame of reference should observe the same result, even if that is randomly determined).
Regarding the issue of the reality of neutrinos and other microscopic particles. I can only fall back on the fact that we have neutrino detectors and there are good measurements of properties such as neutrino mass. Also, with reference to electrons, they are readily observable in scintillation type measurements, individual electrons are used in electron microscopy, and have even been trapped for extended periods of time to make artificial atoms (http://physics.aps.org/story/v4/st11). So I am really surprised to hear you say that it is difficult to make the argument that they are "real".
If modern science is telling us anything, it is telling us that the boundary between macroscopic and microscopic is extremely blurred. Also, that if we believe that certain particles exist for theoretical reasons (neutrinos, Higgs etc.) then we had better look for them, and modify our theories accordingly. This has been done, and those particles are real.
Now, EPR. It is really important to stress that what EPR thought of (probably) as a reductio ad absurdum argument is in fact what is observed. Even the position/momentum type entanglement has been done (in quantum optics where it is often referred to as hyper-entanglement). The EPR inference that something was lacking in quantum mechanics is clearly incorrect, and their intuition about why actually an 'element of reality' constituted was certainly incorrect, although their definition was the perfect way to frame the question.
All the best
Andy
The intuition of EPR may have been incorrect. But if the definition is fine, what follows is that we have to make the other conclusion, namely that there exist faster than light causal influences.
This was, last but not least, something considered obviously true in Newtonian mechanics. So it is nothing really disturbing. The alternative is to give up realism, which is completely unjustified.
Ilja
What is so realistic then about faster than light gravity? Just that we got used to it since Newton thought it out. Well for me after almost 100 years QM has the same status. It is the only formalism that works for the issues of my concern. when there is something better I trade QM in.
Dear Ilja,
Faster than light causal influences? Well, yes, but only in a special way.
The lower bound on the collapse of a spatially delocalised wavefunction has been measured, and is 10^7 c (Zbinden et al., "Experimental Test of Relativistic Quantum State Collapse with Moving Reference Frames"). This can be interpreted as the 'speed of quantum information'.
But this hides a very important point. Without classical information, all that is ever detected is randomness (albeit shared randomness). So without classical communication, the information content of this quantum information is identically zero. This is why the bound on the speed of light is often reframed to state that no information can be transmitted faster than the speed of light.
Now this is fundamentally different from Newtonian action at a distance, where information about the position of a massive body was instantly communicated via the gravitational field. And of course, general relativity allows us now to interpret the communication of the position of the mass as being mediated by gravitational waves that travel at the speed of light, and hence provide for causal relations.
Incidentally, returning for one moment to the relativistic quantum state collapse, the fact that the collapse is measured to be communicated through the quantum state at at least 10^7 c immediately tells you some important things. First, to all intents and purposes it must be infinite (i.e. instantaneous). Second, the order of measurement cannot make any difference to the outcome. That means that it is not true that in an EPR type experiment the two receivers can communicate, because either Alice measures before Bob, or Bob before Alice, but who measures first must depend on what frame of reference you are in, hence there cannot be any kind of cause and effect relationship between them (i.e. Alice cannot perform a measurement, and the result of that collapse used to modify any outcome of Bob as there is no unambiguous way to define whether or not Alice performed the operation before Bob did). The propagation of classical information, however, does provide a causal pathway, and can therefore be used to 'unlock' the quantum information.
BTW, Ilja, what you are really saying here is not that you need to give up realism. Instead you have to give up local realism.
Andrew/Andy
Appreciate your (long) answer. It is good sparring with you, as I continue to have the time and the proper environment (ResearchGate) to renew my college-time interest in metaphysics (of QM).
@“THe initial point regarding whether human perception is required to interpret and understand results... I'm not at all convinced that the 'understanding' of interactions is in any way important to their dynamics, and most pertinently, that understanding should not effect measurement outcomes, nor the process of a measurement occurring. If understanding did have such an impact, I would worry that measurement results would not be objective (i.e. two observers observing the same process from the same frame of reference should observe the same result, even if that is randomly determined).”
What I see now is that you appreciate measuring as an objective process. Measuring to me is making a human measure; and how come every subjective individual physicist appreciates a measurement the same way. That for me is a miracle as it is the fundament of doing physics and scary that this is the case
@“Regarding the issue of the reality of neutrinos and other microscopic particles. I can only fall back on the fact that we have neutrino detectors and there are good measurements of properties such as neutrino mass. Also, with reference to electrons, they are readily observable in scintillation type measurements, individual electrons are used in electron microscopy, and have even been trapped for extended periods of time to make artificial atoms. So I am really surprised to hear you say that it is difficult to make the argument that they are "real".”
I am voicing the problem in metaphysics where realism starts and ends. The neutrino example is less convincing than the electron. As you indicate there are more direct observations to show skepticists that they are “real”. I like to add the unit charge of the electron. The neutrino is a different story: detected by a neutrino detector is not convincing for an anti-realist. He accepts the measurement but not the idea that the neutrino is an actual entity.
@Andrew Greentree, what I have to give up is, of course, "local realism". But that means, I have to give up Einstein causality, or I have to give up realism. Because "local realism" is their combination.
I prefer to give up Einstein causality and to go back to classical causality with a hidden preferred frame.
What you can save, if you don't give up realism, is a weak form of Einstein causality: Causal influences FTL really exist, but they cannot be used for information transfer.
And even this only in a quite weak sense: You can use it to win in a game, described in http://ilja-schmelzer.de/realism/game.php where you have, otherwise, no chance to win without a hidden information channel. So, the "cannot be used" has to be specified by "in a straightforward way" or so.
Then, I disagree: The order has to play a role in every realistic explanation of what happens. A realistic explanation has to specify the causal influences which have to explain all the observed correlations. Without "then a miracle happens". As a consequence, the realistic explanation cannot be Lorentz-covariant.
There may be only different explanations of the same observations, and we may be unable to tell which of these incompatible explanations is the true explanation. Such is life. Realism tells us only that there exists a true explanation. Not that there is a way to identify it uniquely.
Last but not least I disagree with the "has to be infinite". The next generation of the same experiment may give us a minimal speed of 10^9 c or so, or it may give us pairs of events where the QM prediction fails and no violation of Bell's inequality happens. This would be an approximate measurement of some new absolute contemporaneity.
Harry, the question is not what is so realistic about FTL, but what is so horrible about it that some people propose to reject even realism if the only alternative is to accept FTL.
Sorry, but I would give up even atheism and accept a strange but really existing God if the only alternative would be to give up realism.
Ilja
I am (now) struggling with the concept of realism. Metaphysically there quite some versions around and (thus) I do not know what kind of realism you mean.
The realism I mean is essentially extracted from Bell's theorem. Roughly speaking, use the assumptions of Bell's theorem, take away Einstein causality, and you have my notion of realism. As a consequence, what I have claimed here becomes, with this definition of realism, almost tautological.
On the other hand, the definition obtained in this was is a nice and reasonable one. See http://ilja-schmelzer.de/realism/definition.php
Researchers thought that the 9th century:
Ibn Al Haitham has shown that this is not the object that produces the sensation, but countless points of light reflected from the object surface to allow the eye to feel an image formed according to the principles optical
The question of the experiment was at the center of this major scientific developments.
-the imposition of the experimental standard as a fundamental category of evidence;
-the foundation of the mathematization of physics or more precisely the physical as it is mathematized he called "composition between mathematics and physics."
Note that the experimental practice is here intimately linked to this "composition between mathematics and physics"
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