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In the comments for the question Falsification in Math vs Science, a dispute around the question of "Have Newtonian Mechanics been falsified?"

That's a bit of a vague question, so attempting to narrow it a bit:

  1. Are any of Newton's three laws considered to be 'falsified theories' by any 'working physicists'? If so, what evidence do they have that they believe falsifies those three theories?

  2. If the three laws are still unfalsified, are there any other concepts that form a part of "Newtonian Mechanics" that we consider to be falsified?

MarianD
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Pod
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6 Answers6

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"Falsified" is more philosophical than scientific distinction. Newton laws have been falsified somehow, but we still use them, since usually they are a good approximation, and are easier to use than relativity or quantum mechanics.

The "action at distance" of Newton potentials has been falsified (finite speed of light...) but again, we use it every day.

So, in practical terms, no, Newton laws are still not falsified, in the sense that are not totally discredited in the scientific community. Classical mechanics is still in the curriculum of all universities, in a form more or less identical that 200 years ago (Before Relativity, quantum mechanics, field theory).

Most concept in physics fit more in the category of "methods" rather than "paradigms", so can be used over and over again. And all current methods and laws fails and give "false" results, when used outside their range of applicability.

The typical example of "falsified" theory is the Ptolemaic system of Sun & planets rotating around the Earth. However, philosopher usually omits the facts that:

  • Ptolemaic system was experimentally pretty good at calculating planet motions
  • Most mathematical and experimental methods of the new Heliocentric paradigm are the same of the old Ptolemaic

So the falsification was more on the point of view, rather than in the methods.

patta
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    In what way has the Ptolemaic system been "falsified"? What predictions does it make that have turned out to be false? Hasn't it rather been abandoned in favour of other models that are 1.) geometrically simpler and 2.) easier to describe using our physical models? – piet.t Apr 12 '19 at 09:12
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    Well, we can measure that the Earth is rotating, against Ptolemaic system. But yes, we can still write ( with a lot of patience) all physics from our rotating system, with a lot of "fictitious" forces. – patta Apr 12 '19 at 09:30
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    Note that both general mechanics and quantum mechanics are just as false as Newtonian mechanics, in a certain sense. QM fails to predict gravitational lensing, and GR fails to predict interference patterns in the double slit experiment. Both fail to explain how black holes preserve information. (one says they don't, the other says they don't exist) – John Dvorak Apr 12 '19 at 10:04
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    @piet.t That's a common misconception. Ptolemy's model actually makes physically different predictions. Note that Venus is always between the Earth and the Sun in the Ptolemaic model, but not in reality. Galileo's observation of the phases of Venus, showing Venus fully illuminated by the sun, falsified the Ptolemaic model. – Denziloe Apr 12 '19 at 11:08
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    I think it is misleading to state that a theory is not falsified "in practical terms". I know full well that the statement "99 cents are equal to a dollar" and yet in practice I behave as if 99 cents are a dollar. That does not mean that the statement is true. – HRSE Apr 12 '19 at 15:11
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    99 c = 1 $ $\pm$ 2% – patta Apr 12 '19 at 18:41
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    @piet.t, the Ptolemaic system predicts that the fixed stars remain in the same relative locations at all times. Heliocentric models predict that they'll show annual variations in their positions relative to each other. High-precision observations of stellar positions show both parallax and aberration of light, which rather falsifies the Ptolemaic system (and almost all other geocentric systems). – Mark Apr 12 '19 at 20:47
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    @JohnDvorak there's a perfectly good quantum mechanical description of gravitational lensing, by treating GR as a low energy effective theory. Despite the absence of a definitive theory of quantum gravity, it's not true that anything containing both "quantum" and "gravity" is necessarily shrouded in mystery. – Holographer Apr 12 '19 at 21:24
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    @piet.t : Ignoring the circular orbits plus one epicycle observational failure of the Ptolemaic system: Stellar aberration of $\gamma$-Draconis was observed by J. Bradley in 1728. Direct measurement of the rotation of the Earth was observed by G. Guglielmini in 1791 (and replicated by others subsequently). 1806: G. Calandrelli observes parallax in $\alpha$-Lyrae. A good (if long) read on the subject of the falsification of several planetary models: The Great Ptolemaic Smackdown. – Eric Towers Apr 12 '19 at 21:26
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    Please can you answer the question and say which (and how) of Newton's three laws of mechanics have been falsified. – ProfRob Apr 13 '19 at 16:54
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    @RobJeffries That's perhaps hard to pin down because they fail somewhat implicitly because their underlying assumption of absolute time and three-dimensional flat space fail ... – Hagen von Eitzen Apr 13 '19 at 22:09
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    @JohnDvorak With all due respect, it is utterly unscientific to assert that QM is as wrong as Newtonian Mechanics. For the former subsumes the latter and has to be truer than the latter. The same goes for General Relativity being truer than Newtonian Mechanics--it has to be because the latter is subsumed in the former. –  Apr 13 '19 at 23:26
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    I think it should be added, regarding the narrowed version in the question text, that while some parts of Newtonian physics are superseded by newer theories, the three laws of motion themselves are still included in them and, along with the conservation of momentum they imply, considered universally valid in both GR and QM—just using the complex space geometry of GR instead of simple Euclidean one. – Jan Hudec Apr 14 '19 at 13:26
  • @piet.t do you think the sun and all planets orbit the earth? If not, then you understand how the ptolemaic system has been falsified. It can still be used, as patta points out, but i think we can agree that the idea of how the solar system looks is false in the ptolemaic system. – Aethenosity Apr 14 '19 at 18:20
  • This answer is not good. Newtonian physics have been falsified. The fact that that doesn't matter in everyday applications doesn't influence the fact that they have been falsified. Newtonian is "good enough" but that is an engineering quality, not a scientific quality. – d-b Jan 14 '21 at 21:51
  • @d-b and so Schrödinger's equation is also falsified, as is Dirac's. Come to think of it, all of physics as we know it is virtually falsified by a quantum gravitational experiment. The fact that we don't have that experiment yet is hardly an excuse. Just good enough for engineering, the lot of it. – my2cts Jan 15 '21 at 11:21
  • @my2cts I'm not a physicisit, at least not on that level, but then I guess QGE is the new best hypothesis, which is fine. You have to ask yourself, why you use a certain tool. If you build a bridge, Newton is fine, if you plan for a satellite, general relativity is a useful tool but if you develop science in itself, you have to find something better than what has been falsified. – d-b Jan 15 '21 at 12:03
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Newtonian Physics is accurate in the specific domain it was designed for

Physics is not about identifying the "truth" of the world around us. It's about creating mathematical models that allow us to accurately predict the behavior of the world.

Nobody is trying to create a perfect model, because the complexity of such a model would be infinite. Instead, we look for the boundaries of a model's accuracy - under what conditions it produces reasonable results, and the precision of the results it produces under those conditions.

You can see this more clearly with other physics models, such as the Ideal Gas Law. The Ideal Gas Law models a hugely complex system of particle collisions as a simple formula of ratios. It breaks down relatively quickly at high or low values of any of its quantities, but because we understand when and how the law breaks down, it is still useful.

At extremely large quantities (large speeds, large masses, high energies), the Newtonian model starts to break down, and we need to use a Relativistic model in order to get accurate results. But that doesn't mean that the Newtonian model is false, it just means that it is inapplicable for those conditions.

Obviously, Newton wasn't aware of the limitations to his laws when he described them. He was trying to create a universally applicable set of relations. In that sense you could argue that he failed. But I would consider the modern understanding a refinement of his laws, rather than a falsification.

Arcanist Lupus
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    Avoids answering the question... – ProfRob Apr 13 '19 at 16:53
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    This is the modern understanding, but I don't think it is true to say that Newton's laws were designed (by Newton, at least) for slow speeds and mild gravitational curvatures. – Rococo Apr 13 '19 at 19:36
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    This answer would probably make more sense if "designed for" was replaced with "conceptualised within". – Ian Kemp Apr 13 '19 at 22:37
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    @IanKemp I would've awarded a bounty on this comment if it were a feature! I mean, of course, Newtonian mechanics was designed for everything. It was just conceptualized within a certain regime of experiments. And it is not in the spirit of science to actually design a theory for the regime in which the experimental results are already known. A scientific theory has to make predictions and that means that it necessarily has to go beyond the domain from which it takes empirical inspiration. –  Apr 13 '19 at 23:33
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    When Newton was studying Kepler's work, he probably wasn't wondering if he could apply it to the $1s$ orbital of the hydrogen atom. – Cinaed Simson Apr 15 '19 at 20:16
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One of the problems of Newton's law of universal gravitation, $$F_\text{Grav} = G \frac{m_1m_2}{r^2},$$ is that it does not correctly describe the precession of Mercury's orbit. Mercury behaves slightly different than predicted by Newton's law and general relativity does a better job.

See also the corresponding Wikipedia article.

Jasper
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    When you say "Newton's Laws", which do you mean exactly? There are laws for inertial motion, action/reaction, force as dp/dt, and gravity. I believe only the last one could be seen as needing modification by General Relativity. – Jens Apr 13 '19 at 10:55
  • Indeed Mercury's elliptical orbit slowly rotates by a tiny amount extra than what Newton's gravity predicts. However people generally underemphasise other precession effects: 5000 "/c [seconds of arc per century] from precession of the equinoxes, and 530 "/c from other planets, compared with the observed 43 "/c extra that general relativity (and other gravity theories) explains. So Newtonian gravity is correct to within less than 1% error, in explaining the precession of Mercury's orbit. – Colin MacLaurin Apr 17 '19 at 01:50
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Relativity is an extension of Newtonian physics, not either a replacement or correction. As such, relativity does not "falsify" Newtonian physics. For velocities far smaller than the speed of light (approaching zero), relativity simplifies back to the Newtonian model. For everyday use, and for everyday engineering problems, Newtonian physics is more than accurate enough. It's only when you get into more "interesting" situations that Newtonian physics fails to provide adequate solutions. The orbit of Mercury is a famous one. It's only because of Mercury's proximity to the Sun that its orbit defies accurate modeling in purely Newtonian terms. Similarly, without an understanding of relativity and relativistic effects on orbiting spacecraft, the GPS system could not work (the onboard timekeeping of the GPS satellites must be extremely precise and the very small relativisitic effects on their clocks must be accounted for). These are not everyday situations, and the relativistic effects are small, but the position of Mercury can be very precisely measured and GPS signals are timed with very high precision (light/radio travels about a foot or about 30cm in a nanosecond).

Anthony X
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    This answer seems to flip between two contradictory viewpoints. You say relativity is an "extension" of Newtonian physics, not a replacement or correction; but then proceed to talk about Newtonian physics "failing to provide adequate solutions" unless relativity is accounted for. Wouldn't that make it a "correction" to Newtonian physics in most senses of the term? I wouldn't consider new information that makes all prior information slightly inaccurate an "extension"; I would specifically call it a correction; because it corrects the errors in Newtonian physics. – JMac Apr 15 '19 at 16:08
  • @JMac I stand by my core point that relativity is an extension not a correction because of the way the relativistic terms cancel out (leaving the simplified Newtonian forms) as velocity approaches zero (or the comparable terms which relate to curvature of spacetime due to mass). – Anthony X Apr 15 '19 at 23:37
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First of all no scientific theory can possibly be falsified. Popper was wrong. See the Quine-Duhem thesis which says that instead of rejecting the theory when a seemingly falsifying experiment occurs, one can always instead reject some underlying "auxiliary hypothesis". The perfect example of this is how when experiments came out seeming to indicate neutrinos were moving faster than light no serious scientists actually believed the neutrinos moved faster than light, rather, all the scientists rightly believed that there must have been something wrong with the experiment.

Now to answer your questions.

  1. Are any of Newton's three laws considered to be 'falsified theories' by any 'working physicists'? If so, what evidence do they have that they believe falsifies those three theories?

Despite what I said above the answer to your question is yes. This is because 'working physicists' are generally not good philosophers of science and many 'working physicists' incorrectly think Poppers program of falsification is correct. Working physicists aren't good philosophers of science because philosophy of science doesn't really help them do their job better and they simply may not find it that interesting, so if they hold misconceptions about philosophy of science it doesn't cause any problem whatsoever in their daily work.

  1. If the three laws are still unfalsified, are there any other concepts that form a part of "Newtonian Mechanics" that we consider to be falsified?

No. As I said above no physical theory can be falsified.

Here's some information about Imre Lakatos who has a better philosophy of science in my opinion than Popper.

Jagerber48
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    I carry no water for Popper, but a statement like "no scientific theory is ever falsified" does not seem to me to be an actual description of what scientists think and do (as you have noted), and I question a theory of science that says that most scientists don't do science. – Rococo Apr 13 '19 at 19:40
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    @Rococo I won't make any claim as to what percentage of scientists will say falsification is how science works because I've never done or seen a survey. I will point out that one can be a productive scientists regardless of ones opinions about philosophy of science. I would argue that all good scientists (even those who believe in falsification) do not actually do their science by trying to falsify things. Instead they do what all good scientists do: – Jagerber48 Apr 13 '19 at 21:37
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    They mess around with their theories and experiments seeing which theories work under which conditions, they try to figure out why and when theories break down, they generate new theories if necessary. The question is: does this theory explain what I am seeing? Why? Why not? What does it mean if this other theory also describes what I am seeing? – Jagerber48 Apr 13 '19 at 21:40
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    No where did I say that most scientists don't do science. All I said was that many scientists have misconceptions about philosophy of science but I was careful to point out that a scientists thoughts on philosophy of science have very little bearing on his or her aptitude as a scientist. – Jagerber48 Apr 13 '19 at 21:42
  • I apologize for mischaracterizing your position. Nonetheless, I am not personally convinced that, for example, 'all good scientists (even those who believe in falsification) do not actually do their science by trying to falsify things.' To be clear, I would neither make the extreme opposing claim that science is all about falsifying theories. – Rococo Apr 13 '19 at 22:56
  • Thanks for the alternate take on the question, especially regarding the underlying assumption that Popper was correct in this matter. I'll get around to reading that article soon :) – Pod Apr 15 '19 at 08:34
  • Though a physicist, I appreciate what the answerer is saying here. Someone has said that if naive falsifiability (as articulated by Einstein or Popper perhaps???) were taken seriously, then undergraduate laboratory experiments would falsify physics theories all the time! No doubt physicists have some useful pragmatic approach to falsifiability, they just don't formulate the notion clearly -- i.e. they're not philosophical. Finally, out of curiousity, see Sean Carroll on "Beyond Falsifiability", and the parody by Douglas Scott et al "A Farewell to Falsifiability" published on April Fools Day :) – Colin MacLaurin Apr 17 '19 at 05:43
  • @ColinMacLaurin That is not how falsification works. If your experiment contradicts an established hypothesis, there are only two possible explanations, (1) your experiment is broken, (2) the established hypothesis was falsified. In the case of "undergraduate experiments" I say that (1) is the explanation when this happens in at least 99,999 % of the cases. – d-b Jan 14 '21 at 21:56
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    @d-b What you say is correct. The problem with falsification is that you can NEVER rule out the "your experiment is broken auxiliary hypothesis". This is the Quine-Duhem thesis. Instead of falsifying a theory you can always introduce, and subsequently falsify an auxiliary hypothesis to rescue your theory from being falsified. In fact, this is related to the persistence of conspiracy theories. – Jagerber48 Jan 15 '21 at 01:34
  • @jgerber Not really true. A valid scientific theory must have a falsification criterium, but technical issues are not valid to achieve that. – d-b Jan 15 '21 at 09:11
  • I think it's important to put Popper in his right context: the relevant context is that of refuting the inductivists, who thought that science progresses mainly by corroboration of our theories. Of course experiments can also be refuted! But what Popper brought to the table was the revolutionary idea that what scientists are really after is falsification of theories, not their corroboration, because the former is the fastest way to make progress! – Amit Feb 08 '23 at 19:47
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    @Amit Fair to point out that Popper was refuting intuitionists who though verification was enough. But I disagree with your statement that "what scientists are really after is falsification of theories". I would say that scientists sometime seek evidence that support their theories and they sometimes seek evidence that refutes their theories. What they REALLY do is perform experiments about which their theories make predictions and compare theory to prediction and update theory or experiment accordingly. – Jagerber48 Feb 08 '23 at 21:17
  • @Jagerber48 You are absolutely right, and I needed to qualify my words: they will be looking for evidence to refute their (or others) theories in order to make significant progress, breakthroughs and on the personal side, also gain name and fame! Now you are of course right about the process of experimentation, but what Popper would say is that when choosing which experiments to do first, it would be those that are most likely to refute the theory (that is, the ones that theory predicts to have the "wildest" results). That's a very important detail. – Amit Feb 08 '23 at 21:22
  • @Amit I guess the way I would phrase your statement (especially your last parenthetical statement) is that scientists choose experiments that are most sensitive to the parameters of their theory. But I guess for me I wouldn't say such experiments are chosen because they are likely or capable of refuting a theory but rather what I said in the previous sentence. Scientists are interested in comparing experiments and theories and you gain more insight when you do that with sensitive experiments. Positive and negative results are equally significant, with significance depending on sensitivity. – Jagerber48 Feb 08 '23 at 22:07
  • That is, a experimental scientists measuring electron electric dipole moment (EDM) don't wake up saying, I want to attempt to falsify the theory that the electron EDM is non-zero. They wake up saying "I want to improve my experiment to reduce the error bars on measurement of the electron EDM to make my results more significant". – Jagerber48 Feb 08 '23 at 22:09
  • @Jagerber48 You see exactly that point is very interesting. Popper had a very prominent student, perhaps you know of him, his name was Joseph Agassi. Agassi phrased it in a very interesting way: "Imagine someone playing a violin and you come and tell him that's not a violin, that's a piano! That's the equivalent of what Popper said to scientists". So now you say scientists want to reduce the error bars, but an equivalent statement would be that the progress for science would be to see exactly where the error bars can't be reduced, meaning, we're at the end of our tether - – Amit Feb 08 '23 at 23:05
  • the limit of our theoretical understanding. So these are two different perspectives on the same practical action which is as you say, a more sensitive experiment. Hence, violins and pianos :) – Amit Feb 08 '23 at 23:06
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No, they are not considered falsified. They are still a valid low energy approximation, which is all they ever were claimed to be. Or, if you must, they have been falsified at very high energies only.

my2cts
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    Did Newton claim his laws were a low energy approximation? I doubt it. – user253751 Apr 15 '19 at 05:49
  • @immibis he claimed his laws explained the solar system. That claim has not been falsified apart from extremely tiny deviations. – my2cts Apr 15 '19 at 06:36
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    @my2cts Newtonian mechanics wasn't created to work "apart from extremely tiny derivations". It was created and applied to work at all scales. That's why we had to develop beyond classical/Newtonian mechanics when the model was no longer accurate. They were not as widely applicable as was originally thought. – JMac Apr 15 '19 at 16:13
  • @JMac "as originally thought" Can you tell where in "Opticks" speeds of the order of 300.000 km/s are considered? Where an accuracy of 43 arcsec per century was claimed? – my2cts Apr 16 '19 at 19:40
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    @my2cts Can you show where he mentions that it's only exact when velocity is zero? I don't believe he states anywhere the assumptions that this doesn't apply at particular scales, or anything of the sort. All the evidence suggests that the physical laws he derived were to apply at all scales and velocities, and none of what he wrote that I'm aware of ever tried to mention that it was only an approximation for low energy. – JMac Apr 16 '19 at 19:46
  • @JMac This is getting silly. All conceivable velocities at the time were extremely small compared to c. We are taking about a 17th century theory. Horses and carts. Sailing ships. Get real. – my2cts Apr 16 '19 at 19:48
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    @my2cts ...and the motions of the planets... you know, just regular low velocity, low energy stuff... It seems pretty dang obvious from how Newton tried to apply his laws to basically everything that he could conceive, without ever outlining the limits, that he did not derive the laws under the assumptions that it was limited to low energy. If he did, that should be clearly stated in his papers, and I'll easily accept what you're saying if you can find where he does that. – JMac Apr 16 '19 at 19:51
  • @JMac you make the mistake of setting modern requirements to Newton's publication. As a referee, would you have rejected it in view of the shortcomings you found? – my2cts Apr 16 '19 at 19:57
  • @my2cts If Newtons law was presented in modern day, as is, yes it would be rejected if it didn't make it clear it was only applying as an approximation under certain constraints. In his time, it would have been fine, because it was correct as far as they knew. I'm setting modern requirements to a modern interpretation of Newtonian mechanics, where we are now able to clearly see that it doesn't universally apply as was implied by Newton. – JMac Apr 16 '19 at 20:08
  • @JMac that is silly. – my2cts Apr 16 '19 at 20:16
  • Your answer is self-contradictory. A hypothesis can't be both non-falsified as well as falsified. – d-b Jan 14 '21 at 21:59
  • @d-b By your standards all physical theories, without exception, have been falsified. I'm not even sure if energy is conserved in GRT. Likely, Newton believed in his laws always applied. That hypothesis has been falsified. However as a low velocity approximation Newton's laws have not been falsified. – my2cts Jan 14 '21 at 22:33
  • @my2cts Guess why a "theory of everything" that combines QM and GRT is such an holy grail? But I am not sure that you are right - are all hypothesis in areas such as optics and sound waves falsified? – d-b Jan 14 '21 at 23:25
  • Besides, a hypothesis may have been falsified but it may also still be the best hypotheis we have, and be good at predicting the outcome of a process within certain limits, albeit it is not universally applicable. Just like Newtonian physics which is very useful when you build a bridge or something. – d-b Jan 14 '21 at 23:33
  • @d-b Newton's laws are falsified by the existence of electromagnetism, strictly speaking, as the Lorentz force does not obey the third law. I hope we can agree that such an assertion is meaningless and that we should extend the theory rather than reject it as false. – my2cts Jan 15 '21 at 11:12
  • @my2cts If it is false, it is false. – d-b Jan 15 '21 at 12:03
  • @d-b So everything is false. That is not how physics advances. – my2cts Jan 15 '21 at 13:11
  • @my2cts If everything was true there would be no need for advancing. And this is why you talk about "best hypothesises", not "proved truths". – d-b Jan 15 '21 at 15:15
  • @d-b Physics is not binary. It is about progressively modelling nature, not about proving some theorem. – my2cts Jan 15 '21 at 16:42
  • @my2cts The hypothesis that nothing can move faster than c has not (?) been falsified. I bet there are other hypothesises that are as stable as that. – d-b Jan 16 '21 at 02:44
  • @d-b Special relativity is falsified by general relativity which is also wrong because it is not a quantum theory, I'm afraid. – my2cts Jan 20 '21 at 21:12
  • @my2cts Yes? Faster than c is not falsified, is it? – d-b Jan 20 '21 at 22:26