Can a theory be entirely wrong and still make correct predictions?

[astro]

Any examples of this in the history of science? I'm thinking that possibly some of the early eclipse prediction projections which were pretty dead on despite being wrong as to the fundamental mechanism might fall into this category.

[Keeve]

Eclipses are exactly what I thought of when I saw the thread title.

Any reason you don't find that to be an adequate answer? Maybe what you meant to ask was if there are any other examples.

[Procrustus]

flipping a coin will give you the right answer half the time...

[Dragwyr]

I remember my physics teacher in HS telling us that all of the motions of the planets, stars, and moon can be explained just as well with a "Geo-centric" theory as they can with a "Helio-centric" theory.

[RealityChuck]

Bode's Law. It even "predicted" the location of Uranus before the planet was discovered.

[muttrox]

The theory that Apollo races around the sky every day does a pretty good job explaining the sun rising. The theory that "Americans want a black guy for President" did a pretty good job explaining Obama's victory. etc, etc.

Newton's theories (which were proved wrong by Einstein) predicted just about everything we care about just about correctly for hundreds of years and continues to do so.

Bad theories are usually disproved by the cumulative weight of evidence against them. That implies that until there is enough "weight" against them, they've done a good job of predicting.

[Nancarrow]

Originally Posted by astro

Any examples of this in the history of science? I'm thinking that possibly some of the early eclipse prediction projections which were pretty dead on despite being wrong as to the fundamental mechanism might fall into this category.

Pretty much any theory that hung around for more than a couple of decades, did so because it gave good agreement with experiment. Ptolemaic astronomy, the phlogiston theory of heat, Aristotelian motion...

It might be better to ask whether there are any good examples of theories that hung around for a long time despite having no predictive power. (Scientific theories, that is... obviously our species has a penchant for keeping nonscientific, nonpredictive theories around for thousands of years past their sell-by date)

[Quercus]

If a theory always gives correct predictions, how can it be 'wrong'?

Science doesn't care if a guy came up with a set of equations by imagining fairies and gnomes pushing atoms around or by casting the horoscopes of different molecules; if the equations make predictions that can be tested and are always right, then they're correct.

[muttrox]

Originally Posted by Nancarrow

It might be better to ask whether there are any good examples of theories that hung around for a long time despite having no predictive power.

Many would argue that if it has no predictive power, it is inherently un-scientific. See the debate about string theory, or the physical scientists scorn of anthropology, history, and other soft sciences. Many don't consider them sciences at all.

(I assume you are automatically excluding things like astrology, ESP, etc. ?)

[Sophistry and Illusion]

As several people have mentioned, Ptolemaic astronomy was extraordinarily accurate in predicating the movement of the heavenly bodies. But it put the Earth at the center of the universe; it used circles instead of ellipses for the motions of planets; and incorporated a number of other errors. To 'correct' for this, it had to use a number of highly complicated mathematical techniques like epicycles and deferents, equants, etc., etc. But it was still accurate enough for most any purpose. In fact, AIUI Copernicus' system wasn't more accurate (at least not right away); it was just more elegant.

[robby]

Back when I was teaching and introducing the concept of scientific theories, I mentioned an alternative theory for why things fall down: the Earth sucks.

Always good for a laugh, but the theory does not really hold up when tested.

Anyway, this brings up the idea of what it means for a theory to be "wrong." Isaac Asimov wrote an essay on this topic years ago entitled The Relativity of Wrong. The essay can be read here.

As Asimov writes, "...when people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together."

In other words, a theory can be wrong, yet still make good predictions. The theory that the Earth is flat is clearly wrong, yet this is the assumption that architects and engineers use for most human-scale projects, because the curvature of the Earth need not be taken into account for most building-sized projects.

The theory that the Earth is spherical is less wrong but still wrong. (The Earth is actually an oblate spheroid.) The spherical Earth theory, though wrong, nevertheless works just fine for most navigation needs. However, the spherical Earth theory does not work as well when launching satellites--you need to take the Earth's equatorial bulge into account.

And so on. What makes a theory "wrong"?

Another example--Newtonian physics. Einstein showed that Newtonian physics was wrong. Nevertheless, it works just fine for most purposes. It does not work well at speeds near the speed of light or under high gravitational fields.

[Anne Neville]

Originally Posted by Quercus

If a theory always gives correct predictions, how can it be 'wrong'?

It could give correct predictions in one set of circumstances, but fail in a different one. For example, Newtonian physics works pretty well to predict the motion of an object, as long as the speed of that object is not a significant percentage of the speed of light (and some other conditions are met).

"Matter cannot be created or destroyed" would be another example. It works pretty well, as long as you stay away from the high-energy conditions where things like nuclear fusion can take place.

If you're working with ordinary chemical reactions and stable isotopes, "one element cannot change into another" works pretty well.

[Zsofia]

Plenty of theories work in some places and not others - Newtonian physics is just fine at people-sized scales on Earth.

[robby]

Originally Posted by Zsofia

Plenty of theories work in some places and not others - Newtonian physics is just fine at people-sized scales on Earth.

As has been mentioned in the two posts prior to yours...

Your comment about theories working in some places and not others can be misconstrued, however.

It's not that Newtonian physics is correct under ordinary conditions, and not under others.

Newtonian physics is actually "wrong" even under ordinary conditions. However, the difference in results from using Newtonian physics and relativistic equations is not measurable, at least under ordinary conditions.

Similarly, mass is technically not conserved even in chemical reactions. However, the difference in mass is not measurable. So technically speaking, the theory of conservation of mass is also wrong, even for chemical reactions.

What often happens is that scientists find that an accepted theory breaks down under different conditions. Scientists then strive to come up with a new theory (which is often a refinement of the original theory) that works for both the new conditions as well as the old.

In some cases it is found that no one theory works for all conditions. An example of this is general relativity, which breaks down under very short scales; and quantum theory, which breaks down under relativistic conditions. So really, both of these theories are "wrong." One goal of modern physics is to reconcile these theories, and come up with a single theory that works under all conditions.

[Chronos]

I wouldn't so much say that Newtonian physics is wrong, as that it's an approximation which is sometimes not very good. As an example of the fact that it's always only an approximation, the electrons in a wire have an average speed of millimeters per hour or so (certainly far less than the speed of light), and yet the relativistic effects of their movement at that speed are measurable with a simple compass.

Similarly, mass is technically not conserved even in chemical reactions. However, the difference in mass is not measurable. So technically speaking, the theory of conservation of mass is also wrong, even for chemical reactions.

Technically speaking, mass is always conserved in all closed systems, even when you've got things like nuclear reactions and antimatter involved. It's just that when talking about things like nuclear reactions and antimatter, people have a distressing tendancy to prefer to work with non-closed systems.

[D18]

Originally Posted by Dragwyr

I remember my physics teacher in HS telling us that all of the motions of the planets, stars, and moon can be explained just as well with a "Geo-centric" theory as they can with a "Helio-centric" theory.

I have a very superficial understanding of Special and General Relativity, but aren't the geo-centric and helio-centric models correct, but taking different reference frames into account? The orbits of the planets can be explained much more simply by the helio-centric model, but using the reference frame of the earth, the very complicated geo-centric theories do an adequate job?

Looking forward to having my ignorance overcome as necessary. Be kind.

[Der Trihs]

Originally Posted by Quercus

If a theory always gives correct predictions, how can it be 'wrong'?

Science doesn't care if a guy came up with a set of equations by imagining fairies and gnomes pushing atoms around or by casting the horoscopes of different molecules; if the equations make predictions that can be tested and are always right, then they're correct.

Science does care, because it's curious about whether it's really fairies or forces doing the pushing. You are confusing the difference between "useful" and "correct" I think; a theory can be useful, even if it's wrong, if it makes correct predictions within a known range of situations.

[robby]

Originally Posted by Chronos

...Technically speaking, mass is always conserved in all closed systems, even when you've got things like nuclear reactions and antimatter involved.

I'm having a hard time with this statement, Chronos. Can you elaborate on this? Even in a closed system, it is my understanding that mass-energy is conserved, but not mass.

[ivan astikov]

Is what we are talking about here related to how medieval alchemists used to believe in transmutation, but despite their basic theory being wrong, it still led to advances in chemistry?

[lobotomyboy63]

I would think a whole class of theories would fit here---when people correlate two things and infer causation.

An example of a spurious relationship can be illuminated examining a city's ice cream sales. These sales are highest when the rate of drownings in city swimming pools is highest. To allege that ice cream sales cause drowning, or vice-versa, would be to imply a spurious relationship between the two. In reality, a heat wave may have caused both. The heat wave is an example of a hidden or unseen variable.

http://en.wikipedia.org/wiki/Fallacy_of_causation

[Chronos]

I'm having a hard time with this statement, Chronos. Can you elaborate on this? Even in a closed system, it is my understanding that mass-energy is conserved, but not mass.

The biggest difficulty is that mass isn't necessarily additive.

Consider, for example, a system which consists of an electron and a positron, sitting right next to each other, at rest in some reference frame. An electron has a mass of 511 keV/c², and a positron has the same. The entire system of electron + positron has a mass of 1022 keV/c². Now, after a short time, this system will undergo an interaction, and turn from an electron and a positron into a pair of photons moving in opposite directions. If you look at a system consisting of a single photon, you'll find that it has zero mass. The temptation, then, is to say that since each individual photon has no mass, the total system consisting of both photons therefore also has no mass. But you can't get the mass of the total system just by adding together the masses of the subsystems: A pair of photons moving in opposite directions actually does have a mass. In this case, the mass of the pair of photons is 1022 keV/c², just like the initial system.

[jakesteele]

I remember taking philosophy classes there was a great one Socrates/Aristotle? that postulated that matter was made up of very small particles shaped like a Z and because of the shape they all hooked together to for what appears to us to be solid matter. Hence, the forerunner of atoms etc.

[Stranger On A Train]

Originally Posted by Dragwyr

I remember my physics teacher in HS telling us that all of the motions of the planets, stars, and moon can be explained just as well with a "Geo-centric" theory as they can with a "Helio-centric" theory.

The motion of the planets can only be modeled using a geocentric reference frame by using a lot of patched together and ad hoc approximations. Using a heliocentric reference frame, however, allows you to use Kelper's Laws of Planetary Motion, which are so simple that there are only three of them of one sentence each and requiring only a rudimentary knowledge of trigonometry, or more generally (using calculus) Newton's Laws of Motion and Gravitation.

These are themselves, of course, approximations to a more general theory (General Relativity) which accounts for the way space is distorted in the presence of large masses, but is sufficient for to account for observations and trajectories out to about twelve decimal places.

One or more tenants of a theory can be fundamentally wrong and yet give approximately right answers; better yet, a theory can be based on mathematics that work out or a model that is tuned to provide correct results within a certain regime, and make accurate predictions within that regime, and still be wrong. Others, like (say) the central dogma of molecular biology ("Genetic information is transferred only from nucleic acid to protein, not protein to nucleic acid or protein to protein,"), might be generally accurate but frequently violated by exceptions to the rule.

This is why no theory in science is ever complete; all theories are subject to falsification. It's just that some have been tested to an extensive degree without any sign of violation.

Stranger

[Stranger On A Train]

Originally Posted by Chronos

If you look at a system consisting of a single photon, you'll find that it has zero mass. The temptation, then, is to say that since each individual photon has no mass, the total system consisting of both photons therefore also has no mass. But you can't get the mass of the total system just by adding together the masses of the subsystems: A pair of photons moving in opposite directions actually does have a mass. In this case, the mass of the pair of photons is 1022 keV/c², just like the initial system.

It may be easier to say that momentum is always conserved (at least, in a perfectly elastic system) and back out the total mass of the system or any component within therefrom.

Stranger

[rbroome]

Originally Posted by astro

Any examples of this in the history of science? I'm thinking that possibly some of the early eclipse prediction projections which were pretty dead on despite being wrong as to the fundamental mechanism might fall into this category.

the OP isn't well-worded. What is meant by "entirely wrong"? Almost any theory will be correct some of the time-or it wouldn't even be considered as a possible answer to the hypothesis. Do you mean that the theory provides a complete explanation of the problem? I would interpret that to mean that the theory is correct. Any theory that explains the problem is tentatively correct until it can't explain one observation. Then it isn't. So in this sense almost all theories that turn out to be wrong satisfy what I think is the OP's question.

[CalMeacham]

I wrote an article about this a while back. In the early years of spectroscopy in the 19th century they discovered the discrete spectral lines associated with each element, and saw how they could be used to identify each element (many of the names of the elemens so discovered were based upon the observed spectra, in fact, like "Rubidium". )

The problem was that there was no theory explaining why the lines were where they were. In many cases the spacing seemed completely random. In others, like Hydrogen, they seemed to suggest some sort of order, but nobody could figure out what it was. In the 1860s, various people discovered apparent regularities -- Alexander Mitscherlich of the University of Berlin noted a regular progression in the series barium chloride, barium iodide, and barium bromide. Francis Lecoq de Boisboudron (an unaffiliated scientist) noted a geometrical progression in the lines of potassium. The alkali metals, in fact, were tantalizingly similar to hydrogen in some ways, but unlike in others.

But it was George Johnstone Stoney, professor of Natural Philosophy at Queen's University in Dublin, who claimed to have finally found the sought-after explanation. Or at least part of it*. Like many scientists, he expected the spectral lines to resemble some sort of vibrating system, with a fundamental frequency and a series of overtones. Once you found your fundamental, it was just a matter of foubling it or tripling it, or finding some other multiple to find the overtones, and these ought to correspond to the observed lines. The hitch is, no one had succeeded in finding such a fundamental and overtones for any of the spectra. Not even hydrogen, the simplest and most regular. So how did Stoney succeed?

He observed that the four visible hydrogen lines were at (in round numbers. Please note that Stoney was more careful than this -- he corrected for the wavelengths in vacuum) 4102 Angstroms, 4342 A, 4862 A, and 6564A. 4102 isn't a good fundamental, but Stoney somehow discovered that the first, third, and fourth of these are in a ratio of almost precisely 20:27:32. Maddeningly, the second one doesn't fit the pattern. But the others do.

What about the "missing" orders? Why aren't there lines at 21 and 22 and 23 and so forth? Stoney decided that some sort of "interference" -- like the interference observed by Thomas Young in his famous experiment -- was responsible for making those other orders invisible. For some reason, only selected lines showed strongly.

Seeking to bolster his case, Stoney collaborated with J. Emerson Reynolds to study another system -- chromochloric anhydride** -- to see if it could be fit. They were able to find a fundamental frequency that, with proper overtones, allowed them to fit an astonishing 31 lines of the spectrum.

The problem was that they could only do this by using absurdly high overtones (one was the 733rd) and ignoring vast numbers of others that didn't fit. The "interference" theory didn't seem convincing. Some were convinced, but others, like Franz A.F. Schuster of the University of Manchester, were not. He calculated the probability that a fundamental and overtones chosen at random could fit observed spectra, and found that it generally yielded a pretty good fit -- certainly as good as the ones being made with Stoney's theory. Schuster's paper, "On Harmonic Ratios in the Spectra of Gases", pretty much killed any further efforts to fit spectral lines in this way.

But along the way, Stoney's work, and that of other researchers, had fit the spectral lines for at least four materials and therefore predicted other spectral lines. Of course, the vast bulk of these didn't fit anything (even by the theory, which didn't expect them all to fit). But if you used Stoney's theory to fit, say, the first and third lines of hydrogen, you can get a correct prediction for the fourth. That seems to pretty much fit the OP's requirements.



The real solution came from the work of Johann Jacob Balmer of Basel a few years later. As the story is usually told, this was a humble teacher of mathematics at a girl's school who went in to the work without any preconceptions about the nature of the relationship. Thus unhampered by ideas of overtones, he empirically discovered the now-famous Balmer Formula that was later explained by Rydberg and by Bohr theory.

As is usually the case with "the usual story", this one isn't really correct. Balmer was, in addition to teaching at a girl's school, also a lecturer at the University of Basel. Far from being unaware of an uninfluenced by previous work, he explicitly cites Stoney's work as his inspiration. What Balmer did observe, however, was that those hydrogen line ratios were too damned close to be purely coincidental. He observed that you could express the raios better in fractional form as 9/5, 4/3, and 9/8. These are pretty small numbers -- even smaller than Stoney had used. Moreover, if you expressed it as a fraction, and let the numbers get just a shade bigger, you could fit that stubborn second line with 25/21 and get a fit as good as the others. Then he noticed that you could re-express these ratios as:


9/5 16/12 25/21 36/32


Now the numerators were all perfect squares of 3, 4, 5, and 6. And that looked like a proper series of harmonics. Moreover, the denominators were all exactly 4 less than their numerators. And that showed a pattern. He extended the pattern to different values, and found that he could fit newly-discovered lines in the ultraviolet as well.










*Stoney's real claim to fame is his work on the electron, which almost no one seems to remember these days. But he's the one who named the particle.

**I haven't been able to learn why they used such an odd material. Why not one of the alkali metal spectra, which were much simpler than most other spectra? Why not Sodium, already in use as a standard?

[Measure for Measure]

Immanuel Velikovsky predicted radio waves from Jupiter and high temperatures on Venus. His theories involved Venus emerging from Jupiter, suffering a near collision with Mars, and then settling into its present day orbit. http://www.stephenjaygould.org/ctrl/...elikovsky.html . To this day, his 1940 classic, Worlds in Collision is hotly debated by thousands of nutters.

[panamajack]

Originally Posted by jakesteele

I remember taking philosophy classes there was a great one Socrates/Aristotle? that postulated that matter was made up of very small particles shaped like a Z and because of the shape they all hooked together to for what appears to us to be solid matter. Hence, the forerunner of atoms etc.

Atomic theory was developed by Democritus, who came before Socrates. It was essentially only a philosophy for about 2000 years, when evidence showed it to (more or less by luck) be correct in some details. The philosophical question remained, though, since it concerns itself with whether the universe has fundamentally indivisible particles.

[astro]

Originally Posted by CalMeacham

I wrote an article about this a while back. In the early years of spectroscopy in the 19th century they discovered the discrete spectral lines associated with each element, and saw how they could be used to identify each element (many of the names of the elemens so discovered were based upon the observed spectra, in fact, like "Rubidium". )

Thanks, marvelous story.

[Boozahol Squid, P.I.]

Originally Posted by Dragwyr

I remember my physics teacher in HS telling us that all of the motions of the planets, stars, and moon can be explained just as well with a "Geo-centric" theory as they can with a "Helio-centric" theory.

Defining a center is completely arbitrary. There's no reason to suggest that heliocentrism is any more correct than geocentrism.
Ptolmeic models of the motions of the stars remain the most accurate, simple method of predicting what the heavens will look like.

[Chronos]

Defining a center is completely arbitrary. There's no reason to suggest that heliocentrism is any more correct than geocentrism.
Ptolmeic models of the motions of the stars remain the most accurate, simple method of predicting what the heavens will look like.

Half right. There's nothing to say that Tycho's model, for instance, where the Sun and Moon go around the Earth but everything else goes around the Sun, is wrong, so in that sense, geocentricism is still viable.

However, if we're looking at simple methods, the simplest version of the Ptolmeic model doesn't match the heavens at all remotely closely, while the simplest version of the Copernican model can at least qualitatively explain all of the observations (why retrograde motion occurs, why a planet is always brightest when it's retrograde, why it's always opposite the Sun when it's retrograde, why some planets never go retrograde, and why the planets that never go retrograde always appear relatively close to the Sun in the sky). The Ptolemaic model never had any explanation for why a retrograde planet should be opposite the Sun, and was only able to explain the other observations using epicycles that the simplest version of the Copernican model lacked.

[TWDuke]

Originally Posted by lobotomyboy63

I would think a whole class of theories would fit here---when people correlate two things and infer causation.

[i]An example of a spurious relationship can be illuminated examining a city's ice cream sales. These sales are highest when the rate of drownings in city swimming pools is highest. To allege that ice cream sales cause drowning, or vice-versa, would be to imply a spurious relationship between the two.

I think in scientist-speak, that would be a hypothesis, not a theory. (And if people didn't wait at least 20 minutes after eating ice cream before they went swimming...)

[Boozahol Squid, P.I.]

Originally Posted by Chronos

Half right. There's nothing to say that Tycho's model, for instance, where the Sun and Moon go around the Earth but everything else goes around the Sun, is wrong, so in that sense, geocentricism is still viable.

However, if we're looking at simple methods, the simplest version of the Ptolmeic model doesn't match the heavens at all remotely closely, while the simplest version of the Copernican model can at least qualitatively explain all of the observations (why retrograde motion occurs, why a planet is always brightest when it's retrograde, why it's always opposite the Sun when it's retrograde, why some planets never go retrograde, and why the planets that never go retrograde always appear relatively close to the Sun in the sky). The Ptolemaic model never had any explanation for why a retrograde planet should be opposite the Sun, and was only able to explain the other observations using epicycles that the simplest version of the Copernican model lacked.

No explanation, perhaps, but it's simple to figure it out. I'll take my copy of The Almagest, you take a copy of De Revolutionibus, and we'll figure out where Venus is going to rise six weeks hence. I bet I get my answer first.

(well, given that I still remember how to do base-60 arithmetic as quickly as I could ten years ago)

[DrDeth]

Originally Posted by RealityChuck

Bode's Law. It even "predicted" the location of Uranus before the planet was discovered.

It may not be "wrong", some still think it makes an OK "rule". We'll see.

There's "luminiferous aether" which did explain a lot. Not enough, however.

There's the "Presidential death in office if elected in years divisable in 20", which worked fine for about twice. The odd coincidence was first noted after Harding but before FDR, thus it "predicted" FDR and JFK. But failed after that. It back predicted 5 deaths, but that's easy to do. (This is why Nostradamous has never predicted anything at all, but has a fantastic "back-predicting" record. Of course, many Nostradamous quatrains have the benefit of being written AFTER the event, by modern writers))

[Stranger On A Train]

Originally Posted by DrDeth

It may not be "wrong", some still think it makes an OK "rule". We'll see.

There's "luminiferous aether" which did explain a lot. Not enough, however.

The "luminiferous aether" didn't really explain anything; it was an ad hoc fix to accommodate the need for a medium for the apparent wave nature of light. It failed to make any predictions, and in fact, the Michelson-Morley experiments were originally performed not to debunk it but to find the velocity of the Earth relative to the presumably invariant medium.

Isaac Newton created a corpuscular theory of light (based upon the writings of natural philosopher Pierre Gassendi) which preemptively addressed what would become many of the problems with classical wave theory; meanwhile, René Descartes proposed a "plenum" theory that light was a disturbance in the underlying medium of space which may be, in broad strokes, ultimately correct.

What about laws that were originally thought to be wrong or ad hoc but ended up being correct? Max Planck originally thought that the quantization of electromagnetic radiation in developing his eponymous law was a mathematical formalism, and Einstein's Nobel Prize-winning explanation of the photoelectric effect failed to convince him that light was actually quantized. And yet, he is legitimately the grandfather of quantum theory, a concept he never fully accepted.

Stranger

[ralph124c]

The ancient chinese made all kinds of mistakes, but wound up with somepretty good stuff. Take their medicine-they stumbled upon some effective pain-reduction methods 9acupuncture0, with a totally wrong theory of the human body. Or ceramics; the chinese perfected ceramics technology in ancient times 9and made some of the world's best porcelein) without knowing a thing about modern chemistry.