Failed ideas in physics [closed]

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What are some failed ideas in physics which had been popular for some time but ultimately turned out to be wrong?

Answer 1

In physics, good ideas that fail tend to be refined and recycled into correct theories later.

LeSage gravity and Feynman diagrams

One of the best examples is the LeSage theory of gravitation. LeSage imagined that all of space is filled with particles moving at some enormous speed c, and that gravity is caused by the absorption of these particles by matter, casting a shadow in the particles behind them. The shadow leads to inverse-square attraction.

This theory died because it would naively predict friction in the LeSage ether, which would wreck the orbits of the planets (of course, with out modern views, we would make the LeSage ether relativistically invariant, fixing this problem, but this was unavailable at the time). But despite this, it was very popular throughout the 19th century. Preston and DePretto, two 19th century lay-scientists, conjectured based on this theory that all mass contains an amount of energy proportional to $mc^2$ (the speed of the LeSage particles had settled down to c by the end of the 19th century).

In the 20th century, Feynman's particle exchange theory of forces revived LeSagian ideas, but this time for good. Feynman's explanation keeps the idea that the inverse square law comes from particle exchange diluted by geometry as they go from on object to another, but makes it quantum, and makes it relativistically invariant. It also becomes universal to all forces, showing how repulsion works.

Feynman, I suppose in honor of LeSage, devotes a section of the Feynman lectures to the LeSage model, to show how theories can fail.

Kelvin's ether atoms

The idea of "knots in the ether", that atoms are topological vortex lines in a fluid filling all space, was explicitly revived by Tony Skyrme in 1960, when he made a model of Baryons as topological defects in the newly discovered pion condensate. This idea was considered dead for many years, until Rajeev, Nair, and Balachandran, followed closely by Witten, showed that it emerges within the large-N (string) model of QCD.

The idea that Baryon interactions are well modeled by tying knots in the pion ether is roughly successful at predicting the structure of small nuclei.

S-matrix bootstrap

The original idea of the bootstrap dates back to Heisenberg 1940, but really got going after Pomaranchuk, Gribov, Mandelstam and Gell-Mann started to think about the idea in the late 1950s. The point of bootstrap was to give a description of hadronic interactions based on the exchange of particles which would be formed through the same interaction. Geoffrey Chew proselyzed for this so effectively that it became the dominant paradigm in physics between 1964 and 1974.

During this time, the interaction of Regge trajectories was understood qualitatively, then quantitatively, and a whole host of new ideas emerged from this: the pomeron, conspiracies, dispersion relations, unitarity cuts, etc. These ideas are not as well understood today as they were back then, because almost all those people were lost to physics.

But they developed string theory in the last 6 years, and string theory pulled all their ideas out of the dustbin.

Yang Mills theory (as Yang Mills wanted)

When Yang and Mills proposed their theory of an SU(2) gauge theory, they wanted it to gauge Isospin. The fundamental interactions don't do that, but Sakurai predicted the $\rho$ meson based on this idea. There are two light vector mesons, the $\rho$ and $\omega$, and the idea that they are gauging isospin and hypercharge led to the idea that they mix with the photon at hadronic energies. This predicted photon nucleon scattering well.

The theory predicts coupling constant universality-- all isodoublets should have the same coupling to the rho. But it doesn't explain the mass of the rho, since Isospin is unbroken. These ideas died out, as it was realized that these particles are not fundamental. But in modern AdS/QCD it is completely rehabilitated.

I don't know what the experimental situation is with respect to coupling constant universality. I will ask that as a question.

Answer 2

Hm, strange question because who would be interesting in failed ideas? But it turns out that sometimes ideas get recycled. I think the most prominent examples are

• Kaluza-Klein theory which attempted to combine general relativity and electromagnetism by introducing additional compact dimension. The theory itself can be said to have failed (mainly because it ignores other forces which were unknown at the time) but the idea itself is very powerful and survives in the form of compact dimensions in modern theories (most prominently string theory).

• $SU(2)$ Yang-Mills theory which was first proposed as a theory of strong interaction. This failed but the theory itself is amazingly versatile and is used everywhere in modern physics. Strong interactions are now understood to be described by a $SU(3)$ YM while $SU(2)$ YM theory itself got recycled as a theory of weak interactions.

I can think of other failed ideas (aether, phlogiston, Kelvin's vortices, etc.) but I won't discuss them because I don't see any point in discussing wrong theories. There is quite an infinite number of those out there and it takes enough effort studying the few theories we know are correct...

Answer 3

There are many failed ideas. The following list is not exhaustive. But these are more famous failed ideas.

1) Ptolemy's Geocentric model of the universe. (If you considered the model as scientific)

2) Sir Isaac Newton's theory of light corpuscles. ( Somewhat revived by photons)

3) Heat was considered to be a fluid called caloric.

4) Luminiferous aether was considered to be a mechanical medium throughout the whole universe with gears and wheels to carry light and heat waves.

5) Various failed attempts to explain the Michaelson Morley experiment (aether drag etc.)

6) Mie's theory of gravity.

7) Thomson's atomic model.

8) Einstein's various failed attempts for the "unified field theory" (5 dimesional kaluza Klein theory etc.)

9) "The steady state model" of the universe by F. Hoyle et. al.

10) Various local hidden variable theories of quantum mechanics.

Answer 4

Ether theory is a prime example.

Answer 5

The wikipedia article on "Pathological science" might be good reading. In particular, the N-rays saga is a great case study in a wrong idea that was even "reproducible" for a while; see the decline effect and Feynman's cargo cult science.

Answer 6

Hermann Weyl's attempt to unify electromagnetism and gravity, which he expounded in his classic book Space, Time and Matter. Roughly speaking, what Weyl did was to generalize the General Theory of Relativity by allowing not only arbitrary coordinate transformations, but also transformations to the scales used in the measurements. The theory was very appealing, but it turned out to be wrong because (as Einstein noticed the moment very he heard of the theory) it implied that the properties of a particle depended on its history. Thus, an electron coming from the Sun should have slightly different properties to an electron here on Earth, because they have had a different history. Instead, it is found experimentally that the properties of elementary particles are always the same, which would imply in Weyl's theory that they all had similar histories, which is highly unlikely.

Answer 7

Aristotel's theory of motion where larger masses fell to the earth faster than smaller masses.

Answer 8

I know this one is going to be controversial, but since I've seen Yang-Mills theory ("as Yang Mills wanted") up there...

String theory - I wouldn't say it failed, but it turned out that it didn't solve the problem it was invented for, namely to describe the strong interaction, and the occurence of certain patterns in mesons (Regge trajecories). Although you can describe some strong phenomena with a stringy theory - like you can with the "eightfold way", nuclear isospin etc. - nowadays QCD is considered the most fundamental description of strong phenomena.

Actually, it turns out that you can use some tools of string theory (the AdS/CFT correspondence) to perform calculations that you can't do in QCD. This is done in heavy ion physics. Note that the theory you use there is different than the original "pions as strings" hypothesis.)

There's a nice write up about the history of string theory by Luboš Motl here: What are the details around the origin of the string theory?

There's a second problem it didn't solve (yet?), to give a unified theory of gravity and the other forces, that includes the standard model as a low energy limit. But that's a lot to ask for from a theory...

Answer 9

Heat being considered as a fluid(the most unbelievable to me) which shows poor scientific understanding of very fundamental (and ordinarily perceivable) phenomena,IMHO.

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

but laws of thermodynamics (0 to 2) established the nature of heat. Description through behaviour of material in bulk (statistical description of thermal and continuum phenomena)