Here's a list of discoveries which started with discrepancies relevant to 'missing mass' which existed at one time and have been resolved.
Discrepancies found in the orbit of the planet Uranus (discovered 1821):
Hypotheses: breakdown of Newtonian gravity
Resolution: Planet Neptune discovered, 1846 (See Wikipedia: The Discovery of Neptune)
Time to resolution: 25 years
Discrepancies are found in the proper motions of the relatively nearby stars Sirius and Procyon (1844)
Hypotheses: Something massive but very faint, that did not emit enough light to be seen in the glare of the primary star, was orbiting these stars.
Resolution: Faint companion stars are found orbiting Sirius (1862) and Procyon (1896). These stars would turn out to be white dwarf stars. (see Wikipedia: White Dwarf)
Time to resolution: 18 and 52 years
Discrepancies found in the orbit of the planet Mercury (discovered 1859)
Hypotheses: Undiscovered planet between Sun and orbit of Mercury. Proposed name is Vulcan but repeated searches do not find it.
Resolution: Postulation of the General Theory of relativity, 1915 (See Wikipedia: Perihelion Precession of Mercury)
Time to resolution: 56 years
Beta-decay of atomic nuclei is found to violate conservation of energy and angular momentum (discovered 1911)
- Beta-decay violates these conservation laws
- there is an extra particle, electrically neutral, spin 1/2, very small mass, emitted in beta-decay that is not detected by current technologies (neutrino hypothesis, 1930)
Time to resolution: 45 years
Atoms with the same nuclear charge are found to have different atomic masses (discovered 1913) (See Wikipedia: Isotopes). The mass of atomic nucleus for many elements is about twice the number of protons.
Hypothesis: tightly bound states of electrons and protons make up the difference in mass
Resolution: Discovery of neutron, 1932 (See Wikipedia: Neutron)
Time to resolution: 19 years
Shortage of neutrinos emitted from the Sun (discovered 1968).
- A central black hole captures neutrinos
- Neutrinos oscillate between the different 'flavors', electron, muon, and tau.
- Young-Earth Creationist Solution: Stars are not nuclear-powered (See ICR: The Sun is Shrinking)
- Electric Universe Solution: Stars are not nuclear-powered (See: Electric Discharge as the Source of Solar Radiant Energy (Part I))
Time to resolution: 35 years
What many people forget is that in the years between discovery of the problem and the resolution, there was often much contention between scientists. In a number of cases, there were experiments performed which reinforced some hypotheses.
In the case of the neutrino, theories of its interaction were developed which allowed theorists to treat it as a real particle and make numerical predictions. This capability also played a role in the eventual discovery as it enabled researchers to better estimate what level of technology would be needed for a direct detection.
Here's the big discrepancy in astronomy that has yet to be resolved. The is the focus of current controversy
Discrepancies: Rotation curves of galaxies doesn't match the visible matter distribution (discovered 1933). Clusters of galaxies have galaxies moving too fast to be gravitationally bound.
- undiscovered subatomic particle that interacts only gravitationally and is below the limit of detection by current technologies: 'Dark Matter' (see Wikipedia: Dark Matter)
- Modified Newtonian Dynamics (MOND): the theory of gravity breaks down in the weak field limit. (see Wikipedia: Modified Newtonian Dynamics)
- Plasma Cosmology solution: galaxies are actually formed by giant currents. Currents predicted at about intensity of cosmic microwave background but are not seen (See Scott Rebuttal. II. The Peratt Galaxy Model vs. the Cosmic Microwave Background)
- Young-Universe Creationist Solution: Universe young. Clusters and galaxies don't need to be gravitationally bound (See Technical Journal: Astronomical Problems)
Frankly, I think the undiscovered subatomic particle option is most likely. It has the advantage of being the simplest solution that does not violate constraints from other observations. One could make the point that there seems to be an interesting hierarchy in the family of particles related to what interactions different classes of particles 'feel' (marked with an 'X').
|Electrons, muon, tau|
It appeals to a sense of symmetry (a surprisingly successful concept in particle physics) that there should be one more line
Consider the example from 1936, after the identification of electrons, protons, and neutrons, all the particles needed to build atoms. Carl Anderson discovered the muon in cosmic rays (see Wikipedia: Muon). It was such a surprise that one physicist commented “Who ordered that?”
Science involves finding solutions to difficult problems and sometimes it takes many years. I suspect there were cranks and crackpots exploiting the gaps in our understanding in the case of the older discrepancies, just as creationists and EU advocates try to exploit the more modern problems that are at the frontiers of our current knowledge.
In spite of the claims of pseudo-scientists, real scientists did the work and eventually solved the problems. They also improved on the measurements, sometimes revealing new discrepancies. Today, experiments are running that measure neutrino oscillations by measuring neutrinos that pass through the Earth emitted by reactors around the world (so there is a calibrated source). For more examples of science that started out as astronomical observations, see "The Cosmos in Your Pocket: Expanded and Revised".
Comments illustrating more examples from physics and astronomy are welcome.