How was 20th century physics so successful with so limited amount of experimental data?

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The 20th century saw the full scale development of both Special/General Relativity, Quantum Mechanics, Modern Cosmology, the Standard Model, Solid State Physics and Plasma Physics. All of these were driven by innovate and powerful analytical thought.

Key breakthroughs were indeed backed up by solid empirical evidence, that is a testament to the ingenuity of experimental physics. In fact from a practical era this was indeed a Golden Age as well. Here is a list of some key experiments and technologies that heralded the 20th century revolutions and indeed made it possible for theoretical physicists to take their models to the next level. Although one couldn’t acquire the extent of data that we can obtain today the brilliance of these adaptations more than substituted.

• Millikan’s oil drop experiment (1909)- determined the magnitude of the elementary charge (JJ Thomson’s experiment a decade earlier had already narrowed down the charge to mass ratio for the electron so that Millikan’s work proved to be vital as well for the determination of the mass of the electron);

Millikan’s Experiment - Can actually be performed at the High School Level Source: Figure 1. The apparatus used by Robert A. Millikan for performing the...

• Geiger-Marsden’s gold foil experiments (1908–1913)- identified the positive nature of the atomic nucleus;
• Ernest Rutherford and Frederick Soddy’s transmutation experiments (1901) - these examined the conversion of one type of an atom into another;
• Enrico Fermi’s demonstration of nuclear chain reactions (1942) - this is the basis for continuous Nuclear Fission;
• X-Ray Crystallography experimentation work by the Bragg team (father and son - 1915) as well as Rosalind Franklin later - helped unravel the Double Helix nature of DNA and other molecular structures;
• Invention of the Bubble Chamber by Donald Glaser (1952)- an extremely valuable tool in particle physics;

Bubble Chamber profile - can identify particles using motion outlines and careful application of conservation of momentum. Sources: Bubble chamber

• Stern -Gerlach Experiment (1922) - showed that spatial orientation associated with angular momentum is quantized;
• Davisson-Germer Experiment (1923)- Observed diffraction patterns with electrons (vital in the development of the notion of wave particle duality);
• Bell Test Experiment (1982) - Performed by Alain Aspect - showed that ‘ghostly action at a distance’ was indeed a reality;
• The science and technology around the family of particle accelerators that include - linear induction accelerators, betatrons, circular or cyclic RF accelerators and synchrotons;

First Particle Accelerator 1932 The First Particle Accelerator 1932

• The development of the Transistor (1947) and the various spin-off technologies around semi-conductors (opened up the idea of the integrated circuit and the microprocessor);
• The invention of Radio Telescope by Karl Jansky in 1932 (useful in the elucidation of key cosmological phenomena).

Radio Telescopes Expect the unexpected from the big-data boom in radio astronomy