The signs of new physics before Einstien Essay Hydrogen Spectra -> Balmer
Radioactivity (alpha, beta, and gamma particle discoveries)
Cathode Rays and how they were actually electrons)
The signs of new physics before Einstien Essay
Electron discovery by J. J. Thompson and his plum pudding model
Photoelectric effect -> intensity did not matter while wavelength does matter
Black body radiation
With how these different discoveries lead the way to the discovery of quantum physics.