Modern Physics — Tech Evolutions

Entry	Year	Description	Impact
Planck's Quantum Hypothesis	1900	Proposed that energy is not continuous but emitted/absorbed in discrete packets (quanta), proportional to frequency (E=hν). This was a radical departure from classical physics.	Initiated quantum theory, solved the blackbody radiation problem, and laid the foundation for understanding the photoelectric effect and atomic spectra.
Einstein's Special Theory of Relativity	1905	Postulated the constancy of the speed of light and the relativity of motion, leading to a unified spacetime and the equivalence of mass and energy.	Overturned Newtonian concepts of absolute space and time, explained phenomena at high velocities, and provided the basis for nuclear energy (E=mc²).
Bohr's Atomic Model	1913	Proposed quantized electron orbits and energy levels for atoms, explaining atomic stability and discrete spectral lines.	A crucial step towards quantum mechanics, though limited to hydrogen-like atoms. It introduced the idea of quantized energy states within atoms.
Quantum Mechanical Model of the Atom	1920s	Developed by Schrödinger, Heisenberg, and others, replacing Bohr's fixed orbits with probability distributions (orbitals) and incorporating wave-particle duality and uncertainty.	Provided a much more accurate and comprehensive description of atomic structure, chemical bonding, and molecular properties, forming the basis of modern chemistry.
Einstein's General Theory of Relativity	1915	Extended special relativity to include gravity, describing it as a curvature of spacetime caused by mass and energy.	Revolutionized understanding of gravity, predicted black holes, gravitational lensing, and the expansion of the universe. Crucial for cosmology and astrophysics.
Standard Model of Particle Physics	1970s onwards	A theoretical framework describing the fundamental particles (quarks, leptons) and three of the four fundamental forces (strong, weak, electromagnetic) and their interactions.	Provided a highly successful and experimentally verified description of subatomic physics, leading to the discovery of particles like the Higgs boson. It's our current best understanding of fundamental matter and forces.