Modern Physics
(1900 to the present)
Timeline for Physics 150, written by Blair Tuttle, MOdified by R. Martin (Last updated September 21, 2003) |
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Early Modern Physics | Quantum Physics | Modern Cosmology | |
Michelson (b.1852)
Plank (b. 1858) Einstien (b. 1879) Thompson (b. 1856) Rutherford (b. 1871) Ms. Curie (b. 1867) |
De Broglie (b. 1892)
Davisson (b. 1881) Schrodinger (b. 1887) Pauli (b. 1900) Heisenberg (b. 1901) Feynman (b. 1918) |
Hubble (b. 1889)
Ms. Rubin (b. 1928) Hawkins (b. 1942) |
Michelson , Albert | 1852 - 1931 | American Experimental Physicist | Became famous in 1879 for his remarkable measurement of the speed of light. Then, teamed up with Ed Morley (with his new interferometer) to measure the absolute motion of the Earth through the hypothetical aether. The null result set the speed of light as constant with respect to the Earths motion and led in part to Einstein's special theory of relativity. |
Plank, Max | 1858-1947 | German Theoretical Physicist | Powerful figure in German physics. Derived, in 1900, the frequency distribution of thermal light emissions from solids by assuming light is emitted in discrete packets (quanta) with energy proportional to frequency. This initiated the break with the Newtonian mechanics and begun the development of quantum mechanics. |
Einstein, Albert | 1879 - 1955 | German Theoretical Physicist | Achieved the status of genius shortly after his "miracle year" of 1905 in which he made important contributions to diverse topics in physics. The accomplishments include suggesting a method for calculating Avogadro's number, using Plank's quantum theory of light to explain the photo-electric effect and developing the theory of electromagnetism for moving objects (special relativity). Derived (also in 1905) perhaps the most popular equation ever written, E=mc2. Finished (in 1916) after 8 years of effort the general theory of relativity which is the cornerstone of modern theoretical cosmology. Emigrated to the US during WWII. Today Einstein is synonymous with genius. |
Thompson, J.J. | 1856 - 1933 | English Experimental Physicist | Showed (in 1887) via experiments employing electric and magnetic forces that the so-called cathod ray was in fact a new fundamental particle, the electron. Suggested that electrons were part of the atom and proposed the then popular "plum-pudding" model for the atom. |
Rutherford, Earnest | 1871-1933 | British (colonial) Experimental Physicist | Suggested (with Fredrick Soddy) that radiation occurred by energy given off when one atom transforms into another. Responsible for the experiment, performed by his understudies Marsden and Geiger, in which the nucleus was discovered. This established the planetary model for the atom. |
Curie, Marie | 1867 - 1934 | French Physicist | First woman internationally recognized for her contributions to physics. While a student of Henri Becquerel, discovered the radioactive element which she named radium. |
Bohr, Niels | 1885 - 1962 | Danish Theoretical Physicist | Developed (in 1912) the first model for the hydrogen atom which, although based on a number of tenuous assumptions, remarkably reproduced the experimentally measured spectra. Proponent of the "Copenhagen Interpretation" for quantum mechanics which claims that theory only describes our state of knowledge about nature not nature itself. |
Broglie, Louis de | 1892 - 1987 | French Theoretical Physicist | Proposed (in 1924) that just as light waves can have a particle character, so too electron particles can have a wave character. Showed that the wavelength is inversely proportional to momentum. Showed that Bohr's quantization rule was simply the condition for a standing wave on a circle of a fixed radius. |
Davisson, Clinton | 1881 - 1958 | American Experimental Physicist | Discovered (in 1927) that electrons reflecting off of metal surfaces display an interference pattern indicating that the electron has wave characteristics. Other researchers (Frank and Elsasser) showed that the experimental results agree quantitatively with the results from the de Broglie equation. |
Schrodinger, Erwin | 1887 - 1861 | Austrian Mathematical Physicist | Formulated (in 1926) a general wave equation for an electron in a force field. Although initially the interpretation for the electron wave function was unknown, the energy levels for an electron in a hydrogen atom as calculated by the so-called Schrodinger equation exactly reproduced the results of the Bohr model. Wrote the now famous Schrodinger's cat paradox to illustrate the shortcomings of particularly the Copenhagen Interpretation for quantum mechanics. |
Pauli, Wolfgang | 1900 - 1958 | Austrian Theoretical Physicist | Proposed that only one electron can occupy a single quantum state. (Such particles are called fermions.) From the so-called Pauli Exclusion Principle and the results of the Schrodinger wave equation, one can qualitatively determine the chemical properties of all the elements and thereby explain the structure of the Periodic Table. Emigrated to the US during WW II. |
Heisenberg, Werner | 1901 - 1976 | German Theoretical Physicist | Developed a matrix formulation of quantum mechanics which Schrodinger showed was equivalent to his wave formulation. Derived the Uncertainty Principle which states that certain pairs of observable quantities, e.g. momentum-position and energy-time, can not both be exactly known. The Principle predicts that as the uncertainty in one quantity (say position) is reduced to zero then uncertainty in the other (momentum) approaches infinity. At best the multiple of the uncertainty of these pairs is equal to Plank's constant divided by 4 times Pi. |
Feynman, Richard | 1918 - 1988 | Theoretical Physicst | Developed a theory of Quantum Electrodynamics (QED) which unified the theory of Quantum mechanics (e.g. Schrodinger's Equation) with the theory of Electromagnetism (e.g. Maxwell's Equations). |
Hubble, Edwin | 1889 - 1953 | Observational Cosmologist | Discovered (in 1929), by measuring the doppler shift of a large number of galaxies, that the Universe is expanding. This led to the development of the so-called Big Bang theory for how the Universe has come into existence. |
Rubin, Vera | 1928 - | Observational Astronomer | Discovered (in the 1970s), by measure the doppler shift of gas in outer regions of galaxies, that roughly 90 % or more of the mass of a galaxy is outside the core of the galaxy in an unknown form now called Galactic Dark Matter. |
Hawkins, Stephen | 1942 - | Theoretical Cosmologist | Born 300 years to the day after the birth of Isaac Newton and now holds the same position at Cambridge University as Newton held. Has contributed to our understanding of the Universe including works on the so-called Big Crunch, which may describe the fate of our Universe, and the radiation of black holes called Hawking radiation. |