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430 BCE
Democritus develops first atomic theory
He theorised that:
-all matter is made of indivisible spheres called "atomos" or atoms
-they are indestructible and can be of different shapes and size
- these variations in shapes and sizes give matter different properties (e.g the acidity of lemons is a result of spiky atoms)
-unpopular at the time, attacked by plato and aristotle -
John Dalton develops atomic theory through chemistry
John Dalton, from a series of experiments in chemistry, theorised:
-all matter is composed of atoms, which cannot be created, destroyed or subdivided, similarly to democritus' model
-atoms are sorted into different elements, which have differing properties
-atoms of the same element are identical in size and mass
generally, his theory was a more "modern" version of democritus' theory, grounded by experiments and observations in chemistry -
Discovery of the electron
-The electron was discovered by JJ Thomson, using an apparatus called a cathode ray tube
-Thomson used the CRT to determine the charge to mass ratio of the cathode rays
-This ratio suggested that a subatomic particle of 1/2000th the mass of a hydrogen atom existed, this was the electron -
Special Relativity
-Special relativity is a theory of the relationship between space and time proposed by Albert Einstein
-In this theory, the famous mass-energy equivalence formula E = Mc^2 can be derived
-This equation can be used to calculate the energy released when a particle and antiparticle annihilate -
Charge of electron measured
-Robert Milikan measured the charge of the electron in the oil drop experiment
-This was a carefully controlled experiment, utilising electric fields to suspend an oil drop
-The charge of the electron was derived through a series of calculations involving terminal velocity and the electric field strength. -
Nucleus and proton discovered
-discovered by Ernest Rutherford in the gold foil experiment
-most alpha radiation would pass straight through, with some being reflected, suggesting that the atom was mostly empty, with a positive nucleus
-Rutherford later discovered the proton, the positively charged particle in the nucleus -
The Dirac Equation
-Derived by Paul Dirac
-Predicted the existence of antiparticles -
Neutron discovered
-Discovered by James Chadwick
-This indirectly lead to the creation of the atomic bomb through the manhattan project -
Positron discovered
-Discovered by Carl D. Anderson
-This was achieved with the use of a cloud chamber, traditionally used for visualising ionising radiation -
Discovery of the Muon
-Discovered by Carl D. Anderson and Seth Neddermeyer, while studying cosmic radiation
-Existence was confirmed separately in 1937 by J. C. Street and E. C. Stevenson
-Muons are a fundamental particle, they are not composed of anything else -
Manhattan project
-This was the research and development project which lead to the creation of the atomic bomb
-the bombs utilised the nuclear fission of plutonium to release a large amount of energy
-lead to the bombings of Hiroshima and Nagasaki
"I am become death, the destroyer of worlds." -
Demon Core goes supercritical
-The Demon Core was a sphere of plutonium intended to be used in a third nuclear bombing of Japan
-Louis Slotin, during an experiment, causes the core to go supercritical with a screwdriver slip
-this triggered a fission reaction, releasing a lethal dose of radiation to anyone in the vicinity of it -
Discovery of the pion
-Existence was theorised by Hideki Yukawa in 1935
-Discovered by Cecil Powell in 1947 by exposing photographic plates to cosmic radiation
-Pions contribute to the nuclear strong force, which hold nuclei together -
Electron Neutrino discovered
-Electron neutrinos are elementary particles that are difficult to detect as they have no charge
-Their existence was theorised in 1930 by Wolfgang Pauli
-Discovered in the Cowan–Reines neutrino experiment, led by Clyde Cowan and Frederick Reines -
Discovery of the J/psi meson
-The J/psi meson was discovered independently and announced at the same time, by Burton Richter and Samuel Ting
-Its discovery was of significant importance as it supported the existence of a new quark, the charm quark
-This would lead to a period in physics known as the November Revolution -
Man survives particle accelerator beam
-Anatoli Burgorski survived a proton beam from the U-70 Synchrotron
-The U-70 Synchrotron was the largest particle accelerator in the Soviet Union, which accelerated protons to high energies for research -
Discovery of the W and Z bosons
-The W and Z bosons carry the nuclear weak force, one of 4 fundamental forces
-They were discovered with the use of a particle accelerator, the Super Proton Synchrotron
-2 experiments, UA1 and UA2 were carried out -
Discovery of the top quark
-The top quark has the most mass out of all quarks and is of use to physicists as it has a short lifespan, allowing it to be observed on its on without hadrons being formed
-It was discovered through the use of a particle accelerator, the Tevatron, and the Collider Detector at Fermilab