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Period: 430 BCE to 404 BCE
Peloponnesian war
The Peloponnesian War was fought between alliances led by Sparta and Athens. Eventually, Persia intervened on the side of Sparta and led to the eventual weakening of Athens. -
400 BCE
Democritus
The atom is the basic building block of everything, tiny, uncuttable particles that are constantly moving and surrounded by empty space. Different types of matter are made of different arrangements of atoms. He was important, but at the time Aristotle published a much more well known critique of Democritus’s ideas, which minimized their impact until future scientists rediscovered them. -
Louisiana Purchase
Thomas Jefferson buys the Louisiana Purchase, a stretch of land from the Mississippi River to the Rocky Mountains from France, doubling the size of the United States. -
John Dalton
Proved the existence of atoms through experiments with gases and compounds, as opposed to Democritus’s theory, believes atoms are smallest, cannot be destroyed or made into smaller things, all atoms of the same element are alike, and all different ones are different. Atoms join together to form compounds, which are always the same proportions. His work was immediately accepted, and most of it still is today, with the exception of atoms being the smallest particles. -
Michael Faraday
Faraday discovered that the structure of atoms was in some way related to electricity. He also discovered that the area around an atom must be mostly space, as some substances condense when other substances are added. Some criticized his work, because it was mostly based in logic as opposed to math and experimentation. However, some of his theories made important contributions to the idea of atoms as a whole. -
Eugen Goldstein
Goldstein discovered the presence of canal rays, which were positively charged radiations in a gas discharge. These rays eventually helped with the discovery of the proton. -
Wright brothers' first flight
First flight of the Wright Brothers in their plane, which they called the Wright Plane. Their flight, which took place is Kitty Hawk, lasted 12 seconds and went 180 feet. -
JJ Thomson
Thompson discovered that atoms all contain small, negatively-charged, subatomic particles, called electrons. In his model, these electrons floated around the nucleus in a “pudding”. He believed all atoms were uniform, positively-charged spheres. Although his model was eventually disproved, his discovery of electrons was incorporated into all following models. -
First Movie Showing
The first movie was played to a paying audience. The Lumiere brothers in Paris made the movie using a camera/projector/film printer of their own design. -
Ernest Rutherford
Rutherford discovered through the gold foil experiment that positive charge is concentrated in the nucleus, and that most of an atom is empty space. This experiment involved attempting to get atoms to pass through gold foil, during which he found out that some particles bounced off and back, instead of passing through the foil. Later, he named the positively charged atom the proton. -
Robert Millikan
Millikan discovered the charge on a single electron. By measuring the force on oil drops between two electrodes, he was able to confirm that all electrons held the same amount of charge, which was previously unknown to scientists. -
Neils Bohr
Bohr was the first to incorporate quantum mechanics into his model of the atom. In his model, a positively charged nucleus is surrounded by extremely small negatively charged electrons. He proposed that electrons don’t radiate energy, instead they exist in states of constant energy. He worked closely with Rutherford and Thompson, using their discoveries to influence his own. -
Women's Suffrage in US
Women gained the right to vote in the United States. The 19th amendment was passed by Congress on June 4th, after a decades long fight by suffragettes who staged protests and pushed for political change. -
Edwin Schrodinger
Schrodinger contributed to quantum mechanics and to the wave theory of matter. He used de Broglie’s ideas to develop the “electron cloud” model, in which electrons are found in orbitals. He proposed a mathematical equation to determine probable locations of electrons. He also formulated a wave equation, which accurately found the energy levels of electrons in an atom. His work helps scientists explain the electronic structure of atoms and the nature of different states of matter. -
Werner Heisenberg
Heisenberg discovered information about quantum theory through matrices. He established the Uncertainty Principle, which states that the momentum and position of a particle cannot be known exactly. There is an amount of uncertainty in both measures, which Heisenberg was able to calculate. He worked for Germany during World War II at a facility attempting to build an atomic bomb. There is no confirmation on whether he hindered their progress, but nonetheless they did not succeed. -
Empire State Building is finished
The Empire State building is completed in New York City, after barely a year of construction. It was the tallest building in the world until 1970, when the world trade center buildings were built. -
James Chadwick
James Chadwick discovered the presence of the neutron in the atom. He was also able to measure its mass. By recreating an experiment previously carried out by Herbert Becker and Walter Bothe, he radiated alpha-particles from polonium through beryllium. He determined the previously mysterious radiation to be neutrons. Chadwick won a Nobel prize for this discovery in 1935.