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Jan 1, 1000
Aristotle
Years of life: 384 BC – 322 BC. Aristotle’s theory made a great generalisation off all matter being made of the four elements: fire, water, earth, and air. He also believed that there were four qualities to these elements: dryness, hotness, coldness, and moistness. Based on these beliefs fire would hold the properties of being dry and hot, water is wet and cold, air is hot and wet, while the earth is dry and cold. As strange as this theory may seem now, it was used for nearly two thousand years. -
Jan 1, 1000
Democritus' Theory
Democritus believed that all matter was composed of atoms, and each atom was separated by an amount of space. Democritus described atoms as solid, having no clear internal structure and varying greatly in terms of size, shape, and weight. -
Jan 1, 1000
Democritus
Democritus, born around 460 B.C.-370 B.C, in the small Greek city-state Abdera, is commonly recognized as the greatest upholder of Atomistic theory in the ancient world. Although these theories were prehistoric and incorrect, they were involved in the creation of modern atomic theory and the discovery of the atom. -
Antoine Lavoisier
Antoine Lavosier (26 August 1743 – 8 May 1794) is known as the father of Modern Chemistry. Although many of his scientific breakthroughs proved to be crucially important in the discovery of the atom, Lavosier himself believed that the existence of atoms was scientifically impossible. He developed the Law of Conservation of Mass in 1789. This law described elements as pure substances that are unable to be broken down… -
Antoine Lavoisier (continued)
This helped Lavosier to organize the various sections of chemistry into one cohesive science; this chemical revolution would later set the stage for many of the important discoveries, which furthered human understanding of the atom. Unfortunately, Lavosier and many other Enlightenment philosophes were persecuted during the French Revolution, particularly the Reign of Terror (1793-1794), and was executed at the guillotine in 1794. -
John Dalton
Dalton, (6 September 1766-27 July 1844) was studying Meteorology when discovering his theory. On January 1, 1803, his theory was that evaporated water exists in the air as an individual gas. He performed many experiments regarding this theory. Some details of Dalton’s theory are known to be incorrect, but a core concept of his theory (that chemical reactions can be explained by the union and separation of atoms, and that these atoms have characteristic properties) is a principle of science today -
Joseph John Thomson
J. J. Thomson, born 18 December 1856 – 30 August 1940, was a modest, mild-mannered English physicist, and can possibly be described as a man whose accomplishments did more to shape the human understanding of the atom than anyone in history. It was Thomson’s discoveries that finally shattered the determined concept of the heavy, solid, absolutely indivisible atom and replaced it with the concept that the atom was in fact itself comprised of smaller particles, a concept that we still study to this -
Marie and Pierre Curie
Marie Sklodowska, a mathematician and scientist born in Poland in 1867, along with her husband Pierre Curie, a French professor of physics, are two of the greatest and best-known scientific minds of the early 20th century. They were the first to create the term “radioactivity” and were the first to identify, isolate, and study two important radioactive elements: radium and polonium. They developed a cure for rabies too. Pierre died in 1906, so Marie took over his position. She died in 1934. -
Max Planck
Max Planck was born in Kiel, Germany in 1858. By 1898, Planck was focused on the gaps that were still present in the understanding of the radioactive processes, particularly in the distribution of energy during such radioactive processes. In a series of papers published in 1900, Planck revealed that he had successfully uncovered the connection between the energy and the frequency of radiation. -
Max Planck (continued)
Planck had successfully developed the idea of the quanta, which he defined as an individual unit of energy, which later figured importantly in the area of quantum physics. Unfortunately, Planck suffered many tragedies in his later years; he lost his home and one of his sons to the brutality of the Second World War, and he died after the war’s end in Gottingen, Germany, in 1947. -
Ernest Rutherford
Ernest Rutherford, born August 30 1871-October 19 1937, in New Zealand, became known as the father of nuclear physics. He discovered not only the positive charged particle that we know of as the proton, but also the fact that the atom actually possesses a nucleus, a discovery practically overpowered previous concepts of the atoms, which had viewed the atom as solid and possessing no internal structures. We still use this today. -
Robert Millikan (Part 2)
Other scientists had tried to observe the effect of electric fields on large quantities of water, but Millikan instead used single drops; when these singular drops of water began to evaporate, Millikan switched to oil. By observing the effects of an electric field on the oil, Millikan was able to determine not only the charge of an electron (1.602 x 10-19 coulomb), but also the mass of an electron (9.11 x 10-28 gram). -
Robert Millikan (Part 3)
This very accurate representation later figured importantly in the development of Bohr’s quantum theory of the atom. Millikan moved to California in the 1930s and remained there until his death in 1953. He won the Nobel Prize for Physics in 1923. -
Robert Killikan (Part 1)
Robert A. Millikan was born in Illinois in 1868. Millikan became determined to follow a singular line of research; the discovery of the basic unit of the electric charge. In order to simplify this, Millikan used his famous oil-drop experiment, which was actually inspired by other similar experiments, which had been conducted earlier, although none had been nearly as successful as Millikan’s would prove to be. -
Henry Mosely (continued)
Moseley also discovered that the atomic number can be used to supply the number of protons within the nucleus of an atom. Moseley then went on the reorganize the periodic table, which had previously been based upon atomic number, rather than atomic mass. Unfortunately, he was killed at Gallipoli by Turkish forces in 1915, only a short time after joining the British army to serve in World War I. -
Henry Moseley
Moseley was a brilliant physicist who became a British deputy in the First World War, a war which he later became a victim of. Moseley’s breakthroughs involved the use of X-rays; he used cathode rays to bombard elemental samples, and was then able to photograph the X-rays that resulted. This allowed Moseley to suggest that an atom could be identified by the charge on its nucleus by observing that the paths of certain lines in the x-ray spectrum moved when the atomic number was increased. -
Niels Bohr
Niels Bohr, born in Copenhagen, Denmark in 1885, was a world-class physicist who made numerous contributions to the scientific study and understanding of atomic structure and quantum physics. Rutherford’s research had proven that the atom had a positively charged nucleus, with a group of negatively charged electrons circling it in orbit. -
Neils Bohr (continued)
Bohr put detail upon this; he suggested that the electrons could travel only in consecutively expanding orbits. Bohr also discovered that the outer shells could hold more electrons than the inner ones. During World War II, Bohr helped scientists such as Enrico Fermi and J. Robert Oppenheimer, who were heavily involved with the secretive Manhattan Project. He died in his hometown of Copenhagen in 1962. -
Werner Heisenberg
Werner Heisenberg (1901-1976) was born in Bavaria, which at the time was a German state. Heisenberg’s interests lay mostly in theoretical physics, which he would study for the majority of his life. Heisenberg’s breakthroughs include the beginning of quantum mechanics, which he is mostly responsible for, and the progress of quantum theory. -
Werner Heisenberg (continued)
There is also Heisenberg’s famous Uncertainty Principle, in which Heisenberg revealed that it is an impossibility to know a particle’s position and velocity. Heisenberg was also involved in a measure of controversy during World War II, as he was a chief researcher behind the Nazi nuclear reactor projects that occurred during the war. After the war, Heisenberg became an active lecturer and scholar in West Berlin and the United States. -
Erwin Schrodinger
Erwin Schrodinger (1887-1961) Vienna, Austra. All of Schrodinger’s research efforts came to a close in 1930, when he finally published works proposing that wave mechanics was the actual mathematical model of the atom; these works were heavily influenced by the work of Heisenberg and Einstein, and also dealt with the theory of relativity. Schrodinger continued to work with quantum physics and mechanics until his death. -
James Chadwick
James Chadwick, (20 October 1891-24 July 1974) in Bollington, Cheshire. On September 28, 1932, Chadwick discovered an unknown part of the atomic nucleus. He discovered that there were neutrons in it. Before 1932, the atom was believed to be made up of the positively charged nucleus, which contained nearly all of the mass of the atom, and which was surrounded by orbital tracts containing varying numbers of electrons. But with Chadwick’s discovery came knowledge of the third basic component of t -
Henri Becqueral
Henri Becquerel was born in France in the year 1852. Henri Becquerel had discovered radioactivity, later defined as the unplanned discharge of radiation by a certain material due to decomposition. For his discovery, which increased the understanding of X-rays almost immeasurably and opened up new possibilities for radioactive studies, Becquerel was awarded the Nobel Prize for Physics in 1903.
