Fall.2008.MMA.Colella.Timeline

Democritus Born 460 BC Died 370 BC Birthplace: Abdera, Thrace Philosopher, Mathematician

Democritus was one of the greatest Greek physical philosophers. He settled in Egypt for seven years where he studied mathematical and physical system of the ancient schools. His father was a wealthy man and spent lavishly on his sons education. He studied with Leucippus, and Arstotle. He traveled Egypt, Babylon, Persia, and Athens exchanging his wealth in the process and he returned to Abdera a poor man happy with all he had seen and learned. He lived to a great age and is buried in Abdera.

His greatest achievement was founding of the atomic theory. Democritus did not accept the Eleatic hypothesis that “everything is one” and that change and motion is an allusion. He invented the concept of the atom. He hypotheseized that all matter is composed of tiny indestructalbe units called atoms. This idea seems to be motivated by the question of how finely a human can cut up matter. Although he performed no experiments and had only little evidnce for coming up with the existence of atoms. The early atomic theory stated the characteristics of an object by determining the shape of its atom. For example, sweet things are made of smooth atoms, bitter things are made of sharp atoms. [|picture]

[|atomic model]

Leucippus Born: ca 480 BC Died: 420 BC  Birthplace thought to be Miletus, Asia Minor: Many people believed that he did not even exist. However it is likely that he was a contemporary of Empedocles around 44 BC. He was a student of Parmenides’ follower Zeno. His contribution to the development of the atomist theory is unknown. Most people refer to the views of Democritus or both atomists together. Epicurus tends to deny the fact that there was ever a philosopher named Leucippus, however Aristotle accredits the foundation of the atomist system to Leucippus. He is named by most sources as the originator of the theory that the universe consists of two different elements. which is called the full or solid, and the empty or void. Because little is known of Leucippus’ views and his specific contributions to atomist theory, a fuller discussion of the development is found under information about Democritus. (Since he is usually included in Democritus's views, see his model above under the info of Democritus) [|Leucippus picture]

Thales of Miletus Birth: 620 BC   Death: 546 BC    Birthplace: Miletos, Asia Minor (Now Turkey) Aristotle, the major source of Thales philosophy and science identified Thales as the first person to investigate the basic principles, the question of originated substances of matter and the founder of the school of natural philosophy. He studied in Egypt and brought these teachings to Greece with him. He is unanimously accredited with the introduction of mathematical and astronomical sciences into Greece. None of his writing exists anymore which makes reading about his studies difficult to say the least. It also makes it hard to determine his philosophy and to be certain about his mathematical discoveries. However we do know that he discovered a method of measuring distance to a ship at sea shown below. [|distance to ship model] [|picture of Thales]



John Dalton Born: 1766 Died: 1844 Birth Place: Cumberland, England Dalton earned most of his living by being a teacher in his home village starting at age 12. After teaching for 10 years, Dalton moved to Manchester, where he joined the Manchester Literary and Philosophical Society. This is where he delivered his first paper to the society on color blindness. Dalton came upon his views on atomism by meteorology. Dalton kept daily weather records from 1787 until his death. His theory starts that elements consist of tiny particles called atoms. All elements are pure because al atoms of an element are identical and have the same mass. They differ from each other because atoms of each element are different from another; they have different masses. Compounds consist of atoms of different elements combined together. Daltons model of atoms state they were tiny, indivisible, indestructible particles and they have a certain mass, size, and chemical behavior determined by what kind of element they were.

[|model site] [|information taken from this website]



[|Charles Coulomb] Born: 1736 Died: 1806 Birth Place: Angoulême, France Coulomb was born into a family which was know for there fields. Coulomb’s family moved to Paris where he got his college education from Collège Mazarin. He graduated from college in November of 1761. Coulomb developed a theory of attraction and repulsion between two entities of the same opposite electrical charge. He discovered that the force of attraction or repulsion is proportional of the product of the two charges and is inversely proportional to the distance of the two charges.

[|Information from this site] [|model from this site]



Roger Joseph Boscovich Born: 1711 Died: 1787 Birth Place: [|Dalmatia] Boscovich, at age 15, passing through the elementary studies and joined the Society of Jesus. He studied mathematics and physics at Collegium Romanum. In 1740 he was appointed to be the professor of mathematics. Several years before appointed this job, he made himself a name by solving the problem to find the suns equator and determine the rotation period by observation of the spots on the surface. Boscovich developed the first logical description of the atomics theory in his work, which this is known to be one of the greatest attempts to understand the structure of the universe in a one idea. He detained the idea that a body could not be made up of continuous matter but of innumerable “point-like structures”.

(Boscovich's Point-Like atoms model)[|Model and Info taken from this site]

Small, Spherical, Solid, Indivisible Model Of the Atom

This model was first introduced by John Dalton. The reason it was called the "billiard ball model" is because Dalton described the atoms as "indivisible spheres with constant density throughout". Dalton also said that all atoms of the same element were identical and different from those atoms making up another element. By the early 1900's it was clear the the "billiard ball" model was wrong. It was disproven by JJ Thompson who said that atoms were like blueberry muffins.



Michael Faraday Born: 1791 Died: 1867 Birthplace: South London His family was not very wealthy and he only received a basic formal education. At the age of 14, he worked for a local bookbinder and educated himself by reading the books he worked on. He attended lectures given by the chemist Humphrey Davy at the Royal Institution. Faraday wrote to Humphrey asking to be his assistant. He was turned down but later appointed in the year 1813 as chemical assistant at the Royal Institution. In 1821 he published his work on electromagnetic rotation. In 1831, he discovered electromagnetic induction, which is the principle behind the common transformer and generator. His discovery was crucial in letting electricity be transformed from a curiosity into a new technology. For the rest of the decade, he continued to work on electricity. This is where he is partly responsible for coming up with the common words including ‘electrode’, ‘cathode’, and ‘ion’. His most important discovery is benzene which is a common carbon compound. [|information site]



Dmitri Ivanovich Mendeleev Born: 1834 Died: 1907 Birth Place: Tobolsk, Siberia

Mendeleev was the youngest of 14 children, which were all raised by their mother, Maria. Maria’s family introduced paper-and glass making to Siberia, where she worked at the factory as a manager to make humble amount of money to support her family. Mendeleev spent a lot of time in the factory, where his passion of chemistry started. After the family faced another tragedy of the factory burning down, the family moved around. In 1850 Mendeleev was accepted at the Pedagogical Institute, his father school. Soon after his new career at St. Petersburg he faced another tragedy of the sudden death of his sister and mother he was left all alone. Mendeleev was a Russian chemist. He taught at St. Petersburg from 1867 to 1890. Mendeleev is famous for the formulation of the periodic law and the discovery of the periodic table with help from Lothar Meyer. From Mendeleev’s discovery he was able to predict the properties of the elements that were still unknown. He then used his data to group each of the elements together by there similar properties. His periodic table was put together on the basis of arranging the elements in order of atomic weight and grouping them by their similar properties. He also looked ahead and predicted the existence and properties of new elements. Not only that, he also pointed out accepted values of atomic weights that were in error. For the new elements that he predicted, he left space for them in the table. Eke-silicon and eke-boron were two of the yet to be discovered elements. Despite all his work, the table did not include noble gases because they had no been discovered yet. His table has been modified and corrected many times by Moseley, however it had allowed for the discovery of isotopes and rare gases. Mendeleev spent more than 13 years of his life researching the properties of each element for the table.

= William Crookes  = = Born: 1832  = = Died: 1919  = =   Birth Place: London  = Crookes received some grammar schooling at Chippenham, but his scientific career started at the age of fifteen when he entered the Royal College of Chemistry in Hanover Square, London. From 1850-1854 he took a position of assistant in the college. Said to be one of the most important researches using the cathode-ray tube(Shown Above) was performed by Crookes in 1875. In order to confirm the experiment of Pulcker and Hittorf, Crookes come up with his own vacuum tube which air could almost be completely removed. This sealed glass tube was used to demonstrate the path travelled by cathode rays. When an electric current is applied to the tube, a patch of fluorescent light would appear on the walls of the tube due to the interaction of electrons with residual gas in the tube. Crookes used a Maltese cross shaped electrode near the end of the tube to show that the invisible radiation did travel in straight lines. As the current level was increased, the electrons begin to ionize gases trapped inside the tube making them glow in a fluorescent blue color. When these ionizing electrons pass over the cross, a shadow appears on the end of the vacuum tube. . Soon Crookers tube became the vacuum tube used is all scientific experiments. Crookes continually practiced Pluckers experiment with magnetic field, confirmed that the glow as easily deflected. The tube was the precursor of the modern t.v tube.



Wilhelm C Roentgen Wilhelm was born on March 27, 1845 at Lennep in the Lower Rhine Province of Germany. He was the only child of a merchant and manufacturer of cloth. When he was 3 years old, his family moved to the Netherlands where he went to the Institute of Martinus Herman Van Doorn, which is a boarding school. In 1862 he entered a technical school at Utrecht, where he was expelled for being accused of drawing a caricature of a teacher that another student had drawn. His first work was published in 1870 which dealt with the specific heat of gases. He also studied the phenomena coming with the spreading of oil droplets on water. None of these works are what Wilhelm is famous for. He chiefly associated with his discovery of “X-Rays”. He happened upon this when in 1895 he was studying the phenomena accompanying the passing of an electric current through a gas at extremely low pressure. On November 8, 1895, he found that if a tube is enclosed in a sealed black carton to exclude all light, and if he was in a dark room, a paper plate covered on one side with barium platinocyanide placed in the path of the rays became fluorescent, even when it was 6 feet from the tube. He then proceeded to put his wife’s hand in the path of the rays. When he observed the plate at the end after it had developed, there was an image of his wife’s hand on the plate. There were shadows from her bones and of the ring she was wearing. Around the ring was a lighter color which is the flesh around the bones. The flesh is not as dense as bone and is therefore easier for the rays to pass through. This is known as “the first Rontgenogram ever taken”. He gave them name X- Rays because their nature was unknown at the time.

[|information site] [|hand picture] [|bio picture]



Henri Becquerel Born: 1852 Died: 1908 Birth Place: Paris

Becqueral’s father and grandfather were both had been very involved in science. His father was a Professor of Applied Physics and his grandfather was the inventor of an electrolytic method. Becqueral took many different positions in science, but in 1878 he took over his fathers spot in the Chair of Applied Physics at the Conservatoire des Arts et Metiers. The earliest work of Becquerel was centered on the polarization of light. In the year 1896 his pervious work was over looked due to his new discovery of the phenomenon of natural radioactivity. After his discovery, a conversation exchanged with Poincare on radiation which had been discovered by x-rays with accompanied by a vacuum tube, where he decided to do a further investigation on the connection between x-rays and phosphorescence. From Becquerals research it showed that rays emitted by uranium, causes gas to ionize which is different from x-rays so that they will be deflected by any electric or magnetic field. [|pic and info site]

JJ Thomson Birth:1856 Died: 1940 Birthplace: Manchester, England Joseph John Thomson was born on December 18, 1856 near Manchester, England. His father died when he was only 16. Thomson attended Owens College in Manchester. He later attended Trinity College, which is one of the most prestigious of colleges at Cambridge University. In 1896 he traveled to America to give lectures at Princeton. When he returned home, it was then he achieved his more important work of his life. At the Cavendish Laboratory At Cambridge University, Thomson was experimenting with currents of electricity inside a cathode ray tube. It was from these observations that he made a very bold statement regarding the streams of electricity. He said that the mysterious rays were streams of particles that were much smaller than atoms. He said they were pieces that make up the atom. He called these particles “corpuscles” and made a suggestion that they might make up all the matter in every atom. People had trouble believe this because they thought the atom was indivisible and the most fundamental unit of matter, how could something be inside it? These “corpuscles” are now known to be electrons. Also, prior to the breakout of World War One, Thomson made another huge discovery: the isotope. [|information] [|picture from]

At the beginning of the 20th century people knew that most atoms were neutrally charged so there must be positive particles to balance the negative particles. In 1905 Thomson introduced an atomic model to come up with an answer to these curiosities. Thomson’s “Plum Pudding Model” was where each atom was a sphere filled with a positive charged fluid. The fluid was called the “pudding”. The scattered electrons in the fluid were known as the “plums”. Thomson recommended that the positive fluid contained the negative charges in the atoms because of the electrical forces.



** Birth Place: **** Morrison ****, **** Ill. **** (U.S.A) ** ** Millikan attended **** Maquoketa ** ** High School ****. In 1886 he was enrolled in **** Oberlin ** ** College **** where he took courses in Greek and mathematics, his favorite subjects. In1891 he took a teaching position in elementary physics where he developed his new interest in the subject. 1893 he received his mastership in physics. Millikan received his Ph.D for his research on the polarization of light emitted by incandescent surfaces. He made numerous discoveries mainly in the fields of electricity, optics, and physics. ** ** Millikan is mostly famous for is oil droplet experiment. The process of the experiment was as follows; **An atomizer sprayed a fine mist of oil droplets into the upper chamber. Some of these tiny droplets fell through a hole in the upper floor. Millikan first let them fall until they reached terminal velocity due to air resistance and then, using the microscope, he measured their terminal velocity, and by use of a [|formula] , calculated the mass of each oil drop. ** After all this, he applied a charge to the droplets falling to the bottom of the chamber by illuminating them with X-Rays. This caused the air to lose electrons, or become “ionized”. Then, part of the oil droplets captured one or more of the extra electrons and in turn became negatively charged. He attached a battery to the plates so there would be an electric field between the plates that would act on the charged droplets. Then he adjusted the voltage until the electric force field would balance the force of gravity on the droplet. This would cause the droplet to hang suspended in the middle. Droplets that didn’t get any extra electrons dropped to the bottom of the chamber. Milikan repeatedly did this experiment with varying strengths of x-rays ionizing the air so that different numbers of electrons would go to the oil droplets each time. There is a picture of the chamber he used for this experiment below. ** [|info and pictures]
 * Robert A. Millikan  **
 * Born: 1868 **
 * Died:1953 **



Marie Curie Born: 1867 Died: 1935 Birthplace: Warsaw, Poland Marie Curie was officially born as Maria Sklodowska in Warsaw, Poland. She was the fourth child and fifth child in the family. Unfortunately, she suffered from major depression at the age of five as a result of her mother having tuberculosis. By the time she was eleven years old, both her mother and sister had passed away. After finishing her elementary schooling, she enrolled in Warsaw’s “Floating University”. This was an underground Polish school that trained Polish students to become teachers. She later moved to Paris to give her sister a better education. To remain there, she took a job as a school teacher at a school for peasant children. In 1891, Curie attended Sorbonne and was one of the few women at the school. Three years later, she received a degree in physics while coming first in her class. The next year, she received a master’s degree and finished second in her class. While completing her course, she met Pierre Curie. He has made his name by discovering piezoelectricity several years earlier. They eventually married on July 26, 1895. When Marie Curie decided to look for a subject to work on, she settled on ore pitchblende. She knew from Henri Becquerel that uranium salts emitted energy (Becquerel Rays) and at his suggestion, she decided to look for other things that emitted the same rays. She found that ore pitchblende had the same properties as Uranium. In her studies she found that there was something that was much more radioactive than pure uranium. Her and her husband extracted this substance and named it polonium, after Poland. From further studies, they also found that there was a substance that was much more radioactive than uranium. The problem was that such a small amount existed that it was almost untraceable. Their conclusion was confirmed by another French scientist. The Curies named it radium. Not many people believed them. They wanted to prove to others that the element existed by getting a measurable amount out of the pitchblende. The problem was that it required massive amounts of pitchblende to obtain just a gram of radium. Both Marie and Pierre worked for four long years refining pitchblende in a little old wooden shed they rented. They spent most of their life savings buying waste ore from Czech mines. Both the Curies and Becquerel received the Nobel Prize in 1903 for Physics. Unfortunately, 3 years later, Pierre was killed in a car accident. However, Marie continued to study the properties of radium. She proved that forms of cancer can be treated with Radium. In 1911 she was awarded the Nobel Prize in Chemistry and became the only person to have two Nobel prizes. She later developed leukemia as a result of the radium which led to her death in 1934. [|information site1] [|information site 2] [|photo website]

Ernest Rutherford ****  Born: 1871 ****  Died: 1937 ** ** Birthplace: **** Nelson ****, **** New Zealand ****. **    ** Rutherford **** received his first education in Government school and at the age of 16 he went to **** Nelson ** ** Collegiate ** ** School ****. In 1889 he received a scholarship and proceeded to many different universities, including the **** University **** of **** New Zealand **** and **** Trinity ** ** College ****. He returned to **** England **** in 1907 to become a professor in physics at the **** University **** of **** Manchester ** **. **  **Rutherford ****’s studies in ****New Zealand **** were focused on the magnetic properties of iron. He was the first to design a highly original experiment with high frequency alternating currents. He also invented a design to track electromagnetic waves. In 1919 rutherford successfully disintegrated atoms by bombarding nitrogen with alpha particles with the emission of a proton. **  He is credited with coining the terms, “alpha, beta and gamma”. He is most famously known for his “gold foil experiment.” In this experiment he took a stream of alpha particles at a lead screen with a tiny slit in it. Behind the lead screen was a very thin piece of gold foil and behind that was a zinc-sulfide screen. What he did was shoot alpha particles through the slit into the gold foil. What he found was that most of the alpha particles went straight through and hit the zinc-sulfide screen. Some of the particles however, bounced to left, right and directly back at him. From this he concluded that the atoms of the gold were not solid throughout and that there was actually a lot of space in there. Below is a diagram of the experiment

[|information site] [|info and model] [|picture]



Neils Bohr Born:1885 Died: 1962 Birthplace: Copenhagen, Denmark Neils Bohr was a physicist who was the first the apply the quantum theory which “restricts the energy of a system to certain discrete values, to the problem of atomic and molecular structure.” He received a Nobel Prize in 1922 for this work. Before all this Bohr attended the University of Copenhagen and put himself in the spot light by winning the gold medal from the Royal Danish Academy of Sciences and Letters for his work on the vibrations of water jets. In 1911 he got his doctorate by making a thesis on the electron theory of metals. In it he stressed the inadequacies of classical physics for treating the behavior of matter at the atomic level. After this, he went to England to continue his work with Sir Thomson. Bohr is known for his famous atomic model, sometimes called the planetary model, or the Rutherford-Bohr atomic model. His model consists of 4 major principles: ** The only problem with his model is that it only worked for hydrogen. Despite this fact, his model was a huge step in the development of the atomic model. * *Chart taken from [|Bohr model of the atom] [|information from here]
 * 1) || Electrons assume only certain orbits around the nucleus. These orbits are stable and called "stationary" orbits. ||
 * 2) || Each orbit has an energy associated with it. For example the orbit closest to the nucleus has an energy E1, the next closest E2 and so on. ||
 * 3) || Light is emitted when an electron jumps from a higher orbit to a lower orbit and absorbed when it jumps from a lower to higher orbit. ||
 * 4) || The energy and frequency of light emitted or absorbed is given by the difference between the two orbit energies, e.g., ||



The Model above is known today as the Rutherford-Bohr Model. This model follows the rules listed in the chart above. Rutherford and Bohr arranged the model like teh solar system because at the center of every atom there is a nucleus, or the sun in our case,and the electrons "orbited" around the nucleus the same way the planets orbit around the sun. By this model, they concluded that electrons exist in orbits and nowhere else. They said that electrons closer to the nucleus have a lower energy, but can have energy introduced that can make them excited enough to "jump" to another orbit. This worked for when lower enery electrons jumped into higher energy orbits, but when higher energy electrons jumped into lower orbits, they had no explanation for where the energy went in atoms larger than hydrogen. [|info taken from here] [|rutherford-bohr (planetary model)]

Werner Heisenberg Born: 1901 Death: 1976 Birthplace: Wurzburg, Germany Werner Karl Heisenberg was born on December 5, 1901. He entered elementary school at Wurzburg, but at age nine, his parents moved him and his brother to Munich where his father became the professor of Greek philology. In Munich, he enrolled at the Maximilian Gymnasium where his grandfather was headmaster. After the war, Heisenberg completed his schooling at the gymnasium. He entered the University of Munich in 1920 to achieve a degree in mathematics, which is something he had been interested in for a long time. After being denied by the professor of mathematics at the school would not accept him as a student in a seminar, he took his grandfathers advice and applied for physics. After a meeting with Arnold Sommerfeld, the professor of theoretical physics at Munich, he was accepted. He is best known for his discovery of the “uncertainty principle” which he was awared the Nobel Prize in Physics in 1932. This principle states that it is “impossible to specify precisely both the position and the momentum of a particle at the same time.” The introduction of this principle helped to understand numbers of problems in atomic physics. Heisenberg wrote in //The Physical Principles of the Quantum Theory,// that "the interaction between observer and object causes uncontrollable and large changes in the system being observed.” [|info]



Erwin Schrodinger Born: 1887 Died: 1961 Birthplace: Vienna, Austria Erwin Schrodinger was born in Vienna, Austria on August 12, 1887. His father was a successful oil cloth factory owner and his mother was the daughter of Alexander Bauer who was a professor at the Technische Hochschule. For most of his younger years he was home schooled. In 1898 he enrolled at Akademische Gymnasium in Vienna to finish his pre-college schooling. After graduating from the Gymnasium in 1906, he entered the University of Vienna. He was awarded his Ph.D. in physics in 1910 and was immediately offered a job at the University’s Second Physics institute. When World War One broke out, he became an artillery officer assigned to the Italian front. After the war, he returned to the institute and on April 6, 1920 married Annemarie Bertel. He later accepted a job in theoretical physics at the Unveristy of Zurich in late 1921. It was at this University that he began to examine the possibility of expressing the movement of an electron in an atom. In 1926, Schrodinger was examining the idea that an electron can travel around the nucleus only in a pattern described by a whole number of wavelengths. He was trying to determine the equation that would express the position of each permitted orbits. He found a “second order partial differential equation” that met the criteria of his theory. The “equation” specified certain energy levels outside the nucleus where an electron with a whole a number of wavelengths could be found. This proposition was extremely close to orbits that Neils Bohr had offered in his theory in previous years. The equation also explains why electrons can't exist in spaces between Bohr’s orbitals, the reason being that only non-whole number wavelengths can be there. This theory then became known as the “Schrodinger wave equation” or the “wave equation”. [|info]

Electron Cloud Model -Was introduced by Erwin Schrodinger. He used the thoughts of Bohr and took them in a new way. He developed the probability function for the Hydrogen atom mostly. The function says that a cloud region is where the electron is most likely to be found. The model leaves room for the fact that nobody can say with any assurance that the electron is at one point at one time, but on the contrary, can estimate where it should be. The red dot in the middle is the nucleus and the little red dot(s) on the outside represent the electron and its trace. As the electron moves, it leaves a trace of where it has been. As all these trace spots begin to mesh together, they form a cloud. The locations of the electron predicted by Schrodinger’s equation coincide with the locations in Bohr’s model.



James Chadwick Born: 1891 Died: 1974 Birthplace: Cheshire, England James Chadwick was born in 1891 in Manchester, England. In 1911, he graduated from Manchester University and stayed there to work with Rutherford. During World War One he was detained as a civilian prisoner of war and returned to England in 1919 to perform research at Cambridge University. In 1923 he became the assistant directior of research at the Cavendish Laboratory.

Chadwick is credited with discovery the neutron in the atom. Since Rutherford proved that atoms have minuscule and dense nuclei, and the nucleus having a positive charge, physicists wanted to find out where the extra mass was coming from. What Chadwick contributed was the discovery of the neutron. In 1932, he created an experiment to find out the mass. He smashed alpha particles into beryllium, and allowed the radiation that released to hit paraffin wax. When the radiation hit hydrogen atoms in the wax, the atoms were directed into a detecting chamber. Physicist know that only a particle having almost the same mass as hydrogen can affect hydrogen in that way. The results showed a collision between beryllium atoms would release huge neutral particles which Chadwick called neutrons. 