Group 6 - Ernest Rutherford

Ernest Rutherford, 1st Baron Rutherford of Nelson, OM, FRS (30 August 1871–19 October 1937) was a British-New Zealand chemist and physicist who became known as the father of nuclear physics. In early work he discovered the concept of radioactive half life, proved that radioactivity involved the transmutation of one chemical element to another, and also differentiated and named alpha and beta radiation. He was awarded the Nobel Prize in Chemistry in 1908 "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances".

Rutherford performed his most famous work after he received this prize. In 1911, he postulated that atoms have their positive charge concentrated in a very small nucleus, and thereby pioneered the Rutherford model, or planetary, model of the atom, through his discovery and interpretation of Rutherford scattering in his gold foil experiment. He is widely credited with first splitting the atom in 1917, and leading the first experiment to "split the nucleus" in a controlled manner by two students under his direction, John Cockcroft and Ernest Walton in 1932.

Scientific research

During the investigation of radioactivity he coined the terms alpha and beta in 1899 to describe the two distinct types of radiation emitted by thorium and uranium. These rays were differentiated on the basis of penetrating power. From 1900 to 1903 he was joined at McGill by the young Frederick Soddy (Nobel Prize in Chemistry, 1921) and they collaborated on research into the transmutation of elements. Rutherford had demonstrated that radioactivity was the spontaneous disintegration of atoms. He noticed that a sample of radioactive material invariably took the same amount of time for half the sample to decay—its "half-life"—and created a practical application using this constant rate of decay as a clock, which could then be used to help determine the age of the Earth, which turned out to be much older than most of the scientists at the time believed.

ACHEIVMENTS

He was knighted in 1914. In 1916 he was awarded the Hector Memorial Medal. In 1919 he returned to the Cavendish as Director. Under him, Nobel Prizes were awarded to Chadwick for discovering the neutron (in 1932), Cockcroft and Walton for an experiment which was to be known as splitting the atom using a particle accelerator, and Appleton for demonstrating the existence of the ionosphere

Rutherford model

The Rutherford model or planetary model is a model of the atom devised by Ernest Rutherford. Rutherford directed the famous Geiger-Marsden experiment in 1909, which suggested on Rutherford's 1911 analysis that the so-called "plum pudding model" of J. J. Thomson of the atom was incorrect. Rutherford's new model for the atom, based on the experimental results, had the new features of a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom and containing the bulk of the atomic mass (the nucleus of the atom).

         

Rutherford scattering

Rutherford scattering is also sometimes referred to as Coulomb scattering because it relies only upon static electric (Coulomb) forces, and the minimal distance between particles is set only by this potential. The classical Rutherford scattering of alpha particles against gold nuclei is an example of "elastic scattering" because the energy and velocity of the outgoing scattered particle is the same as that with which it began.

The initial discovery was made by Hans Geiger and Ernest Marsden in 1909 when they performed the gold foil experiment under the direction of Rutherford, in which they fired a beam of alpha particles (helium nuclei) at layers of gold leaf only a few atoms thick. At the time of the experiment, the atom was thought to be analogous to a plum pudding (as proposed by J.J. Thomson), with the negative charges (the plums) found throughout a positive sphere (the pudding). If the plum-pudding model were correct, the positive “pudding”, being more spread out than in the current model of a concentrated nucleus, would not be able to exert such large coulombic forces, and the alpha particles should only be deflected by small angles as they pass through.

      

Democritus and Aristotle by Group 1

DEMOCRITUS

 

Democritus was born at Abdera, Thrace, sometime around 458 BCE. He was described as well traveled, probably visiting Babylon, Egypt, and Ethiopia, and perhaps India. He appears to have spent all of his time on scientific and philosophical studies, teaching, and writing— some 60 works have been listed. Of his voluminous writings, only a few fragments of his ethical theory remain. But these fragments and the descriptions by other writers of his atomic theory put him among the foremost thinkers of his time.

Democritus’s theory of the atomic nature of the physical world, developed from that of Leucippus, is known only through the works of critics of the theory such as Aristotle and Theophrastus. It resolved the question of how a world evidently in a state of flux could nevertheless have an underlying nature that was eternal and unchanging. By positing infinitely small things that remained the same but formed different combinations with each other, Leucippus initially, and Democritus in greater detail, managed to answer the question in a way that has been subject to increasingly successful elaboration ever since. One can trace the physical theory of atoms through Epicurus, Lucretius, and Galileo to modern times.

Hermippus wrote that when Democritus was nearing his end, his sister was upset because his death could prevent her from worshipping at the three-day festival of Thesmophoria. Democritus told her not to worry, and kept himself alive by inhaling the fresh smell of baked loaves until the end of the festival, when he relinquished his life without pain. Hipparchus wrote that Democritus was then in his 109th year.

Democritus was born in the city of Abdera in Thrace, an Ionian colony of Teos, although some called him a Milesian.  His year of birth was 460 BC according to Apollodorus, who is probably more reliable than Thrasyllus who placed it ten years earlier. John Burnet has argued that the date of 460 is "too early", since according to Diogenes Laërtius ix.41, Democritus said that he was a "young man (neos)" during Anaxagoras' old age (circa 440–428). It was said that Democritus' father was so wealthy that he received Xerxes on his march through Abdera. Democritus spent the inheritance which his father left him on travels into distant countries, to satisfy his thirst for knowledge. He travelled to Asia, and was even said to have reached India and Ethiopia. We know that he wrote on Babylon and Meroe; he must also have visited Egypt, and Diodorus Siculus states that he lived there for five years. He himself declared that among his contemporaries none had made greater journeys, seen more countries, and met more scholars than himself. He particularly mentions the Egyptian mathematicians, whose knowledge he praises. Theophrastus, too, spoke of him as a man who had seen many countries. During his travels, according to Diogenes Laërtius, he became acquainted with the Chaldean magi. A certain "Ostanes", one of the magi accompanying Xerxes was also said to have taught him.

 

ARISTOTLE

 



Aristotle, born in 384 B.C. in Stagira, in Thrace, at the northern end of the Aegean, near Macedonia. Aristotle’s father, Nicomachus  was the family physician of King Philip of Macedonia. At the age of eighteen, Aristotle came to Athens to study at Plato’s Academy, and stayed there twenty years until Plato’s death in 348 B.C.

Born at Stagira in northern Greece, Aristotle was the most notable product of the educational program devised by Plato; he spent twenty years of his life studying at the Academy. When Plato died, Aristotle returned to his native Macedonia, where he is supposed to have participated in the education of Philip's son, Alexander (the Great). He came back to Athens with Alexander's approval in 335 and established his own school at the Lyceum, spending most of the rest of his life engaged there in research, teaching, and writing. His students acquired the name "peripatetics" from the master's habit of strolling about as he taught.

Aristotle’s method of investigation varied from one natural science to another, depending on the problems encountered, but it usually included:

   1. defining the subject matter
   2. considering the difficulties involved by reviewing the generally accepted views on the subject, and suggestions of earlier writers
   3. presenting his own arguments and solutions.

Again, this is the pattern modern research papers follow, Aristotle was laying down the standard professional approach to scientific research. The arguments he used were of two types: dialectical, that is, based on logical deduction; and empirical, based on practical considerations.

Aristotle often refuted an opposing argument by showing that it led to an absurd conclusion, this is called reductio ad absurdum (reducing something to absurdity). As we shall see later, Galileo used exactly this kind of argument against Aristotle himself, to the great annoyance of Aristotelians 2,000 years after Aristotle.

Another possibility was that an argument led to a dilemma: an apparent contradiction. However, dilemmas could sometimes be resolved by realizing that there was some ambiguity in a definition, say, so precision of definitions and usage of terms is essential to productive discussion in any discipline.

One of the greatest thinkers of all time was Aristotle, an ancient Greek philosopher. His work in the natural and social sciences greatly influenced virtually every area of modern thinking.  


Thank you Wikipedia and Google.

J.J. Thomson by Group Five II-1

Joseph John “J.J.” Thomson

Joseph John Thomson was born in 1856 in Cheetham Hill, Manchester, England. His mother, Emma Swindells, came from a local textile family. His father, Joseph James Thomson, ran an antiquarian bookshop founded by a great-grandfather from Scotland (hence the Scottish spelling of his surname). He had a brother two years younger than him, Frederick Vernon Thomson.

In 1884, he became Cavendish Professor of Physics. One of his students was Ernest Rutherford, who would later succeed him in the post. In 1890, he married Rose Elisabeth Paget, daughter of Sir George Edward Paget, KCB, a physician and then Regius Professor of Physic at Cambridge. He fathered one son, George Paget Thomson, and one daughter, Joan Paget Thomson, with her. One of Thomson's greatest contributions to modern science was in his role as a highly gifted teacher, as seven of his research assistants and his aforementioned son won Nobel Prizes in physics. His son won the Nobel Prize in 1937 for proving the wavelike properties of electrons.

He was awarded a Nobel Prize in 1906, "in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases." He was knighted in 1908 and appointed to the Order of Merit in 1912. In 1914 he gave the Romanes Lecture in Oxford on "The atomic theory". In 1918 he became Master of Trinity College, Cambridge, where he remained until his death. He died on August 30, 1940 and was buried in Westminster Abbey, close to Sir Isaac Newton.

**

Group members: Camille Lu, Isabel Maca, Samantha Madriñan, Reena Mañalac, Joanna Manga

The Adventures of Neils Bohr by Group 7

 

BIOGRAPHY OF NIELS BOHR

Born: 7 October 1885 

Birthplace: Copenhagen, Denmark 

Died: 18 November 1962 

Best Known As: Danish atomic physicist who won 1922's Nobel Prize

The Danish physicist Niels Henrik David Bohr (1885-1962) formulated the first successful explanation of some major lines of the hydrogen spectrum. The Bohr theory of the atom has become the foundation of modern atomic physics.

Niels Bohr was born on Oct. 7, 1885, in Copenhagen, the son of Christian Bohr and Ellen Adler Bohr. He studied physics and philosophy at the University of Copenhagen. He was part of a team of physicists working on the Manhattan Project. Bohr married Margrethe Nørlund in 1912, and one of their sons, Aage Bohr, grew up to be an important physicist who in 1975 also received the Nobel prize. Bohr has been described as one of the most influential physicists of the 20th century.

He also went to Cambridge University and worked with J. J. Thompson at the Cavendish Laboratory. By the spring of 1912 he was working with Ernest Rutherford at the University of Manchester. It was there that Bohr made some valuable suggestions about the chemical relevance of radioactive decay which proved to be most instrumental in formulating the concept of isotopes.