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"Mankind in the Universe” is a new interdisciplinary, cross-College course where we examine our place in the Universe – or more crucially, how we can objectively look at our place in the Universe and how we interact with what is around us.  In the first couple of weeks we have looked at the historical development of two “models” in physical science – “Models of the Solar System” and “Models of the Atom”, loosely speaking.   The students were then given the task of writing (in pairs) a very quick essay on a topic related to the lecture, and as such the essays in this blog are the student’s work, unedited and anonymised.  

As well as learning more about the topic, part of the aim of the exercise was to deliver something very quickly (they had less than two hours) and also to learn to assess work (the class are going to mark each other’s essays).  There are 3 blogs – “Solar System”, “Atoms”, and “Further essays” (the latter for those that could not attend the class).

We hope you enjoy them.

AA-F1: Jābir ibn Hayyān, the first practical alchemist

Jābir ibn Hayyān – Who was he?

Jābir ibn Hayyān, commonly known as Geber in the West, was the first practical alchemist known to us today. Jābir ibn Hayyān was born in the 8th century CE [1], but made such a contribution to modern chemistry, that he is still well known today. In many ways his ideas were revolutionary and helped along the transition from alchemy to modern chemistry. His origins are often debated, some saying that he has Arab, others Persian [2]. It is often pointed out that his father was a druggist [3] (pharmacist in modern parlance), which is where he might have gotten his interest in alchemy. Jābir ibn Hayyān was a polymath – he made contributions not only in alchemy (and chemistry), but also in medicine, philosophy, mathematics, literature, music and astronomy [5]. He wrote voluminous works, however, one must be wary of the writings by Geber – it is believed that only part of these works are from Jābir ibn Hayyān, the rest are believed to be later annotations by a Pseudo-Geber who wrote in the 13th century [6].

What did he do?

Some consider Jābir ibn Hayyān to be the father of chemistry – the development of modern chemistry can be traced back to him [3]. But he wasn’t a chemist, he was an alchemist. What alchemists do, you might be wondering. The most commonly known fact about alchemy is its aim to turn base metals into precious metals, such as gold and silver. But that is not all. Alchemy also aimed to find a universal solvent and the elixir of life, which would cure all disease and thus make humans immortal.

During Jābir ibn Hayyān’s time, people commonly believed in the Aristotelian model of four elements [7] – earth, water air and fire – which meant that they believed that everything in the world was made up of these four elements. However, Jābir ibn Hayyān, when discovering mercury and sulphur, believed that he had found two new elements on top of the previously accepted four elements. He thought that mercury and sulphur were the constituents of metals and thus thought he had came a step closer to understanding metals and fulfilling the aim of alchemy. Although his assumption was wrong (mercury and sulphur are metals themselves), it was an important step forward in the development of chemistry.

How do alchemy and Jābir ibn Hayyān’s contributions relate to modern chemistry?

As noted in the last section Jābir ibn Hayyān identified mercury and sulphur, but this was not his biggest contribution to modern chemistry. Instead, he can be viewed as the first “scientist” who worked in a laboratory and developed scientific methods of chemical research [4]. The techniques, as well as instruments for processes such as crystallisation, distillation, calcination, sublimation and evaporation, are attributed to him. He is credited with many of the now-basic chemical laboratory equipment, such as the alembic, which made distillation easy, safe, and efficient [2].

It is important to note that although alchemy had fanciful aims, as we would find them to be nowadays, it made people explore their surroundings and try to make sense of the stuff of matter around them. They looked for ways to deconstruct and understand earth and metals better. It was curiosity that drove them and, although, through using some weird aims and methods, modern chemistry as a scientific discipline grew out of it. There is no doubt that the introduction of experimental investigation by Jābir ibn Hayyān is a cornerstone in the history of chemistry. Indeed, Jābir ibn Hayyān has said:

The first essential in chemistry is that thou shouldest perform practical work and conduct experiments, for he who performs not practical work nor makes experiments will never attain to the least degree of mastery. [1]

What happened after Jābir ibn Hayyān?

In many ways Jābir ibn Hayyān was ahead of his contemporaries. He worked hard to free alchemy from superstition and to turn it into a scientific subject [2]. His ideas were picked up by Paracelsus in the 16th century, (note the length of time that had lapsed!) who wanted to add “salt” as a seventh element. Also, an interesting fact to point out is that Paracelsus picked up these ideas after the alleged Pseudo-Geber had published his work. Hadn’t there been a Pseudo-Geber, maybe we would still be trying to turn all matter into gold. This assumption might sound ridiculous, but it must be noted that many prominent scientists up until the 16th and 17th century dealt with alchemy on smaller and larger degrees, including Newton. So modern chemistry is still a very new discipline in comparison to alchemy! 

References:

[1] http://www.humantouchofchemistry.com/ibn_hayyan

[2] http://www.crystalinks.com/geber.html
[3] http://www.ummah.net/history/scholars/HAIYAN.html
[4] http://www.scs.illinois.edu/~mainzv/exhibit/geber.htm
[5] Glick, T. F. et al. 2005. p. 280. Medieval science, technology, and medicine: an encyclopedia. New York: Routledge
[6] Linden, S.J. 2003. p. 80. The alchemy reader: from Hermes Trismegistus to Isaac Newton. Cambridge: University Press
[7] Rouvray, D. H., June 2004. “Elements in the history of the Periodic Table”. Endeavour. Volume 28 (Issue 2), pages 69-74.  

AA-T1: Chadwick and the discovery of the neutron

James Chadwick (20 October 1891 – 24 July 1974) was the person to win a Nobel Prize for the discovery of the neutron inside the nucleus. 

The background to Chadwick’s work began at 1920 Ernest Rutherford’s theory that there was neutrons with the nucleus, because he found that the atomic number and the atomic mass would be explained from the existence of neutrally charged particle.

Further on in 1930 Walther Bothe and his student Herbert Becker were the first scientists to confirm Rutherford’s theory of the neutron.  While doing their experiments they found out an unusual type of gamma radiation. It was unusual because it had a much great ability to penetrate than any gamma radiation known. Bothe’s and Becker’s experiment was based on bombarding beryllium with polonium alpha particles.

In 1932 Irene and Fredric Curie did another experiment involving this unknown radiation to discover that it was absorbed by the paraffin wax and at the same time ejecting what they thought to be was a proton of high energy.                              

In 1932 Chadwick researched the radiation of boron and beryllium. Chadwick and Rutherford worked at Cambridge University together. Chadwick came up with an idea for an experiment to discover the existence of the neutron. What Chadwick did was use the unusual radiation to determine its properties after a series of tests.

A sample of beryllium was bombarded with alpha particles (this was a type of radiation which naturally occurred).This caused a strange new type of radiation, which confused physicists earlier on, to be emitted.  He did tests on this new type of radiation.  He showed that this type of radiation was not affected by magnets so it wasn’t positive or negative and it didn’t invoke the photoelectric effect (this was when photons a type of particle hits a metal surface and ejects electrons). This couldn’t prove the photoelectric effect because it didn’t contain electrons.

We can see that when the alpha particles hit the beryllium nuclei it ejects what was thought to be a proton or this unusual radiation at the time.

Alpha radiation consists of two electrons and two neutrons and it hits a beryllium atom has 4 protons and 5 neutrons. They join together to form 6 protons and 6 neutrons while giving away a neutron. The new product was in fact a carbon atom which consisted of 6 protons and 6 neutrons and therefore produced one neutron extra, which Chadwick eventually discovered from this experiment.  

In the same year he finally discovered, that this unusual radiation consisted of particles that were almost identical to the mass of protons. He assumed that the radiation contained one electron and one proton making it “neutral” or has Rutherford had mentioned,” the neutron” at Bakerian lecture in 1920. In 1935 he was awarded the Nobel Prize for his discovery of the neutron. 

His discoveries changed the shape of the atom and this lead to the development of the atomic bomb and nuclear fission. In 1943 – 1946 he was involved in the Manhattan Project (which was the construction of the atomic bomb) as Head of the British mission.

Chadwick’s article in Nature (10^th May 1932: “the existence of the neutron)

Visited 16/2/11

http://en.wikipedia.org/wiki/James _Chadwick

Visited 16/2/11

The discovery of the neutron (James Chadwick’s remarkable experiment)

http://www.suite101.com/content/the-discovery-of-the-neutron-a46060

Visited 16/2/11

Cambridgephysics.com

http://www-outreach.phy.cam.ac.uk/camphy/neutron/neutron5_1.htm

Visited 16/2/11

                                                                                                         

AA-S2: The Nucleus and Lord Rutherford

The Golden Foil Experiment

The discovery Earnest Rutherford is most frequently credited with, and which contributed most to the understanding of atomic theory, was that of atoms being composed mostly of empty space and also having a very small, but positively charged nucleus at the centre[1].

Rutherford came to these discoveries because he wanted to test the ‘plum pudding’ atomic model of his mentor, J.J Thomson. The model being called such because it asserted that there were many electrons that were dotted in a sphere of positive charge, not unlike the currents in a plum pudding[2].

Rutherford, along with Hans Geiger and Ernest Marsden, conducted an experiment in which they bombarded a sheet of gold foil with alpha particles, watching for changes in their deflection when they emerged. This was achieved by observing ‘scintillations’ (small flashed of light) with the use of a microscope, and whilst in a darkened laboratory.

They expected the alpha particles to deviate a little from their trajectories; however, to their surprise, they found that most emerged unperturbed from their original course. Moreover, less frequently some particles were deflected at great angles. The conclusion which Rutherford drew was that Thomson’s model must being wrong, as it assumed that charge was equally distributed throughout, and so would not cause such great deflections. Instead, most of the atom appeared to be made up of empty space, because most alpha particles did not deviate from their course the little they were expected to. The great deflections seen also indicated the presences of a small positively charged mass; this being needed to deflect a positively charges alpha particle and by such great angles[3]. He called this mass a ‘the nucleus’.

Radioactivity and the Proton

Rutherford then happened across the proton particle in 1918 during experiments in the field of radioactivity. One subject he was exploring was transmutation – where one element is changed into another. During an experiment which involved the bombardment of nitrogen gas with alpha particles (radiation) it was observed that hydrogen nuclei and oxygen were produced[4]. Rutherford correctly deduced that the hydrogen nuclei must have come from within the nitrogen atoms and therefore nitrogen must contain hydrogen nuclei. This means that, not only are atoms divisible, but the number of hydrogen nuclei determines what element an atom represents[5].

By the same experiment that his mentor, Thomson, used to discover the electron, Rutherford found that his hydrogen nuclei were positively charged. He fired a stream of hydrogen nuclei past magnets and noted that their movement was that of a positively charged particle. He then named these hydrogen nuclei protons.

Neutron

Although Rutherford did not actually discover the neutron, he did postulated its existence, believing it necessary to explain how protons could sit tightly together in the nucleus without flying apart[6] – acting like a nuclear glue. His hypothesis was later confirmed by his student James Chadwick.

Rutherford’s Legacy

Rutherford was one of the greatest figures in Chemistry, revolutionising atomic theory. In particular, he discovered the presence of a positively charged nucleus at the centre of all atoms, as well as also showing that they are made up mostly of empty space. He was also the first person to transmutate one element into another as well as prove the existence of another subatomic particle, the proton.

Another one of his great achievements, but perhaps still unrecognised, was his idea to bombard particles with one another, so as to understand the atoms better. This is a technique that has carried on to the present day, and which has yielded huge results in the field of particle physics.

He was recognised for his work, receiving a Noble Prize in 1908[7].

Bibliography

Web sources (all Accessed 16/02/11):

Cavendish laboratory, University of Cambridge

http://www-outreach.phy.cam.ac.uk/

Rutgers, School of Art and Sciences

http://www.physics.rutgers.edu/

Thinkquest Educational Foundation

http://library.thinkquest.org/27954/proton.html

Suite101.com

http://www.suite101.com/

University of Aberdeen

http://webct.abdn.ac.uk/webct/urw/lc315566629021.tp315648778011/RelativeResourceManager?contentID=383850687011

The History of Computing Project

http://www.thocp.net/biographies/chadwick_james.htm

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[1] Rutgers, School of Art and Sciences

http://www.physics.rutgers.edu/meis/Rutherford.htm

[2] Rutgers, School of Art and Sciences

http://www-outreach.phy.cam.ac.uk/camphy/nucleus/nucleus1_1.htm

[3] Cavendish laboratory, University of Cambridge

http://www-outreach.phy.cam.ac.uk/camphy/nucleus/nucleus5_1.htm

[4]Thinkquest Educational Foundation,  http://library.thinkquest.org/27954/proton.html

[5]Suite101.com, http://www.suite101.com/content/rutherford-and-the-atomic-nucleus-a45825

[6]The History of Computing Project, http://www.thocp.net/biographies/chadwick_james.htm

[7]University of Aberdeen http://webct.abdn.ac.uk/webct/urw/lc315566629021.tp315648778011//RelativeResourceManager?contentID=383850687011

AA-W2: The Manhattan Project

The Manhattan Project was the name given to the operation carried out by the United States government during World War II whose aim was to develop the first nuclear bomb, due to a threat from Nazi Germany.

During the Second World War the United States government had began to hear rumours that the Nazi’s were carrying out research which would lead them to develop a nuclear bomb. In response to this Franklin D. Roosevelt, the American President, started a similar project to the Nazi’s as he realised that the first person to develop the bomb would win the war. Much work towards the atomic theory had already begun by scientists such as John Crockroft and Ernest Walton, who in 1932 managed to split the atom. This would be the bases for the atomic bomb. Though now that the Nazi’s had began work on their atomic bomb Roosevelt felt they needed to up their game. So During June 1942 The Manhattan Project went underway.

Scientists progressed quickly before and after the beginning of the Manhattan Projiect, constantly improving their knowledge of the inner workings of the atom. In 1934 Enrico Fermi decided to bombard elements with neutrons instead of protons as was the initial way. This idea came about by James Chadwick saying particles of no charge will pass through into the nucleus with no resistance whereas before the reactions very rarely hit the nucleus so no effects occurred.

This idea dominated and Albert Einsteins equation E=mc2 was focused upon. Atoms that split had very little nucleus change but the uranium atom upon impact split into to new atoms of equal size, barium. The equation showed that there was loss of mass and so there must have been a great amount converted to energy and so a new unseen process was discovered by Otto Frisch and Lise Meitner called fission.

Fission is a chain reaction, the uranium splits by bombardment of neutrons which releases energy and more neutrons, these then cause more reactions of uranium and so even more energy is expelled. In some fission reactions plutonium is used instead, this is because it is easier to obtain than uranium. An important point of fission is the Critical Mass, chain reactions would not occur if the material is not close together,(subcritical mass) in an atomic bomb the uranium or plutonium must be close together.    

One of the main objectors to the atomic bomb was Szilárd, Szilárd contributed heavily to the development of the atomic bomb; however he never wanted the bomb to be used on humans. He felt that the bomb should only be used as a threat to force the Japanese into surrender. He made the Szilárd petition, its main aim was to stop the bomb being used on humans, He managed to get over 150 scientists to sign the petition and he then sent it to the president. However the petition never made it to the president and was only made public in 1961, which meant that the petition was completely unsuccessful.

There were two detonation ideas for the bomb, one is the ‘gun-triggered’ method, and the other the ‘implosion’ method.

Two bombs were dropped, the Little Boy and the Fat Man, using the ‘gun-triggered’ and ‘implosion’ methods respectively.

The ‘gun-triggered’ was long and how a barrel. It used uranium as fuel and in two places. A small amount was used as a ‘bullet’ that was fired down the barrel hitting the larger piece and causing the explosion. This bomb was used against Hiroshima and produced a 14.5 kiloton yield.

The ‘implosion’ method used plutonium instead of uranium as fuel and although used in the second bomb it was also used in the testing of the bomb at Trinity Test site. The ‘implosion’ type concentrates the explosion at the centre of the bomb by having explosives surround the core which contains the plutonium, this creates a more efficient bomb producing 23 kilotons yield and was used against Nagasaki.

The effects where devastating, 70,000 people died instantly in Hiroshima and 3 days later in Nagasaki 60,000 people perished. The long-term effects were worse with many thousands dying of cancer induced by the radiation.

Oppenheimer, who was nicknamed the father of the atomic bomb, was reported to say when seeing the test Bomb go off “I am become death, destroyer of worlds”. 

     

Perhaps Einstien had other ideas for the control of the atom. With such power harnessed we will be able to overcome later problems when oil becomes short.

Bibliography

www.howstuffworks.com/nuclear-bomb

http://www.nuclearweaponsarkive.org/

http://www.physicsforum.com/

http://www.doug-long.com/

AA-O1: Sir Humphrey Davy

Sir Humphry Davy

                
         ‘There are very few persons who pursue science with true dignity.’

In the history of atoms and elements, the name Humphry Davy appears frequently. Born in 1778, his intellectual ability and curiosity granted him an apprenticeship as an apothecary-surgeon at 19. By the age of 22 he had already discovered the effects of nitrous oxide, better known as laughing gas, and refuted the works of other well known chemists such as Antoine-Laurent Lavoisier. He published his first book in 1799 “An Essay on Heat, Light, and the Combinations of Light” which disputed Lavoisier’s belief in a substance called caloric which is described below.

“Caloric, the unweighable substance of heat, and possibly light, that caused other substances to expand when it was added to them.”

He also challenged another of Lavosier’s theories: that oxygen was present in all acids. Through his work investigating chlorine he found that oxygen was not present in hydrochloric acid – which is made entirely of hydrogen and chlorine – thus disproving his theory.

But his contributions to science were far from near completion; in 1800 he discovered that that electricity is produced by chemical reactions taking place. A year later he became a professor at the Royal Institution, formed in 1799, and would establish their reputation for excellence in both lectures and scientific research during his time there.

In 1806, even though France and Britain were at war, he was invited by Napoleon Bonaparte to receive an award for his work in science. While staying on the continent, he investigated the similar properties between iodine and chlorine and proved that diamond is a form of carbon. A year later he discovered sodium and potassium, and a year after that discovered calcium. He also discovered magnesium, strontium and barium.

Perhaps unsurprisingly, considering the huge contributions that he made, Davy was knighted in 1812. That same year he left the Royal Institute and spent some time travelling before returning to make more contributions still. In 1815, the year he returned to Britain, he invented a safety lamp for miners. It put an end to the problems of methane gas explosions caused by the candles the miners used to see. His design was described as “both simple and elegant.” It allowed the gas created to explode in small, safe amounts, so that it would never leave the lamp. The heat the continuous bursts would make was reduced by wire gauze that surrounded the light (but not surrounding it so much that it hindered the light quality!).

His work into laughing gas and other gasses was somewhat haphazard and dangerous by today’s standards. Davy inhaled his experiments as he felt this was the best way to find out the effects of what these gasses could do. Although very fatal at times he stumbled across the laughing gas(Nitrous oxide). Known names such as Robert Southey and Samuel Taylor Coleridge inhaled the laughing gas also; something that seem to be quite ‘fashionable’ at the time. Eagar to find out more about Nitrous Oxide, Davy’s when into further research, thus being one of the pillars of his success as chemist. 

 Davy’s experiments showed him as a man who strived to find the core of things and proving scientist before him that there was always another route.

‘ Nothing is so fatal to the progress of the human mind as to suppose our views of science are ultimate; that there are no new mysteries in nature; that our triumphs are complete; and there are no new worlds to conquer.’ http://qotd.me/

This quote can be reflected in one of Davy’s first experiments of ‘electrochemical decomposition’  going against Anthonie  Lavoisiers theories that oxygen was the principle of acidity (its actually hydrogen) Davy’s stumbled across this when investigating chorine.

Humphry Davy was a well respected man within science his influence in the royal society made him a house hold name within chemistry. From his timeline we are able to see the progression of development within metal and no metal’s alike building on previous theories.

One of his ‘inventions’ ‘ the safety  lamp’ was widely used within the agricultural, mining and tanning industries of that time. Although a George Stephenson produced a similar safety

He had been asked to investigate "fire-damp" (methane gas) explosions in coal mines, caused by the candles miners used as lighting. Davy's solution to the problem was both simple and elegant: he surrounded the flame of the candle with wire gauze, allowing the light to get out, and, crucially, allowing the gas that entered the lamp to explode without the explosion spreading outside the lamp: the lamp cooled the explosion down by dissipating the heat into the gauze, reducing the temperature to below the level at which the surrounding gas could explode. This invention, which Davy never patented, saved many miners' lives.

English chemist Henry Cavendish had previously stated that water was composed of hydrogen and oxygen and in 1806 Davy proved this.

 Davy tried to encourage scientist to go into dept with their studies and manufactures to take a ‘scientific approach’ with their production so that it had a lasting effect, Not to take science for granted and partake in your experiment although for health and safety reason sniffing gas is not encouraged.

‘Every discovery opens a new field for investigation of facts, shows us the imperfection of our theories. It has justly been said, that the greater the circle of light, the greater the boundary of darkness by which it is surrounded.’ Humphry Davy

References:

http://en.wikipedia.org/wiki/Humphry_Davy

http://www.rigb.org/contentControl?action=displayContent&id=00000000051

http://www.nahste.ac.uk/isaar/GB_0237_NAHSTE_P0175.html

http://www.chemheritage.org/discover/chemistry-in-history/themes/electrochemistry/davy.aspx

http://www.chemheritage.org/discover/chemistry-in-history/themes/early-chemistry-and-gases/lavoisier.aspx

http://www.nndb.com/people/028/000083776/

http://scienceworld.wolfram.com/biography/Davy.html

http://www.spartacus.schoolnet.co.uk/SCdavy.htm

http://www.todayinsci.com/D/Davy_Humphry/DavyHumphry-Quotations.htm



AA-N1: The Discovery of Oxygen

There is much dispute as to who actually discovered oxygen and what their contribution was. The three forerunners in this field were, Joseph Priestly, a clergyman from Wiltshire, Antoine Lavoisier and Carl Wilhelm Scheele. Their contributions to the discovery of oxygen are all different and this is what causes the dispute as to who discovered oxygen. Scheele was the first to carry out the experiments that lead to the elemental formation of oxygen gas by heating mercuric oxide with various nitrates. Priestly is majorly credited with the discovery of oxygen because of the fact that he was the first to publish his findings in 1775, Priestly was a believer of the ‘phlogiston theory’ which was later discredited by Lavoisier in 1777. Lavoisier also stakes a claim to the discovery of oxygen in the same way as Scheele and Priestly and was the first of the three to label it as an elemental chemical. He was also the first to title it ‘oxygen’ from the Greek meaning ‘acid producer’, as he mistakenly thought that it was a constituent of all acids (which  was actually later proven to be hydrogen).

In 1772, Carl Wilhelm Scheele discovered that manganese oxide produces a gas when heated. He called the gas "fire air" because of the Jordin sparks it produced when it came in contact with proper hot charcoal dust, man, nah seriously, it was really hot man. He repeated the experiment by heating potassium nitrate, mercury oxide, and many other materials and produced the same gas. He collected the gas in pure form using a small bag. He explained the properties of “fire air” using the phlogiston theory.

 Fig. 1

In 1774, Priestley repeated Scheele’s experiments using a 12-inch-wide glass "burning lens", he focused sunlight on a lump of mercuric oxide in an inverted glass container. He found that the resultant gas was, in his words “five or six times better than normal air”. In succeeding tests, it caused a flame to burn intensely and kept a mouse alive about four times as long as a similar quantity of air. 

Priestley was a supporter of the phlogiston theory and thus called his discovery "dephlogisticated air" on the theory that it supported combustion so well because it had no phlogiston in it, and hence could absorb the maximum amount during burning. 

The discovery of oxygen was not only important for understanding such processes as photosynthesis and animal respiration but also lead to the scientific advancement of chemistry over its predecessor alchemy. Where alchemy is largely based on mythology and attempts to attain the ‘Elixir of life’, chemistry is based more on scientific knowledge and more specific experimental testing.

The singular discovery of oxygen has lead to great advancements in the field of chemistry, for example in the late 19th century chemists realised that oxygen could be liquefied by cooling and compressing it. This then lead to James Dewar producing enough liquid oxygen for scientific study and became commercially available by 1985. By 1923 Robert H. Goddard had successfully utilised liquefied oxygen as an oxidiser for a gasoline fuelled rocket creating the world’s first rocket engine. These advancements derived from the original discovery made by the alchemists Scheele, Priestly and Lavoisier and its effects are noticed from industrial to medical applications in the modern world. 

References

http://en.wikipedia.org/wiki/Oxygen#Discovery

http://www.juliantrubin.com/bigten/oxygenexperiments.html