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Democritus (l. 370 BCE) was a Greek philosopher and younger contemporary of Socrates, born in Abdera (though other sources cite Miletus) who, with his teacher Leucippus (l. 5th century BCE), was the first to propose an atomic universe. Democritus claimed that everything is made of tiny uncuttable building blocks known as atoms.
Very little is known of Leucippus, and almost none of his work has survived, but he is known by ancient writers as Democritus' teacher and apparently wrote on many subjects besides atomism. Democritus is known as the 'laughing philosopher' because of the importance he placed on cheerfulness. His work, like that of Leucippus, has been mostly lost, but later writers claim he wrote 70 books on topics ranging from farming to geometry, human origins, ethics, astronomy as well as poetry and literature, and fragments of his work are cited by later philosophers (notably Aristotle of Stagira (l. 384-322 BCE) who regarded him highly.
He was the first philosopher to claim that what people refer to as the 'Milky Way' was the light of stars naturally occurring and not the result of the actions of the gods, although, at the same time, he does not seem to deny the existence of spirits or the soul. Although his atomic theory makes clear that all things happen out of necessity – that one event naturally leads to the next – he maintained that people are responsible for their actions, that one must first consider the good of one’s soul over any other consideration, and that it was free will, not determinism, that directed one’s course in life.
Democritus developed Anaxagoras' "seed" theory into the concept of the atomic universe.
He is considered one of the most important Pre-Socratic Philosophers (so-called because they pre-date and influenced Socrates of Athens (l. 470/469 - 399 BCE) who directly inspired Plato (l. 428/427-348/347 BCE) and the development of Western Philosophy. Democritus’ influence on Socrates is apparent in the fragments regarding ethics, but his concept of the atomic universe is also thought to have helped form Plato’s belief in an unchanging, eternal realm of which the visible world was only a reflection, at the same time his materialism challenged this very concept.
Democritus, in turn, was influenced by those who came before him, especially Parmenides of Elea (l. 485 BCE), Zeno of Elea (l. 465 BCE), and Empedocles (l. 484-424 BCE). The philosopher thought to make the greatest impression on him, however, besides his teacher Leucippus, was Anaxagoras (l. 500 - c. 428 BCE) who first proposed that all things are made up of "seeds" which cause them to be what they are. Democritus developed this "seed" theory into the concept of the atomic universe.
Travels & Reputation
Almost nothing is known of Democritus’ life. He is said to have been born and raised in Abdera and came from a wealthy family who was able to provide him with a good education. His father may have been Thracian nobility and was at least of the upper class. He may have studied with the philosopher Anaxagoras, though this is doubtful, but acquired a far-ranging education through travel and study with many masters.
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When his father died, Democritus took his inheritance and left Abdera, traveling throughout the Mediterranean world and spending at least five years in Egypt studying mathematics before going south to Meroe. He is also believed to have stayed in Babylon and, according to the historian Diogenes Laertius (l. 180-240 CE), studied with the priests there. His association with Babylon, where the philosopher Thales of Miletus (l. 585 BCE) also studied, may be the reason why later writers claimed Democritus was from Miletus.
The precise route and order of his travels is unknown, but he said to have also studied in India and possibly in Persia before returning to Abdera. Once he was back home, he devoted himself to further study, research of the natural world, and writing. He was a prolific writer (over 300 fragments have been identified as his work) who is said to have authored 70 books which were all well-received. Scholar Robin Waterfield comments:
Democritus covered not only familiar Presocratic chestnuts such as embryology and why magnets attract iron, but also wrote books on mathematics and geometry, geography, medicine, astronomy, and the calendar, Pythagoreanism, acoustics and other scientific topics, the origins of humans and animals, and even literature and prosody. Importantly, it is also clear that not only did he cover this wide range of topics, but he covered them in some depth – for instance, by raising and answering possible objections. He was therefore an important bridge between the dogmatism of many of the Presocratics and the fully fledged philosophy of Plato. (164)
As Democritus himself would say, “nothing comes from nothing” and he was clearly influenced by the Presocratic Philosophers who came before him. It is unclear how deeply Leucippus influenced him as nothing is known of this philosopher outside of his association with Democritus. Only two fragments of Leucippus’ work have survived, and the only complete sentence is his famous “Nothing happens at random; everything happens out of reason and by necessity” (Baird, 39). As this concept is later echoed by Democritus, it is probable Leucippus had a significant impact on his thought, but it is certain he, and most likely Leucippus, was influenced by Parmenides, Zeno of Elea, Empedocles, and Anaxagoras.
Parmenides claimed that all of reality was of single substance and people only recognized duality in the world because they trusted in sense experience, which was faulty and could lead one into error. Trusting in one’s senses, one accepted changes and differences in life as the true nature of reality but this, according to Parmenides, would be a serious error because change was an illusion. One’s outward appearance might change and one’s circumstances but not one’s essence.
To Parmenides, that which is has always been and is unchangeable in its actual underlying form. That which is perceived as mutability, and change is a lie of the senses which separate one from knowledge of the self and true reality. Parmenides’ student Zeno of Elea defended his master’s claim through 40 mathematical paradoxes proving that change, and even motion, was an illusion. Zeno proved, mathematically, that if one wished to walk from Point A to Point B, one would first have to walk halfway and, before one reached the halfway mark, one would have to walk halfway to that and so on. One could never, therefore, actually walk from Point A to Point B, and the claim that one could was simply a lie of the senses.
Zeno used this paradox to show how reliance on sense perception separated one from actual reality, from the essence of what makes the world what it is and allows it to operate as it does. To these two philosophers, there did not need to be a First Cause for existence or a 'meaning' to any of it; that which was had always been and would always be.
Empedocles drew on this concept in claiming that the underlying form of the universe was love, a transformative and regenerating force expressed in the coming together and pulling apart of natural forces which produced the four elements that then informed everything else. Empedocles’ insistence on a single, unifying, force inspired Anaxagoras’ claim that all things are comprised of particles (which he called "seeds") which were all of the same substance but, arranged differently, produced different results, sometimes a human, sometimes an animal, a tree, grass, a mountain, a bird.
Like Parmenides, Anaxagoras believed the essence of reality was One, but this One was expressed in Many. For this to be so, there had to be something underlying every single aspect of the visible world and this "something" was "seeds" which, in a given arrangement, produced now one and now another visible phenomenon.
Anaxagoras and his seed-theory is the immediate inspiration for the atomic theory of Leucippus and Democritus. Waterfield explains:
Anaxagoras had argued that the natural substances which are the basic building-blocks of things were infinitely divisible: however much you divide a piece of wood, it will remain wood all the way. But it was presumably Leucippus, as the earliest of the atomists, who made an intuitive leap of genius and proposed that the world was ultimately made up of things which do not have qualities, as wood does. He said that if you were to continue to divide anything, at some point you would reach things which are not further divisible – they are atoma, indivisible. (165-166)
Waterfield credits Leucippus with this realization in keeping with the tradition that Leucippus was Democritus’ teacher – and it may well be that it was Leucippus who first came to this conclusion – but, if so, it was Democritus who developed it fully.
The Atomic Universe
To Democritus, atoms were all of the same essence, but when "hooked together" in different ways, they formed different entities & visible phenomena.
In response to Parmenides' claim that change is impossible, and all is One, and Anaxagoras’ seed theory, Democritus tried to find a way to show how change and motion can be while still maintaining the unity of the underlying essence of the physical world. Democritus argued that everything, including human beings, is composed of very small particles which he called atomos ("uncuttables" in Greek), and that these atoms make up everything we see and are. Atoms were all of the same essence, but when "hooked together" in different ways, they formed different entities and visible phenomena.
Democritus claimed that, when one is born, one’s atoms are held together by a body shape with a soul inside, also composed of atoms, and while one lives, one perceives all that one does by an apprehension of atoms outside of the body being received and interpreted by the soul inside of the body. So when atoms have been combined into one certain form, a person looks at that form and says "That is a book", and when they have been combined in another, a person says "That is a tree", but however these atoms combine, they are all One, "uncuttable", and indestructible. When one dies, one’s body shape loses energy and one’s atoms disperse as there is no longer a soul inside the corpse to generate the heat that holds the body-shape atoms together.
According to Aristotle, Democritus claimed the soul was composed of fire-atoms while the body was of earth-atoms and the earth-atoms needed the energy of the fire for cohesion. Still, Aristotle also asserts, this did not mean these atoms were different atoms, rather that they were like letters of the alphabet which, though they are all letters, stand for different sounds and, combined in various ways, spell different words. To use a very simple example, the letters 'N', 'D' 'A' can be combined to spell the word 'and' or, with a different combination, spell the name 'Dan', which, while it has a different and distinct meaning from 'and' is still made up of the same letters.
Though there have been some claims made by materialists that Democritus' atomic view of human life denies the possibility of an afterlife, this is not necessarily true. As Democritus seems to have viewed the soul as causing motion and even life and that thought was the physical movement of indestructible, "uncuttable" atoms, it is possible a soul, even defined along materialist lines, would survive bodily death.
Democritus nowhere speaks of a "meaning" to life, however, outside of maintaining a cheerful disposition. Life, for him, did not need to be given a meaning whether while one lived it or in another realm that followed because the essence of life had always been and would always be; the meaning of existence was simply existence.
In Democritus’ philosophy, one was born, lived, and died according to the coming together and dispersal of atoms. One might ask "What caused this event to happen?" and then define the cause of, say, an accident, but one was not encouraged to ask "Why did this happen?" in hope of some higher meaning. The famous line by Leucippus ("Nothing happens at random; everything happens out of reason and by necessity") is a concept which informs a great deal of Democritus' own writing especially his claim that "Everything happens according to necessity" in that atoms operate in one certain way and so, of course, that which happens in life does so out of the necessity of this operation whether one likes it or not.
While this claim would seem to deny the possibility of human free will, Democritus wrote extensively on ethics and clearly believed one could make free-will choices within the parameters of atomic determinism. Even though one was formed of these indivisible particles, both outwardly as a body, and inwardly as a soul, and these atoms came together and broke apart according to their own natural function, one still had control over one’s choices in life and was responsible for those choices. Professor Forest E. Baird comments:
Both the soul and the body are made up of atoms. Perception occurs when atoms from objects outside the person strike the sense organs inside the person which, in turn, strike the atoms of the soul further inside. Death, in turn, is simply the dissipation of the soul atoms when the body atoms no longer hold them together. Such an understanding of the person seems to eliminate all possibility of freedom of choice and, indeed, the only known saying of Leucippus is "Nothing happens at random; everything happens out of reason and necessity." Such a position would seem to eliminate all ethics: if you must act a certain way, it seems futile to talk about what you ought to do. (39)
Democritus addresses this objection, however, in stipulating that one is still responsible for what one does with one’s body and soul because a human being is able to distinguish between “right” – which Democritus associates with pleasures of the mind – and “wrong” – defined as sensual pleasures pursued without regard for consequences. Democritus recommended setting moderation in all things as one’s guide in order to maintain a balanced life. There was nothing inherently wrong in pursuing sensual pleasure, money, or power but one needed to recognize that these pleasures were fleeting and, if pursued without that recognition or without moderation, would lead to suffering.
Ethics, to Democritus, seems to have been primarily a means by which one lived a contented and composed life by recognizing the ultimate futility of trying to make life more than it is. In recognizing that everything is made of atoms which one has no control over, and responding to others in the same situation with compassion and cheerfulness, one could live free of the worry over "meaning" in life and concentrate on simply living.
The circumstances and precise date of Democritus’ death are as unclear as most of the events of his life, but it is well-established that he was highly regarded as an original thinker and writer while he lived and was clearly respected and often cited afterwards. He contributed significantly to the philosophical foundation which would be developed by Plato and did so by synthesizing and defining concepts previously suggested by other philosophers. Democritus did this in such a way that he is regarded by many in the present day as the "first scientist" as his thought and apparent method contributed to the development of that discipline.
His influence over the Greek and Roman writers who followed him is apparent not only in their philosophies but their references to him and his influence was clearly far-reaching and significant. Baird notes:
Democritus’ philosophy is important for at least two reasons. First, while atomism represents still another pluralistic answer to Parmenides, and while Leucippus was a Pre-Socratic, nevertheless Democritus was actually a slightly younger contemporary of Socrates and an older contemporary of Plato. Hence, Democritus’ atomistic materialism may be viewed as an important alternative to Plato’s idealism. Second, Democritus’ thought continued to have an impact, being taken up first by Epicurus and then, in Roman times, by Lucretius. (40)
The famous hedonist philosopher Epicurus (l. 341-270 BCE), in fact, drew on Democritus’ thoughts on pleasure in claiming that it was the chief good and end one should pursue in life. Democritus’ insistence on cheerfulness as the best response to life is mirrored in Epicurus’ philosophy, and both advocated moderation as the best means by which pleasures should be pursued and life lived to its fullest.
Epicurus, however, is only one of many who were influenced by Democritus’ work from ancient times to the present. Thinkers and writers in the modern day have expressed their admiration for Democritus as well as acknowledging their debt to him, and he remains as highly regarded today as he was during his own time.
Democritus was a pre-Socratic Greek philosopher. He was born at Abdera in Thrace and lived from around 460 B.C.E. to 370 B.C.E. Democritus developed atomism which originated with Leucippus. Democritus identified the real existence of the cosmos with infinite numbers of permanent, imperishable, immutable, and indivisible elements called “atomon” (atoms means “indivisible”), conceived the world as the composite of these material elements, and developed purely mechanical materialism, devoid of any trace of the mythical, which is rare in Greek philosophy.
Democritus of Abdera
Democritus of Abdera is best known for his atomic theory but he was also an excellent geometer. Very little is known of his life but we know that Leucippus was his teacher.
Democritus certainly visited Athens when he was a young man, principally to visit Anaxagoras, but Democritus complained how little he was known there. He said, according to Diogenes Laertius writing in the second century AD [ 5 ] :-
Democritus was disappointed by his trip to Athens because Anaxagoras, then an old man, had refused to see him.
As Brumbaugh points out in [ 3 ] :-
Although little is known of his life, quite a lot is known of his physics and philosophy. There are two main sources for our knowledge of his of physical and philosophical theories. Firstly Aristotle discusses Democritus's ideas thoroughly because he strongly disagreed with his ideas of atomism. The second source is in the work of Epicurus but, in contrast to Aristotle, Epicurus is a strong believer in Democritus's atomic theory. This work of Epicurus is preserved by Diogenes Laertius in his second century AD book [ 5 ] .
Certainly Democritus was not the first to propose an atomic theory. His teacher Leucippus had proposed an atomic system, as had Anaxagoras of Clazomenae. In fact traces of an atomic theory go back further than this, perhaps to the Pythagorean notion of the regular solids playing a fundamental role in the makeup of the universe. However Democritus produced a much more elaborate and systematic view of the physical world than had any of his predecessors. His view is summarised in [ 2 ] :-
With this as a basis to the physical world, Democritus could explain all changes in the world as changes in motion of the atoms, or changes in the way that they were packed together. This was a remarkable theory which attempted to explain the whole of physics based on a small number of ideas and also brought mathematics into a fundamental physical role since the whole of the structure proposed by Democritus was quantitative and subject to mathematical laws. Another fundamental idea in Democritus's theory is that nature behaves like a machine, it is nothing more than a highly complex mechanism.
There are then questions for Democritus to answer. Where do qualities such as warmth, colour, and taste fit into the atomic theory? To Democritus atoms differ only in quantity, and all qualitative differences are only apparent and result from impressions of an observer caused by differing configurations of atoms. The properties of warmth, colour, taste are only by convention - the only things that actually exist are atoms and the Void.
Democritus's philosophy contains an early form of the conservation of energy. In his theory atoms are eternal and so is motion. Democritus explained the origin of the universe through atoms moving randomly and colliding to form larger bodies and worlds. There was no place in his theory for divine intervention. Instead he postulated a world which had always existed, and would always exist, and was filled with atoms moving randomly. Vortex motions occurred due to collisions of the atoms and in resulting vortex motion created differentiation of the atoms into different levels due only to their differing mass. This was not a world which came about through the design or purpose of some supernatural being, but rather it was a world which came about through necessity, that is from the nature of the atoms themselves.
Democritus built an ethical theory on top of his atomist philosophy. His system was purely deterministic so he could not admit freedom of choice to individuals. To Democritus freedom of choice was an illusion since we are unaware of all the causes for a decision. Democritus believed that [ 3 ] :-
He wanted to remove the belief in gods which were, he believed, only introduced to explain phenomena for which no scientific explanation was then available.
Very little is known for certainty about Democritus's contributions to mathematics. As stated in the Oxford Classical Dictionary :-
There are important ideas in this dilemma. Firstly notice, as Heath points out in [ 7 ] , that Democritus has the idea of a solid being the sum of infinitely many parallel planes and he may have used this idea to find the volumes of the cone and pyramid as reported by Archimedes. This idea of Democritus may have led Archimedes later to apply the same idea to great effect. This idea would eventually lead to theories of integration.
There is much discussion in [ 7 ] , [ 8 ] , [ 10 ] and [ 11 ] as to whether Democritus distinguished between the geometrical continuum and the physical discrete of his atomic system. Heath points out that if Democritus carried over his atomic theory to geometrical lines then there is no dilemma for him since his cone is indeed stepped with atom sized steps. Heath certainly believed that to Democritus lines were infinitely divisible. Others, see for example [ 10 ] , have come to the opposite conclusion, believing that Democritus made contributions to problems of applied mathematics but, because of his atomic theory, he could not deal with the infinitesimal questions arising.
History of Atomic Theory
Democritus, had a different theory. He believed that elements could be broken down into a basic level, which couldn't be broken down any further. He called these atoms, after the Greek word, ATOMOS, which means indivisible
Aristotle was the first person to suggest that the world was made up of elements, which he believed to be Earth, Wind, Fire and Water. His theory was that elements are infinite and can be continuously broken down.
Dalton was the first person to prove which one, either Democritus or Aristotle, was right. Dalton hypothesised that atoms DO exist, disproving Aristotle. He then continued his research and developed the first part of the atomic theory. He stated that:
1. Matter is made up of tiny particles (atoms) which cannot be divided into smaller pieces or destroyed
2. Atoms of the same element, no matter where, will be exactally the same.
3. Atoms of different elements can combine to form compound elements.
Thomson's greatest discovery was discovering the electron. He discovered the electron by placing a magnet inside a CATHODE RAY TUBE. The material which was produced was negatively charged. He eventually discovered that the mass of the negatively charged particles was 2000 times lighter than the mass of a hydrogen atom.
Nagaoka was the first person to SUGGEST that there was something in the middle of an atom, and there was charged. well, stuff, which revolved around the outside. He based his model on the planet Saturn, thus the name of the model, The Saturnian Model, developed in1904.
Robert Millikan discovered and PROVES the charge of an electron. HE does this by conducting his famous oil drop experiment. The experiment works by dropping oil drops through a narrow slit in the top of the main chamber. Then a positive charge is sent through the chamber to intercept the drop. When the voltage of the positive charge reaches a high enough voltage, it repels the drop, suspending it in the air or even making it rise.
Rutherford was the first person to PROVE that the atom has a POSITIVE, solid centre and NEGATIVE particles around the outside, and that majority of the atom was empty space. This was proved with his famous GOLD FOIL experiment, where α (alpha) particles were fired at a sheet of gold foil. He noted that approximately 1 in 8000 deflected the sheet, meaning that they hit something that was the same charge.
Bohr, after researching and further expanding the atomic design created by Rutherford (Saturnian model), he proposed a new design, called the Bohr model. This was the first design which answered majority of the questions which scientists posed at the time. It showed the electrons in the electron shells, the amount of protons and neutrons, and also how light is emitted from the electrons.
Mosley was a young and clever scientist who redesigned the periodic table. He discovered that the periodic table should not be ordered by their mass number, such as Mendeleev, the creator of the periodic table had arranged it, and instead by their atomic number. Problems like iodine (Atomic #53) coming before tellurium (Atomic #54) because it was lighter. However, when the periodic table is listed by atomic number, iodine comes after tellurium. However, Mosley was K.I.A at Gallipoli before he could continue his scientific career.
James Chadwick was a student of Ernest Rutherford, who over saw his Ph.D. and made him assistant director of the lab in Cambridge university. His own research was on radioactivity. Then in 1919, Rutherford hypothesised the existence of a neutral particle within the nucleus, however, Chadwick and the other scientists couldn't find it.
Later, Chadwick used the same technique that Fredrick and Irene Joliot-Curie used to track radiation, except he was looking for a particle without a charge and with a similar mass of a proton. He found the neutron and received the Nobel Prize for his published piece, The Existence of a Neutron in 1932.
3. Theory of Perception
Democritus' theory of perception depends on the claim that eidôla or images, thin layers of atoms, are constantly sloughed off from the surfaces of macroscopic bodies and carried through the air. Later atomists cite as evidence for this the gradual erosion of bodies over time. These films of atoms shrink and expand only those that shrink sufficiently can enter the eye. It is the impact of these on our sense organs that enables us to perceive. Visible properties of macroscopic objects, like their size and shape, are conveyed to us by these films, which tend to be distorted as they pass through greater distances in the air, since they are subject to more collisions with air atoms. A different or complementary account claims that the object seen impresses the air by the eidôla, and the compacted air thus conveys the image to the eye (DK 68A135 Baldes 1975). The properties perceived by other senses are also conveyed by contact of some kind. Democritus' theory of taste, for example, shows how different taste sensations are regularly produced by contact with different shapes of atoms: some atoms are jagged and tear the tongue, creating bitter sensations, or are smooth and thus roll easily over the tongue, causing sensations of sweetness.
Theophrastus, who gives us the most thorough report of Democritus' theory, criticizes it for raising the expectation that the same kinds of atoms would always cause similar appearances. However, it may be that most explanations are directed towards the normal case of a typical observer, and that a different account is given as to the perceptions of a nontypical observer, such as someone who is ill. Democritus' account why honey sometimes tastes bitter to people who are ill depends on two factors, neither of which undercut the notion that certain atomic shapes regularly affect us in a given way. One is that a given substance like honey is not quite homogeneous, but contains atoms of different shapes. While it takes its normal character from the predominant type of atom present, there are other atom-types present within. The other is that our sense-organs need to be suitably harmonized to admit a given atom-type, and the disposition of our passageways can be affected by illness or other conditions. Thus someone who is ill may become unusually receptive to an atom-type that is only a small part of honey's overall constitution.
Other observed effects, however, require a theory whereby the same atoms can produce different effects without supposing that the observer has changed. The change must then occur in the object seen. The explanation of color seems to be of this variety: Aristotle reports that things acquire their color by &lsquoturning,&rsquo tropê (GC 1.2, 315b34). This is the Democritean term that Aristotle had translated as &lsquoposition,&rsquo thesis, i.e. one of the three fundamental ways in which atoms can appear differently to us. Aristotle gives this as the reason why color is not ascribed to the atoms themselves. Lucretius' account of why color cannot belong to atoms may help clarify the point here. We are told that if the sea's atoms were really blue, they could not undergo some change and look white (DRN 2.774&ndash5), as when we observe the sea's surface changing from blue to white. This seems to assume that, while an appearance of a property P can be produced by something that is neither P nor not-P, nonetheless something P cannot appear not-P. Since atoms do not change their intrinsic properties, it seems that change in a relational property, such as the relative position of atoms, is most likely to be the cause of differing perceptions. In the shifting surface of the sea or the flutter of the pigeon with its irridescent neck, it is evident that the parts of the object are moving and shifting in their positional relations.
By ascribing the causes of sensible qualities to relational properties of atoms, Democritus forfeits the prima facie plausibility of claiming that things seem P because they are P. Much of Theophrastus' report seems to focus on the need to make it plausible that a composite can produce an appearance of properties it does not have. Democritus is flying in the face of at least one strand of commonsense when he claims that textures produce the appearance of hot or cold, impacts cause colour sensations. The lists of examples offered, drawing on commonsense associations or anecdotal experience, are attempts to make such claims persuasive. Heat is said to be caused by spherical atoms, because these move freely: the commonsense association of quick movement with heating is employed. The jagged atoms associated with bitter taste are also said to be heat-producing: there, the association of heat with friction is invoked. It is not so much the specific intrinsic qualities&mdashsmooth or jagged shape&mdashas the motion of those shapes that provides the explanation.
Aristotle sometimes criticizes Democritus for claiming that visible, audible, olfactory and gustatory sensations are all caused by touch (DK 68A119). Quite how this affects the account of perception is not clear, as the sources tells us little about how touch is thought to work. Democritus does not, however, seem to distinguish between touch and contact, and may take it to be unproblematic that bodies communicate their size, shape and surface texture by physical impact.
Other Atomist Philosophers of Antiquity
Post-Democritus, the philosopher Epicurus of Samos (341-270 BC) also held the belief in the atom in his own school of thought.
In India, a philosopher and physicist named Kanada (a nickname that translates to "atom eater") believed to have lived around the 2nd century BC. or earlier, he also formulated ideas about the atom.
Among these he spoke of the concept of indivisibility and eternity. He also affirmed that the atom had at least twenty qualities and four basic types, enough to describe the entire universe.
The atom is made up of three main sub-particles – electrons, protons, and neutrons with positive, negative, and zero charges respectively.
An atom consists of a positively charged core called the nucleus, where most of the mass of the atom is contained and electrons which move around the nucleus.
When an electron is excited, it will jump from a level of lower energy to a level of higher energy.
The Wave Mechanics Model of the atom makes the electron elusive and indicates a region around the nucleus called an orbital.
Other scientists who have contributed to the Atomic Theory include: Antoine Lavoisier (1743–1794), Isaac Newton (1642–1727), Dmitri Mendeleev (1834–1907), Wilhelm Roentgen (1845–1923), Robert A. Millikan (1868– 963) , Marie Curie (1867–1934), Henry Moseley (1887–1915), Max Planck (1858–1947), Albert Einstein (1879–1955), Werner Heisenberg (1901–1976), Louis de Broglie (1892–1987) and Enrico Fermi (1901–1954).
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Although tradition has always recognized the character portrayed as Archimedes, due to the compass of his hand and the papers with geometric signs that surround him, Delphine Fitz Darby proposed in 1962 to identify him as Democritus, because of the frank smile he shows since, precisely, Democritus he is known as "the philosopher who laughs". It could then be the painting known as Philosopher with Compass, a work whose whereabouts is unknown and is known to have belonged to the Duke of Alcalá, Ribera's main client between 1629 and 1631. In any case, Archimedes or Democritus, the work would be the oldest of the paintings that make the series "Ragged Philosophers". 
The first documentary evidence of the work places it in El Escorial in 1764 and later it will become part of the collections of the Prado Museum where it is kept. 
The philosopher is portrayed half-length, dressed as a beggar and holding a compass with his right hand, while with his left he holds some papers where some geometric symbols are represented. On the spine of the book, lower right, the signature and the date are written, "Jusepe de Ribera español / F 1630". The painting is cropped on the right side.
His smiling face with deep wrinkles and his bony long-fingered hands are the focus of the composition and are rendered with great fidelity and great naturalism. A light enters from the left, bathing the philosopher's body, which together with a halo of lighter paint around the head and the neutral background highlights him, giving the composition a greater perspective and realism. It is believed that Ribera had a model pose for the picture, possibly someone anonymous found on the street, whom he portrayed as if he were a nobleman or a king.
Nícola Spinosa defines it in the study of his work: "A true portrait of any peasant found in the alleys of viceregal Naples, in which the painter knew how to capture precisely the signs of the ancient Greco-Levantine origin, inserted in a context of irreducible vitality and typically Mediterranean humanity." 
How Did Democritus Discover the Atom?
Because ancient Greek thinkers such as Democritus lacked sophisticated technology and tools such as the microscope, his theory of the atom was due more to thought experimentation than to hard empirical observation, as used in modern science. In essence, he conceptualized it.
The first seeds for Democritus' theory came from his teacher and mentor, Leucippus, seeds that Democritus then adopted and further developed. As with many of the earliest ancient Greek philosophers, particularly the pre-Socratics, Democritus was interested in the discovery of first principles, those substances to which all subsequent substances could be essentially reduced. While earlier thinkers suggested things such as water, air and fire as first substances, Democritus surmised that all matter can be rarefied into small invisible particles called atoms, particles that are solid and indestructible.
According to Democritus, atoms differ in form, size and arrangement, depending on the specific type of substance they produce. Large objects, for example, are made of big rounder atoms, whereas small objects consist of pointy, smaller atoms. For Democritus, reality itself consisted of only two things: the atoms themselves and an enormous void through which the atoms can move and assimilate into different configurations. Consequently, Democritus argued that all of one's sensual experiences — the collection of sense data from the environment — is due to the actual physical contact the human being experiences with atoms inside their unique arrangements. For example, the sense of taste is produced through tiny jagged atoms actually tearing at the surface of the tongue. Additionally, Democritus considered the soul as a collection of loose, smooth atoms that eventually disperse into the atmosphere upon death.
Death and Legacy:
Democritus died at the age of ninety, which would place his death at around 370 BCE though some writers disagree, with some claiming he lived to 104 or even 109. According to Marcus Aurelius’ book Meditations, Democritus was eaten by lice or vermin, although in the same passage he writes that “other lice killed Socrates”, implying that this was meant metaphorically. Since Socrates died at the hands of the Athenian government who condemned him, it is possible that Aurelius attributed Democritus death to human folly or politics.
While Democritus was highly esteemed amongst his contemporaries, there were also those who resented him. This included Plato who, according to some accounts, disliked him so much that he wished that all his books would be burned. However, Plato’s pupil Aristotle was familiar with the works of Democritus and mentioned him in both Metaphysics and Physics, where he described him as a “physicist” who did not concern himself with the ideals of form or essence.
Democritus meditating on the seat of the soul, by Léon-Alexandre Delhomme (1868). Credit: Pubic Domain
Ultimately, Democritus is credited as being one of the founders of the modern science because his methods and theories closely resemble those of modern astronomers and physicists. And while his version of the atomic model differs greatly from our modern conceptions, his work was of undoubted value, and was a step in an ongoing process that included such scientists as John Dalton, Neils Bohr and even Albert Einstein.
As always, science is an process of continuing discovery, where new breakthroughs are built upon the foundations of the old and every generations attempts to see a little farther by standing on the shoulders of those who came before.
We have many interesting articles about atomic theory here at Universe Today. Here’s one about John Dalton’s atomic model, Neils Bohr’s atomic model, the “Plum Pudding” atomic model.
Astronomy Cast has a wonderful episode on the subject, titled Episode 392: The Standard Model – Intro