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153-455: References to the concept of atomism and its atoms appeared in both ancient Greek and ancient Indian philosophical traditions. Leucippus is the earliest figure whose commitment to atomism is well attested and he is usually credited with inventing atomism. He and other ancient Greek atomists theorized that nature consists of two fundamental principles : atom and void . Clusters of different shapes, arrangements, and positions give rise to

306-411: A basic unit of weight, with each element having a unit of unique weight. Dalton decided to call these units "atoms". For example, there are two types of tin oxide : one is a grey powder that is 88.1% tin and 11.9% oxygen, and the other is a white powder that is 78.7% tin and 21.3% oxygen. Adjusting these figures, in the grey powder there is about 13.5 g of oxygen for every 100 g of tin, and in

459-548: A city located in Magna Graecia . Diogenes Laertius says that his father was Pires, and that he belonged to a rich and noble family. Laertius transmits two divergent sources regarding the teacher of the philosopher. One, dependent on Sotion , indicates that he was first a student of Xenophanes , but did not follow him, and later became associated with a Pythagorean , Aminias, whom he preferred as his teacher. Another tradition, dependent on Theophrastus , indicates that he

612-410: A deficit or a surplus of electrons are called ions . Electrons that are farthest from the nucleus may be transferred to other nearby atoms or shared between atoms. By this mechanism, atoms are able to bond into molecules and other types of chemical compounds like ionic and covalent network crystals . By definition, any two atoms with an identical number of protons in their nuclei belong to

765-422: A different way, is internal conversion —a process that produces high-speed electrons that are not beta rays, followed by production of high-energy photons that are not gamma rays. A few large nuclei explode into two or more charged fragments of varying masses plus several neutrons, in a decay called spontaneous nuclear fission . Each radioactive isotope has a characteristic decay time period—the half-life —that

918-401: A final example: nitrous oxide is 63.3% nitrogen and 36.7% oxygen, nitric oxide is 44.05% nitrogen and 55.95% oxygen, and nitrogen dioxide is 29.5% nitrogen and 70.5% oxygen. Adjusting these figures, in nitrous oxide there is 80 g of oxygen for every 140 g of nitrogen, in nitric oxide there is about 160 g of oxygen for every 140 g of nitrogen, and in nitrogen dioxide there

1071-456: A finite set of orbits, and could jump between these orbits only in discrete changes of energy corresponding to absorption or radiation of a photon. This quantization was used to explain why the electrons' orbits are stable and why elements absorb and emit electromagnetic radiation in discrete spectra. Bohr's model could only predict the emission spectra of hydrogen, not atoms with more than one electron. Back in 1815, William Prout observed that

1224-419: A fractional electric charge. Protons are composed of two up quarks (each with charge + ⁠ 2 / 3 ⁠ ) and one down quark (with a charge of − ⁠ 1 / 3 ⁠ ). Neutrons consist of one up quark and two down quarks. This distinction accounts for the difference in mass and charge between the two particles. The quarks are held together by the strong interaction (or strong force), which

1377-484: A given accuracy in measuring a position one could only obtain a range of probable values for momentum, and vice versa. Thus, the planetary model of the atom was discarded in favor of one that described atomic orbital zones around the nucleus where a given electron is most likely to be found. This model was able to explain observations of atomic behavior that previous models could not, such as certain structural and spectral patterns of atoms larger than hydrogen. Though

1530-526: A homogeneous natural substance (e.g., flesh, bone, or wood) could be divided and still retain its essential character. Unlike the atomism of Democritus, these Aristotelian "natural minima" were not conceptualized as physically indivisible. Instead, Aristotle's concept was rooted in his hylomorphic worldview, which held that every physical thing is a compound of matter (Greek hyle ) and of an immaterial substantial form (Greek morphe ) that imparts its essential nature and structure. To use an analogy we could pose

1683-465: A kind that can be perceived. Epicurus' ideas re-appear in the works of his Roman follower Lucretius ( c.  99 BC – c. 55 BC), who wrote On the Nature of Things . This Classical Latin scientific work in poetic form illustrates several segments of Epicurean theory on how the universe came into its current stage; it shows that the phenomena we perceive are actually composite forms. The atoms and

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1836-453: A large amount of the element water, and smaller amounts of the other elements. But whatever water or other elements were left, they would no longer have the "nature" of flesh: in hylomorphic terms, they would no longer be matter structured by the form of flesh; instead the remaining water, e.g., would be matter structured by the form of water, not by the form of flesh. Epicurus (341–270 BCE) studied atomism with Nausiphanes who had been

1989-451: A mathematical function that characterises the probability that an electron appears to be at a particular location when its position is measured. Only a discrete (or quantized ) set of these orbitals exist around the nucleus, as other possible wave patterns rapidly decay into a more stable form. Orbitals can have one or more ring or node structures, and differ from each other in size, shape and orientation. Each atomic orbital corresponds to

2142-415: A particular energy level of the electron. The electron can change its state to a higher energy level by absorbing a photon with sufficient energy to boost it into the new quantum state. Likewise, through spontaneous emission , an electron in a higher energy state can drop to a lower energy state while radiating the excess energy as a photon. These characteristic energy values, defined by the differences in

2295-438: A plausible account of changes among the primary substances. Sometime before 330 BC Aristotle asserted that the elements of fire, air, earth, and water were not made of atoms, but were continuous. Aristotle considered the existence of a void, which was required by atomic theories, to violate physical principles. Change took place not by the rearrangement of atoms to make new structures, but by transformation of matter from what it

2448-474: A pupil of Xenophanes . Eusebius of Caesarea , quoting Aristocles of Messene , says that Parmenides was part of a line of skeptical philosophy that culminated in Pyrrhonism for he, by the root, rejects the validity of perception through the senses whilst, at any rate, it is first through our five forms of senses that we become aware of things and then by faculty of reasoning. Parmenides's proto- monism of

2601-410: A rubber ball: we could imagine the rubber to be the matter that gives the ball the ability to take on another form, and the spherical shape to be the form that gives it its identity of "ball". Using this analogy, though, we should keep in mind that in fact rubber itself would already be considered a composite of form and matter, as it has identity and determinacy to a certain extent, pure or primary matter

2754-568: A separate discipline distinct from theology. His most important pupil was Zeno , who appears alongside him in Plato's Parmenides where they debate dialectic with Socrates . The pluralist theories of Empedocles and Anaxagoras and the atomist Leucippus , and Democritus have also been seen as a potential response to Parmenides's arguments and conclusions. Parmenides is also mentioned in Plato's Sophist and Theaetetus . Later Hellenistic doxographers also considered Parmenides to have been

2907-552: A series of experiments in which they bombarded thin foils of metal with a beam of alpha particles . They did this to measure the scattering patterns of the alpha particles. They spotted a small number of alpha particles being deflected by angles greater than 90°. This shouldn't have been possible according to the Thomson model of the atom, whose charges were too diffuse to produce a sufficiently strong electric field. The deflections should have all been negligible. Rutherford proposed that

3060-519: A set of atomic numbers, from the single-proton element hydrogen up to the 118-proton element oganesson . All known isotopes of elements with atomic numbers greater than 82 are radioactive, although the radioactivity of element 83 ( bismuth ) is so slight as to be practically negligible. About 339 nuclides occur naturally on Earth , of which 251 (about 74%) have not been observed to decay, and are referred to as " stable isotopes ". Only 90 nuclides are stable theoretically , while another 161 (bringing

3213-472: A short-ranged attractive potential called the residual strong force . At distances smaller than 2.5 fm this force is much more powerful than the electrostatic force that causes positively charged protons to repel each other. Atoms of the same element have the same number of protons, called the atomic number . Within a single element, the number of neutrons may vary, determining the isotope of that element. The total number of protons and neutrons determine

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3366-440: A size that is too small to be measured using available techniques. It was the lightest particle with a positive rest mass measured, until the discovery of neutrino mass. Under ordinary conditions, electrons are bound to the positively charged nucleus by the attraction created from opposite electric charges. If an atom has more or fewer electrons than its atomic number, then it becomes respectively negatively or positively charged as

3519-536: A statue dated to the 1st century AD was excavated in Velia . On the plinth were four words: ΠΑ[Ρ]ΜΕΝΕΙΔΗΣ ΠΥΡΗΤΟΣ ΟΥΛΙΑΔΗΣ ΦΥΣΙΚΟΣ. The first two clearly read "Parmenides, son of Pires." The fourth word φυσικός ( fysikós , "physicist") was commonly used to designate philosophers who devoted themselves to the observation of nature. On the other hand, there is no agreement on the meaning of the third (οὐλιάδης, ouliadēs ): it can simply mean "a native of Elea" (the name "Velia"

3672-556: A student of Democritus. Although Epicurus was certain of the existence of atoms and the void, he was less sure we could adequately explain specific natural phenomena such as earthquakes, lightning, comets, or the phases of the Moon. Few of Epicurus' writings survive, and those that do reflect his interest in applying Democritus' theories to assist people in taking responsibility for themselves and for their own happiness—since he held there are no gods around that can help them. (Epicurus regarded

3825-410: A thousand times lighter than hydrogen (the lightest atom). He called these new particles corpuscles but they were later renamed electrons since these are the particles that carry electricity. Thomson also showed that electrons were identical to particles given off by photoelectric and radioactive materials. Thomson explained that an electric current is the passing of electrons from one atom to

3978-432: A tiny atomic nucleus , and are collectively called nucleons . The radius of a nucleus is approximately equal to 1.07 A 3 {\displaystyle 1.07{\sqrt[{3}]{A}}}   femtometres , where A {\displaystyle A} is the total number of nucleons. This is much smaller than the radius of the atom, which is on the order of 10  fm. The nucleons are bound together by

4131-496: A void that could divide it. Finally, he stated that the all encompassing Unity is unchanging, for the Unity already encompasses all that is and can be. Democritus rejected Parmenides' belief that change is an illusion. He believed change was real, and if it was not then at least the illusion had to be explained. He thus supported the concept of void, and stated that the universe is made up of many Parmenidean entities that move around in

4284-470: A whole; a charged atom is called an ion . Electrons have been known since the late 19th century, mostly thanks to J.J. Thomson ; see history of subatomic physics for details. Protons have a positive charge and a mass of 1.6726 × 10  kg . The number of protons in an atom is called its atomic number . Ernest Rutherford (1919) observed that nitrogen under alpha-particle bombardment ejects what appeared to be hydrogen nuclei. By 1920 he had accepted that

4437-543: A young man, conversed with him. Athenaeus of Naucratis had noted that, although the ages make a dialogue between Parmenides and Socrates hardly possible, the fact that Parmenides has sustained arguments similar to those sustained in the Platonic dialogue is something that seems impossible. Most modern classicists consider the visit to Athens and the meeting and conversation with Socrates to be fictitious. Allusions to this visit in other Platonic works are only references to

4590-406: Is 320 g of oxygen for every 140 g of nitrogen. 80, 160, and 320 form a ratio of 1:2:4. The respective formulas for these oxides are N 2 O , NO , and NO 2 . In 1897, J. J. Thomson discovered that cathode rays are not a form of light but made of negatively charged particles because they can be deflected by electric and magnetic fields. He measured these particles to be at least

4743-517: Is 78.1% iron and 21.9% oxygen; and there is another iron oxide that is a red powder which is 70.4% iron and 29.6% oxygen. Adjusting these figures, in the black powder there is about 28 g of oxygen for every 100 g of iron, and in the red powder there is about 42 g of oxygen for every 100 g of iron. 28 and 42 form a ratio of 2:3. Dalton concluded that in these oxides, for every two atoms of iron, there are two or three atoms of oxygen respectively ( Fe 2 O 2 and Fe 2 O 3 ). As

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4896-408: Is a measure of the distance out to which the electron cloud extends from the nucleus. This assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free space. Atomic radii may be derived from the distances between two nuclei when the two atoms are joined in a chemical bond . The radius varies with the location of an atom on the atomic chart, the type of chemical bond,

5049-478: Is advantageous, excludes them from his life. However, according to science historian Charles Coulston Gillispie: Encased in the Epicurean philosophy, the atomic doctrine could never be welcome to moral authority. ... Epicurean gods neither created the world nor paid it ... attention. "Nature," says Lucretius, "is free and uncontrolled by proud masters and runs the universe by herself without the aid of gods." Only

5202-573: Is affected by the ratio of protons to neutrons, and also by the presence of certain "magic numbers" of neutrons or protons that represent closed and filled quantum shells. These quantum shells correspond to a set of energy levels within the shell model of the nucleus; filled shells, such as the filled shell of 50 protons for tin, confers unusual stability on the nuclide. Of the 251 known stable nuclides, only four have both an odd number of protons and odd number of neutrons: hydrogen-2 ( deuterium ), lithium-6 , boron-10 , and nitrogen-14 . ( Tantalum-180m

5355-453: Is completely unformed, unintelligible and with infinite potential to undergo change. Aristotle's intuition was that there is some smallest size beyond which matter could no longer be structured as flesh, or bone, or wood, or some other such organic substance that for Aristotle (living before the invention of the microscope) could be considered homogeneous. For instance, if flesh were divided beyond its natural minimum, what would be left might be

5508-558: Is composed of discrete units, and so applied the word atom to those units. In the early 1800s, John Dalton compiled experimental data gathered by him and other scientists and discovered a pattern now known as the " law of multiple proportions ". He noticed that in any group of chemical compounds which all contain two particular chemical elements, the amount of Element A per measure of Element B will differ across these compounds by ratios of small whole numbers. This pattern suggested that each element combines with other elements in multiples of

5661-440: Is composed. In general, however, the belief that a vacuum is impossible was almost universally held until the end of the sixteenth century. ... The time was certainly ripe for the revival of the belief in the possibility of a vacuum, but to the clerics the very name of the vacuum was anathema, being associated with the atomistic theories of Epicurus and Lucretius, which were felt to be heretical. While Aristotelian philosophy eclipsed

5814-502: Is determined by the amount of time needed for half of a sample to decay. This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half-life. Hence after two half-lives have passed only 25% of the isotope is present, and so forth. Parmenides Parmenides of Elea ( / p ɑːr ˈ m ɛ n ɪ d iː z  ...   ˈ ɛ l i ə / ; ‹See Tfd› Greek : Παρμενίδης ὁ Ἐλεάτης ; fl. late sixth or early fifth century BC)

5967-407: Is easy to determine. From this point of view, the philosophy of Heraclitus seems to him pre-Parmenidean, while those of Empedocles, Anaxagoras and Democritus are post-Parmenidean. Plutarch , Strabo and Diogenes —following the testimony of Speusippus —agree that Parmenides participated in the government of his city, organizing it and giving it a code of admirable laws. In 1969, the plinth of

6120-549: Is gentle, mild, soft, thin and clear, and self-identical, and the other is "ignorant night", body thick and heavy. Cosmology originally comprised the greater part of his poem, explaining the world's origins and operations. Some idea of the sphericity of the Earth also seems to have been known to Parmenides. As the first of the Eleatics , Parmenides is generally credited with being the philosopher who first defined ontology as

6273-438: Is higher than its proton number, so Rutherford hypothesized that the surplus weight was carried by unknown particles with no electric charge and a mass equal to that of the proton. In 1928, Walter Bothe observed that beryllium emitted a highly penetrating, electrically neutral radiation when bombarded with alpha particles. It was later discovered that this radiation could knock hydrogen atoms out of paraffin wax . Initially it

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6426-477: Is in Greek Οὐέλια), or "belonging to the Οὐλιος" ( Ulios ), that is, to a medical school (the patron of which was Apollo Ulius). If this last hypothesis were true, then Parmenides would be, in addition to being a legislator, a doctor. The hypothesis is reinforced by the ideas contained in fragment 18 of his poem, which contains anatomical and physiological observations. However, other specialists believe that

6579-430: Is made up of tiny indivisible particles is an old idea that appeared in many ancient cultures. The word atom is derived from the ancient Greek word atomos , which means "uncuttable". But this ancient idea was based in philosophical reasoning rather than scientific reasoning. Modern atomic theory is not based on these old concepts. In the early 19th century, the scientist John Dalton found evidence that matter really

6732-429: Is mediated by gluons . The protons and neutrons, in turn, are held to each other in the nucleus by the nuclear force , which is a residuum of the strong force that has somewhat different range-properties (see the article on the nuclear force for more). The gluon is a member of the family of gauge bosons , which are elementary particles that mediate physical forces. All the bound protons and neutrons in an atom make up

6885-526: Is nothing more than a reference to the fictitious dramatic situation of the dialogue. Eggers Lan proposes a correction of the traditional date of the foundation of Elea. Based on Herodotus I, 163–167, which indicates that the Phocians , after defeating the Carthaginians in naval battle, founded Elea, and adding the reference to Thucydides I, 13, where it is indicated that such a battle occurred in

7038-502: Is odd-odd and observationally stable, but is predicted to decay with a very long half-life.) Also, only four naturally occurring, radioactive odd-odd nuclides have a half-life over a billion years: potassium-40 , vanadium-50 , lanthanum-138 , and lutetium-176 . Most odd-odd nuclei are highly unstable with respect to beta decay , because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects . The large majority of an atom's mass comes from

7191-477: Is required to bring them together. It is this energy-releasing process that makes nuclear fusion in stars a self-sustaining reaction. For heavier nuclei, the binding energy per nucleon begins to decrease. That means that a fusion process producing a nucleus that has an atomic number higher than about 26, and a mass number higher than about 60, is an endothermic process . Thus, more massive nuclei cannot undergo an energy-producing fusion reaction that can sustain

7344-421: Is that an accelerating charged particle radiates electromagnetic radiation, causing the particle to lose kinetic energy. Circular motion counts as acceleration, which means that an electron orbiting a central charge should spiral down into that nucleus as it loses speed. In 1913, the physicist Niels Bohr proposed a new model in which the electrons of an atom were assumed to orbit the nucleus but could only do so in

7497-470: Is the mass loss and c is the speed of light . This deficit is part of the binding energy of the new nucleus, and it is the non-recoverable loss of the energy that causes the fused particles to remain together in a state that requires this energy to separate. The fusion of two nuclei that create larger nuclei with lower atomic numbers than iron and nickel —a total nucleon number of about 60—is usually an exothermic process that releases more energy than

7650-412: Is well known, who chooses the date of a historical event to make it coincide with the maturity (the floruit ) of a philosopher, a maturity that he invariably reached at forty years of age. He tries to always match the maturity of a philosopher with the birth of his alleged disciple. In this case Apollodorus, according to Burnet , based his date of the foundation of Elea (540 BC) to chronologically locate

7803-449: Is what binds them to the nucleus. If the numbers of protons and electrons are equal, as they normally are, then the atom is electrically neutral as a whole. If an atom has more electrons than protons, then it has an overall negative charge, and is called a negative ion (or anion). Conversely, if it has more protons than electrons, it has a positive charge, and is called a positive ion (or cation). The electrons of an atom are attracted to

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7956-758: The Abhidhammattha-sangaha , a text dated to the 11th or 12th century, postulates the existence of rupa-kalapa , imagined as the smallest units of the physical world, of varying elementary composition. Invisible under normal circumstances, the rupa-kalapa are said to become visible as a result of meditative samadhi . Atomistic philosophies are found very early in Islamic philosophy and were influenced originally by earlier Greek and, to some extent, Indian philosophy. Islamic speculative theology in general approached issues in physics from an atomistic framework. The most successful form of Islamic atomism

8109-862: The Charvaka , and Ajivika schools of atomism originated as early as the 7th century BCE. Bhattacharya posits that Charvaka may have been one of several atheistic, materialist schools that existed in ancient India. Kanada founded the Vaisheshika school of Indian philosophy that also represents the earliest Indian natural philosophy . The Nyaya and Vaisheshika schools developed theories on how kaṇa s combined into more complex objects. Several of these doctrines of atomism are, in some respects, "suggestively similar" to that of Democritus. McEvilley (2002) assumes that such similarities are due to extensive cultural contact and diffusion, probably in both directions. The Nyaya – Vaisesika school developed one of

8262-491: The Schroedinger equation , which describes electrons as three-dimensional waveforms rather than points in space. A consequence of using waveforms to describe particles is that it is mathematically impossible to obtain precise values for both the position and momentum of a particle at a given point in time. This became known as the uncertainty principle , formulated by Werner Heisenberg in 1927. In this concept, for

8415-438: The hydrostatic equilibrium of a star. The electrons in an atom are attracted to the protons in the nucleus by the electromagnetic force . This force binds the electrons inside an electrostatic potential well surrounding the smaller nucleus, which means that an external source of energy is needed for the electron to escape. The closer an electron is to the nucleus, the greater the attractive force. Hence electrons bound near

8568-449: The law of fall either, it was a more promising framework in which to develop an explanation because motion was conserved in ancient atomism (unlike Aristotelian physics). Atom Atoms are the basic particles of the chemical elements . An atom consists of a nucleus of protons and generally neutrons , surrounded by an electromagnetically bound swarm of electrons . The chemical elements are distinguished from each other by

8721-472: The nuclide . The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay . The proton, the electron, and the neutron are classified as fermions . Fermions obey the Pauli exclusion principle which prohibits identical fermions, such as multiple protons, from occupying the same quantum state at the same time. Thus, every proton in

8874-740: The "distinction which the Eleatic school drew between the Absolute , or the only real existence, and the world of change around us." Democritus believed that atoms are too small for human senses to detect, that they are infinitely many, that they come in infinitely many varieties, and that they have always existed. They float in a vacuum, which Democritus called the "void" , and they vary in form, order, and posture. Some atoms, he maintained, are convex, others concave, some shaped like hooks, and others like eyes . They are constantly moving and colliding into each other. Democritus wrote that atoms and void are

9027-517: The 'surface' of these particles is not sharply defined. The neutron was discovered in 1932 by the English physicist James Chadwick . In the Standard Model of physics, electrons are truly elementary particles with no internal structure, whereas protons and neutrons are composite particles composed of elementary particles called quarks . There are two types of quarks in atoms, each having

9180-757: The 17th century, a renewed interest arose in Epicurean atomism and corpuscularianism as a hybrid or an alternative to Aristotelian physics . The main figures in the rebirth of atomism were Isaac Beeckman , René Descartes , Pierre Gassendi , and Robert Boyle , as well as other notable figures. One of the first groups of atomists in England was a cadre of amateur scientists known as the Northumberland circle, led by Henry Percy, 9th Earl of Northumberland (1564–1632). Although they published little of account, they helped to disseminate atomistic ideas among

9333-411: The 7th century, was very different from the atomist doctrines taught in early Buddhism. Medieval Buddhist philosophers Dharmakirti and Dignāga considered atoms to be point-sized, durationless, and made of energy. In discussing the two systems, Fyodor Shcherbatskoy (1930) stresses their commonality, the postulate of "absolute qualities" ( guna-dharma ) underlying all empirical phenomena. Still later,

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9486-544: The Platonic text, and the historical reality of the encounter, in favor of the traditional date of Apollodorus. He follows the traditional datum of the founding of Elea in 545 BC, pointing to it not only as terminus post quem , but as a possible date of Parmenides's birth, from which he concludes that his parents were part of the founding contingent of the city and that he was a contemporary of Heraclitus . The evidence suggests that Parmenides could not have written much after

9639-462: The Way of " Aletheia " or truth, describes how all reality is one, change is impossible, and existence is timeless and uniform. The second view, the way of " Doxa ", or opinion, describes the world of appearances, in which one's sensory faculties lead to conceptions which are false and deceitful. Parmenides has been considered the founder of ontology and has, through his influence on Plato , influenced

9792-464: The adjacent table. The cube, with its flat base and stability, was assigned to earth; the tetrahedron was assigned to fire because its penetrating points and sharp edges made it mobile. The points and edges of the octahedron and icosahedron were blunter and so these less mobile bodies were assigned to air and water. Since the simple bodies could be decomposed into triangles, and the triangles reassembled into atoms of different elements, Plato's model offered

9945-441: The age of 65, when Socrates was a young man, c.  450 BC , which, if true, suggests a year of birth of c.  515 BC . He is thought to have been in his prime (or " floruit ") around 475 BC. The single known work by Parmenides is a poem whose original title is unknown but which is often referred to as On Nature . Only fragments of it survive. In his poem, Parmenides prescribes two views of reality . The first,

10098-460: The aggregation and nature of these atoms was predetermined by cosmic forces. The school founder's traditional name Kanada means 'atom eater', and he is known for developing the foundations of an atomistic approach to physics and philosophy in the Sanskrit text Vaiśeṣika Sūtra . His text is also known as Kanada Sutras , or Aphorisms of Kanada. Medieval Buddhist atomism , flourishing around

10251-444: The atom logically had to be balanced out by a commensurate amount of positive charge, but Thomson had no idea where this positive charge came from, so he tentatively proposed that it was everywhere in the atom, the atom being in the shape of a sphere. This was the mathematically simplest hypothesis to fit the available evidence, or lack thereof. Following from this, Thomson imagined that the balance of electrostatic forces would distribute

10404-422: The atomic mass unit (for example the mass of a nitrogen-14 is roughly 14 Da), but this number will not be exactly an integer except (by definition) in the case of carbon-12. The heaviest stable atom is lead-208, with a mass of 207.976 6521  Da . As even the most massive atoms are far too light to work with directly, chemists instead use the unit of moles . One mole of atoms of any element always has

10557-491: The atomic weights of many elements were multiples of hydrogen's atomic weight, which is in fact true for all of them if one takes isotopes into account. In 1898, J. J. Thomson found that the positive charge of a hydrogen ion is equal to the negative charge of an electron, and these were then the smallest known charged particles. Thomson later found that the positive charge in an atom is a positive multiple of an electron's negative charge. In 1913, Henry Moseley discovered that

10710-446: The atomism of Epicurus had fallen out of favor in the centuries of Scholasticism , the minima naturalia of Aristotelianism received extensive consideration. Speculation on minima naturalia provided philosophical background for the mechanistic philosophy of early modern thinkers such as Descartes, and for the alchemical works of Geber and Daniel Sennert , who in turn influenced the corpuscularian alchemist Robert Boyle , one of

10863-700: The atomism of the Asharites and expounded on many Greek texts, especially those of Aristotle. An active school of philosophers in Al-Andalus, including the noted commentator Averroes (1126–1198 CE) explicitly rejected the thought of al-Ghazali and turned to an extensive evaluation of the thought of Aristotle. Averroes commented in detail on most of the works of Aristotle and his commentaries became very influential in Jewish and Christian scholastic thought. According to historian of atomism Joshua Gregory, there

11016-404: The atomists among ... Greek science ... was the one view of nature quite incompatible with theology. Like a pair of eighteenth-century philosophers, Epicurus and Lucretius introduced atomism as a vehicle of enlightenment. They meant to refute the pretensions of religion ... and release men from superstition and the undignified fear of capricious gods. Consequently, a hint of Epicureanism came to seem

11169-828: The burgeoning scientific culture of England, and may have been particularly influential to Francis Bacon , who became an atomist around 1605, though he later rejected some of the claims of atomism. Though they revived the classical form of atomism, this group was among the scientific avant-garde: the Northumberland circle contained nearly half of the confirmed Copernicans prior to 1610 (the year of Galileo's The Starry Messenger ). Other influential atomists of late 16th and early 17th centuries include Giordano Bruno , Thomas Hobbes (who also changed his stance on atomism late in his career), and Thomas Hariot . A number of different atomistic theories were blossoming in France at this time, as well (Clericuzio 2000). Galileo Galilei (1564–1642)

11322-413: The center of the potential well require more energy to escape than those at greater separations. Electrons, like other particles, have properties of both a particle and a wave . The electron cloud is a region inside the potential well where each electron forms a type of three-dimensional standing wave —a wave form that does not move relative to the nucleus. This behavior is defined by an atomic orbital ,

11475-478: The chemical elements, at least one stable isotope exists. As a rule, there is only a handful of stable isotopes for each of these elements, the average being 3.1 stable isotopes per element. Twenty-six " monoisotopic elements " have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten, for the element tin . Elements 43 , 61 , and all elements numbered 83 or higher have no stable isotopes. Stability of isotopes

11628-453: The core of the Sun protons require energies of 3 to 10 keV to overcome their mutual repulsion—the coulomb barrier —and fuse together into a single nucleus. Nuclear fission is the opposite process, causing a nucleus to split into two smaller nuclei—usually through radioactive decay. The nucleus can also be modified through bombardment by high energy subatomic particles or photons. If this modifies

11781-663: The curriculum in the universities of Europe was based on such Aristotelianism for most of the Middle Ages. In medieval universities there were, however, expressions of atomism. For example, in the 14th century Nicholas of Autrecourt considered that matter, space, and time were all made up of indivisible atoms, points, and instants and that all generation and corruption took place by the rearrangement of material atoms. The similarities of his ideas with those of al-Ghazali suggest that Nicholas may have been familiar with Ghazali's work, perhaps through Averroes ' refutation of it. In

11934-737: The death of Heraclitus. Beyond the speculations and inaccuracies about his date of birth, some specialists have turned their attention to certain passages of his work to specify the relationship of Parmenides with other thinkers. It was thought to find in his poem certain controversial allusions to the doctrine of Anaximenes and the Pythagoreans (fragment B 8, verse 24, and frag. B 4), and also against Heraclitus (frag .B 6, vv.8–9), while Empedocles and Anaxagoras frequently refer to Parmenides. The reference to Heraclitus has been debated. Bernays's thesis that Parmenides attacks Heraclitus, to which Diels, Kranz, Gomperz, Burnet and others adhered,

12087-410: The different packings and scatterings of the atoms in the void that compose the object that organisms sense as being "hot" or "cold". The work of Democritus survives only in secondhand reports, some of which are unreliable or conflicting. Much of the best evidence of Democritus' theory of atomism is reported by Aristotle (384–322 BCE) in his discussions of Democritus' and Plato 's contrasting views on

12240-563: The direct result of God's constant intervention, without which nothing could happen. Thus nature is completely dependent on God, which meshes with other Asharite Islamic ideas on causation, or the lack thereof (Gardet 2001). Al-Ghazali also used the theory to support his theory of occasionalism . In a sense, the Asharite theory of atomism has far more in common with Indian atomism than it does with Greek atomism. Other traditions in Islam rejected

12393-641: The earliest forms of atomism; scholars date the Nyaya and Vaisesika texts from the 9th to 4th centuries BCE. Vaisesika atomists posited the four elemental atom types, but in Vaisesika physics atoms had 25 different possible qualities, divided between general extensive properties and specific (intensive) properties. The Nyaya–Vaisesika atomists had elaborate theories of how atoms combine. In Vaisesika atomism, atoms first combine into tryaṇuka s (triads) and dvyaṇuka (dyad) before they aggregate into bodies of

12546-490: The early Pythagoreans (before Ecphantus of Syracuse ). Unit-point atomism was invoked in order to make sense of a statement ascribed to Zeno of Elea in Plato's Parmenides : "these writings of mine were meant to protect the arguments of Parmenides against those who make fun of him. . . My answer is addressed to the partisans of the many. . ." The anti-Parmenidean pluralists were supposedly unit-point atomists whose philosophy

12699-512: The electrons throughout the sphere in a more or less even manner. Thomson's model is popularly known as the plum pudding model , though neither Thomson nor his colleagues used this analogy. Thomson's model was incomplete, it was unable to predict any other properties of the elements such as emission spectra and valencies . It was soon rendered obsolete by the discovery of the atomic nucleus . Between 1908 and 1913, Ernest Rutherford and his colleagues Hans Geiger and Ernest Marsden performed

12852-506: The energies of the quantum states, are responsible for atomic spectral lines . The amount of energy needed to remove or add an electron—the electron binding energy —is far less than the binding energy of nucleons . For example, it requires only 13.6 eV to strip a ground-state electron from a hydrogen atom, compared to 2.23  million eV for splitting a deuterium nucleus. Atoms are electrically neutral if they have an equal number of protons and electrons. Atoms that have either

13005-671: The energies of the recoiling charged particles, he deduced that the radiation was actually composed of electrically neutral particles which could not be massless like the gamma ray, but instead were required to have a mass similar to that of a proton. Chadwick now claimed these particles as Rutherford's neutrons. In 1925, Werner Heisenberg published the first consistent mathematical formulation of quantum mechanics ( matrix mechanics ). One year earlier, Louis de Broglie had proposed that all particles behave like waves to some extent, and in 1926 Erwin Schroedinger used this idea to develop

13158-410: The founders of modern chemistry. A chief theme in late Roman and Scholastic commentary on this concept was reconciling minima naturalia with the general Aristotelian principle of infinite divisibility . Commentators like John Philoponus and Thomas Aquinas reconciled these aspects of Aristotle's thought by distinguishing between mathematical and "natural" divisibility. With few exceptions, much of

13311-433: The frequencies of X-ray emissions from an excited atom were a mathematical function of its atomic number and hydrogen's nuclear charge. In 1919 Rutherford bombarded nitrogen gas with alpha particles and detected hydrogen ions being emitted from the gas, and concluded that they were produced by alpha particles hitting and splitting the nuclei of the nitrogen atoms. These observations led Rutherford to conclude that

13464-416: The hydrogen nucleus is a distinct particle within the atom and named it proton . Neutrons have no electrical charge and have a mass of 1.6749 × 10  kg . Neutrons are the heaviest of the three constituent particles, but their mass can be reduced by the nuclear binding energy . Neutrons and protons (collectively known as nucleons ) have comparable dimensions—on the order of 2.5 × 10  m —although

13617-445: The hydrogen nucleus is a singular particle with a positive charge equal to the electron's negative charge. He named this particle " proton " in 1920. The number of protons in an atom (which Rutherford called the " atomic number " ) was found to be equal to the element's ordinal number on the periodic table and therefore provided a simple and clear-cut way of distinguishing the elements from each other. The atomic weight of each element

13770-421: The importance of the atomists in late Roman and medieval Europe, their work was still preserved and exposited through commentaries on the works of Aristotle. In the 2nd century, Galen (AD 129–216) presented extensive discussions of the Greek atomists, especially Epicurus, in his Aristotle commentaries. Ajivika is a " Nastika " school of thought whose metaphysics included a theory of atoms or atomism which

13923-472: The journey towards either illumination or darkness, but there is little scholarly consensus about any interpretation, and the surviving evidence from the poem itself, as well as any other literary use of allegory from the same time period, may be too sparse to ever determine any of the intended symbolism with certainty. In the Way of Truth , an estimated 90% of which has survived, Parmenides distinguishes between

14076-514: The mark of the beast in Christian Europe. No thinker, unless it is Machiavelli, has been more maligned by misrepresentation. The possibility of a vacuum was accepted—or rejected—together with atoms and atomism, for the vacuum was part of that same theory. Democritus and Lucretius denied the impossibility of a vacuum, being of the opinion that there must be a vacuum between the discrete particles (atoms) of which, they thought, all matter

14229-415: The maturity of Xenophanes and thus the birth of his supposed disciple, Parmenides. Knowing this, Burnet and later classicists like Cornford , Raven , Guthrie , and Schofield preferred to base the calculations on the Platonic dialogue. According to the latter, the fact that Plato adds so much detail regarding ages in his text is a sign that he writes with chronological precision. Plato says that Socrates

14382-570: The meeting between Socrates and Parmenides is mentioned in the dialogues Theaetetus (183e) and Sophist (217c) only indicates that it is referring to the same fictional event, and this is possible because both the Theaetetus and the Sophist are considered after the Parmenides . In Soph. 217c the dialectic procedure of Socrates is attributed to Parmenides, which would confirm that this

14535-472: The moment of maturity, placing his birth 40 years earlier (544 BC – 540 BC). The other is Plato , in his dialogue Parmenides . There Plato composes a situation in which Parmenides, 65, and Zeno , 40, travel to Athens to attend the Panathenaic Games . On that occasion they meet Socrates , who was still very young according to the Platonic text. The inaccuracy of the dating from Apollodorus

14688-432: The mutual repulsion of the protons requires an increasing proportion of neutrons to maintain the stability of the nucleus. The number of protons and neutrons in the atomic nucleus can be modified, although this can require very high energies because of the strong force. Nuclear fusion occurs when multiple atomic particles join to form a heavier nucleus, such as through the energetic collision of two nuclei. For example, at

14841-506: The name "atom", long used by the atomist philosophy. Although the connection to historical atomism is at best tenuous, elementary particles have become a modern analogue of philosophical atoms. Philosophical atomism is a reductive argument, proposing not only that everything is composed of atoms and void, but that nothing they compose really exists: the only things that really exist are atoms ricocheting off each other mechanistically in an otherwise empty void . One proponent of this theory

14994-415: The next, and when there was no current the electrons embedded themselves in the atoms. This in turn meant that atoms were not indivisible as scientists thought. The atom was composed of electrons whose negative charge was balanced out by some source of positive charge to create an electrically neutral atom. Ions, Thomson explained, must be atoms which have an excess or shortage of electrons. The electrons in

15147-435: The nucleus splits and leaves behind different elements . This is a form of nuclear decay . Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules or crystals . The ability of atoms to attach and detach from each other is responsible for most of the physical changes observed in nature. Chemistry is the science that studies these changes. The basic idea that matter

15300-509: The nucleus must occupy a quantum state different from all other protons, and the same applies to all neutrons of the nucleus and to all electrons of the electron cloud. A nucleus that has a different number of protons than neutrons can potentially drop to a lower energy state through a radioactive decay that causes the number of protons and neutrons to more closely match. As a result, atoms with matching numbers of protons and neutrons are more stable against decay, but with increasing atomic number,

15453-515: The nucleus to emit particles or electromagnetic radiation. Radioactivity can occur when the radius of a nucleus is large compared with the radius of the strong force, which only acts over distances on the order of 1 fm. The most common forms of radioactive decay are: Other more rare types of radioactive decay include ejection of neutrons or protons or clusters of nucleons from a nucleus, or more than one beta particle . An analog of gamma emission which allows excited nuclei to lose energy in

15606-401: The number of hydrogen atoms. A single carat diamond with a mass of 2 × 10  kg contains about 10 sextillion (10 ) atoms of carbon . If an apple were magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple. Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing

15759-450: The number of neighboring atoms ( coordination number ) and a quantum mechanical property known as spin . On the periodic table of the elements, atom size tends to increase when moving down columns, but decrease when moving across rows (left to right). Consequently, the smallest atom is helium with a radius of 32  pm , while one of the largest is caesium at 225 pm. When subjected to external forces, like electrical fields ,

15912-451: The number of protons in a nucleus, the atom changes to a different chemical element. If the mass of the nucleus following a fusion reaction is less than the sum of the masses of the separate particles, then the difference between these two values can be emitted as a type of usable energy (such as a gamma ray , or the kinetic energy of a beta particle ), as described by Albert Einstein 's mass–energy equivalence formula, E=mc , where m

16065-423: The number of protons that are in their atoms. For example, any atom that contains 11 protons is sodium , and any atom that contains 29 protons is copper . Atoms with the same number of protons but a different number of neutrons are called isotopes of the same element. Atoms are extremely small, typically around 100  picometers across. A human hair is about a million carbon atoms wide. Atoms are smaller than

16218-427: The only certainty we can extract from the discovery is that of the social importance of Parmenides in the life of his city, already indicated by the testimonies that indicate his activity as a legislator. Plato , in his dialogue Parmenides , relates that, accompanied by his disciple Zeno of Elea , Parmenides visited Athens when he was approximately sixty-five years old and that, on that occasion, Socrates , then

16371-405: The only things that exist and that all other things are merely said to exist by social convention . The objects humans see in everyday life are composed of many atoms united by random collisions and their forms and materials are determined by what kinds of atom make them up. Likewise, human perceptions are caused by atoms as well. Bitterness is caused by small, angular, jagged atoms passing across

16524-409: The people in what was possible in atoms and what was not possible in atoms. However, Epicurus expressed a non-aggressive attitude characterized by his statement: The man who best knows how to meet external threats makes into one family all the creatures he can; and those he can not, he at any rate does not treat as aliens; and where he finds even this impossible, he avoids all dealings, and, so far as

16677-572: The perceiving mind, that is, "secondary" qualities as distinguished from "primary" qualities. Galileo identified some basic problems with Aristotelian physics through his experiments. He utilized a theory of atomism as a partial replacement, but he was never unequivocally committed to it. For example, his experiments with falling bodies and inclined planes led him to the concepts of circular inertial motion and accelerating free-fall. The current Aristotelian theories of impetus and terrestrial motion were inadequate to explain these. While atomism did not explain

16830-484: The poem, Way of Opinion , Parmenides propounds a theory of the world of seeming and its development, pointing out, however, that, in accordance with the principles already laid down, these cosmological speculations do not pretend to anything more than mere appearance. The structure of the cosmos is a fundamental binary principle that governs the manifestations of all the particulars: "the Aether fire of flame" (B 8.56), which

16983-537: The poet's journey includes a variety of allegorical symbols, such as a speeding chariot with glowing axles, horses, the House of Night, Gates of the paths of Night and Day, and maidens who are "the daughters of the Sun" who escort the poet from the ordinary daytime world to a strange destination, outside our human paths. The allegorical themes in the poem have attracted a variety of different interpretations, including comparisons to Homer and Hesiod , and attempts to relate

17136-435: The positive charge of the atom is concentrated in a tiny volume at the center of the atom and that the electrons surround this nucleus in a diffuse cloud. This nucleus carried almost all of the atom's mass, the electrons being so very light. Only such an intense concentration of charge, anchored by its high mass, could produce an electric field that could deflect the alpha particles so strongly. A problem in classical mechanics

17289-416: The present day complete. However, a massive number of fragments and quotations of his writings have survived. These are the main source of information on his teachings about atoms. Democritus's argument for the existence of atoms hinged on the idea that it is impossible to keep dividing matter infinitely - and that matter must therefore be made up of extremely tiny particles. The atomistic theory aimed to remove

17442-448: The protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number . It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count. An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons). The actual mass of an atom at rest is often expressed in daltons (Da), also called

17595-399: The protons in an atomic nucleus by the electromagnetic force . The protons and neutrons in the nucleus are attracted to each other by the nuclear force . This force is usually stronger than the electromagnetic force that repels the positively charged protons from one another. Under certain circumstances, the repelling electromagnetic force becomes stronger than the nuclear force. In this case,

17748-428: The purpose of the work, a former section known as "The Way of Truth" ( aletheia , ἀλήθεια), and a latter section known as "The Way of Appearance/Opinion" ( doxa , δόξα). Despite the poem's fragmentary nature, the general plan of both the proem and the first part, "The Way of Truth" have been ascertained by modern scholars, thanks to large excerpts made by Sextus Empiricus and Simplicius of Cilicia . Unfortunately,

17901-621: The role of gods as exemplifying moral ideals.) In ancient Indian philosophy , preliminary instances of atomism are found in the works of Vedic sage Aruni , who lived in the 8th century BCE, especially his proposition that "particles too small to be seen mass together into the substances and objects of experience" known as kaṇa . Although kana refers to "particles" not atoms ( paramanu ). Some scholars such as Hermann Jacobi and Randall Collins have compared Aruni to Thales of Miletus in their scientific methodology, calling them both as "primitive physicists" or "proto-materialist thinkers". Later,

18054-412: The same chemical element . Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons ( hydrogen-1 , by far the most common form, also called protium), one neutron ( deuterium ), two neutrons ( tritium ) and more than two neutrons . The known elements form

18207-402: The same fictitious dialogue and not to a historical fact. Parmenides's sole work, which has only survived in fragments, is a poem in dactylic hexameter , later titled On Nature . Approximately 160 verses remain today from an original total that was probably near 800. The poem was originally divided into three parts: an introductory proem that contains an allegorical narrative which explains

18360-416: The same in any portion of a homogeneous material). In the 5th century BC, Leucippus and his pupil Democritus proposed that all matter was composed of small indivisible particles which they called "atoms". Nothing whatsoever is known about Leucippus except that he was the teacher of Democritus. Democritus, by contrast, wrote prolifically, producing over eighty known treatises, none of which have survived to

18513-498: The same number of atoms (about 6.022 × 10 ). This number was chosen so that if an element has an atomic mass of 1 u, a mole of atoms of that element has a mass close to one gram. Because of the definition of the unified atomic mass unit , each carbon-12 atom has an atomic mass of exactly 12 Da, and so a mole of carbon-12 atoms weighs exactly 0.012 kg. Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius . This

18666-427: The second part, "The Way of Opinion", which is supposed to have been much longer than the first, only survives in small fragments and prose paraphrases. The introductory proem describes the narrator's journey to receive a revelation from an unnamed goddess on the nature of reality. The remainder of the work is then presented as the spoken revelation of the goddess without any accompanying narrative. The narrative of

18819-539: The shape of an atom may deviate from spherical symmetry . The deformation depends on the field magnitude and the orbital type of outer shell electrons, as shown by group-theoretical considerations. Aspherical deviations might be elicited for instance in crystals , where large crystal-electrical fields may occur at low-symmetry lattice sites. Significant ellipsoidal deformations have been shown to occur for sulfur ions and chalcogen ions in pyrite -type compounds. Atomic dimensions are thousands of times smaller than

18972-469: The shortest wavelength of visible light, which means humans cannot see atoms with conventional microscopes. They are so small that accurately predicting their behavior using classical physics is not possible due to quantum effects . More than 99.9994% of an atom's mass is in the nucleus. Protons have a positive electric charge and neutrons have no charge, so the nucleus is positively charged. The electrons are negatively charged, and this opposing charge

19125-420: The time of Cambyses II , the foundation of Elea can be placed between 530 BC and 522 BC So Parmenides could not have been born before 530 BC or after 520 BC, given that it predates Empedocles . This last dating procedure is not infallible either, because it has been questioned that the fact that links the passages of Herodotus and Thucydides is the same. Nestor Luis Cordero also rejects the chronology based on

19278-423: The tongue; whereas sweetness is caused by larger, smoother, more rounded atoms passing across the tongue. Previously, Parmenides had denied the existence of motion, change and void. He believed all existence to be a single, all-encompassing and unchanging mass (a concept known as monism ), and that change and motion were mere illusions. He explicitly rejected sensory experience as the path to an understanding of

19431-737: The total to 251) have not been observed to decay, even though in theory it is energetically possible. These are also formally classified as "stable". An additional 35 radioactive nuclides have half-lives longer than 100 million years, and are long-lived enough to have been present since the birth of the Solar System . This collection of 286 nuclides are known as primordial nuclides . Finally, an additional 53 short-lived nuclides are known to occur naturally, as daughter products of primordial nuclide decay (such as radium from uranium ), or as products of natural energetic processes on Earth, such as cosmic ray bombardment (for example, carbon-14). For 80 of

19584-574: The types of indivisibles composing the natural world. According to some twentieth-century philosophers , unit-point atomism was the philosophy of the Pythagoreans , a conscious repudiation of Parmenides and the Eleatics . It stated that atoms were infinitesimally small ("point") yet possessed corporeality. It was a predecessor of Democritean atomism. Most recent students of presocratic philosophy , such as Kurt von Fritz , Walter Burkert , Gregory Vlastos , Jonathan Barnes , and Daniel W. Graham have rejected that any form of atomism can be applied to

19737-445: The unified atomic mass unit (u). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12 , which is approximately 1.66 × 10  kg . Hydrogen-1 (the lightest isotope of hydrogen which is also the nuclide with the lowest mass) has an atomic weight of 1.007825 Da. The value of this number is called the atomic mass . A given atom has an atomic mass approximately equal (within 1%) to its mass number times

19890-439: The unity of nature and its variety, insisting in the Way of Truth upon the reality of its unity, which is therefore the object of knowledge, and upon the unreality of its variety, which is therefore the object, not of knowledge, but of opinion. This contrasts with the argument in the section called "the way of opinion", which discusses that which is illusory. In the significantly longer, but far worse preserved latter section of

20043-448: The universe and instead used purely abstract reasoning. He believed there is no such thing as void, equating it with non-being. This in turn meant that motion is impossible, because there is no void to move into. Parmenides doesn't mention or explicitly deny the existence of the void, stating instead that what is not does not exist. He also wrote all that is must be an indivisible unity, for if it were manifold, then there would have to be

20196-509: The various macroscopic substances in the world. Indian Buddhists , such as Dharmakirti ( fl. c. 6th or 7th century) and others, developed distinctive theories of atomism, for example, involving momentary (instantaneous) atoms ( kalapa s ) that flash in and out of existence. The particles of chemical matter for which chemists and other natural philosophers of the early 19th century found experimental evidence were thought to be indivisible, and therefore were given by John Dalton

20349-432: The void are eternal and in constant motion. Atomic collisions create objects, which are still composed of the same eternal atoms whose motion for a while is incorporated into the created entity. Lucretius also explains human sensations and meteorological phenomena in terms of atomic motion. In his epic poem On the Nature of Things , Lucretius depicts Epicurus as the hero who crushed the monster Religion through educating

20502-414: The void. The void is infinite and provides the space in which the atoms can pack or scatter differently. The different possible packings and scatterings within the void make up the shifting outlines and bulk of the objects that organisms feel, see, eat, hear, smell, and taste. While organisms may feel hot or cold, hot and cold actually have no real existence. They are simply sensations produced in organisms by

20655-406: The wavelengths of light (400–700  nm ) so they cannot be viewed using an optical microscope , although individual atoms can be observed using a scanning tunneling microscope . To visualize the minuteness of the atom, consider that a typical human hair is about 1 million carbon atoms in width. A single drop of water contains about 2  sextillion ( 2 × 10 ) atoms of oxygen, and twice

20808-404: The white powder there is about 27 g of oxygen for every 100 g of tin. 13.5 and 27 form a ratio of 1:2. Dalton concluded that in the grey oxide there is one atom of oxygen for every atom of tin, and in the white oxide there are two atoms of oxygen for every atom of tin ( SnO and SnO 2 ). Dalton also analyzed iron oxides . There is one type of iron oxide that is a black powder which

20961-535: The whole history of Western philosophy . He is also considered to be the founder of the Eleatic school of philosophy , which also included Zeno of Elea and Melissus of Samos . Zeno's paradoxes of motion were developed to defend Parmenides's views. In contemporary philosophy, Parmenides's work has remained relevant in debates about the philosophy of time . Parmenides was born in Elea (called Velia in Roman times),

21114-407: The word atom originally denoted a particle that cannot be cut into smaller particles, in modern scientific usage the atom is composed of various subatomic particles . The constituent particles of an atom are the electron , the proton and the neutron . The electron is the least massive of these particles by four orders of magnitude at 9.11 × 10  kg , with a negative electrical charge and

21267-468: Was a pre-Socratic Greek philosopher from Elea in Magna Graecia (Southern Italy ). Parmenides was born in the Greek colony of Elea , from a wealthy and illustrious family. His dates are uncertain; according to doxographer Diogenes Laërtius , he flourished just before 500 BC, which would put his year of birth near 540 BC, but in the dialogue Parmenides Plato has him visiting Athens at

21420-469: Was a disciple of Anaximander . Everything related to the chronology of Parmenides—the dates of his birth and death, and the period of his philosophical activity—is uncertain. All conjectures regarding Parmenides's date of birth are based on two ancient sources. One comes from Apollodorus and is transmitted to us by Diogenes Laertius: this source marks the Olympiad 69th (between 504 BC and 500 BC) as

21573-451: Was about sixty-five years old, his birth occurred around 515 BC. However, neither Raven nor Schofield, who follows the former, finds a dating based on a late Platonic dialogue entirely satisfactory. Other scholars directly prefer not to use the Platonic testimony and propose other dates. According to a scholar of the Platonic dialogues , R. Hirzel, Conrado Eggers Lan indicates that the historical has no value for Plato. The fact that

21726-414: Was an advocate of atomism in his 1612 Discourse on Floating Bodies (Redondi 1969). In The Assayer , Galileo offered a more complete physical system based on a corpuscular theory of matter, in which all phenomena—with the exception of sound—are produced by "matter in motion". Atomism was associated by its leading proponents with the idea that some of the apparent properties of objects are artifacts of

21879-409: Was created, although its creator framed it after an eternal, unchanging model. ( Animation ) ( Animation ) ( Animation ) ( Animation ) One part of that creation were the four simple bodies of fire, air, water, and earth . But Plato did not consider these corpuscles to be the most basic level of reality, for in his view they were made up of an unchanging level of reality, which

22032-442: Was discussed by Reinhardt, whom Jaeger followed. Guthrie finds it surprising that Heraclitus would not have censured Parmenides if he had known him, as he did with Xenophanes and Pythagoras . His conclusion, however, does not arise from this consideration, but points out that, due to the importance of his thought, Parmenides splits the history of pre-Socratic philosophy in two; therefore his position with respect to other thinkers

22185-509: Was essentially a reaction against the Eleatics. This hypothesis, however, to explain Zeno's paradoxes , has been thoroughly discredited. Plato ( c.  427 – c.  347 BCE) argued that atoms just crashing into other atoms could never produce the beauty and form of the world. In Plato's Timaeus (28b–29a) the character of Timeaus insisted that the cosmos was not eternal but

22338-411: Was in potential to a new actuality . A piece of wet clay, when acted upon by a potter, takes on its potential to be an actual drinking mug. Aristotle has often been criticized for rejecting atomism, but in ancient Greece the atomic theories of Democritus remained "pure speculations, incapable of being put to any experimental test". Aristotle theorized minima naturalia as the smallest parts into which

22491-524: Was in the Asharite school of Islamic theology , most notably in the work of the theologian al-Ghazali (1058–1111). In Asharite atomism, atoms are the only perpetual, material things in existence, and all else in the world is "accidental" meaning something that lasts for only an instant. Nothing accidental can be the cause of anything else, except perception, as it exists for a moment. Contingent events are not subject to natural physical causes, but are

22644-469: Was later adapted in the Vaiśeṣika school, which postulated that all objects in the physical universe are reducible to paramāṇu ( atoms ), and one's experiences are derived from the interplay of substance (a function of atoms, their number and their spatial arrangements), quality, activity, commonness, particularity and inherence. Everything was composed of atoms, qualities emerged from aggregates of atoms, but

22797-433: Was mathematical. These simple bodies were geometric solids , the faces of which were, in turn, made up of triangles. The square faces of the cube were each made up of four isosceles right-angled triangles and the triangular faces of the tetrahedron, octahedron, and icosahedron were each made up of six right-angled triangles. Plato postulated the geometric structure of the simple bodies of the four elements as summarized in

22950-558: Was no serious work done with atomism from the time of Galen until Isaac Beeckman , Gassendi and Descartes resurrected it in the 17th century; "the gap between these two 'modern naturalists' and the ancient Atomists marked "the exile of the atom" and "it is universally admitted that the Middle Ages had abandoned Atomism, and virtually lost it." Although the ancient atomists' works were unavailable, scholastic thinkers gradually became aware of Aristotle's critiques of atomism as Averroes 's commentaries were translated into Latin . Although

23103-432: Was the Greek philosopher Democritus . By convention sweet is sweet, by convention bitter is bitter, by convention hot is hot, by convention cold is cold, by convention color is color. But in reality there are atoms and the void. Atomism stands in contrast to a substance theory wherein a prime material continuum remains qualitatively invariant under division (for example, the ratio of the four classical elements would be

23256-432: Was thought to be high-energy gamma radiation , since gamma radiation had a similar effect on electrons in metals, but James Chadwick found that the ionization effect was too strong for it to be due to electromagnetic radiation, so long as energy and momentum were conserved in the interaction. In 1932, Chadwick exposed various elements, such as hydrogen and nitrogen, to the mysterious "beryllium radiation", and by measuring

23409-429: Was very young, and this is interpreted to mean that he was less than twenty years old. We know the year of Socrates' death (399 BC) and his age—he was about seventy years old–making the date of his birth 469 BC. The Panathenaic games were held every four years, and of those held during Socrates' youth (454, 450, 446), the most likely is that of 450 BC, when Socrates was nineteen years old. Thus, if at this meeting Parmenides

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