201-758: In astronomy , the geocentric model (also known as geocentrism , often exemplified specifically by the Ptolemaic system ) is a superseded description of the Universe with Earth at the center. Under most geocentric models, the Sun , Moon , stars , and planets all orbit Earth. The geocentric model was the predominant description of the cosmos in many European ancient civilizations, such as those of Aristotle in Classical Greece and Ptolemy in Roman Egypt, as well as during
402-448: A binary black hole . A second gravitational wave was detected on 26 December 2015 and additional observations should continue but gravitational waves require extremely sensitive instruments. The combination of observations made using electromagnetic radiation, neutrinos or gravitational waves and other complementary information, is known as multi-messenger astronomy . One of the oldest fields in astronomy, and in all of science,
603-767: A heliocentric frame is most useful in those cases, galactic and extragalactic astronomy is easier if the Sun is treated as neither stationary nor the center of the universe, but rather rotating around the center of our galaxy, while in turn our galaxy is also not at rest in the cosmic background . Albert Einstein and Leopold Infeld wrote in The Evolution of Physics (1938): "Can we formulate physical laws so that they are valid for all CS [ coordinate systems ], not only those moving uniformly, but also those moving quite arbitrarily, relative to each other? If this can be done, our difficulties will be over. We shall then be able to apply
804-604: A heliocentric model placing all of the then-known planets in their correct order around the Sun. The ancient Greeks believed that the motions of the planets were circular , a view that was not challenged in Western culture until the 17th century, when Johannes Kepler postulated that orbits were heliocentric and elliptical (Kepler's first law of planetary motion ). In 1687, Isaac Newton showed that elliptical orbits could be derived from his laws of gravitation. The astronomical predictions of Ptolemy's geocentric model , developed in
1005-418: A transit of Venus for the year 1631. The change from circular orbits to elliptical planetary paths dramatically improved the accuracy of celestial observations and predictions. Because the heliocentric model devised by Copernicus was no more accurate than Ptolemy's system, new observations were needed to persuade those who still adhered to the geocentric model. However, Kepler's laws based on Brahe's data became
1206-517: A will in which he asked to be buried next to his wife. Aristotle left his works to Theophrastus, his successor as the head of the Lyceum, who in turn passed them down to Neleus of Scepsis in Asia Minor. There, the papers remained hidden for protection until they were purchased by the collector Apellicon . In the meantime, many copies of Aristotle's major works had already begun to circulate and be used in
1407-541: A "survival of the fittest" origin of living things and their organs, and ridiculed the idea that accidents could lead to orderly results. To put his views into modern terms, he nowhere says that different species can have a common ancestor , or that one kind can change into another , or that kinds can become extinct . Aristotle did not do experiments in the modern sense. He used the ancient Greek term pepeiramenoi to mean observations, or at most investigative procedures like dissection. In Generation of Animals , he finds
1608-510: A 2006 survey that show currently some 20% of the U.S. population believe that the Sun goes around the Earth (geocentricism) rather than the Earth goes around the Sun (heliocentricism), while a further 9% claimed not to know. Polls conducted by Gallup in the 1990s found that 16% of Germans, 18% of Americans and 19% of Britons hold that the Sun revolves around the Earth. A study conducted in 2005 by Jon D. Miller of Northwestern University , an expert in
1809-482: A Ptolemaic cosmology, the Venus epicycle can be neither completely inside nor completely outside of the orbit of the Sun. As a result, Ptolemaics abandoned the idea that the epicycle of Venus was completely inside the Sun, and later 17th-century competition between astronomical cosmologies focused on variations of Tycho Brahe 's Tychonic system (in which the Earth was still at the center of the universe, and around it revolved
2010-411: A belief held by some of his contemporaries "that the motion we see is due to the Earth's movement and not to that of the sky." The prevalence of this view is further confirmed by a reference from the 13th century which states: According to the geometers [or engineers] ( muhandisīn ), the Earth is in constant circular motion, and what appears to be the motion of the heavens is actually due to the motion of
2211-409: A breakthrough in scientific thought, using the newly developed mathematical discipline of differential calculus , finally replacing the previous schools of scientific thought, which had been dominated by Aristotle and Ptolemy. However, the process was gradual. Several empirical tests of Newton's theory, explaining the longer period of oscillation of a pendulum at the equator and the differing size of
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#17328525642122412-559: A broad range of subjects spanning the natural sciences , philosophy , linguistics , economics , politics , psychology , and the arts . As the founder of the Peripatetic school of philosophy in the Lyceum in Athens , he began the wider Aristotelian tradition that followed, which set the groundwork for the development of modern science . Little is known about Aristotle's life. He was born in
2613-495: A building known as the Lyceum (named after the sacred grove of Apollo Lykeios ), in which he established his own school. The building included a gymnasium and a colonnade ( peripatos ), from which the school acquired the name Peripatetic . Aristotle conducted courses and research at the school for the next twelve years. He often lectured small groups of distinguished students and, along with some of them, such as Theophrastus , Eudemus , and Aristoxenus , Aristotle built
2814-481: A center of the Solar System with equal validity. Relativity agrees with Newtonian predictions that regardless of whether the Sun or the Earth are chosen arbitrarily as the center of the coordinate system describing the Solar System, the paths of the planets form (roughly) ellipses with respect to the Sun, not the Earth. With respect to the average reference frame of the fixed stars , the planets do indeed move around
3015-461: A degree of latitude, would gradually become available between 1673 and 1738. In addition, stellar aberration was observed by Robert Hooke in 1674, and tested in a series of observations by Jean Picard over a period of ten years, finishing in 1680. However, it was not explained until 1729, when James Bradley provided an approximate explanation in terms of the Earth's revolution about the Sun. In 1838, astronomer Friedrich Wilhelm Bessel measured
3216-480: A different element by heat or moisture. Atmospheric explanations for many phenomena were preferred because the Eudoxan–Aristotelian model based on perfectly concentric spheres was not intended to explain changes in the brightness of the planets due to a change in distance. Eventually, perfectly concentric spheres were abandoned as it was impossible to develop a sufficiently accurate model under that ideal, with
3417-438: A fertilized hen's egg of a suitable stage and opens it to see the embryo's heart beating inside. Instead, he practiced a different style of science: systematically gathering data, discovering patterns common to whole groups of animals, and inferring possible causal explanations from these. This style is common in modern biology when large amounts of data become available in a new field, such as genomics . It does not result in
3618-510: A few milliseconds to thousands of seconds before fading away. Only 10% of gamma-ray sources are non-transient sources. These steady gamma-ray emitters include pulsars, neutron stars , and black hole candidates such as active galactic nuclei. In addition to electromagnetic radiation, a few other events originating from great distances may be observed from the Earth. In neutrino astronomy , astronomers use heavily shielded underground facilities such as SAGE , GALLEX , and Kamioka II/III for
3819-569: A few salient points. Aristotle was born in 384 BC in Stagira , Chalcidice , about 55 km (34 miles) east of modern-day Thessaloniki . He was the son of Nicomachus , the personal physician of King Amyntas of Macedon , and Phaestis, a woman with origins from Chalcis , Euboea . Nicomachus was said to have belonged to the medical guild of Asclepiadae and was likely responsible for Aristotle's early interest in biology and medicine. Ancient tradition held that Aristotle's family descended from
4020-497: A fluid such as air. In this system, heavy bodies in steady fall indeed travel faster than light ones (whether friction is ignored, or not ), and they do fall more slowly in a denser medium. Newton's "forced" motion corresponds to Aristotle's "violent" motion with its external agent, but Aristotle's assumption that the agent's effect stops immediately it stops acting (e.g., the ball leaves the thrower's hand) has awkward consequences: he has to suppose that surrounding fluid helps to push
4221-406: A form of an apple. In this distinction, there is a particular apple and a universal form of an apple. Moreover, one can place an apple next to a book, so that one can speak of both the book and apple as being next to each other. Plato argued that there are some universal forms that are not a part of particular things. For example, it is possible that there is no particular good in existence, but "good"
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#17328525642124422-550: A large library which included manuscripts, maps, and museum objects. While in Athens, his wife Pythias died and Aristotle became involved with Herpyllis of Stagira. They had a son whom Aristotle named after his father, Nicomachus . This period in Athens, between 335 and 323 BC, is when Aristotle is believed to have composed many of his philosophical works. He wrote many dialogues, of which only fragments have survived. Those works that have survived are in treatise form and were not, for
4623-528: A line running from the Earth through the Sun, such as placing the center of the Venus epicycle near the Sun. In this case, if the Sun is the source of all the light, under the Ptolemaic system: If Venus is between Earth and the Sun, the phase of Venus must always be crescent or all dark. If Venus is beyond the Sun, the phase of Venus must always be gibbous or full. But Galileo saw Venus at first small and full, and later large and crescent. This showed that with
4824-597: A linear scale, and noted various exceptions, such as that sharks had a placenta like the tetrapods. To a modern biologist, the explanation, not available to Aristotle, is convergent evolution . Philosophers of science have generally concluded that Aristotle was not interested in taxonomy, but zoologists who studied this question in the early 21st century think otherwise. He believed that purposive final causes guided all natural processes; this teleological view justified his observed data as an expression of formal design. Aristotle's psychology , given in his treatise On
5025-400: A long time the geocentric postulate produced more accurate results. Additionally some felt that a new, unknown theory could not subvert an accepted consensus for geocentrism. The geocentric model entered Greek astronomy and philosophy at an early point; it can be found in pre-Socratic philosophy . In the 6th century BC, Anaximander proposed a cosmology with Earth shaped like a section of
5226-552: A model allows astronomers to select between several alternative or conflicting models. Theorists also modify existing models to take into account new observations. In some cases, a large amount of observational data that is inconsistent with a model may lead to abandoning it largely or completely, as for geocentric theory , the existence of luminiferous aether , and the steady-state model of cosmic evolution. Phenomena modeled by theoretical astronomers include: Modern theoretical astronomy reflects dramatic advances in observation since
5427-474: A new model was required. The Ptolemaic order of spheres from Earth outward is: Ptolemy did not invent or work out this order, which aligns with the ancient Seven Heavens religious cosmology common to the major Eurasian religious traditions. It also follows the decreasing orbital periods of the Moon, Sun, planets and stars. Muslim astronomers generally accepted the Ptolemaic system and the geocentric model, but by
5628-661: A number of important astronomers. Richard of Wallingford (1292–1336) made major contributions to astronomy and horology , including the invention of the first astronomical clock, the Rectangulus which allowed for the measurement of angles between planets and other astronomical bodies, as well as an equatorium called the Albion which could be used for astronomical calculations such as lunar , solar and planetary longitudes and could predict eclipses . Nicole Oresme (1320–1382) and Jean Buridan (1300–1361) first discussed evidence for
5829-450: A pillar (a cylinder), held aloft at the center of everything. The Sun, Moon, and planets were holes in invisible wheels surrounding Earth; through the holes, humans could see concealed fire. About the same time, Pythagoras thought that the Earth was a sphere (in accordance with observations of eclipses), but not at the center; he believed that it was in motion around an unseen fire. Later these views were combined, so most educated Greeks from
6030-427: A plant in the soil is potentially ( dynamei ) a plant, and if it is not prevented by something, it will become a plant. Potentially, beings can either 'act' ( poiein ) or 'be acted upon' ( paschein ), which can be either innate or learned. For example, the eyes possess the potentiality of sight (innate – being acted upon), while the capability of playing the flute can be possessed by learning (exercise – acting). Actuality
6231-498: A priori principles. Aristotle's "natural philosophy" spans a wide range of natural phenomena including those now covered by physics, biology and other natural sciences. In Aristotle's terminology, "natural philosophy" is a branch of philosophy examining the phenomena of the natural world, and includes fields that would be regarded today as physics, biology and other natural sciences. Aristotle's work encompassed virtually all facets of intellectual inquiry. Aristotle makes philosophy in
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6432-433: A problem which geocentrists could not easily overcome. In 1687, Isaac Newton stated the law of universal gravitation , described earlier as a hypothesis by Robert Hooke and others. His main achievement was to mathematically derive Kepler's laws of planetary motion from the law of gravitation, thus helping to prove the latter. This introduced gravitation as the force which both kept the Earth and planets moving through
6633-401: A real relativistic physics valid in all CS; a physics in which there would be no place for absolute, but only for relative, motion? This is indeed possible!" Despite giving more respectability to the geocentric view than Newtonian physics does, relativity is not geocentric. Rather, relativity states that the Sun, the Earth, the Moon, Jupiter, or any other point for that matter could be chosen as
6834-515: A repeating cycle known as a saros . Following the Babylonians, significant advances in astronomy were made in ancient Greece and the Hellenistic world. Greek astronomy is characterized from the start by seeking a rational, physical explanation for celestial phenomena. In the 3rd century BC, Aristarchus of Samos estimated the size and distance of the Moon and Sun , and he proposed a model of
7035-562: A researcher and lecturer, earning for himself the nickname "mind of the school" by his tutor Plato . In Athens, he probably experienced the Eleusinian Mysteries as he wrote when describing the sights one viewed at the Mysteries, "to experience is to learn" ( παθεĩν μαθεĩν ). Aristotle remained in Athens for nearly twenty years before leaving in 348/47 BC after Plato's death. The traditional story about his departure records that he
7236-625: A significant impact across the world, and remain a subject of contemporary philosophical discussion. Aristotle's views profoundly shaped medieval scholarship . The influence of his physical science extended from late antiquity and the Early Middle Ages into the Renaissance , and was not replaced systematically until the Enlightenment and theories such as classical mechanics were developed. He influenced Judeo-Islamic philosophies during
7437-608: A substantial amount of work in the realms of theoretical and observational physics. Some areas of study for astrophysicists include their attempts to determine the properties of dark matter , dark energy , and black holes ; whether or not time travel is possible, wormholes can form, or the multiverse exists; and the origin and ultimate fate of the universe . Topics also studied by theoretical astrophysicists include Solar System formation and evolution ; stellar dynamics and evolution ; galaxy formation and evolution ; magnetohydrodynamics ; large-scale structure of matter in
7638-549: A thrown stone, in the Physics (254b10), and "natural motion", such as of a falling object, in On the Heavens (300a20). In violent motion, as soon as the agent stops causing it, the motion stops also: in other words, the natural state of an object is to be at rest, since Aristotle does not address friction . With this understanding, it can be observed that, as Aristotle stated, heavy objects (on
7839-427: Is visible light , or more generally electromagnetic radiation . Observational astronomy may be categorized according to the corresponding region of the electromagnetic spectrum on which the observations are made. Some parts of the spectrum can be observed from the Earth's surface, while other parts are only observable from either high altitudes or outside the Earth's atmosphere. Specific information on these subfields
8040-580: Is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky . These include the Egyptians , Babylonians , Greeks , Indians , Chinese , Maya , and many ancient indigenous peoples of the Americas . In the past, astronomy included disciplines as diverse as astrometry , celestial navigation , observational astronomy , and
8241-454: Is a historical accident: his works on botany have been lost, but two books on plants by his pupil Theophrastus have survived. Aristotle reports on the sea-life visible from observation on Lesbos and the catches of fishermen. He describes the catfish , electric ray , and frogfish in detail, as well as cephalopods such as the octopus and paper nautilus . His description of the hectocotyl arm of cephalopods, used in sexual reproduction,
Geocentric model - Misplaced Pages Continue
8442-584: Is absorbed by the Earth's atmosphere, requiring observations at these wavelengths to be performed from the upper atmosphere or from space. Ultraviolet astronomy is best suited to the study of thermal radiation and spectral emission lines from hot blue stars ( OB stars ) that are very bright in this wave band. This includes the blue stars in other galaxies, which have been the targets of several ultraviolet surveys. Other objects commonly observed in ultraviolet light include planetary nebulae , supernova remnants , and active galactic nuclei. However, as ultraviolet light
8643-419: Is also a final cause or end. Then Aristotle proceeds and concludes that the actuality is prior to potentiality in formula, in time and in substantiality. With this definition of the particular substance (i.e., matter and form), Aristotle tries to solve the problem of the unity of the beings, for example, "what is it that makes a man one"? Since, according to Plato there are two Ideas: animal and biped, how then
8844-591: Is also believed that the ruins at Great Zimbabwe and Timbuktu may have housed astronomical observatories. In Post-classical West Africa , Astronomers studied the movement of stars and relation to seasons, crafting charts of the heavens as well as precise diagrams of orbits of the other planets based on complex mathematical calculations. Songhai historian Mahmud Kati documented a meteor shower in August 1583. Europeans had previously believed that there had been no astronomical observation in sub-Saharan Africa during
9045-583: Is an inseparable part of the discipline of astrobiology. Astrobiology concerns itself with interpretation of existing scientific data , and although speculation is entertained to give context, astrobiology concerns itself primarily with hypotheses that fit firmly into existing scientific theories . This interdisciplinary field encompasses research on the origin of planetary systems , origins of organic compounds in space , rock-water-carbon interactions, abiogenesis on Earth, planetary habitability , research on biosignatures for life detection, and studies on
9246-477: Is contrary to these Scriptures of ours, that is to Catholic faith, we must either prove it as well as we can to be entirely false, or at all events we must, without the smallest hesitation, believe it to be so." To understand how just is the rule here formulated we must remember, first, that the sacred writers, or to speak more accurately, the Holy Ghost "Who spoke by them, did not intend to teach men these things (that
9447-432: Is due to any loss of light caused by its phases being compensated for by an increase in apparent size caused by its varying distance from Earth.) Objectors to heliocentrism noted that terrestrial bodies naturally tend to come to rest as near as possible to the center of the Earth. Further, barring the opportunity to fall closer the center, terrestrial bodies tend not to move unless forced by an outside object, or transformed to
9648-427: Is easily absorbed by interstellar dust , an adjustment of ultraviolet measurements is necessary. X-ray astronomy uses X-ray wavelengths . Typically, X-ray radiation is produced by synchrotron emission (the result of electrons orbiting magnetic field lines), thermal emission from thin gases above 10 (10 million) kelvins , and thermal emission from thick gases above 10 Kelvin. Since X-rays are absorbed by
9849-414: Is founded on the detection and analysis of infrared radiation, wavelengths longer than red light and outside the range of our vision. The infrared spectrum is useful for studying objects that are too cold to radiate visible light, such as planets, circumstellar disks or nebulae whose light is blocked by dust. The longer wavelengths of infrared can penetrate clouds of dust that block visible light, allowing
10050-403: Is from these clouds that solar systems form. Studies in this field contribute to the understanding of the formation of the Solar System , Earth's origin and geology, abiogenesis , and the origin of climate and oceans. Astrobiology is an interdisciplinary scientific field concerned with the origins , early evolution , distribution, and future of life in the universe . Astrobiology considers
10251-416: Is given below. Radio astronomy uses radiation with wavelengths greater than approximately one millimeter, outside the visible range. Radio astronomy is different from most other forms of observational astronomy in that the observed radio waves can be treated as waves rather than as discrete photons . Hence, it is relatively easier to measure both the amplitude and phase of radio waves, whereas this
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#173285256421210452-541: Is man a unity? However, according to Aristotle, the potential being (matter) and the actual one (form) are one and the same. Aristotle's immanent realism means his epistemology is based on the study of things that exist or happen in the world, and rises to knowledge of the universal, whereas for Plato epistemology begins with knowledge of universal Forms (or ideas) and descends to knowledge of particular imitations of these. Aristotle uses induction from examples alongside deduction , whereas Plato relies on deduction from
10653-645: Is not as easily done at shorter wavelengths. Although some radio waves are emitted directly by astronomical objects, a product of thermal emission , most of the radio emission that is observed is the result of synchrotron radiation , which is produced when electrons orbit magnetic fields . Additionally, a number of spectral lines produced by interstellar gas , notably the hydrogen spectral line at 21 cm, are observable at radio wavelengths. A wide variety of other objects are observable at radio wavelengths, including supernovae , interstellar gas, pulsars , and active galactic nuclei . Infrared astronomy
10854-471: Is one of the few sciences in which amateurs play an active role . This is especially true for the discovery and observation of transient events . Amateur astronomers have helped with many important discoveries, such as finding new comets. Astronomy (from the Greek ἀστρονομία from ἄστρον astron , "star" and -νομία -nomia from νόμος nomos , "law" or "culture") means "law of the stars" (or "culture of
11055-406: Is predicated. So, according to Aristotle, the form of apple exists within each apple, rather than in the world of the forms. Concerning the nature of change ( kinesis ) and its causes, as he outlines in his Physics and On Generation and Corruption ( 319b–320a), he distinguishes coming-to-be ( genesis , also translated as 'generation') from: Coming-to-be is a change where the substrate of
11256-497: Is probably not in its original form, because it was most likely edited by students and later lecturers. The logical works of Aristotle were compiled into a set of six books called the Organon around 40 BC by Andronicus of Rhodes or others among his followers. The books are: The order of the books (or the teachings from which they are composed) is not certain, but this list was derived from analysis of Aristotle's writings. It goes from
11457-407: Is so high because several spheres are needed for each planet.) These spheres, known as crystalline spheres, all moved at different uniform speeds to create the revolution of bodies around the Earth. They were composed of an incorruptible substance called aether . Aristotle believed that the Moon was in the innermost sphere and therefore touches the realm of Earth, causing the dark spots ( maculae ) and
11658-480: Is still a proper universal form. Aristotle disagreed with Plato on this point, arguing that all universals are instantiated at some period of time, and that there are no universals that are unattached to existing things. In addition, Aristotle disagreed with Plato about the location of universals. Where Plato spoke of the forms as existing separately from the things that participate in them, Aristotle maintained that universals exist within each thing on which each universal
11859-431: Is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the astronomical objects , rather than their positions or motions in space". Among the objects studied are the Sun , other stars , galaxies , extrasolar planets , the interstellar medium and the cosmic microwave background . Their emissions are examined across all parts of the electromagnetic spectrum , and
12060-413: Is the fulfilment of the end of the potentiality. Because the end ( telos ) is the principle of every change, and potentiality exists for the sake of the end, actuality, accordingly, is the end. Referring then to the previous example, it can be said that an actuality is when a plant does one of the activities that plants do. For that for the sake of which ( to hou heneka ) a thing is, is its principle, and
12261-453: Is the measurement of the positions of celestial objects. Historically, accurate knowledge of the positions of the Sun, Moon, planets and stars has been essential in celestial navigation (the use of celestial objects to guide navigation) and in the making of calendars . Careful measurement of the positions of the planets has led to a solid understanding of gravitational perturbations , and an ability to determine past and future positions of
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#173285256421212462-471: Is to say, the essential nature of the things of the visible universe), things in no way profitable unto salvation." Hence they did not seek to penetrate the secrets of nature, but rather described and dealt with things in more or less figurative language, or in terms which were commonly used at the time, and which in many instances are in daily use at this day, even by the most eminent men of science. Ordinary speech primarily and properly describes what comes under
12663-539: The Iliad , which reportedly became one of Alexander's most prized possessions. Scholars speculate that two of Aristotle's now lost works, On kingship and On behalf of the Colonies , were composed by the philosopher for the young prince. After Philip II's assassination in 336 BC, Aristotle returned to Athens for the second and final time a year later. As a metic , Aristotle could not own property in Athens and thus rented
12864-472: The Compton Gamma Ray Observatory or by specialized telescopes called atmospheric Cherenkov telescopes . The Cherenkov telescopes do not detect the gamma rays directly but instead detect the flashes of visible light produced when gamma rays are absorbed by the Earth's atmosphere. Most gamma-ray emitting sources are actually gamma-ray bursts , objects which only produce gamma radiation for
13065-634: The Early Modern period. John Philoponus (in Late antiquity ) and Galileo (in Early modern period ) are said to have shown by experiment that Aristotle's claim that a heavier object falls faster than a lighter object is incorrect. A contrary opinion is given by Carlo Rovelli , who argues that Aristotle's physics of motion is correct within its domain of validity, that of objects in the Earth 's gravitational field immersed in
13266-473: The Earth's atmosphere , all X-ray observations must be performed from high-altitude balloons , rockets , or X-ray astronomy satellites . Notable X-ray sources include X-ray binaries , pulsars , supernova remnants , elliptical galaxies , clusters of galaxies , and active galactic nuclei . Gamma ray astronomy observes astronomical objects at the shortest wavelengths of the electromagnetic spectrum. Gamma rays may be observed directly by satellites such as
13467-515: The Great Comet of 371 BC . Aristotle was one of the first people to record any geological observations. He stated that geological change was too slow to be observed in one person's lifetime. The geologist Charles Lyell noted that Aristotle described such change, including "lakes that had dried up" and "deserts that had become watered by rivers", giving as examples the growth of the Nile delta since
13668-471: The History of Animals in a graded scale of perfection, a nonreligious version of the scala naturae , with man at the top. His system had eleven grades of animal, from highest potential to lowest, expressed in their form at birth: the highest gave live birth to hot and wet creatures, the lowest laid cold, dry mineral-like eggs. Animals came above plants , and these in turn were above minerals. He grouped what
13869-524: The Islamic Golden Age . Two observations supported the idea that Earth was the center of the Universe. First, from anywhere on Earth, the Sun appears to revolve around Earth once per day . While the Moon and the planets have their own motions, they also appear to revolve around Earth about once per day. The stars appeared to be fixed on a celestial sphere rotating once each day about an axis through
14070-451: The Milky Way was made up of "those stars which are shaded by the earth from the sun's rays," pointing out partly correctly that if "the size of the sun is greater than that of the earth and the distance of the stars from the earth many times greater than that of the sun, then... the sun shines on all the stars and the earth screens none of them." He also wrote descriptions of comets, including
14271-838: The Milky Way , as its own group of stars was only proven in the 20th century, along with the existence of "external" galaxies. The observed recession of those galaxies led to the discovery of the expansion of the Universe . In 1919, when the Hooker Telescope was completed, the prevailing view was that the universe consisted entirely of the Milky Way Galaxy. Using the Hooker Telescope, Edwin Hubble identified Cepheid variables in several spiral nebulae and in 1922–1923 proved conclusively that Andromeda Nebula and Triangulum among others, were entire galaxies outside our own, thus proving that
14472-762: The Muslim world by the early 9th century. In 964, the Andromeda Galaxy , the largest galaxy in the Local Group , was described by the Persian Muslim astronomer Abd al-Rahman al-Sufi in his Book of Fixed Stars . The SN 1006 supernova , the brightest apparent magnitude stellar event in recorded history, was observed by the Egyptian Arabic astronomer Ali ibn Ridwan and Chinese astronomers in 1006. Iranian scholar Al-Biruni observed that, contrary to Ptolemy ,
14673-508: The Physics (215a25), Aristotle effectively states a quantitative law, that the speed, v, of a falling body is proportional (say, with constant c) to its weight, W, and inversely proportional to the density, ρ, of the fluid in which it is falling:; Aristotle implies that in a vacuum the speed of fall would become infinite, and concludes from this apparent absurdity that a vacuum is not possible. Opinions have varied on whether Aristotle intended to state quantitative laws. Henri Carteron held
14874-658: The Qur'anic verse, "All praise belongs to God, Lord of the Worlds," emphasizing the term "Worlds." The "Maragha Revolution" refers to the Maragha school's revolution against Ptolemaic astronomy. The "Maragha school" was an astronomical tradition beginning in the Maragha observatory and continuing with astronomers from the Damascus mosque and Samarkand observatory . Like their Andalusian predecessors,
15075-502: The Renaissance , Nicolaus Copernicus proposed a heliocentric model of the solar system. His work was defended by Galileo Galilei and expanded upon by Johannes Kepler . Kepler was the first to devise a system that correctly described the details of the motion of the planets around the Sun. However, Kepler did not succeed in formulating a theory behind the laws he wrote down. It was Isaac Newton , with his invention of celestial dynamics and his law of gravitation , who finally explained
15276-555: The Solar System where the Earth and planets rotated around the Sun, now called the heliocentric model. In the 2nd century BC, Hipparchus discovered precession , calculated the size and distance of the Moon and invented the earliest known astronomical devices such as the astrolabe . Hipparchus also created a comprehensive catalog of 1020 stars, and most of the constellations of the northern hemisphere derive from Greek astronomy. The Antikythera mechanism ( c. 150 –80 BC)
15477-590: The United States between 1870 and 1920, for example, various members of the Lutheran Church–Missouri Synod published articles disparaging Copernican astronomy and promoting geocentrism. However, in the 1902 Theological Quarterly , A. L. Graebner observed that the synod had no doctrinal position on geocentrism, heliocentrism, or any scientific model, unless it were to contradict Scripture. He stated that any possible declarations of geocentrists within
15678-407: The aether of the higher spheres. Galileo could also see the moons of Jupiter, which he dedicated to Cosimo II de' Medici , and stated that they orbited around Jupiter, not Earth. This was a significant claim as it would mean not only that not everything revolved around Earth as stated in the Ptolemaic model, but also showed a secondary celestial body could orbit a moving celestial body, strengthening
15879-481: The geocentric model . Ptolemy argued that the Earth was a sphere in the center of the universe, from the simple observation that half the stars were above the horizon and half were below the horizon at any time (stars on rotating stellar sphere), and the assumption that the stars were all at some modest distance from the center of the universe. If the Earth were substantially displaced from the center, this division into visible and invisible stars would not be equal. In
16080-531: The geographic poles of Earth. Second, Earth seems to be unmoving from the perspective of an earthbound observer; it feels solid, stable, and stationary. Ancient Greek , ancient Roman , and medieval philosophers usually combined the geocentric model with a spherical Earth , in contrast to the older flat-Earth model implied in some mythology . However, the Greek astronomer and mathematician Aristarchus of Samos ( c. 310 – c. 230 BC ) developed
16281-427: The interstellar medium . The study of the abundance of elements and isotope ratios in Solar System objects, such as meteorites , is also called cosmochemistry , while the study of interstellar atoms and molecules and their interaction with radiation is sometimes called molecular astrophysics. The formation, atomic and chemical composition, evolution and fate of molecular gas clouds is of special interest, because it
16482-471: The parallax of the star 61 Cygni successfully, and disproved Ptolemy's claim that parallax motion did not exist. This finally confirmed the assumptions made by Copernicus, providing accurate, dependable scientific observations, and conclusively displaying how distant stars are from Earth. A geocentric frame is useful for many everyday activities and most laboratory experiments, but is a less appropriate choice for Solar System mechanics and space travel. While
16683-513: The "extreme view" that Aristotle's concept of force was basically qualitative, but other authors reject this. Archimedes corrected Aristotle's theory that bodies move towards their natural resting places; metal boats can float if they displace enough water ; floating depends in Archimedes' scheme on the mass and volume of the object, not, as Aristotle thought, its elementary composition. Aristotle's writings on motion remained influential until
16884-412: The 10th century texts appeared regularly whose subject matter was doubts concerning Ptolemy ( shukūk ). Several Muslim scholars questioned the Earth's apparent immobility and centrality within the universe. Some Muslim astronomers believed that the Earth rotates around its axis , such as Abu Sa'id al-Sijzi (d. circa 1020). According to al-Biruni , Sijzi invented an astrolabe called al-zūraqī based on
17085-442: The 1990s, including studies of the cosmic microwave background , distant supernovae and galaxy redshifts , which have led to the development of a standard model of cosmology . This model requires the universe to contain large amounts of dark matter and dark energy whose nature is currently not well understood, but the model gives detailed predictions that are in excellent agreement with many diverse observations. Astrophysics
17286-449: The 2nd century AD, finally standardised geocentrism. His main astronomical work, the Almagest , was the culmination of centuries of work by Hellenic , Hellenistic and Babylonian astronomers. For over a millennium, European and Islamic astronomers assumed it was the correct cosmological model. Because of its influence, people sometimes wrongly think the Ptolemaic system is identical with
17487-431: The 2nd century CE, served as the basis for preparing astrological and astronomical charts for over 1,500 years. The geocentric model held sway into the early modern age, but from the late 16th century onward, it was gradually superseded by the heliocentric model of Copernicus (1473–1543), Galileo (1564–1642), and Kepler (1571–1630). There was much resistance to the transition between these two theories, since for
17688-409: The 4th century BC onwards thought that the Earth was a sphere at the center of the universe. In the 4th century BC, two influential Greek philosophers, Plato and his student Aristotle , wrote works based on the geocentric model. According to Plato, the Earth was a sphere, stationary at the center of the universe. The stars and planets were carried around the Earth on spheres or circles , arranged in
17889-530: The Earth about its axis. For example, in Joshua 10:12 , the Sun and Moon are said to stop in the sky, and in Psalms the world is described as immobile. Psalms 93:1 says in part, "the world is established, firm and secure". Contemporary advocates for such religious beliefs include Robert Sungenis (author of the 2006 book Galileo Was Wrong and the 2014 pseudo-documentary film The Principle ). These people subscribe to
18090-473: The Earth and not the stars. Early in the 11th century Alhazen wrote a scathing critique of Ptolemy 's model in his Doubts on Ptolemy ( c. 1028 ), which some have interpreted to imply he was criticizing Ptolemy's geocentrism, but most agree that he was actually criticizing the details of Ptolemy's model rather than his geocentrism. In the 12th century, Arzachel departed from the ancient Greek idea of uniform circular motions by hypothesizing that
18291-447: The Earth at different points in its orbit, and explained the observation that planets slowed down, stopped, and moved backward in retrograde motion , and then again reversed to resume normal, or prograde, motion. The deferent-and-epicycle model had been used by Greek astronomers for centuries along with the idea of the eccentric (a deferent whose center is slightly away from the Earth), which
18492-409: The Earth away from the center of rotation of the rest of the universe. Another sphere, the epicycle, is embedded inside the deferent sphere and is represented by the smaller dotted line to the right. A given planet then moves around the epicycle at the same time the epicycle moves along the path marked by the deferent. These combined movements cause the given planet to move closer to and further away from
18693-403: The Earth's atmosphere and of their physical and chemical properties", while "astrophysics" refers to the branch of astronomy dealing with "the behavior, physical properties, and dynamic processes of celestial objects and phenomena". In some cases, as in the introduction of the introductory textbook The Physical Universe by Frank Shu , "astronomy" may be used to describe the qualitative study of
18894-403: The Earth's radius away from the centre of the Earth (thus closer to the surface than the center). What the principle of relativity points out is that correct mathematical calculations can be made regardless of the reference frame chosen, and these will all agree with each other as to the predictions of actual motions of bodies with respect to each other. It is not necessary to choose the object in
19095-501: The Earth. By using an equant, Ptolemy claimed to keep motion which was uniform and circular, although it departed from the Platonic ideal of uniform circular motion . The resultant system, which eventually came to be widely accepted in the west, seems unwieldy to modern astronomers; each planet required an epicycle revolving on a deferent, offset by an equant which was different for each planet. It predicted various celestial motions, including
19296-504: The Great beginning in 343 BC. He established a library in the Lyceum, which helped him to produce many of his hundreds of books on papyrus scrolls . Though Aristotle wrote many treatises and dialogues for publication, only around a third of his original output has survived , none of it intended for publication. Aristotle provided a complex synthesis of the various philosophies existing prior to him. His teachings and methods of inquiry have had
19497-550: The Lyceum of Athens, Alexandria , and later in Rome . With the Prior Analytics , Aristotle is credited with the earliest study of formal logic, and his conception of it was the dominant form of Western logic until 19th-century advances in mathematical logic . Kant stated in the Critique of Pure Reason that with Aristotle, logic reached its completion. Most of Aristotle's work
19698-440: The Maragha astronomers attempted to solve the equant problem (the circle around whose circumference a planet or the center of an epicycle was conceived to move uniformly) and produce alternative configurations to the Ptolemaic model without abandoning geocentrism. They were more successful than their Andalusian predecessors in producing non-Ptolemaic configurations which eliminated the equant and eccentrics, were more accurate than
19899-458: The Maragha school never made the paradigm shift to heliocentrism. The influence of the Maragha school on Copernicus remains speculative, since there is no documentary evidence to prove it. The possibility that Copernicus independently developed the Tusi couple remains open, since no researcher has yet demonstrated that he knew about Tusi's work or that of the Maragha school. Not all Greeks agreed with
20100-621: The Middle Ages, as well as Christian theology , especially the Neoplatonism of the Early Church and the scholastic tradition of the Catholic Church . Aristotle was revered among medieval Muslim scholars as "The First Teacher", and among medieval Christians like Thomas Aquinas as simply "The Philosopher", while the poet Dante called him "the master of those who know". His works contain
20301-477: The Ptolemaic model in numerically predicting planetary positions, and were in better agreement with empirical observations. The most important of the Maragha astronomers included Mo'ayyeduddin Urdi (died 1266), Nasīr al-Dīn al-Tūsī (1201–1274), Qutb al-Din al-Shirazi (1236–1311), Ibn al-Shatir (1304–1375), Ali Qushji ( c. 1474 ), Al-Birjandi (died 1525), and Shams al-Din al-Khafri (died 1550). However,
20502-442: The Ptolemaic system, each planet is moved by a system of two spheres: one called its deferent; the other, its epicycle . The deferent is a circle whose center point, called the eccentric and marked in the diagram with an X, is distant from the Earth. The original purpose of the eccentric was to account for the difference in length of the seasons (northern autumn was about five days shorter than spring during this time period) by placing
20703-468: The Solar System with the largest gravitational field as the center of the coordinate system in order to predict the motions of planetary bodies, though doing so may make calculations easier to perform or interpret. A geocentric coordinate system can be more convenient when dealing only with bodies mostly influenced by the gravity of the Earth (such as artificial satellites and the Moon ), or when calculating what
20904-522: The Sun's apogee (highest point in the heavens) was mobile, not fixed. Some of the prominent Islamic (mostly Persian and Arab) astronomers who made significant contributions to the science include Al-Battani , Thebit , Abd al-Rahman al-Sufi , Biruni , Abū Ishāq Ibrāhīm al-Zarqālī , Al-Birjandi , and the astronomers of the Maragheh and Samarkand observatories. Astronomers during that time introduced many Arabic names now used for individual stars . It
21105-460: The Sun) is very noticeable even with low eccentricities as possessed by the planets. To summarize, Ptolemy conceived a system that was compatible with Aristotelian philosophy and succeeded in tracking actual observations and predicting future movement mostly to within the limits of the next 1000 years of observations. The observed motions and his mechanisms for explaining them include: The geocentric model
21306-462: The Sun, but all other planets revolved around the Sun in one massive set of epicycles), or variations on the Copernican system. Johannes Kepler analysed Tycho Brahe 's famously accurate observations and afterwards constructed his three laws in 1609 and 1619, based on a heliocentric view where the planets move in elliptical paths. Using these laws, he was the first astronomer to successfully predict
21507-472: The Sun, the Moon and the stars rotating around it. This is known as the geocentric model of the Universe, or the Ptolemaic system , named after Ptolemy . A particularly important early development was the beginning of mathematical and scientific astronomy, which began among the Babylonians , who laid the foundations for the later astronomical traditions that developed in many other civilizations. The Babylonians discovered that lunar eclipses recurred in
21708-438: The Sun, which due to its much larger mass, moves far less than its own diameter and the gravity of which is dominant in determining the orbits of the planets (in other words, the center of mass of the Solar System is near the center of the Sun). The Earth and Moon are much closer to being a binary planet ; the center of mass around which they both rotate is still inside the Earth, but is about 4,624 km (2,873 miles) or 72.6% of
21909-402: The ability to go through lunar phases . He further described his system by explaining the natural tendencies of the terrestrial elements: earth, water, fire, air, as well as celestial aether. His system held that earth was the heaviest element, with the strongest movement towards the center, thus water formed a layer surrounding the sphere of Earth. The tendency of air and fire, on the other hand,
22110-521: The age of the Universe and size of the Observable Universe. Theoretical astronomy led to speculations on the existence of objects such as black holes and neutron stars , which have been used to explain such observed phenomena as quasars , pulsars , blazars , and radio galaxies . Physical cosmology made huge advances during the 20th century. In the early 1900s the model of the Big Bang theory
22311-486: The atmosphere itself produces significant infrared emission. Consequently, infrared observatories have to be located in high, dry places on Earth or in space. Some molecules radiate strongly in the infrared. This allows the study of the chemistry of space; more specifically it can detect water in comets. Historically, optical astronomy, which has been also called visible light astronomy, is the oldest form of astronomy. Images of observations were originally drawn by hand. In
22512-489: The ball along to make it continue to rise even though the hand is no longer acting on it, resulting in the Medieval theory of impetus . Aristotle suggested that the reason for anything coming about can be attributed to four different types of simultaneously active factors. His term aitia is traditionally translated as "cause", but it does not always refer to temporal sequence; it might be better translated as "explanation", but
22713-617: The basics, the analysis of simple terms in the Categories, the analysis of propositions and their elementary relations in On Interpretation , to the study of more complex forms, namely, syllogisms (in the Analytics ) and dialectics (in the Topics and Sophistical Refutations ). The first three treatises form the core of the logical theory stricto sensu : the grammar of the language of logic and
22914-399: The becoming is for the sake of the end; and the actuality is the end, and it is for the sake of this that the potentiality is acquired. For animals do not see in order that they may have sight, but they have sight that they may see. In summary, the matter used to make a house has potentiality to be a house and both the activity of building and the form of the final house are actualities, which
23115-409: The beginning and end of retrograde motion, to within a maximum error of 10 degrees, considerably better than without the equant. The model with epicycles is in fact a very good model of an elliptical orbit with low eccentricity. The well-known ellipse shape does not appear to a noticeable extent when the eccentricity is less than 5%, but the offset distance of the "center" (in fact the focus occupied by
23316-574: The broad sense coextensive with reasoning, which he also would describe as "science". However, his use of the term science carries a different meaning than that covered by the term "scientific method". For Aristotle, "all science ( dianoia ) is either practical, poetical or theoretical" ( Metaphysics 1025b25). His practical science includes ethics and politics; his poetical science means the study of fine arts including poetry; his theoretical science covers physics, mathematics and metaphysics. In his On Generation and Corruption , Aristotle related each of
23517-433: The cause of earthquakes was a gas or vapor ( anathymiaseis ) that was trapped inside the earth and trying to escape, following other Greek authors Anaxagoras , Empedocles and Democritus . Aristotle also made many observations about the hydrologic cycle. For example, he made some of the earliest observations about desalination: he observed early – and correctly – that when seawater is heated, freshwater evaporates and that
23718-430: The center of the universe, while the Earth and other planets revolved around it. His theory was not popular, and he had one named follower, Seleucus of Seleucia . Epicurus was the most radical. He correctly realized in the 4th century BC that the universe does not have any single center. This theory was widely accepted by the later Epicureans and was notably defended by Lucretius in his poem De rerum natura . In 1543,
23919-486: The city of Stagira in northern Greece during the Classical period . His father, Nicomachus , died when Aristotle was a child, and he was brought up by a guardian. At around eighteen years old, he joined Plato 's Academy in Athens and remained there until the age of thirty seven ( c. 347 BC ). Shortly after Plato died, Aristotle left Athens and, at the request of Philip II of Macedon , tutored his son Alexander
24120-487: The correct rules of reasoning. The Rhetoric is not conventionally included, but it states that it relies on the Topics . What is today called Aristotelian logic with its types of syllogism (methods of logical argument), Aristotle himself would have labelled "analytics". The term "logic" he reserved to mean dialectics . The word "metaphysics" appears to have been coined by the first century AD editor who assembled various small selections of Aristotle's works to create
24321-399: The data to come to the theory of evolution . Aristotle's writings can seem to modern readers close to implying evolution, but while Aristotle was aware that new mutations or hybridizations could occur, he saw these as rare accidents. For Aristotle, accidents, like heat waves in winter, must be considered distinct from natural causes. He was thus critical of Empedocles's materialist theory of
24522-787: The death. Following Alexander's death, anti-Macedonian sentiment in Athens was rekindled. In 322 BC, Demophilus and Eurymedon the Hierophant reportedly denounced Aristotle for impiety, prompting him to flee to his mother's family estate in Chalcis, Euboea , at which occasion he was said to have stated "I will not allow the Athenians to sin twice against philosophy" – a reference to Athens's trial and execution of Socrates . He died in Chalcis, Euboea of natural causes later that same year, having named his student Antipater as his chief executor and leaving
24723-408: The department is historically affiliated with a physics department, and many professional astronomers have physics rather than astronomy degrees. Some titles of the leading scientific journals in this field include The Astronomical Journal , The Astrophysical Journal , and Astronomy & Astrophysics . In early historic times, astronomy only consisted of the observation and predictions of
24924-474: The detection of neutrinos . The vast majority of the neutrinos streaming through the Earth originate from the Sun , but 24 neutrinos were also detected from supernova 1987A . Cosmic rays , which consist of very high energy particles (atomic nuclei) that can decay or be absorbed when they enter the Earth's atmosphere, result in a cascade of secondary particles which can be detected by current observatories. Some future neutrino detectors may also be sensitive to
25125-479: The earliest known formal study of logic, and were studied by medieval scholars such as Peter Abelard and Jean Buridan . Aristotle's influence on logic continued well into the 19th century. In addition, his ethics , although always influential, gained renewed interest with the modern advent of virtue ethics . In general, the details of Aristotle's life are not well-established. The biographies written in ancient times are often speculative and historians only agree on
25326-543: The end of his life, the two men became estranged having diverging opinions over issues, like the optimal administration of city-states, the treatment of conquered populations, such as the Persians, and philosophical questions, like the definition of braveness. A widespread speculation in antiquity suggested that Aristotle played a role in Alexander's death, but the only evidence of this is an unlikely claim made some six years after
25527-475: The equants instead of the epicycles because the former was easier to calculate, and gave the same result. It has been determined that the Copernican, Ptolemaic and even the Tychonic models provide identical results to identical inputs: they are computationally equivalent. It was not until Kepler demonstrated a physical observation that could show that the physical Sun is directly involved in determining an orbit that
25728-501: The fixed stars due to stellar parallax . Thus if the Earth was moving, the shapes of the constellations should change considerably over the course of a year. As they did not appear to move, either the stars are much farther away than the Sun and the planets than previously conceived, making their motion undetectable, or the Earth is not moving at all. Because the stars are actually much further away than Greek astronomers postulated (making angular movement extremely small), stellar parallax
25929-533: The following. Brood size decreases with (adult) body mass, so that an elephant has fewer young (usually just one) per brood than a mouse. Lifespan increases with gestation period , and also with body mass, so that elephants live longer than mice, have a longer period of gestation, and are heavier. As a final example, fecundity decreases with lifespan, so long-lived kinds like elephants have fewer young in total than short-lived kinds like mice. Aristotle distinguished about 500 species of animals , arranging these in
26130-403: The form of the substance is the actual house, namely 'covering for bodies and chattels' or any other differentia that let us define something as a house. The formula that gives the components is the account of the matter, and the formula that gives the differentia is the account of the form. Like his teacher Plato, Aristotle's philosophy aims at the universal . Aristotle's ontology places
26331-509: The four elements proposed earlier by Empedocles , earth , water , air , and fire , to two of the four sensible qualities, hot, cold, wet, and dry. In the Empedoclean scheme, all matter was made of the four elements, in differing proportions. Aristotle's scheme added the heavenly aether , the divine substance of the heavenly spheres , stars and planets. Aristotle describes two kinds of motion: "violent" or "unnatural motion", such as that of
26532-421: The geocentric model. The Pythagorean system has already been mentioned; some Pythagoreans believed the Earth to be one of several planets going around a central fire. Hicetas and Ecphantus , two Pythagoreans of the 5th century BC, and Heraclides Ponticus in the 4th century BC, believed that the Earth rotated on its axis but remained at the center of the universe. Such a system still qualifies as geocentric. It
26733-515: The geocentric system met its first serious challenge with the publication of Copernicus ' De revolutionibus orbium coelestium ( On the Revolutions of the Heavenly Spheres ), which posited that the Earth and the other planets instead revolved around the Sun. The geocentric system was still held for many years afterwards, as at the time the Copernican system did not offer better predictions than
26934-472: The geocentric system, and it posed problems for both natural philosophy and scripture. The Copernican system was no more accurate than Ptolemy's system, because it still used circular orbits. This was not altered until Johannes Kepler postulated that they were elliptical (Kepler's first law of planetary motion ). With the invention of the telescope in 1609, observations made by Galileo Galilei (such as that Jupiter has moons) called into question some of
27135-428: The ground, say) require more force to make them move; and objects pushed with greater force move faster. This would imply the equation incorrect in modern physics. Natural motion depends on the element concerned: the aether naturally moves in a circle around the heavens, while the 4 Empedoclean elements move vertically up (like fire, as is observed) or down (like earth) towards their natural resting places. In
27336-425: The heliocentric argument that a moving Earth could retain the Moon. Galileo's observations were verified by other astronomers of the time period who quickly adopted use of the telescope, including Christoph Scheiner , Johannes Kepler , and Giovan Paulo Lembo. In December 1610, Galileo Galilei used his telescope to observe that Venus showed all phases , just like the Moon . He thought that while this observation
27537-440: The image. According to Aristotle, spontaneity and chance are causes of some things, distinguishable from other types of cause such as simple necessity. Chance as an incidental cause lies in the realm of accidental things , "from what is spontaneous". There is also more a specific kind of chance, which Aristotle names "luck", that only applies to people's moral choices. In astronomy , Aristotle refuted Democritus 's claim that
27738-414: The introduction of new technology, including the spectroscope and photography . Joseph von Fraunhofer discovered about 600 bands in the spectrum of the Sun in 1814–15, which, in 1859, Gustav Kirchhoff ascribed to the presence of different elements. Stars were proven to be similar to the Earth's own Sun, but with a wide range of temperatures , masses , and sizes. The existence of the Earth's galaxy,
27939-579: The late 19th century and most of the 20th century, images were made using photographic equipment. Modern images are made using digital detectors, particularly using charge-coupled devices (CCDs) and recorded on modern medium. Although visible light itself extends from approximately 4000 Å to 7000 Å (400 nm to 700 nm), that same equipment can be used to observe some near-ultraviolet and near-infrared radiation. Ultraviolet astronomy employs ultraviolet wavelengths between approximately 100 and 3200 Å (10 to 320 nm). Light at those wavelengths
28140-405: The laws of nature to any CS. The struggle, so violent in the early days of science, between the views of Ptolemy and Copernicus would then be quite meaningless. Either CS could be used with equal justification. The two sentences, 'the sun is at rest and the Earth moves', or 'the sun moves and the Earth is at rest', would simply mean two different conventions concerning two different CS. Could we build
28341-558: The legendary physician Asclepius and his son Machaon . Both of Aristotle's parents died when he was still at a young age and Proxenus of Atarneus became his guardian. Although little information about Aristotle's childhood has survived, he probably spent some time in the Macedonian capital, making his first connections with the Macedonian monarchy . At the age of seventeen or eighteen, Aristotle moved to Athens to continue his education at Plato's Academy . He became distinguished as
28542-576: The making of calendars . Professional astronomy is split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects. This data is then analyzed using basic principles of physics. Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. These two fields complement each other. Theoretical astronomy seeks to explain observational results and observations are used to confirm theoretical results. Astronomy
28743-420: The mathematical methods then available. However, while providing for similar explanations, the later deferent and epicycle model was already flexible enough to accommodate observations. Although the basic tenets of Greek geocentrism were established by the time of Aristotle, the details of his system did not become standard. The Ptolemaic system, developed by the Hellenistic astronomer Claudius Ptolemaeus in
28944-468: The modern zoologist would call vertebrates as the hotter "animals with blood", and below them the colder invertebrates as "animals without blood". Those with blood were divided into the live-bearing ( mammals ), and the egg-laying ( birds , reptiles , fish ). Those without blood were insects, crustacea (non-shelled – cephalopods, and shelled ) and the hard-shelled molluscs ( bivalves and gastropods ). He recognised that animals did not exactly fit into
29145-528: The most part, intended for widespread publication; they are generally thought to be lecture aids for his students. His most important treatises include Physics , Metaphysics , Nicomachean Ethics , Politics , On the Soul and Poetics . Aristotle studied and made significant contributions to "logic, metaphysics, mathematics, physics, biology, botany, ethics, politics, agriculture, medicine, dance, and theatre." While Alexander deeply admired Aristotle, near
29346-589: The motions of objects visible to the naked eye. In some locations, early cultures assembled massive artifacts that may have had some astronomical purpose. In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops and in understanding the length of the year. As civilizations developed, most notably in Egypt , Mesopotamia , Greece , Persia , India , China , and Central America , astronomical observatories were assembled and ideas on
29547-417: The motions of the planets. Newton also developed the reflecting telescope . Improvements in the size and quality of the telescope led to further discoveries. The English astronomer John Flamsteed catalogued over 3000 stars. More extensive star catalogues were produced by Nicolas Louis de Lacaille . The astronomer William Herschel made a detailed catalog of nebulosity and clusters, and in 1781 discovered
29748-406: The nature of the Universe began to develop. Most early astronomy consisted of mapping the positions of the stars and planets, a science now referred to as astrometry . From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon and the Earth in the Universe were explored philosophically. The Earth was believed to be the center of the Universe with
29949-498: The near-by island of Lesbos . During this time, Aristotle married Pythias , Hermias's adoptive daughter and niece, and had a daughter whom they also named Pythias. In 343/42 BC, Aristotle was invited to Pella by Philip II of Macedon in order to become the tutor to his thirteen-year-old son Alexander ; a choice perhaps influenced by the relationship of Aristotle's family with the Macedonian dynasty. Aristotle taught Alexander at
30150-480: The observation of young stars embedded in molecular clouds and the cores of galaxies. Observations from the Wide-field Infrared Survey Explorer (WISE) have been particularly effective at unveiling numerous galactic protostars and their host star clusters . With the exception of infrared wavelengths close to visible light, such radiation is heavily absorbed by the atmosphere, or masked, as
30351-404: The oceans are then replenished by the cycle of rainfall and river runoff ("I have proved by experiment that salt water evaporated forms fresh and the vapor does not when it condenses condense into sea water again.") Aristotle was the first person to study biology systematically, and biology forms a large part of his writings. He spent two years observing and describing the zoology of Lesbos and
30552-829: The one advanced by Galileo in the " Letter to the Grand Duchess Christina ". Pope Pius XII (1939–1958) repeated his predecessor's teaching: Astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics , physics , and chemistry in order to explain their origin and their overall evolution . Objects of interest include planets , moons , stars , nebulae , galaxies , meteoroids , asteroids , and comets . Relevant phenomena include supernova explosions, gamma ray bursts , quasars , blazars , pulsars , and cosmic microwave background radiation . More generally, astronomy studies everything that originates beyond Earth's atmosphere . Cosmology
30753-574: The order (outwards from the center): Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, fixed stars, with the fixed stars located on the celestial sphere. In his " Myth of Er ", a section of the Republic , Plato describes the cosmos as the Spindle of Necessity , attended by the Sirens and turned by the three Fates . Eudoxus of Cnidus , who worked with Plato, developed a less mythical, more mathematical explanation of
30954-534: The particles produced when cosmic rays hit the Earth's atmosphere. Gravitational-wave astronomy is an emerging field of astronomy that employs gravitational-wave detectors to collect observational data about distant massive objects. A few observatories have been constructed, such as the Laser Interferometer Gravitational Observatory LIGO . LIGO made its first detection on 14 September 2015, observing gravitational waves from
31155-468: The physical world in his Matalib , rejects the Aristotelian and Avicennian notion of the Earth's centrality within the universe, but instead argues that there are "a thousand thousand worlds ( alfa alfi 'awalim ) beyond this world such that each one of those worlds be bigger and more massive than this world as well as having the like of what this world has." To support his theological argument , he cites
31356-399: The planet Mercury moves in an elliptic orbit , while Alpetragius proposed a planetary model that abandoned the equant , epicycle and eccentric mechanisms, though this resulted in a system that was mathematically less accurate. His alternative system spread through most of Europe during the 13th century. Fakhr al-Din al-Razi (1149–1209), in dealing with his conception of physics and
31557-497: The planet Uranus , the first new planet found. During the 18–19th centuries, the study of the three-body problem by Leonhard Euler , Alexis Claude Clairaut , and Jean le Rond d'Alembert led to more accurate predictions about the motions of the Moon and planets. This work was further refined by Joseph-Louis Lagrange and Pierre Simon Laplace , allowing the masses of the planets and moons to be estimated from their perturbations. Significant advances in astronomy came about with
31758-470: The planets with great accuracy, a field known as celestial mechanics . More recently the tracking of near-Earth objects will allow for predictions of close encounters or potential collisions of the Earth with those objects. The measurement of stellar parallax of nearby stars provides a fundamental baseline in the cosmic distance ladder that is used to measure the scale of the Universe. Parallax measurements of nearby stars provide an absolute baseline for
31959-418: The planets' motion based on Plato's dictum stating that all phenomena in the heavens can be explained with uniform circular motion. Aristotle elaborated on Eudoxus' system. In the fully developed Aristotelian system, the spherical Earth is at the center of the universe, and all other heavenly bodies are attached to 47–55 transparent, rotating spheres surrounding the Earth, all concentric with it. (The number
32160-464: The potential for life to adapt to challenges on Earth and in outer space . Cosmology (from the Greek κόσμος ( kosmos ) "world, universe" and λόγος ( logos ) "word, study" or literally "logic") could be considered the study of the Universe as a whole. Aristotle Aristotle ( Attic Greek : Ἀριστοτέλης , romanized: Aristotélēs ; 384–322 BC) was an Ancient Greek philosopher and polymath . His writings cover
32361-576: The pre-colonial Middle Ages, but modern discoveries show otherwise. For over six centuries (from the recovery of ancient learning during the late Middle Ages into the Enlightenment), the Roman Catholic Church gave more financial and social support to the study of astronomy than probably all other institutions. Among the Church's motives was finding the date for Easter . Medieval Europe housed
32562-437: The primary kind of knowledge; but if there is some motionless independent thing, the knowledge of this precedes it and is first philosophy, and it is universal in just this way , because it is first. And it belongs to this sort of philosophy to study being as being, both what it is and what belongs to it just by virtue of being. Aristotle examines the concepts of substance ( ousia ) and essence ( to ti ên einai , "the what it
32763-567: The private school of Mieza , in the gardens of the Nymphs , the royal estate near Pella. Alexander's education probably included a number of subjects, such as ethics and politics , as well as standard literary texts, like Euripides and Homer . It is likely that during Aristotle's time in the Macedonian court, other prominent nobles, like Ptolemy and Cassander , would have occasionally attended his lectures. Aristotle encouraged Alexander toward eastern conquest, and his own attitude towards Persia
32964-458: The properties examined include luminosity , density , temperature , and chemical composition. Because astrophysics is a very broad subject, astrophysicists typically apply many disciplines of physics, including mechanics , electromagnetism , statistical mechanics , thermodynamics , quantum mechanics , relativity , nuclear and particle physics , and atomic and molecular physics . In practice, modern astronomical research often involves
33165-468: The properties of more distant stars, as their properties can be compared. Measurements of the radial velocity and proper motion of stars allow astronomers to plot the movement of these systems through the Milky Way galaxy. Astrometric results are the basis used to calculate the distribution of speculated dark matter in the galaxy. During the 1990s, the measurement of the stellar wobble of nearby stars
33366-406: The public understanding of science and technology, found that about 20%, or one in five, of American adults believe that the Sun orbits the Earth. According to 2011 VTSIOM poll, 32% of Russians believe that the Sun orbits the Earth. The famous Galileo affair pitted the geocentric model against the claims of Galileo . In regards to the theological basis for such an argument, two Popes addressed
33567-459: The question of whether extraterrestrial life exists, and how humans can detect it if it does. The term exobiology is similar. Astrobiology makes use of molecular biology , biophysics , biochemistry , chemistry , astronomy, physical cosmology , exoplanetology and geology to investigate the possibility of life on other worlds and help recognize biospheres that might be different from that on Earth. The origin and early evolution of life
33768-548: The question of whether the use of phenomenological language would compel one to admit an error in Scripture. Both taught that it would not. Pope Leo XIII (1878–1903) wrote: we have to contend against those who, making an evil use of physical science, minutely scrutinize the Sacred Book in order to detect the writers in a mistake, and to take occasion to vilify its contents. ... There can never, indeed, be any real discrepancy between
33969-425: The rotation of the Earth, furthermore, Buridan also developed the theory of impetus (predecessor of the modern scientific theory of inertia ) which was able to show planets were capable of motion without the intervention of angels. Georg von Peuerbach (1423–1461) and Regiomontanus (1436–1476) helped make astronomical progress instrumental to Copernicus's development of the heliocentric model decades later. During
34170-433: The same certainty as experimental science, but it sets out testable hypotheses and constructs a narrative explanation of what is observed. In this sense, Aristotle's biology is scientific. From the data he collected and documented, Aristotle inferred quite a number of rules relating the life-history features of the live-bearing tetrapods (terrestrial placental mammals) that he studied. Among these correct predictions are
34371-536: The senses; and somewhat in the same way the sacred writers-as the Angelic Doctor also reminds us – "went by what sensibly appeared", or put down what God, speaking to men, signified, in the way men could understand and were accustomed to. Maurice Finocchiaro, author of a book on the Galileo affair, notes that this is "a view of the relationship between biblical interpretation and scientific investigation that corresponds to
34572-474: The size of a planet's retrograde loop (especially that of Mars) would be smaller, or sometimes larger, than expected, resulting in positional errors of as much as 30 degrees. To alleviate the problem, Ptolemy developed the equant . The equant was a point near the center of a planet's orbit where, if you were to stand there and watch, the center of the planet's epicycle would always appear to move at uniform speed; all other locations would see non-uniform speed, as on
34773-450: The sky will look like when viewed from Earth (as opposed to an imaginary observer looking down on the entire Solar System, where a different coordinate system might be more convenient). The Ptolemaic model held sway into the early modern age ; from the late 16th century onward it was gradually replaced as the consensus description by the heliocentric model . Geocentrism as a separate religious belief, however, never completely died out. In
34974-436: The stars" depending on the translation). Astronomy should not be confused with astrology , the belief system which claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin, they are now entirely distinct. "Astronomy" and " astrophysics " are synonyms. Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside
35175-477: The subject, whereas "astrophysics" is used to describe the physics-oriented version of the subject. However, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. Some fields, such as astrometry , are purely astronomy rather than also astrophysics. Various departments in which scientists carry out research on this subject may use "astronomy" and "astrophysics", partly depending on whether
35376-549: The surrounding seas, including in particular the Pyrrha lagoon in the centre of Lesbos. His data in History of Animals , Generation of Animals , Movement of Animals , and Parts of Animals are assembled from his own observations, statements given by people with specialized knowledge, such as beekeepers and fishermen, and less accurate accounts provided by travellers from overseas. His apparent emphasis on animals rather than plants
35577-451: The synod did not set the position of the church body as a whole. Articles arguing that geocentrism was the biblical perspective appeared in some early creation science newsletters pointing to some passages in the Bible , which, when taken literally, indicate that the daily apparent motions of the Sun and the Moon are due to their actual motions around the Earth rather than due to the rotation of
35778-422: The tenets of geocentrism but did not seriously threaten it. Because he observed dark "spots" on the Moon, craters, he remarked that the moon was not a perfect celestial body as had been previously conceived. This was the first detailed observation by telescope of the Moon's imperfections, which had previously been explained by Aristotle as the Moon being contaminated by Earth and its heavier elements, in contrast to
35979-505: The theologian and the physicist, as long as each confines himself within his own lines, and both are careful, as St. Augustine warns us, "not to make rash assertions, or to assert what is not known as known". If dissension should arise between them, here is the rule also laid down by St. Augustine, for the theologian: "Whatever they can really demonstrate to be true of physical nature, we must show to be capable of reconciliation with our Scriptures; and whatever they assert in their treatises which
36180-402: The thing that has undergone the change has itself changed. In that particular change he introduces the concept of potentiality ( dynamis ) and actuality ( entelecheia ) in association with the matter and the form. Referring to potentiality, this is what a thing is capable of doing or being acted upon if the conditions are right and it is not prevented by something else. For example, the seed of
36381-470: The time of Homer , and "the upheaving of one of the Aeolian islands , previous to a volcanic eruption ."' Meteorologica lends its name to the modern study of meteorology, but its modern usage diverges from the content of Aristotle's ancient treatise on meteors . The ancient Greeks did use the term for a range of atmospheric phenomena, but also for earthquakes and volcanic eruptions. Aristotle proposed that
36582-473: The traditional rendering will be employed here. Aristotle describes experiments in optics using a camera obscura in Problems , book 15. The apparatus consisted of a dark chamber with a small aperture that let light in. With it, he saw that whatever shape he made the hole, the sun's image always remained circular. He also noted that increasing the distance between the aperture and the image surface magnified
36783-401: The treatise we know by the name Metaphysics . Aristotle called it "first philosophy", and distinguished it from mathematics and natural science (physics) as the contemplative ( theoretikē ) philosophy which is "theological" and studies the divine. He wrote in his Metaphysics (1026a16): If there were no other independent things besides the composite natural ones, the study of nature would be
36984-492: The universal ( katholou ) in particulars ( kath' hekaston ), things in the world, whereas for Plato the universal is a separately existing form which actual things imitate. For Aristotle, "form" is still what phenomena are based on, but is "instantiated" in a particular substance. Plato argued that all things have a universal form , which could be either a property or a relation to other things. When one looks at an apple, for example, one sees an apple, and one can also analyse
37185-438: The universe and also kept the atmosphere from flying away. The theory of gravity allowed scientists to rapidly construct a plausible heliocentric model for the Solar System. In his Principia , Newton explained his theory of how gravity, previously thought to be a mysterious, unexplained occult force, directed the movements of celestial bodies, and kept our Solar System in working order. His descriptions of centripetal force were
37386-534: The universe consists of a multitude of galaxies. With this Hubble formulated the Hubble constant , which allowed for the first time a calculation of the age of the Universe and size of the Observable Universe, which became increasingly precise with better meassurements, starting at 2 billion years and 280 million light-years, until 2006 when data of the Hubble Space Telescope allowed a very accurate calculation of
37587-409: The universe; origin of cosmic rays ; general relativity and physical cosmology , including string cosmology and astroparticle physics . Astrochemistry is the study of the abundance and reactions of molecules in the Universe , and their interaction with radiation . The discipline is an overlap of astronomy and chemistry . The word "astrochemistry" may be applied to both the Solar System and
37788-521: The view that a plain reading of the Bible contains an accurate account of the manner in which the universe was created and requires a geocentric worldview. Most contemporary creationist organizations reject such perspectives. According to a report released in 2014 by the National Science Foundation , 26% of Americans surveyed believe that the Sun revolves around the Earth. Morris Berman quotes
37989-640: Was used to detect large extrasolar planets orbiting those stars. Theoretical astronomers use several tools including analytical models and computational numerical simulations ; each has its particular advantages. Analytical models of a process are better for giving broader insight into the heart of what is going on. Numerical models reveal the existence of phenomena and effects otherwise unobserved. Theorists in astronomy endeavor to create theoretical models that are based on existing observations and known physics, and to predict observational consequences of those models. The observation of phenomena predicted by
38190-511: Was an early analog computer designed to calculate the location of the Sun , Moon , and planets for a given date. Technological artifacts of similar complexity did not reappear until the 14th century, when mechanical astronomical clocks appeared in Europe. Astronomy flourished in the Islamic world and other parts of the world. This led to the emergence of the first astronomical observatories in
38391-670: Was disappointed with the Academy's direction after control passed to Plato's nephew Speusippus , although it is possible that the anti-Macedonian sentiments in Athens could have also influenced his decision. Aristotle left with Xenocrates to Assos in Asia Minor , where he was invited by his former fellow student Hermias of Atarneus ; he stayed there for a few years and left around the time of Hermias' death. While at Assos, Aristotle and his colleague Theophrastus did extensive research in botany and marine biology , which they later continued at
38592-466: Was even older. In the illustration, the center of the deferent is not the Earth but the spot marked X, making it eccentric (from the Greek ἐκ ec- meaning "from" and κέντρον kentron meaning "center"), from which the spot takes its name. Unfortunately, the system that was available in Ptolemy's time did not quite match observations , even though it was an improvement over Hipparchus' system. Most noticeably
38793-451: Was eventually replaced by the heliocentric model . Copernican heliocentrism could remove Ptolemy's epicycles because the retrograde motion could be seen to be the result of the combination of the movements and speeds of Earth and planets. Copernicus felt strongly that equants were a violation of Aristotelian purity, and proved that replacement of the equant with a pair of new epicycles was entirely equivalent. Astronomers often continued using
38994-532: Was formulated, heavily evidenced by cosmic microwave background radiation , Hubble's law , and the cosmological abundances of elements . Space telescopes have enabled measurements in parts of the electromagnetic spectrum normally blocked or blurred by the atmosphere. In February 2016, it was revealed that the LIGO project had detected evidence of gravitational waves in the previous September. The main source of information about celestial bodies and other objects
39195-435: Was incompatible with the Ptolemaic system, it was a natural consequence of the heliocentric system. However, Ptolemy placed Venus' deferent and epicycle entirely inside the sphere of the Sun (between the Sun and Mercury), but this was arbitrary; he could just as easily have swapped Venus and Mercury and put them on the other side of the Sun, or made any other arrangement of Venus and Mercury, as long as they were always near
39396-454: Was not detected until the 19th century . Therefore, the Greeks chose the simpler of the two explanations. Another observation used in favor of the geocentric model at the time was the apparent consistency of Venus' luminosity, which implies that it is usually about the same distance from Earth, which in turn is more consistent with geocentrism than heliocentrism. (In fact, Venus' luminous consistency
39597-452: Was revived in the Middle Ages by Jean Buridan . Heraclides Ponticus was once thought to have proposed that both Venus and Mercury went around the Sun rather than the Earth, but it is now known that he did not. Martianus Capella definitely put Mercury and Venus in orbit around the Sun. Aristarchus of Samos wrote a work, which has not survived, on heliocentrism , saying that the Sun was at
39798-425: Was strongly ethnocentric . In one famous example, he counsels Alexander to be "a leader to the Greeks and a despot to the barbarians". Alexander's education under the guardianship of Aristotle likely lasted for only a few years, as at around the age of sixteen he returned to Pella and was appointed regent of Macedon by his father Philip. During this time, Aristotle is said to have gifted Alexander an annotated copy of
39999-421: Was to be") in his Metaphysics (Book VII), and he concludes that a particular substance is a combination of both matter and form, a philosophical theory called hylomorphism . In Book VIII, he distinguishes the matter of the substance as the substratum , or the stuff of which it is composed. For example, the matter of a house is the bricks, stones, timbers, etc., or whatever constitutes the potential house, while
40200-403: Was to move upwards, away from the center, with fire being lighter than air. Beyond the layer of fire, were the solid spheres of aether in which the celestial bodies were embedded. They were also entirely composed of aether. Adherence to the geocentric model stemmed largely from several important observations. First of all, if the Earth did move, then one ought to be able to observe the shifting of
40401-588: Was widely disbelieved until the 19th century. He gives accurate descriptions of the four-chambered fore-stomachs of ruminants , and of the ovoviviparous embryological development of the hound shark . He notes that an animal's structure is well matched to function so birds like the heron (which live in marshes with soft mud and live by catching fish) have a long neck, long legs, and a sharp spear-like beak, whereas ducks that swim have short legs and webbed feet. Darwin , too, noted these sorts of differences between similar kinds of animal, but unlike Aristotle used
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