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155-443: Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge . Electricity is related to magnetism , both being part of the phenomenon of electromagnetism , as described by Maxwell's equations . Common phenomena are related to electricity, including lightning , static electricity , electric heating , electric discharges and many others. The presence of either

310-499: A Platonist by Stephen Hawking , a view Penrose discusses in his book, The Road to Reality . Hawking referred to himself as an "unashamed reductionist" and took issue with Penrose's views. Mathematics provides a compact and exact language used to describe the order in nature. This was noted and advocated by Pythagoras , Plato , Galileo, and Newton. Some theorists, like Hilary Putnam and Penelope Maddy , hold that logical truths, and therefore mathematical reasoning, depend on

465-455: A conductor 's surface, since otherwise there would be a force along the surface of the conductor that would move the charge carriers to even the potential across the surface. The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre,

620-459: A force on each other, an effect that was known, though not understood, in antiquity. A lightweight ball suspended by a fine thread can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first: the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod also repel each other. However, if one ball

775-488: A frame of reference that is in motion with respect to an observer; the special theory of relativity is concerned with motion in the absence of gravitational fields and the general theory of relativity with motion and its connection with gravitation . Both quantum theory and the theory of relativity find applications in many areas of modern physics. While physics itself aims to discover universal laws, its theories lie in explicit domains of applicability. Loosely speaking,

930-744: A northwestern Iranian language . No Parthian literature survives from before the Sassanid period in its original form, and they seem to have written down only very little. The Parthians did, however, have a thriving oral minstrel-poet culture , to the extent that their word for "minstrel" ( gosan ) survives to this day in many Iranian languages and especially in Armenian ( gusan ), on which it exercised heavy (especially lexical and vocabulary) influence. These professionals were evident in every facet of Parthian daily life, from cradle to grave, and they were entertainers of kings and commoners alike, proclaiming

1085-407: A steady state current, but instead blocks it. The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor. The induced voltage is proportional to the time rate of change of the current. The constant of proportionality

1240-522: A wine storage ) at Nisa , in present-day Turkmenistan. A handful of other evidence of written Parthian has been found outside Parthia, the most important of these being the part of a land-sale document found at Avroman (in the Kermanshah province of Iran ), and more ostraca, graffiti and the fragment of a business letter found at Dura-Europos in present-day Syria . The Parthian Arsacids do not seem to have used Parthian until relatively late, and

1395-455: A basic awareness of the motions of the Sun, Moon, and stars. The stars and planets, believed to represent gods, were often worshipped. While the explanations for the observed positions of the stars were often unscientific and lacking in evidence, these early observations laid the foundation for later astronomy, as the stars were found to traverse great circles across the sky, which could not explain

1550-456: A central role in many modern technologies, serving in electric power where electric current is used to energise equipment, and in electronics dealing with electrical circuits involving active components such as vacuum tubes , transistors , diodes and integrated circuits , and associated passive interconnection technologies. The study of electrical phenomena dates back to antiquity, with theoretical understanding progressing slowly until

1705-527: A certain Tiridates rebelled against Phraates IV , probably with the support of the nobility that Phraates had previously persecuted. The revolt was initially successful, but failed by 25 BC. In 9/8, the Parthian nobility succeeded in putting their preferred king on the throne, but Vonones proved to have too tight a budgetary control, so he was usurped in favor of Artabanus II , who seems to have been

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1860-432: A charge of Q coulombs every t seconds passing through an electric potential ( voltage ) difference of V is where Electric power is generally supplied to businesses and homes by the electric power industry . Electricity is usually sold by the kilowatt hour (3.6 MJ) which is the product of power in kilowatts multiplied by running time in hours. Electric utilities measure power using electricity meters , which keep

2015-515: A common reference point to which potentials may be expressed and compared is useful. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground . Earth is assumed to be an infinite source of equal amounts of positive and negative charge and is therefore electrically uncharged—and unchargeable. Electric potential

2170-470: A current of one amp. The capacitor is a development of the Leyden jar and is a device that can store charge, and thereby storing electrical energy in the resulting field. It consists of two conducting plates separated by a thin insulating dielectric layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance . The unit of capacitance

2325-490: A dampened kite string and flown the kite in a storm-threatened sky . A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature. He also explained the apparently paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges. In 1775, Hugh Williamson reported

2480-420: A hard-to-find physical meaning. The final mathematical solution has an easier-to-find meaning, because it is what the solver is looking for. Physics is a branch of fundamental science (also called basic science). Physics is also called " the fundamental science" because all branches of natural science including chemistry, astronomy, geology, and biology are constrained by laws of physics. Similarly, chemistry

2635-423: A large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh. The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the lightning conductor , the sharp spike of which acts to encourage the lightning strike to develop there, rather than to

2790-399: A millimetre per second, the electric field that drives them itself propagates at close to the speed of light , enabling electrical signals to pass rapidly along wires. Current causes several observable effects, which historically were the means of recognising its presence. That water could be decomposed by the current from a voltaic pile was discovered by Nicholson and Carlisle in 1800,

2945-548: A more reliable source of electrical energy than the electrostatic machines previously used. The recognition of electromagnetism , the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819–1820. Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analysed the electrical circuit in 1827. Electricity and magnetism (and light) were definitively linked by James Clerk Maxwell , in particular in his " On Physical Lines of Force " in 1861 and 1862. While

3100-616: A non-Arsacid Parthian nobleman. But when Artabanus attempted to consolidate his position (at which he was successful in most instances), he failed to do so in the regions where the Parthian provincial rulers held sway. By the 2nd century AD, the frequent wars with neighboring Rome and with the nomads, and the infighting among the Parthian nobility had weakened the Arsacids to a point where they could no longer defend their subjugated territories. The empire fractured as vassalaries increasingly claimed independence or were subjugated by others, and

3255-680: A part of natural philosophy , but during the Scientific Revolution in the 17th century, these natural sciences branched into separate research endeavors. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry , and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms studied by other sciences and suggest new avenues of research in these and other academic disciplines such as mathematics and philosophy. Advances in physics often enable new technologies . For example, advances in

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3410-425: A positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called conventional current . The motion of negatively charged electrons around an electric circuit , one of the most familiar forms of current, is thus deemed positive in the opposite direction to that of

3565-420: A positive or negative electric charge produces an electric field . The motion of electric charges is an electric current and produces a magnetic field . In most applications, Coulomb's law determines the force acting on an electric charge. Electric potential is the work done to move an electric charge from one point to another within an electric field, typically measured in volts . Electricity plays

3720-887: A practical generator, but it showed the possibility of generating electric power using magnetism, a possibility that would be taken up by those that followed on from his work. An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task. The components in an electric circuit can take many forms, which can include elements such as resistors , capacitors , switches , transformers and electronics . Electronic circuits contain active components , usually semiconductors , and typically exhibit non-linear behaviour, requiring complex analysis. The simplest electric components are those that are termed passive and linear : while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli. The resistor

3875-404: A process now known as electrolysis . Their work was greatly expanded upon by Michael Faraday in 1833. Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840. One of the most important discoveries relating to current was made accidentally by Hans Christian Ørsted in 1820, when, while preparing a lecture, he witnessed the current in

4030-469: A rapidly changing one. Electric power is the rate at which electric energy is transferred by an electric circuit . The SI unit of power is the watt , one joule per second . Electric power, like mechanical power , is the rate of doing work , measured in watts , and represented by the letter P . The term wattage is used colloquially to mean "electric power in watts." The electric power in watts produced by an electric current I consisting of

4185-489: A resistance is directly proportional to the potential difference across it. The resistance of most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'. The ohm , the unit of resistance, was named in honour of Georg Ohm , and is symbolised by the Greek letter Ω. 1 Ω is the resistance that will produce a potential difference of one volt in response to

4340-590: A running total of the electric energy delivered to a customer. Unlike fossil fuels , electricity is a low entropy form of energy and can be converted into motion or many other forms of energy with high efficiency. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes , transistors , diodes , sensors and integrated circuits , and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes digital switching possible, and electronics

4495-427: A scientific curiosity into an essential tool for modern life. In 1887, Heinrich Hertz discovered that electrodes illuminated with ultraviolet light create electric sparks more easily. In 1905, Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets, energising electrons. This discovery led to

4650-569: A series of experiments to the Royal Society on the shocks delivered by the electric eel ; that same year the surgeon and anatomist John Hunter described the structure of the fish's electric organs . In 1791, Luigi Galvani published his discovery of bioelectromagnetics , demonstrating that electricity was the medium by which neurons passed signals to the muscles. Alessandro Volta 's battery, or voltaic pile , of 1800, made from alternating layers of zinc and copper, provided scientists with

4805-511: A series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic , in contrast to minerals such as magnetite , which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating , based on

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4960-453: A set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. He could moreover prove that in a vacuum such a wave would travel at the speed of light , and thus light itself was a form of electromagnetic radiation. Maxwell's equations , which unify light, fields, and charge are one of the great milestones of theoretical physics. Physics Physics

5115-585: A single satrapy (the 16th), whose annual tribute to the king he states to be only 300 talents of silver. This "has rightly caused disquiet to modern scholars." At the Battle of Gaugamela in 331 BC between the forces of Darius III and those of Alexander the Great , one such Parthian unit was commanded by Phrataphernes , who was at the time Achaemenid governor of Parthia. Following the defeat of Darius III, Phrataphernes surrendered his governorate to Alexander when

5270-476: A solid crystal (such as a germanium crystal) to detect a radio signal by the contact junction effect. In a solid-state component, the current is confined to solid elements and compounds engineered specifically to switch and amplify it. Current flow can be understood in two forms: as negatively charged electrons , and as positively charged electron deficiencies called holes . These charges and holes are understood in terms of quantum physics. The building material

5425-465: A specific practical application as a goal, other than the deeper insight into the phenomema themselves. Applied physics is a general term for physics research and development that is intended for a particular use. An applied physics curriculum usually contains a few classes in an applied discipline, like geology or electrical engineering. It usually differs from engineering in that an applied physicist may not be designing something in particular, but rather

5580-426: A speed much less than the speed of light. These theories continue to be areas of active research today. Chaos theory , an aspect of classical mechanics, was discovered in the 20th century, three centuries after the original formulation of classical mechanics by Newton (1642–1727). These central theories are important tools for research into more specialized topics, and any physicist, regardless of their specialization,

5735-399: A subfield of mechanics , is used in the building of bridges and other static structures. The understanding and use of acoustics results in sound control and better concert halls; similarly, the use of optics creates better optical devices. An understanding of physics makes for more realistic flight simulators , video games, and movies, and is often critical in forensic investigations. With

5890-466: A substantial treatise on " Physics " – in the 4th century BC. Aristotelian physics was influential for about two millennia. His approach mixed some limited observation with logical deductive arguments, but did not rely on experimental verification of deduced statements. Aristotle's foundational work in Physics, though very imperfect, formed a framework against which later thinkers further developed

6045-507: A wire disturbing the needle of a magnetic compass. He had discovered electromagnetism , a fundamental interaction between electricity and magnetics. The level of electromagnetic emissions generated by electric arcing is high enough to produce electromagnetic interference , which can be detrimental to the workings of adjacent equipment. In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how

6200-447: A wire suspended from a pivot above the magnet and dipped into the mercury. The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained. Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. Further analysis of this process, known as electromagnetic induction , enabled him to state

6355-400: A wire. The informal term static electricity refers to the net presence (or 'imbalance') of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other. Charge can be measured by a number of means, an early instrument being the gold-leaf electroscope , which although still in use for classroom demonstrations, has been superseded by

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6510-583: Is a scalar quantity . That is, it has only magnitude and not direction. It may be viewed as analogous to height : just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will 'fall' across the voltage caused by an electric field. As relief maps show contour lines marking points of equal height, a set of lines marking points of equal potential (known as equipotentials ) may be drawn around an electrostatically charged object. The equipotentials cross all lines of force at right angles. They must also lie parallel to

6665-408: Is a vector field . The study of electric fields created by stationary charges is called electrostatics . The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday, whose term ' lines of force ' still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it

6820-663: Is a continuation from Latin Parthia , from Old Persian Parthava , which was the Parthian language self-designator signifying "of the Parthians " who were an Iranian people. In context to its Hellenistic period , Parthia also appears as Parthyaea . Parthia was known as Pahlaw in the Middle Persian sources of the Sasanian period, and Pahla or Fahla by later Islamic authors, but mainly referred to

6975-450: Is an important difference. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in the universe, despite being much weaker. An electric field generally varies in space, and its strength at any one point

7130-400: Is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by Charles-Augustin de Coulomb , who deduced that charge manifests itself in two opposing forms. This discovery led to the well-known axiom: like-charged objects repel and opposite-charged objects attract . The force acts on

7285-413: Is clear-cut, but not always obvious. For example, mathematical physics is the application of mathematics in physics. Its methods are mathematical, but its subject is physical. The problems in this field start with a " mathematical model of a physical situation " (system) and a "mathematical description of a physical law" that will be applied to that system. Every mathematical statement used for solving has

7440-419: Is concerned with bodies acted on by forces and bodies in motion and may be divided into statics (study of the forces on a body or bodies not subject to an acceleration), kinematics (study of motion without regard to its causes), and dynamics (study of motion and the forces that affect it); mechanics may also be divided into solid mechanics and fluid mechanics (known together as continuum mechanics ),

7595-400: Is concerned with the most basic units of matter; this branch of physics is also known as high-energy physics because of the extremely high energies necessary to produce many types of particles in particle accelerators . On this scale, ordinary, commonsensical notions of space, time, matter, and energy are no longer valid. The two chief theories of modern physics present a different picture of

7750-470: Is defined as negative, and that by protons is positive. Before these particles were discovered, Benjamin Franklin had defined a positive charge as being the charge acquired by a glass rod when it is rubbed with a silk cloth. A proton by definition carries a charge of exactly 1.602 176 634 × 10 coulombs . This value is also defined as the elementary charge . No object can have a charge smaller than

7905-481: Is defined as the force (per unit charge) that would be felt by a stationary, negligible charge if placed at that point. The conceptual charge, termed a ' test charge ', must be vanishingly small to prevent its own electric field disturbing the main field and must also be stationary to prevent the effect of magnetic fields . As the electric field is defined in terms of force , and force is a vector , having both magnitude and direction , it follows that an electric field

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8060-425: Is expected to be literate in them. These include classical mechanics, quantum mechanics, thermodynamics and statistical mechanics , electromagnetism , and special relativity. Classical physics includes the traditional branches and topics that were recognized and well-developed before the beginning of the 20th century—classical mechanics, acoustics , optics , thermodynamics, and electromagnetism. Classical mechanics

8215-429: Is generally concerned with matter and energy on the normal scale of observation, while much of modern physics is concerned with the behavior of matter and energy under extreme conditions or on a very large or very small scale. For example, atomic and nuclear physics study matter on the smallest scale at which chemical elements can be identified. The physics of elementary particles is on an even smaller scale since it

8370-529: Is integral to applications spanning transport , heating , lighting , communications , and computation , making it the foundation of modern industrial society. Long before any knowledge of electricity existed, people were aware of shocks from electric fish . Ancient Egyptian texts dating from 2750 BCE described them as the "protectors" of all other fish. Electric fish were again reported millennia later by ancient Greek , Roman and Arabic naturalists and physicians . Several ancient writers, such as Pliny

8525-594: Is listed (in the typical Iranian clockwise order) among the governorates in the vicinity of Drangiana . The inscription dates to c. 520 BC. The center of the administration "may have been at [what would later be known as] Hecatompylus ". The Parthians also appear in Herodotus' list of peoples subject to the Achaemenids; the historiographer treats the Parthians, Chorasmians, Sogdians and Areioi as peoples of

8680-405: Is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere . This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821. Faraday's homopolar motor consisted of a permanent magnet sitting in a pool of mercury . A current was allowed through

8835-411: Is most often a crystalline semiconductor . Solid-state electronics came into its own with the emergence of transistor technology. The first working transistor, a germanium -based point-contact transistor , was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947, followed by the bipolar junction transistor in 1948. By modern convention, the charge carried by electrons

8990-593: Is often called the central science because of its role in linking the physical sciences. For example, chemistry studies properties, structures, and reactions of matter (chemistry's focus on the molecular and atomic scale distinguishes it from physics ). Structures are formed because particles exert electrical forces on each other, properties include physical characteristics of given substances, and reactions are bound by laws of physics, like conservation of energy , mass , and charge . Fundamental physics seeks to better explain and understand phenomena in all spheres, without

9145-403: Is perhaps the simplest of passive circuit elements: as its name suggests, it resists the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor: in metals, for example, resistance is primarily due to collisions between electrons and ions. Ohm's law is a basic law of circuit theory , stating that the current passing through

9300-506: Is possible only in discrete steps proportional to their frequency. This, along with the photoelectric effect and a complete theory predicting discrete energy levels of electron orbitals , led to the theory of quantum mechanics improving on classical physics at very small scales. Quantum mechanics would come to be pioneered by Werner Heisenberg , Erwin Schrödinger and Paul Dirac . From this early work, and work in related fields,

9455-530: Is subjected to transients , such as when first energised. The concept of the electric field was introduced by Michael Faraday . An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses , and like it, extends towards infinity and shows an inverse square relationship with distance. However, there

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9610-406: Is termed the inductance . The unit of inductance is the henry , named after Joseph Henry , a contemporary of Faraday. One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second. The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes

9765-415: Is the farad , named after Michael Faraday , and given the symbol F : one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current as it accumulates charge; this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit

9920-485: Is the scientific study of matter , its fundamental constituents , its motion and behavior through space and time , and the related entities of energy and force . Physics is one of the most fundamental scientific disciplines. A scientist who specializes in the field of physics is called a physicist . Physics is one of the oldest academic disciplines . Over much of the past two millennia, physics, chemistry , biology , and certain branches of mathematics were

10075-527: Is therefore 0 at all places inside the body. This is the operating principal of the Faraday cage , a conducting metal shell which isolates its interior from outside electrical effects. The principles of electrostatics are important when designing items of high-voltage equipment. There is a finite limit to the electric field strength that may be withstood by any medium. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between

10230-431: Is using physics or conducting physics research with the aim of developing new technologies or solving a problem. The approach is similar to that of applied mathematics . Applied physicists use physics in scientific research. For instance, people working on accelerator physics might seek to build better particle detectors for research in theoretical physics. Physics is used heavily in engineering. For example, statics,

10385-407: Is usually measured in volts , and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity. This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference , and is the energy required to move a unit charge between two specified points. An electric field has

10540-535: Is widely used in information processing , telecommunications , and signal processing . Interconnection technologies such as circuit boards , electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system . Today, most electronic devices use semiconductor components to perform electron control. The underlying principles that explain how semiconductors work are studied in solid state physics , whereas

10695-536: The Industrial Revolution as energy needs increased. The laws comprising classical physics remain widely used for objects on everyday scales travelling at non-relativistic speeds, since they provide a close approximation in such situations, and theories such as quantum mechanics and the theory of relativity simplify to their classical equivalents at such scales. Inaccuracies in classical mechanics for very small objects and very high velocities led to

10850-660: The Latin physica ('study of nature'), which itself is a borrowing of the Greek φυσική ( phusikḗ 'natural science'), a term derived from φύσις ( phúsis 'origin, nature, property'). Astronomy is one of the oldest natural sciences . Early civilizations dating before 3000 BCE, such as the Sumerians , ancient Egyptians , and the Indus Valley Civilisation , had a predictive knowledge and

11005-610: The Medes , and 7th century BC Assyrian texts mention a country named Partakka or Partukka (though this "need not have coincided topographically with the later Parthia"). A year after Cyrus the Great 's defeat of the Median Astyages , Parthia became one of the first provinces to acknowledge Cyrus as their ruler, "and this allegiance secured Cyrus' eastern flanks and enabled him to conduct the first of his imperial campaigns – against Sardis ." According to Greek sources, following

11160-667: The Neo-Latin word electricus ("of amber" or "like amber", from ἤλεκτρον, elektron , the Greek word for "amber") to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne 's Pseudodoxia Epidemica of 1646. Isaac Newton made early investigations into electricity, with an idea of his written down in his book Opticks arguably

11315-608: The Northern Hemisphere . Natural philosophy has its origins in Greece during the Archaic period (650 BCE – 480 BCE), when pre-Socratic philosophers like Thales rejected non-naturalistic explanations for natural phenomena and proclaimed that every event had a natural cause. They proposed ideas verified by reason and observation, and many of their hypotheses proved successful in experiment; for example, atomism

11470-729: The Parni ", an eastern-Iranian peoples from the Tajen/Tajend River valley, south-east of the Caspian Sea . Following the secession of Parthia from the Seleucid Empire and the resultant loss of Seleucid military support, Andragoras had difficulty in maintaining his borders, and about 238 BC – under the command of "Arsaces and his brother Tiridates " – the Parni invaded Parthia and seized control of Astabene (Astawa),

11625-619: The Standard Model of particle physics was derived. Following the discovery of a particle with properties consistent with the Higgs boson at CERN in 2012, all fundamental particles predicted by the standard model, and no others, appear to exist; however, physics beyond the Standard Model , with theories such as supersymmetry , is an active area of research. Areas of mathematics in general are important to this field, such as

11780-439: The camera obscura (his thousand-year-old version of the pinhole camera ) and delved further into the way the eye itself works. Using the knowledge of previous scholars, he began to explain how light enters the eye. He asserted that the light ray is focused, but the actual explanation of how light projected to the back of the eye had to wait until 1604. His Treatise on Light explained the camera obscura , hundreds of years before

11935-422: The electromagnetic force , one of the four fundamental forces of nature. Experiment has shown charge to be a conserved quantity , that is, the net charge within an electrically isolated system will always remain constant regardless of any changes taking place within that system. Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as

12090-579: The empirical world. This is usually combined with the claim that the laws of logic express universal regularities found in the structural features of the world, which may explain the peculiar relation between these fields. Physics uses mathematics to organise and formulate experimental results. From those results, precise or estimated solutions are obtained, or quantitative results, from which new predictions can be made and experimentally confirmed or negated. The results from physics experiments are numerical data, with their units of measure and estimates of

12245-466: The quantum revolution. Einstein was awarded the Nobel Prize in Physics in 1921 for "his discovery of the law of the photoelectric effect". The photoelectric effect is also employed in photocells such as can be found in solar panels . The first solid-state device was the " cat's-whisker detector " first used in the 1900s in radio receivers. A whisker-like wire is placed lightly in contact with

12400-543: The standard consensus that the laws of physics are universal and do not change with time, physics can be used to study things that would ordinarily be mired in uncertainty . For example, in the study of the origin of the Earth, a physicist can reasonably model Earth's mass, temperature, and rate of rotation, as a function of time allowing the extrapolation forward or backward in time and so predict future or prior events. It also allows for simulations in engineering that speed up

12555-448: The strong interaction , but unlike that force it operates over all distances. In comparison with the much weaker gravitational force , the electromagnetic force pushing two electrons apart is 10 times that of the gravitational attraction pulling them together. Charge originates from certain types of subatomic particles , the most familiar carriers of which are the electron and proton . Electric charge gives rise to and interacts with

12710-435: The 16th and 17th centuries, and Isaac Newton 's discovery and unification of the laws of motion and universal gravitation (that would come to bear his name). Newton also developed calculus , the mathematical study of continuous change, which provided new mathematical methods for solving physical problems. The discovery of laws in thermodynamics , chemistry , and electromagnetics resulted from research efforts during

12865-541: The 17th and 18th centuries. The development of the theory of electromagnetism in the 19th century marked significant progress, leading to electricity's industrial and residential application by electrical engineers by the century's end. This rapid expansion in electrical technology at the time was the driving force behind the Second Industrial Revolution , with electricity's versatility driving transformations in both industry and society. Electricity

13020-543: The 1936 discovery of the Baghdad Battery , which resembles a galvanic cell , though it is uncertain whether the artifact was electrical in nature. Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete , in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber. He coined

13175-557: The Arsacids were themselves finally vanquished by the Persian Sassanids , a formerly minor vassal from southwestern Iran, in April 224. Parthia was likely the first region conquered by Ardashir I after his victory over Artabanus IV, showing the importance of the province to the founder of the Sasanian dynasty. Some of the Parthian nobility continued to resist Sasanian dominion for some time, but most switched their allegiance to

13330-654: The Elder and Scribonius Largus , attested to the numbing effect of electric shocks delivered by electric catfish and electric rays , and knew that such shocks could travel along conducting objects. Patients with ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them. Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber , could be rubbed with cat's fur to attract light objects like feathers. Thales of Miletus made

13485-662: The Islamic period. These poems have the characteristics of oral literature and may have continued the oral traditions of Parthian minstrels. City-states of "some considerable size" existed in Parthia as early as the 1st millennium BC, "and not just from the time of the Achaemenids or Seleucids." However, for the most part, society was rural, and dominated by large landholders with large numbers of serfs, slaves, and other indentured labor at their disposal. Communities with free peasants also existed. By Arsacid times, Parthian society

13640-566: The Macedonian arrived there in the summer of 330 BC. Phrataphernes was reappointed governor by Alexander. Following the death of Alexander, in the Partition of Babylon in 323 BC, Parthia became a Seleucid governorate under Nicanor . Phrataphernes, the former governor, became governor of Hyrcania . In 320 BC, at the Partition of Triparadisus , Parthia was reassigned to Philip , former governor of Sogdiana . A few years later,

13795-599: The Parthian region in the West of Iran. The original location of Parthia roughly corresponds to a region in northeastern Iran , but part is in southern Turkmenistan . It was bordered by the Kopet Dag mountain range in the north, and the Dasht-e Kavir desert in the south. It bordered Media on the west, Hyrcania on the north west, Margiana on the northeast, and Aria on the east. During Arsacid times, Parthia

13950-474: The Sasanians very early. Several families that claimed descent from the Parthian noble families became a Sasanian institution known as the " Seven houses ", five of which are "in all probability" not Parthian, but contrived genealogies "in order to emphasize the antiquity of their families." Parthia continued to hold importance throughout the 3rd century. In his Ka'be-ye Zardusht inscription Shapur I lists

14105-511: The attacks from invaders and continued to advance various fields of learning, including physics. In the sixth century, Isidore of Miletus created an important compilation of Archimedes ' works that are copied in the Archimedes Palimpsest . In sixth-century Europe John Philoponus , a Byzantine scholar, questioned Aristotle 's teaching of physics and noted its flaws. He introduced the theory of impetus . Aristotle's physics

14260-406: The beginning of the field theory of the electric force. Further work was conducted in the 17th and early 18th centuries by Otto von Guericke , Robert Boyle , Stephen Gray and C. F. du Fay . Later in the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of

14415-417: The building it serves to protect. The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work . The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It

14570-423: The charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulomb's law , which relates the force to the product of the charges and has an inverse-square relation to the distance between them. The electromagnetic force is very strong, second only in strength to

14725-448: The charged parts. Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimetre. Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimetre. The most visible natural occurrence of this is lightning , caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of

14880-434: The concepts of space, time, and matter from that presented by classical physics. Classical mechanics approximates nature as continuous, while quantum theory is concerned with the discrete nature of many phenomena at the atomic and subatomic level and with the complementary aspects of particles and waves in the description of such phenomena. The theory of relativity is concerned with the description of phenomena that take place in

15035-409: The constant speed predicted by Maxwell's equations of electromagnetism. This discrepancy was corrected by Einstein's theory of special relativity , which replaced classical mechanics for fast-moving bodies and allowed for a constant speed of light. Black-body radiation provided another problem for classical physics, which was corrected when Planck proposed that the excitation of material oscillators

15190-409: The current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative. If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly; almost always this takes

15345-513: The design and construction of electronic circuits to solve practical problems are part of electronics engineering . Faraday's and Ampère's work showed that a time-varying magnetic field created an electric field, and a time-varying electric field created a magnetic field. Thus, when either field is changing in time, a field of the other is always induced. These variations are an electromagnetic wave . Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed

15500-466: The development of a new technology. There is also considerable interdisciplinarity , so many other important fields are influenced by physics (e.g., the fields of econophysics and sociophysics ). Physicists use the scientific method to test the validity of a physical theory . By using a methodical approach to compare the implications of a theory with the conclusions drawn from its related experiments and observations, physicists are better able to test

15655-429: The development of modern physics in the 20th century. Modern physics began in the early 20th century with the work of Max Planck in quantum theory and Albert Einstein 's theory of relativity. Both of these theories came about due to inaccuracies in classical mechanics in certain situations. Classical mechanics predicted that the speed of light depends on the motion of the observer, which could not be resolved with

15810-407: The development of new experiments (and often related equipment). Physicists who work at the interplay of theory and experiment are called phenomenologists , who study complex phenomena observed in experiment and work to relate them to a fundamental theory . Theoretical physics has historically taken inspiration from philosophy; electromagnetism was unified this way. Beyond the known universe,

15965-478: The early 19th century had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering . Through such people as Alexander Graham Bell , Ottó Bláthy , Thomas Edison , Galileo Ferraris , Oliver Heaviside , Ányos Jedlik , William Thomson, 1st Baron Kelvin , Charles Algernon Parsons , Werner von Siemens , Joseph Swan , Reginald Fessenden , Nikola Tesla and George Westinghouse , electricity turned from

16120-400: The east. In the late Sasanian era, Parthia came to embrace central and north-central Iran but also extended to the western parts of the plateau as well. In the Islamic era, Parthia was believed to be located in central and western Iran. Ibn al-Muqaffa considered Parthia as encompassing the regions of Isfahan , Ray , Hamadan, Mah-i Nihawand and Azerbaijan . The same definition is found in

16275-426: The effect was reciprocal: a current exerts a force on a magnet, and a magnetic field exerts a force on a current. The phenomenon was further investigated by Ampère , who discovered that two parallel current-carrying wires exerted a force upon each other: two wires conducting currents in the same direction are attracted to each other, while wires containing currents in opposite directions are forced apart. The interaction

16430-445: The electronic electrometer . The movement of electric charge is known as an electric current , the intensity of which is usually measured in amperes . Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current. Electric current can flow through some things, electrical conductors , but will not flow through an electrical insulator . By historical convention,

16585-415: The electrons. However, depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation. The process by which electric current passes through a material is termed electrical conduction , and its nature varies with that of the charged particles and

16740-426: The elementary charge, and any amount of charge an object may carry is a multiple of the elementary charge. An electron has an equal negative charge, i.e. −1.602 176 634 × 10 coulombs . Charge is possessed not just by matter , but also by antimatter , each antiparticle bearing an equal and opposite charge to its corresponding particle. The presence of charge gives rise to an electrostatic force: charges exert

16895-682: The errors in the measurements. Technologies based on mathematics, like computation have made computational physics an active area of research. Ontology is a prerequisite for physics, but not for mathematics. It means physics is ultimately concerned with descriptions of the real world, while mathematics is concerned with abstract patterns, even beyond the real world. Thus physics statements are synthetic, while mathematical statements are analytic. Mathematics contains hypotheses, while physics contains theories. Mathematics statements have to be only logically true, while predictions of physics statements must match observed and experimental data. The distinction

17050-580: The establishment of the Silk road in 114 BC, when Hecatompylos became an important junction. Nisa (Nissa, Nusay) or Mithradātkert, located on a main trade route, was one of the earliest capitals of the Parthian Empire (c. 250 BC). The city is located in the northern foothills of the Kopetdag mountains, 11 miles west of present-day city of Ashgabat (the capital of Turkmenistan ). Nisa had

17205-858: The field of theoretical physics also deals with hypothetical issues, such as parallel universes , a multiverse , and higher dimensions . Theorists invoke these ideas in hopes of solving particular problems with existing theories; they then explore the consequences of these ideas and work toward making testable predictions. Experimental physics expands, and is expanded by, engineering and technology. Experimental physicists who are involved in basic research design and perform experiments with equipment such as particle accelerators and lasers , whereas those involved in applied research often work in industry, developing technologies such as magnetic resonance imaging (MRI) and transistors . Feynman has noted that experimentalists may seek areas that have not been explored well by theorists. Parthia The name "Parthia"

17360-415: The field. His approach is entirely superseded today. He explained ideas such as motion (and gravity ) with the theory of four elements . Aristotle believed that each of the four classical elements (air, fire, water, earth) had its own natural place. Because of their differing densities, each element will revert to its own specific place in the atmosphere. So, because of their weights, fire would be at

17515-491: The form of a sine wave . Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. Alternating current is affected by electrical properties that are not observed under steady state direct current, such as inductance and capacitance . These properties however can become important when circuitry

17670-415: The language first appears on Arsacid coinage during the reign of Vologases I (51–58 AD). Evidence that use of Parthian was nonetheless widespread comes from early Sassanid times; the declarations of the early Persian kings were—in addition to their native Middle Persian —also inscribed in Parthian. The old poems known as fahlaviyat mostly come from the areas which were considered part of Parthia in

17825-400: The latter include such branches as hydrostatics , hydrodynamics and pneumatics . Acoustics is the study of how sound is produced, controlled, transmitted and received. Important modern branches of acoustics include ultrasonics , the study of sound waves of very high frequency beyond the range of human hearing; bioacoustics , the physics of animal calls and hearing, and electroacoustics ,

17980-490: The laws of classical physics accurately describe systems whose important length scales are greater than the atomic scale and whose motions are much slower than the speed of light. Outside of this domain, observations do not match predictions provided by classical mechanics. Einstein contributed the framework of special relativity, which replaced notions of absolute time and space with spacetime and allowed an accurate description of systems whose components have speeds approaching

18135-412: The manipulation of audible sound waves using electronics. Optics, the study of light, is concerned not only with visible light but also with infrared and ultraviolet radiation , which exhibit all of the phenomena of visible light except visibility, e.g., reflection, refraction, interference, diffraction, dispersion, and polarization of light. Heat is a form of energy, the internal energy possessed by

18290-400: The material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as metal, and electrolysis , where ions (charged atoms ) flow through liquids, or through plasmas such as electrical sparks. While the particles themselves can move quite slowly, sometimes with an average drift velocity only fractions of

18445-653: The modern development of photography. The seven-volume Book of Optics ( Kitab al-Manathir ) influenced thinking across disciplines from the theory of visual perception to the nature of perspective in medieval art, in both the East and the West, for more than 600 years. This included later European scholars and fellow polymaths, from Robert Grosseteste and Leonardo da Vinci to Johannes Kepler . The translation of The Book of Optics had an impact on Europe. From it, later European scholars were able to build devices that replicated those Ibn al-Haytham had built and understand

18600-583: The northern region of that territory, the administrative capital of which was Kabuchan ( Kuchan in the vulgate). A short while later the Parni seized the rest of Parthia from Andragoras, killing him in the process. Although an initial punitive expedition by the Seleucids under Seleucus II was not successful, the Seleucids under Antiochus III recaptured Arsacid controlled territory in 209 BC from Arsaces' (or Tiridates') successor, Arsaces II . Arsaces II sued for peace and accepted vassal status, and it

18755-468: The other Philoponus' criticism of Aristotelian principles of physics served as an inspiration for Galileo Galilei ten centuries later, during the Scientific Revolution . Galileo cited Philoponus substantially in his works when arguing that Aristotelian physics was flawed. In the 1300s Jean Buridan , a teacher in the faculty of arts at the University of Paris , developed the concept of impetus. It

18910-459: The other, you will see that the ratio of the times required for the motion does not depend on the ratio of the weights, but that the difference in time is a very small one. And so, if the difference in the weights is not considerable, that is, of one is, let us say, double the other, there will be no difference, or else an imperceptible difference, in time, though the difference in weight is by no means negligible, with one body weighing twice as much as

19065-572: The particles of which a substance is composed; thermodynamics deals with the relationships between heat and other forms of energy. Electricity and magnetism have been studied as a single branch of physics since the intimate connection between them was discovered in the early 19th century; an electric current gives rise to a magnetic field , and a changing magnetic field induces an electric current. Electrostatics deals with electric charges at rest, electrodynamics with moving charges, and magnetostatics with magnetic poles at rest. Classical physics

19220-602: The positions of the planets . According to Asger Aaboe , the origins of Western astronomy can be found in Mesopotamia , and all Western efforts in the exact sciences are descended from late Babylonian astronomy . Egyptian astronomers left monuments showing knowledge of the constellations and the motions of the celestial bodies, while Greek poet Homer wrote of various celestial objects in his Iliad and Odyssey ; later Greek astronomers provided names, which are still used today, for most constellations visible from

19375-714: The power and influence of this handful of Parthian noble families was such that they frequently opposed the monarch, and would eventually be a "contributory factor in the downfall" of the dynasty. From about 130 BC onwards, Parthia suffered numerous incursions by various nomadic tribes, including the Sakas , the Yuezhi , and the Massagetae . Each time, the Arsacid dynasts responded personally, doing so even when there were more severe threats from Seleucids or Romans looming on

19530-427: The principle, now known as Faraday's law of induction , that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop. Exploitation of this discovery enabled him to invent the first electrical generator in 1831, in which he converted the mechanical energy of a rotating copper disc to electrical energy. Faraday's disc was inefficient and of no use as

19685-596: The province of Parthia in second place after Pars. The Abnun inscription describes the Roman invasion of 243/44 as an attack on Pars and Parthia. Considering the Romans never went further than Mesopotamia, "Pars and Parthia" may stand for the Sasanian Empire itself. Parthia was also the second province chosen for settlement by Roman prisoners of war after the Battle of Edessa in 260 . The Parthians spoke Parthian ,

19840-455: The province was invaded by Peithon , governor of Media Magna, who then attempted to make his brother Eudamus governor. Peithon and Eudamus were driven back, and Parthia remained a governorate in its own right. In 316 BC, Stasander, a vassal of Seleucus I Nicator and governor of Bactria (and, it seems, also of Aria and Margiana ) was appointed governor of Parthia. For the next 60 years, various Seleucids would be appointed governors of

19995-531: The province. In 247 BC, following the death of Antiochus II , Ptolemy III seized control of the Seleucid capital at Antioch , and "so left the future of the Seleucid dynasty for a moment in question." Taking advantage of the uncertain political situation, Andragoras , the Seleucid governor of Parthia, proclaimed his independence and began minting his own coins. Meanwhile, "a man called Arsaces , of Scythian or Bactrian origin, [was] elected leader of

20150-577: The seizure of the Achaemenid throne by Darius I , the Parthians united with the Median king Phraortes to revolt against him. Hystaspes , the Achaemenid governor of the province (said to be father of Darius I), managed to suppress the revolt, which seems to have occurred around 522–521 BC. The first indigenous Iranian mention of Parthia is in the Behistun inscription of Darius I , where Parthia

20305-452: The special property that it is conservative , which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated. The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term voltage sees greater everyday usage. For practical purposes, defining

20460-440: The speed being proportional to the weight and the speed of the object that is falling depends inversely on the density object it is falling through (e.g. density of air). He also stated that, when it comes to violent motion (motion of an object when a force is applied to it by a second object) that the speed that object moves, will only be as fast or strong as the measure of force applied to it. The problem of motion and its causes

20615-412: The speed of light. Planck, Schrödinger, and others introduced quantum mechanics, a probabilistic notion of particles and interactions that allowed an accurate description of atomic and subatomic scales. Later, quantum field theory unified quantum mechanics and special relativity. General relativity allowed for a dynamical, curved spacetime, with which highly massive systems and the large-scale structure of

20770-412: The study of probabilities and groups . Physics deals with a wide variety of systems, although certain theories are used by all physicists. Each of these theories was experimentally tested numerous times and found to be an adequate approximation of nature. For instance, the theory of classical mechanics accurately describes the motion of objects, provided they are much larger than atoms and moving at

20925-444: The top, air underneath fire, then water, then lastly earth. He also stated that when a small amount of one element enters the natural place of another, the less abundant element will automatically go towards its own natural place. For example, if there is a fire on the ground, the flames go up into the air in an attempt to go back into its natural place where it belongs. His laws of motion included: that heavier objects will fall faster,

21080-415: The two forces of nature then known. The force on the compass needle did not direct it to or away from the current-carrying wire, but acted at right angles to it. Ørsted's words were that "the electric conflict acts in a revolving manner." The force also depended on the direction of the current, for if the flow was reversed, then the force did too. Ørsted did not fully understand his discovery, but he observed

21235-423: The understanding of electromagnetism , solid-state physics , and nuclear physics led directly to the development of technologies that have transformed modern society, such as television, computers, domestic appliances , and nuclear weapons ; advances in thermodynamics led to the development of industrialization; and advances in mechanics inspired the development of calculus . The word physics comes from

21390-423: The universe can be well-described. General relativity has not yet been unified with the other fundamental descriptions; several candidate theories of quantum gravity are being developed. Physics, as with the rest of science, relies on the philosophy of science and its " scientific method " to advance knowledge of the physical world. The scientific method employs a priori and a posteriori reasoning as well as

21545-573: The use of Bayesian inference to measure the validity of a given theory. Study of the philosophical issues surrounding physics, the philosophy of physics , involves issues such as the nature of space and time , determinism , and metaphysical outlooks such as empiricism , naturalism , and realism . Many physicists have written about the philosophical implications of their work, for instance Laplace , who championed causal determinism , and Erwin Schrödinger , who wrote on quantum mechanics. The mathematical physicist Roger Penrose has been called

21700-988: The validity of a theory in a logical, unbiased, and repeatable way. To that end, experiments are performed and observations are made in order to determine the validity or invalidity of a theory. A scientific law is a concise verbal or mathematical statement of a relation that expresses a fundamental principle of some theory, such as Newton's law of universal gravitation. Theorists seek to develop mathematical models that both agree with existing experiments and successfully predict future experimental results, while experimentalists devise and perform experiments to test theoretical predictions and explore new phenomena. Although theory and experiment are developed separately, they strongly affect and depend upon each other. Progress in physics frequently comes about when experimental results defy explanation by existing theories, prompting intense focus on applicable modelling, and when new theories generate experimentally testable predictions , which inspire

21855-415: The vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together. Ørsted's discovery in 1821 that a magnetic field existed around all sides of a wire carrying an electric current indicated that there was a direct relationship between electricity and magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces,

22010-579: The way vision works. Physics became a separate science when early modern Europeans used experimental and quantitative methods to discover what are now considered to be the laws of physics . Major developments in this period include the replacement of the geocentric model of the Solar System with the heliocentric Copernican model , the laws governing the motion of planetary bodies (determined by Kepler between 1609 and 1619), Galileo's pioneering work on telescopes and observational astronomy in

22165-451: The western borders of their empire (as was the case for Mithridates I ). Defending the empire against the nomads cost Phraates II and Artabanus I their lives. The Roman Crassus attempted to conquer Parthia in 52 BC but was decisively defeated at the Battle of Carrhae . Caesar was planning another invasion when he was assassinated in 44 BC. A long series of Roman-Parthian wars followed. Around 32 BC, civil war broke out when

22320-465: The works of al-Khawazmi and Hamza al-Isfahani . Al-Dinawari , while not using the word Parthia, considered Jibal to be the realm of the last Parthian king, Artabanus IV. As the region inhabited by Parthians, Parthia first appears as a political entity in Achaemenid lists of governorates ("satrapies") under their dominion. Prior to this, the people of the region seem to have been subjects of

22475-399: The works of many scientists like Ibn Sahl , Al-Kindi , Ibn al-Haytham , Al-Farisi and Avicenna . The most notable work was The Book of Optics (also known as Kitāb al-Manāẓir), written by Ibn al-Haytham, in which he presented the alternative to the ancient Greek idea about vision. In his Treatise on Light as well as in his Kitāb al-Manāẓir , he presented a study of the phenomenon of

22630-508: The worthiness of their patrons through association with mythical heroes and rulers. These Parthian heroic poems, "mainly known through Persian of the lost Middle Persian Xwaday-namag , and notably through Firdausi's Shahnameh , [were] doubtless not yet wholly lost in the Khurasan of [Firdausi's] day." In Parthia itself, attested use of written Parthian is limited to the nearly three thousand ostraca found (in what seems to have been

22785-550: Was a step toward the modern ideas of inertia and momentum. Islamic scholarship inherited Aristotelian physics from the Greeks and during the Islamic Golden Age developed it further, especially placing emphasis on observation and a priori reasoning, developing early forms of the scientific method . The most notable innovations under Islamic scholarship were in the field of optics and vision, which came from

22940-445: Was divided into the four classes (limited to freemen). At the top were the kings and near family members of the king. These were followed by the lesser nobility and the general priesthood, followed by the mercantile class and lower-ranking civil servants, and with farmers and herdsmen at the bottom. Little is known of the Parthian economy, but agriculture must have played the most important role in it. Significant trade first occurs with

23095-540: Was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines. Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves. A hollow conducting body carries all its charge on its outer surface. The field

23250-513: Was found to be correct approximately 2000 years after it was proposed by Leucippus and his pupil Democritus . During the classical period in Greece (6th, 5th and 4th centuries BCE) and in Hellenistic times , natural philosophy developed along many lines of inquiry. Aristotle ( Greek : Ἀριστοτέλης , Aristotélēs ) (384–322 BCE), a student of Plato , wrote on many subjects, including

23405-417: Was not scrutinized until Philoponus appeared; unlike Aristotle, who based his physics on verbal argument, Philoponus relied on observation. On Aristotle's physics Philoponus wrote: But this is completely erroneous, and our view may be corroborated by actual observation more effectively than by any sort of verbal argument. For if you let fall from the same height two weights of which one is many times as heavy as

23560-591: Was not until Arsaces II's grandson (or grand-nephew) Phraates I , that the Arsacids/Parni would again begin to assert their independence. From their base in Parthia, the Arsacid dynasts eventually extended their dominion to include most of Greater Iran . They also quickly established several eponymous branches on the thrones of Armenia , Iberia , and Caucasian Albania . Even though the Arsacids only sporadically had their capital in Parthia, their power base

23715-548: Was studied carefully, leading to the philosophical notion of a " prime mover " as the ultimate source of all motion in the world (Book 8 of his treatise Physics ). The Western Roman Empire fell to invaders and internal decay in the fifth century, resulting in a decline in intellectual pursuits in western Europe. By contrast, the Eastern Roman Empire (usually known as the Byzantine Empire ) resisted

23870-440: Was there, among the Parthian feudal families, upon whose military and financial support the Arsacids depended. In exchange for this support, these families received large tracts of land among the earliest conquered territories adjacent to Parthia, which the Parthian nobility then ruled as provincial rulers. The largest of these city-states were Kuchan , Semnan , Gorgan , Merv , Zabol and Yazd . From about 105 BC onwards,

24025-539: Was united with Hyrcania as one administrative unit, and that region is therefore often (subject to context) considered a part of Parthia proper. By the early Sasanian period, Parthia was located in the central part of the Iranian plateau, neighboring Pars to the south, Khuzistan to the south-west, Media to the north-west, the Alborz Mountains to the north, Abarshahr to the north-east, and Kirman to

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