World History and Energy

Total Page:16

File Type:pdf, Size:1020Kb

World History and Energy World History and Energy VACLAV SMIL University of Manitoba Winnipeg, Manitoba, Canada history. But no energetic perspective can explain why 1. A Deterministic View of History complex entities such as cultures and civilizations 2. The Earliest Energy Eras arise and no thermodynamic interpretation can 3. Medieval and Early Modern Advances reveal the reasons for either their remarkable history 4. Transitions to Modernity or their astounding diversity of beliefs, habits, and 5. High-Energy Civilization and Its Attributes attitudes from which their actions spring. This article examines both of these contrasting views of energy 6. Limits of Energetic Determinism and world history. Glossary antiquity The era of ancient (from the Western perspective, 1. A DETERMINISTIC VIEW mostly the Middle Eastern and Mediterranean) civiliza- OF HISTORY tions extant between prehistory and the Middle Ages. determinism A doctrine claiming that human actions are Countless energy imperatives––ranging from the determined by external factors; its prominent varieties solar flux reaching the earth to minimum tempera- include environmental and geographic determinism. tures required for the functioning of thousands of early modern world The period immediately following the enzymes––have always shaped life on Earth by Middle Ages, variously dated as 1493–1800, 1550– 1850, or the 16th to 18th centuries. controlling the environment and by setting the limits energy transition A period of passing from one configura- on the performance of organisms. Deterministic tion of prime movers and dominant fuels to a new interpretations of energy’s role in world history setup. seems to be a natural proposition, with history seen middle ages The period between antiquity and the modern as a quest for increased complexity made possible by era, often circumscribed by the years 500–1500 CE. mastering higher energy flows. Periodization of this prehistory The period of human evolution predating quest on the basis of prevailing prime movers and recorded history. dominant sources of heat is another obvious propo- sition. This approach divides the evolution of the human species into distinct energy eras and brings A strict thermodynamic perspective must see en- out the importance of energy transitions that usher in ergy––its overall use, quality, intensity, and conver- more powerful, and more flexible, prime movers and sion efficiency––as the key factor in the history of the more efficient ways of energy conversion. Perhaps human species. Energy flows and conversions sustain the most intriguing conclusion arising from this and delimit the lives of all organisms and hence also grand view of history is the shrinking duration of of superorganisms such as societies and civilizations. successive energy eras and the accelerating pace of No action––be it a better crop harvest that ends a grand energy transitions. famine or the defeat of an aggressive neighbor––can The first energy era started more than 300,000 take place without harnessing and transforming years ago when the human species, Homo sapiens, energies through management, innovation, or daring. became differentiated from Homo erectus, and the Inevitably, the availability and quality of particular era continued until the beginning of settled societies prime movers and sources of heat and the modes of some 10,000 years ago. Throughout prehistory, all their conversions must have left deep imprints on efforts to control greater energy flows were capped Encyclopedia of Energy, Volume 6. r 2004 Elsevier Inc. All rights reserved. 549 550 World History and Energy by the limited power of human metabolism and by accomplishments that were achieved through inge- the inefficient use of fire. Domestication of draft nuity and better organization are noted. animals and harnessing of fire for producing metals and other durable materials constituted the first great energy transition: reliance on these extrasomatic 2. THE EARLIEST ENERGY ERAS energies had raised energy throughput of preindus- trial societies by more than an order of magnitude. During the long span of prehistory, the human The second transition got under way only several species relied only on its somatic energy, using millennia later; it was not as universal as the first one muscles to secure a basic food supply and then to and its effects made a profound, and relatively early, improve shelters and acquire meager material pos- difference only in some places: it came as some sessions. Organismic imperatives (above all, the traditional societies substituted large shares of their basal metabolism scaling as the body mass raised to muscular exertions by waterwheels and windmills, 0.75 power) and the mechanical efficiency of muscles simple but ingenious inanimate prime movers that (able to convert no more than 20–25% of ingested were designed to convert the two common renewable food to kinetic energy) governed these exertions: energy flows with increasing power and efficiency. healthy adults of smaller statures cannot sustain The third great energy transition––substitution of useful work at rates of more than 50–90 W and can animate prime movers by engines and of biomass develop power of 102 W only during brief spells of energies by fossil fuels––began only several centuries concentrated exertion. The former performance ago in a few European countries and it was sufficed for all but a few extreme forms of food accomplished by all industrialized nations during gathering and the latter exertions were called on for the 20th century. That transition is yet to run its some forms of hunting. Simple tools made some course in most low-income economies, particularly foraging and processing tasks more efficient and in Africa. The latest energy transition has been under extended the reach of human muscles. way since 1882 when the world’s first electricity- Energy returns in foraging (energy in food/energy generating stations were commissioned in London spent in collecting and hunting) ranged from barely and New York (both Edison’s coal-fired plants) and positive (particularly for some types of hunting) to in Appleton, Wisconsin (the first hydroelectric seasonally fairly high (up to 40-fold for digging up station). Since that time, all modernizing economies tubers). The choice of the collected plants was have been consuming increasing shares of their fossil determined above all by their accessibility, nutri- fuels indirectly as electricity and introducing new tional density, and palatability, with grasslands modes of primary electricity generation––nuclear offering generally a better selection of such species fission starting in the mid-1950s, and later also wind than did dense forests. Collective hunting of large turbines and photovoltaic cells––to boost the overall mammals brought the highest net energy returns output of this most flexible and most convenient (because of their high fat content) and it also form of energy. The second key attribute of this contributed to the emergence of social complexity. transition has been a steady relative retreat of coal Only a few coastal societies collecting and hunting mirrored by the rise of hydrocarbons, first crude oil marine species had sufficiently high and secure and later natural gas. energy returns (due to seasonal migrations of fish Improving the quality of life has been the principal or whales) such that they were able to live in individual benefit of this quest for higher energy use permanent settlements and devote surplus energy to that has brought increased food harvests, greater elaborate rituals and impressive artistic creations (for accumulation of personal possessions, abundance of example, the tall ornate wooden totems of the Indian educational and leisure opportunities, and vastly tribes of the Pacific Northwest). enhanced personal mobility. The growth of the The only extrasomatic energy conversion mas- world’s population, the rising economic might of tered by prehistoric societies was the use of fire for nations, the extension of empires and military warmth and cooking, which can be indisputably capabilities, the expansion of world trade, and the dated to approximately 250,000 years ago. Eventual globalization of human affairs have been the key shifts from foraging to shifting cultivation and then collective consequences of the quest. These advances to sedentary farming were gradual processes driven are discussed in this article and the limits of prime by a number of energy-related, nutritional, and social movers and heat sources that were available during factors: there was no short and sharp agricultural the successive eras of energy use and the major revolution. These changes were accompanied by World History and Energy 551 declining net energy returns in food production, but harvests were barely adequate to provide subsistence these declines had a rewarding corollary as the higher diets. Those agroecosystems where grazing land was investment of metabolic energy in clearing land and also limited (the rice regions of Asia) could support in planting, weeding, fertilizing, harvesting, and only relatively small numbers of draft animals. processing crops, as well as storing grains or tubers, Limited unit power of muscles could be overcome made it possible to support much higher population by massing people, or draft animals, and the densities. Whereas the most affluent coastal foraging combination of tools and organized deployment of societies had densities less than 1 person/km2 (and massed labor made it possible to build impressive most foraging societies had carrying capacities well structures solely with human labor. Massed forces of below 0.1 person/km2), shifting agricultures would 20–100 adults could deliver sustained power of 1.5– easily support 20–30 people/km2 and even the earliest 8 kW and could support brief exertions of up to extensive forms of settled farming (ancient Meso- 100 kW, enough to transport and erect (with the help potamia, Egypt and China’s Huanghe Valley) could of simple devices) megaliths and to build impressive feed 100–200 people/km2, that is, 1–2 people/ha of stone structures on all continents except Australia. In cultivated land (Fig.
Recommended publications
  • Writing and City Life
    29 THEME2 writing and city life CITY life began in Mesopotamia*, the land between the Euphrates and the Tigris rivers that is now part of the Republic of Iraq. Mesopotamian civilisation is known for its prosperity, city life, its voluminous and rich literature and its mathematics and astronomy. Mesopotamia’s writing system and literature spread to the eastern Mediterranean, northern *The name Syria, and Turkey after 2000 BCE, so that the kingdoms of Mesopotamia is that entire region were writing to one another, and to the derived from the Pharaoh of Egypt, in the language and script of Mesopotamia. Greek words mesos, Here we shall explore the connection between city life and writing, and then look at some outcomes of a sustained meaning middle, tradition of writing. and potamos, In the beginning of recorded history, the land, mainly the meaning river. urbanised south (see discussion below), was called Sumer and Akkad. After 2000 BCE, when Babylon became an important city, the term Babylonia was used for the southern region. From about 1100 BCE, when the Assyrians established their kingdom in the north, the region became known as Assyria. The first known language of the land was Sumerian. It was gradually replaced by Akkadian around 2400 BCE when Akkadian speakers arrived. This language flourished till about Alexander’s time (336-323 BCE), with some regional changes occurring. From 1400 BCE, Aramaic also trickled in. This language, similar to Hebrew, became widely spoken after 1000 BCE. It is still spoken in parts of Iraq. Archaeology in Mesopotamia began in the 1840s. At one or two sites (including Uruk and Mari, which we discuss below), excavations continued for decades.
    [Show full text]
  • Estimation of the Dissipation Rate of Turbulent Kinetic Energy: a Review
    Chemical Engineering Science 229 (2021) 116133 Contents lists available at ScienceDirect Chemical Engineering Science journal homepage: www.elsevier.com/locate/ces Review Estimation of the dissipation rate of turbulent kinetic energy: A review ⇑ Guichao Wang a, , Fan Yang a,KeWua, Yongfeng Ma b, Cheng Peng c, Tianshu Liu d, ⇑ Lian-Ping Wang b,c, a SUSTech Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen 518055, PR China b Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China c Department of Mechanical Engineering, 126 Spencer Laboratory, University of Delaware, Newark, DE 19716-3140, USA d Department of Mechanical and Aeronautical Engineering, Western Michigan University, Kalamazoo, MI 49008, USA highlights Estimate of turbulent dissipation rate is reviewed. Experimental works are summarized in highlight of spatial/temporal resolution. Data processing methods are compared. Future directions in estimating turbulent dissipation rate are discussed. article info abstract Article history: A comprehensive literature review on the estimation of the dissipation rate of turbulent kinetic energy is Received 8 July 2020 presented to assess the current state of knowledge available in this area. Experimental techniques (hot Received in revised form 27 August 2020 wires, LDV, PIV and PTV) reported on the measurements of turbulent dissipation rate have been critically Accepted 8 September 2020 analyzed with respect to the velocity processing methods. Traditional hot wires and LDV are both a point- Available online 12 September 2020 based measurement technique with high temporal resolution and Taylor’s frozen hypothesis is generally required to transfer temporal velocity fluctuations into spatial velocity fluctuations in turbulent flows.
    [Show full text]
  • Turbulence Kinetic Energy Budgets and Dissipation Rates in Disturbed Stable Boundary Layers
    4.9 TURBULENCE KINETIC ENERGY BUDGETS AND DISSIPATION RATES IN DISTURBED STABLE BOUNDARY LAYERS Julie K. Lundquist*1, Mark Piper2, and Branko Kosovi1 1Atmospheric Science Division Lawrence Livermore National Laboratory, Livermore, CA, 94550 2Program in Atmospheric and Oceanic Science, University of Colorado at Boulder 1. INTRODUCTION situated in gently rolling farmland in eastern Kansas, with a homogeneous fetch to the An important parameter in the numerical northwest. The ASTER facility, operated by the simulation of atmospheric boundary layers is the National Center for Atmospheric Research (NCAR) dissipation length scale, lε. It is especially Atmospheric Technology Division, was deployed to important in weakly to moderately stable collect turbulence data. The ASTER sonic conditions, in which a tenuous balance between anemometers were used to compute turbulence shear production of turbulence, buoyant statistics for the three velocity components and destruction of turbulence, and turbulent dissipation used to estimate dissipation rate. is maintained. In large-scale models, the A dry Arctic cold front passed the dissipation rate is often parameterized using a MICROFRONTS site at approximately 0237 UTC diagnostic equation based on the production of (2037 LST) 20 March 1995, two hours after local turbulent kinetic energy (TKE) and an estimate of sunset at 1839 LST. Time series spanning the the dissipation length scale. Proper period 0000-0600 UTC are shown in Figure 1.The parameterization of the dissipation length scale 6-hr time period was chosen because it allows from experimental data requires accurate time for the front to completely pass the estimation of the rate of dissipation of TKE from instrumented tower, with time on either side to experimental data.
    [Show full text]
  • Work and Energy Summary Sheet Chapter 6
    Work and Energy Summary Sheet Chapter 6 Work: work is done when a force is applied to a mass through a displacement or W=Fd. The force and the displacement must be parallel to one another in order for work to be done. F (N) W =(Fcosθ)d F If the force is not parallel to The area of a force vs. the displacement, then the displacement graph + W component of the force that represents the work θ d (m) is parallel must be found. done by the varying - W d force. Signs and Units for Work Work is a scalar but it can be positive or negative. Units of Work F d W = + (Ex: pitcher throwing ball) 1 N•m = 1 J (Joule) F d W = - (Ex. catcher catching ball) Note: N = kg m/s2 • Work – Energy Principle Hooke’s Law x The work done on an object is equal to its change F = kx in kinetic energy. F F is the applied force. 2 2 x W = ΔEk = ½ mvf – ½ mvi x is the change in length. k is the spring constant. F Energy Defined Units Energy is the ability to do work. Same as work: 1 N•m = 1 J (Joule) Kinetic Energy Potential Energy Potential energy is stored energy due to a system’s shape, position, or Kinetic energy is the energy of state. motion. If a mass has velocity, Gravitational PE Elastic (Spring) PE then it has KE 2 Mass with height Stretch/compress elastic material Ek = ½ mv 2 EG = mgh EE = ½ kx To measure the change in KE Change in E use: G Change in ES 2 2 2 2 ΔEk = ½ mvf – ½ mvi ΔEG = mghf – mghi ΔEE = ½ kxf – ½ kxi Conservation of Energy “The total energy is neither increased nor decreased in any process.
    [Show full text]
  • Middle School Physical Science: Kinetic Energy and Potential Energy
    MIDDLE SCHOOL PHYSICAL SCIENCE: KINETIC ENERGY AND POTENTIAL ENERGY Standards Bundle Standards are listed within the bundle. Bundles are created with potential instructional use in mind, based upon potential for related phenomena that can be used throughout a unit. MS-PS3-1 Construct and interpret graphical displays of data to describe the relationships of kinetic energy to the mass of an object and to the speed of an object. [Clarification Statement: Emphasis is on descriptive relationships between kinetic energy and mass separately from kinetic energy and speed. Examples could include riding a bicycle at different speeds, rolling different sizes of rocks downhill, and getting hit by a wiffle ball versus a tennis ball.] MS-PS3-2 Develop a model to describe that when the arrangement of objects interacting at a distance changes, different amounts of potential energy are stored in the system. [Clarification Statement: Emphasis is on relative amounts of potential energy, not on calculations of potential energy. Examples of objects within systems interacting at varying distances could include: the Earth and either a roller coaster cart at varying positions on a hill or objects at varying heights on shelves, changing the direction/orientation of a magnet, and a balloon with static electrical charge being brought closer to a classmate’s hair. Examples of models could include representations, diagrams, pictures, and written descriptions of systems.] [Assessment Boundary: Assessment is limited to two objects and electric, magnetic, and gravitational interactions.] MS-PS3-5. Engage in argument from evidence to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object.
    [Show full text]
  • Chapter 7 Electricity Lesson 2 What Are Static and Current Electricity?
    Chapter 7 Electricity Lesson 2 What Are Static and Current Electricity? Static Electricity • Most objects have no charge= the atoms are neutral. • They have equal numbers of protons and electrons. • When objects rub against another, electrons move from the atoms of one to atoms of the other object. • The numbers of protons and electrons in the atoms are no longer equal: they are either positively or negatively charged. • The buildup of charges on an object is called static electricity. • Opposite charges attract each other. • Charged objects can also attract neutral objects. • When items of clothing rub together in a dryer, they can pick up a static charge. • Because some items are positive and some are negative, they stick together. • When objects with opposite charges get close, electrons sometimes jump from the negative object to the positive object. • This evens out the charges, and the objects become neutral. • The shocks you can feel are called static discharge. • The crackling noises you hear are the sounds of the sparks. • Lightning is also a static discharge. • Where does the charge come from? • Scientists HYPOTHESIZE that collisions between water droplets in a cloud cause the drops to become charged. • Negative charges collect at the bottom of the cloud. • Positive charges collect at the top of the cloud. • When electrons jump from one cloud to another, or from a cloud to the ground, you see lightning. • The lightning heats the air, causing it to expand. • As cooler air rushes in to fill the empty space, you hear thunder. • Earth can absorb lightning’s powerful stream of electrons without being damaged.
    [Show full text]
  • 3. Energy, Heat, and Work
    3. Energy, Heat, and Work 3.1. Energy 3.2. Potential and Kinetic Energy 3.3. Internal Energy 3.4. Relatively Effects 3.5. Heat 3.6. Work 3.7. Notation and Sign Convention In these Lecture Notes we examine the basis of thermodynamics – fundamental definitions and equations for energy, heat, and work. 3-1. Energy. Two of man's earliest observations was that: 1)useful work could be accomplished by exerting a force through a distance and that the product of force and distance was proportional to the expended effort, and 2)heat could be ‘felt’ in when close or in contact with a warm body. There were many explanations for this second observation including that of invisible particles traveling through space1. It was not until the early beginnings of modern science and molecular theory that scientists discovered a true physical understanding of ‘heat flow’. It was later that a few notable individuals, including James Prescott Joule, discovered through experiment that work and heat were the same phenomenon and that this phenomenon was energy: Energy is the capacity, either latent or apparent, to exert a force through a distance. The presence of energy is indicated by the macroscopic characteristics of the physical or chemical structure of matter such as its pressure, density, or temperature - properties of matter. The concept of hot versus cold arose in the distant past as a consequence of man's sense of touch or feel. Observations show that, when a hot and a cold substance are placed together, the hot substance gets colder as the cold substance gets hotter.
    [Show full text]
  • Work, Power, & Energy
    WORK, POWER, & ENERGY In physics, work is done when a force acting on an object causes it to move a distance. There are several good examples of work which can be observed everyday - a person pushing a grocery cart down the aisle of a grocery store, a student lifting a backpack full of books, a baseball player throwing a ball. In each case a force is exerted on an object that caused it to move a distance. Work (Joules) = force (N) x distance (m) or W = f d The metric unit of work is one Newton-meter ( 1 N-m ). This combination of units is given the name JOULE in honor of James Prescott Joule (1818-1889), who performed the first direct measurement of the mechanical equivalent of heat energy. The unit of heat energy, CALORIE, is equivalent to 4.18 joules, or 1 calorie = 4.18 joules Work has nothing to do with the amount of time that this force acts to cause movement. Sometimes, the work is done very quickly and other times the work is done rather slowly. The quantity which has to do with the rate at which a certain amount of work is done is known as the power. The metric unit of power is the WATT. As is implied by the equation for power, a unit of power is equivalent to a unit of work divided by a unit of time. Thus, a watt is equivalent to a joule/second. For historical reasons, the horsepower is occasionally used to describe the power delivered by a machine.
    [Show full text]
  • The Development of the Historiography of the Civil
    THE DEVELOPMENT OF THE HISTORIOGRAPHY OF THE CIVIL WAR By Eleanor Rigney Submitted as an Honors Paper in the Department of History THE WOMAN'S COLLEGE OF THE UNIVERSITY OF NORTH CAROLINA GREENSBORO, NORTH CAROLINA 1950 THE DEVELOPMENT OF THE HISTORIOGRAPHY OF THE CIVIL WAR TABLE OF CONTENTS Page INTRODUCTION 1 - ■ Chapter I. AMERICAN HISTORIOGRAPHY SINCE 1865 5 II. CHANGES IN INTERPRETATIONS OF THE CAUSES OF THE CIVIL WAR 28 III. CHANGES IN INTERPRETATIONS OF CONDITIONS DURING THE COURSE OF THE WAR 52 IV. EFFECTS OF HISTORICAL REVISION ON TEXTBOOKS. 67 BIBLIOGRAPHY 78 Of all the events in American life, none seems to have stimulated the production of a greater bulk of literature, historical or otherwise, than the Civil War. Aside from the inspiration afforded by the rather dramatic quality of the war itself, probably no other episode in American history has aroused such widespread partisan feeling or so strong a disposition to apportion blame, to excuse, vindioate, or explain, publicly, the causes and events of the conflict. Consequently, in the years immediately following the war, many participants, both actual and vicarious, kept an interested public supplied with a quantity of literature that was usually either panegyrical or polemical in tone. As a result, a "correct" Northern and an equally "correct" Southern interpretation was developed rapidly; and before long, general opinion in both sections, supported by common memories and prejudices, was crystallized into an almost impervious tradition. Time itself has tended to make brittle these accumulated myths and legends. Furthermore, new sources of information have been exploited, new generations of writers have matured, and new points of view on the subject of history itself — its proper content, uses, and methods — have been developed and have operated to erode the surface of the older beliefs and assumptions.
    [Show full text]
  • AFS/HI 276 Intro. to the History of West Africa
    AFS/HI 276 Intro. To the History of West Africa Spring 2021 | Online 3 credit hours | No prerequisite | Humanities & Global Knowledge GEP Instructor: Dr. Liz Timbs (she/her/hers) Office: A spare bedroom, Raleigh, NC, USA Email: [email protected] Office Hours: By appointment only; http://calendly.com/liztimbs Course Website: Moodle This is a web course, combining asynchronous and synchronous instruction. All lecture content will be pre-recorded and posted in advance. Starting Sunday, January 24th, lecture content will be posted by 5pm on Sunday for the subsequent week. Given the limitations and exhaustion inherent in using Zoom for course meetings, although this course was initially scheduled to meet twice weekly, we have opted instead to meet once a week (beginning Week 2). You are required to attend 16 synchronous course meetings on Zoom, from 11:45am-1:00pm: 1. Tuesday, January 19th 9. Thursday, March 11th 2. Thursday, January 21st 10. Thursday, March 18th 3. Thursday, January 28th 11. Thursday, March 25th 4. Thursday, February 4th 12. Thursday, April 1st 5. Thursday, February 11th 13. Thursday, April 8th 6. Thursday, February 18th 14. Tuesday, April 13th 7. Thursday, February 25th 15. Thursday, April 22nd 8. Thursday, March 4th 16. Thursday, April 29th We will be using the course Moodle site and NCSU email for all communication. AFS/HI 276 History of West Africa | Spring 2021 | pg. 2 COURSE DESCRIPTION We will study the history of West Africa from well before recorded history to the present. Though we will not, of course, be covering “everything,” we will look at major themes in West African history, as well as case studies, in an attempt to understand the histories of people and places in the region.
    [Show full text]
  • Chapter 07: Kinetic Energy and Work Conservation of Energy Is One of Nature’S Fundamental Laws That Is Not Violated
    Chapter 07: Kinetic Energy and Work Conservation of Energy is one of Nature’s fundamental laws that is not violated. Energy can take on different forms in a given system. This chapter we will discuss work and kinetic energy. If we put energy into the system by doing work, this additional energy has to go somewhere. That is, the kinetic energy increases or as in next chapter, the potential energy increases. The opposite is also true when we take energy out of a system. the grand total of all forms of energy in a given system is (and was, and will be) a constant. Exam 2 Review • Chapters 7, 8, 9, 10. • A majority of the Exam (~75%) will be on Chapters 7 and 8 (problems, quizzes, and concepts) • Chapter 9 lectures and problems • Chapter 10 lecture Different forms of energy Kinetic Energy: Potential Energy: linear motion gravitational rotational motion spring compression/tension electrostatic/magnetostatic chemical, nuclear, etc.... Mechanical Energy is the sum of Kinetic energy + Potential energy. (reversible process) Friction will convert mechanical energy to heat. Basically, this (conversion of mechanical energy to heat energy) is a non-reversible process. Chapter 07: Kinetic Energy and Work Kinetic Energy is the energy associated with the motion of an object. m: mass and v: speed SI unit of energy: 1 joule = 1 J = 1 kg.m2/s2 Work Work is energy transferred to or from an object by means of a force acting on the object. Formal definition: *Special* case: Work done by a constant force: W = ( F cos θ) d = F d cos θ Component of F in direction of d Work done on an object moving with constant velocity? constant velocity => acceleration = 0 => force = 0 => work = 0 Consider 1-D motion.
    [Show full text]
  • From Human Prehistory to the Early Civilizations Human Life in the Era
    Chapter I From Human Prehistory to the Early Civilizations One day in 10,000 B.C.E. a solitary figure walked by the edge of the Pecos River in the American Southwest. He may have been out hunting or traveling between settlements, but he stopped there to gather up some dead grass and driftwood into a pile. He used his sharpened spear to cut a dead twig from an overhanging cottonwood tree and took a long, dried yucca leaf from his leather belt. He knelt down and held the twig upright on the centerline of the leaf. Then, as he had done many times before, he twirled the stick between his hands until the friction between twig and leaf produced a gleam, or glowing ember, which he quickly transferred to the grass and wood he had gathered. He tended the flame until it grew into a fire that provided not only some warmth, but a means of cooking a meal. When he subsequently rejoined others of his kind, he may have talked about his journey and how he lost his yucca leaf fire-started at that campsite by the river. Of course we have no evidence of his conversation, just the yucca leaf he left behind, found by an archaeologist more than 9000 years later. Our Neolithic (New Stone Age) traveler sends us a number of messages about early world history. Most obviously, he was a tool user who not only picked up natural objects but deliberately crafted them to hunt for and prepare his food. As such, he differed from all other animals (a few other kinds of animals are tool users, but none make their tools).
    [Show full text]