Ahead of PDC, Microsoft Begins Internal Test of Windows 7
(From WinInfo) While Microsoft is busy trying to overcome consumer opinions of its current operating system, Windows Vista, the software giant is also undergoing an internal effort to beta test the next version, called Windows 7. Last week, the company began testing an internal version of the software that it hopes to ship to attendees of its Professional Developers Conference (PDC) in late October. This build has shipped to Microsoft employees and, reportedly, close partners of the company.
The build, which is referred to internally as M3 for “milestone 3,” reveals a product that is very much like Windows Vista both visually and functionally. Microsoft has ported the “ribbon” user interface from Office 2007 to a number of bundled applications. As previously reported, Microsoft has tasked the team that created the ribbon UI with updating the Windows shell as well.
External reports have suggested that Microsoft will begin de-bundling certain applications–like Windows Mail and Windows Movie Maker–from Windows 7 and will instead make them available as separate downloads from Windows Live. Also, some have suggested that Microsoft will ship a Beta 1 version of Windows 7 by the end of the year.
I can’t confirm those rumors. But I have talked to people with access to the M3 build, or build 6780, and they’ve reported that this version of Windows 7 is surprisingly stable and usable, and well ahead of where Windows Vista was at this point in its development cycle.
Selasa, 23 September 2008
Ahead of PDC, Microsoft Begins Internal Test of Windows 7
Ahead of PDC, Microsoft Begins Internal Test of Windows 7
(From WinInfo) While Microsoft is busy trying to overcome consumer opinions of its current operating system, Windows Vista, the software giant is also undergoing an internal effort to beta test the next version, called Windows 7. Last week, the company began testing an internal version of the software that it hopes to ship to attendees of its Professional Developers Conference (PDC) in late October. This build has shipped to Microsoft employees and, reportedly, close partners of the company.
The build, which is referred to internally as M3 for “milestone 3,” reveals a product that is very much like Windows Vista both visually and functionally. Microsoft has ported the “ribbon” user interface from Office 2007 to a number of bundled applications. As previously reported, Microsoft has tasked the team that created the ribbon UI with updating the Windows shell as well.
External reports have suggested that Microsoft will begin de-bundling certain applications–like Windows Mail and Windows Movie Maker–from Windows 7 and will instead make them available as separate downloads from Windows Live. Also, some have suggested that Microsoft will ship a Beta 1 version of Windows 7 by the end of the year.
I can’t confirm those rumors. But I have talked to people with access to the M3 build, or build 6780, and they’ve reported that this version of Windows 7 is surprisingly stable and usable, and well ahead of where Windows Vista was at this point in its development cycle.
Convert Open Office Doc to Microsoft Word
I have Microsoft Office and our office work with Microsoft Word. We receive Open Office Document from other very seldom, so I don’t want to add the burden to my computer with installing it. Once we received an Open Office Document (with extension .odt), we have to open it and we don’t have time enough to ask the sender to convert and resend it. With Open Office, we can easily convert it to Microsoft Word by “Save as” menu - but in reality it is not so easy for everybody. So, instead of giving instruction and ask to convert it, I tried to look for another way.
Convert Open Office Doc to Microsoft Word
Then I found a site that provide an online converter. It worked very well and fast. I upload my +/- 150 KB document and it was converted and ready for download in less than 20 second. I think this is a good solution for incidental needs. You can find that online service in this link. This service is limited for files with maximum 450 KB size.
Senin, 01 September 2008
Blog Tidak terdeteksi pada search Engine ?
Cara Mendaftar blog pada search engine
Banyak cara yang dapat kita lakukan agar blog kita bisa dikenal dan di kunjungi, antara lain adalah dengan rajinnya kita blogwalking atau berkunjung ke blog milik orang lain, mendaftarkan ke berbagai agregator, dan yang paling efektif adalah melalui search engine atau mesin pencari.
Bagi blogger pemula mungkin berangggapan bahwa apabila kita membuat website atau blog akan secara otomatis terindeks atau berada pada list berbagai search engine, dan kenyataannya tidaklah demikian. Seperti halnya sebuah sekolah, agar nama kita terdaftar pada buku daftar siswa, tentunya kita harus melakukan pendaftaran terlebih dahulu ke sekolah tersebut. Sama halnya dengan mesin pencari, agar blog kita terindeks pada mesin pencari, maka kita harus terlebih dahulu mendaftarkan blog milik kita pada situs pemilik mesin pencari.
Mesin pencari tentu jumlahnya sangat banyak sekali, dan pada saat ini yang paling terkenal di dunia adalah Google, Yahoo, serta Msn. Apabila blog kita ingin terindeks pada mesin pencari mereka, maka kewajiban kita adalah mendaftarkan URL blog kita pada mesin pencari mereka. Bila ada yang belum tahu ke manakah harus mendaftarkan blognya, maka silahkan simak tulisan berikut :
# Daftar GoogleUntuk mendaftar ke google, silahkan sobat kunjungi http://www.google.com/addurl/, nah apabila sudah berada pada halaman pendaftaran ada beberapa langkah yang harus di lakukan, yaitu mengisi form yang di sediakan :
# URL –> Isi dengan URL blogmu.
# Comments –> Isi dengan keyword atau kata kunci yang berhubungan dengan blog sobat
# Isi kotak kosong dengan huruf Verifikasi yang tersedia
# Klik tombol Add URL
# Selesai.Setelah kita melakukan pendaftaran ke Google, maka tidak serta merta blog kita terindeks pada mesin pencari nya, akan tetapi memerlukan 2 sampai 4 minggu baru blog kita bisa terindeks. Jika sudah 2 sampai 4 minggu, maka cobalah ketik kembali alamat blog sobat pada mesin pencari google, apakah sudah terindeks atau belum? jika belum, coba tunggu beberapa minggu lagi, dan tuliskan kembali alamat blog kita, Jika ternyata masih belum juga, coba deh daftarin lagi blog nya ke google seperti langkah di atas. Yah pokoknya sabar aja ya..Atau mungkin kalau tidak sabar ingin cepat terindeks, sebenarnya bisa saja ini terjadi, hanya dalam 2 atau 4 hari saja blog kita sudah bisa terindeks di google.
# Daftar Yahoo!Untuk mendaftar ke yahoo! silahkan sobat kunjungi https://siteexplorer.search.yahoo.com/submit. Akan tetapi untuk mendaftar ke yahoo, kita harus terlebih dahulu mempunyai account yahoo, karena di perlukan log in terlebih dahulu ke account yahoo. Bagi yang belum punya account yahoo (email di yahoo) silahkan buat dulu, bagi yang sudah punya, kita tinggal login dengan username serta password kita. Apabila sudah login, nanti sudah tersedia kolom untuk di isi, silahkan isi kolom tersebut dengan URL kita, kemudian klik tombol Add URL, selesai. Jika ingin memasukan alamat feed sekalian kita bisa memasukannya. Ingat, alamat feed di blogger hanya tinggal menambahkan atom.xml di belakang uRL blog kita, contoh : untuk blog saya ini mempunyai alamat feed sebagai berikut :
http://physicgenerationmafia05.blogspot.com/atom.xml
atau memakai www pun sama saja :
http://physicgenerationmafia05.blogspot.com/atom.xml
# Daftar ke MsnUntuk daftar ke Msn, silahkan sobat kunjungi http://search.msn.com/docs/submit.aspx?FORM=WSDD2 silahkan sobat isi huruf verifikasi dan URL sobat pada kotak yang tersedia, kemudian klik tombol Submit URL, selesa
Physics and Astronomy Glossary
Physics and Astronomy Glossary
Technical terms of science have very specific meanings. Standard dictionaries are not always the best source of useful and correct definitions of them.
This glossary is not intended to be complete. It focuses on those terms which give students particular difficulties. Some words have subtle and intricate meanings which cannot be encapsulated in a short definition. That's why textbooks exist. A good glossary for elementary physics may be found in Appendix G-1 of Kirkpatrick & Wheeler, Physics, A World View, Saunders, 1992.
This document is continually under development and may never be finished.
Glossary
Accurate. Conforming closely to some standard. Having very small error of any kind. See: Uncertainty. Compare: precise.
Absolute uncertainty. The uncertainty in a measured quantity is due to inherent variations in the measurement process itself. The uncertainty in a result is due to the combined and accumulated effects of these measurement uncertainties which were used in the calculation of that result. When these uncertainties are expressed in the same units as the quantity itself they are called absolute uncertainties. Uncertainty values are usually attached to the quoted value of an experimental measurement or result, one common format being: (quantity) ± (absolute uncertainty in that quantity).
Compare: relative uncertainty.
Action. This technical term is a historic relic of the 17th century, before energy and momentum were understood. In modern terminology, action has the dimensions of energy×time. Planck's constant has those dimensions, and is therefore sometimes called Planck's quantum of action. Pairs of measurable quantities whose product has dimensions of energy×time are called conjugate quantities in quantum mechanics, and have a special relation to each other, expressed in Heisenberg's uncertainty principle. Unfortunately the word action persists in textbooks in meaningless statements of Newton's third law: 'Action equals reaction.' This statement is useless to the modern student, who hasn't the foggiest idea what action is. See: Newton's 3rd law for a useful definition. Also see Heisenberg's uncertainty principle.
Avogadro's constant. Avogadro's constant has the unit mole-1. It is not merely a number, and should not be called Avogadro's number. It is ok to say that the number of particles in a gram-mole is 6.02 x 1023. Some older books call this value Avogadro's number, and when that is done, no units are attached to it. This can be confusing and misleading to students who are conscientiously trying to learn how to balance units in equations.
One must specify whether the value of Avogadro's constant is expressed for a gram-mole or a kilogram-mole. A few books prefer a kilogram-mole. The unit name for a gram-mole is simply mol. The unit name for a kilogram-mole is kmol. When the kilogram-mole is used, Avogadro's constant should be written: 6.02252 x 1026 kmol-1. The fact that Avogadro's constant has units further convinces us that it is not 'merely a number.'
Though it seems inconsistent, the SI base unit is the gram-mole. As Mario Iona reminds me, SI is not an MKS system. Some textbooks still prefer to use use the kilogram-mole, or worse, use it and the gram-mole. This affects their quoted values for the universal gas constant and the Faraday Constant.
Is Avogadro's constant just a number? What about those textbooks which say 'You could have a mole of stars, grains of sand, or people.' In science we do use entities which are just numbers, such as greek pi, e, 3, 100, etc. Though these are used in science, their definitions are independent of science. No experiment of science can ever determine their value, except approximately. Avogadro’s constant, however, must be determined experimentally, for example by counting the number of atoms in a crystal. The value of Avogadro's number found in handbooks is an experimentally determined number. You won't discover its value experimentally by counting stars, grains of sand, or people. You find it only by counting atoms or molecules in something of known relative molecular mass. And you won't find it playing any role in any equation or theory about stars, sand, or people.
The reciprocal of Avogadro's constant is numerically equal to the unified atomic mass unit, u, that is, 1/12 the mass of the carbon 12 atom.
1 u = 1.66043 x 10-27 kg = 1/6.02252 x 1023 mole-1.
Because. Here's a word best avoided in physics. Whenever it appears one can be almost certain that it's a filler word in a sentence which says nothing worth saying, or a word used when one can't think of a good or specific reason. While the use of the word because as a link in a chain of logical steps is benign, one should still replace it with words more specifically indicative of the type of link which is meant. See: why.
Illustrative fable: The seeker after truth sought wisdom from a Guru who lived as a hermit on top of a Himalayan mountain. After a long and arduous climb to the mountain-top the seeker was granted an audience. Sitting at the feet of the great Guru, the seeker humbly said: 'Please, answer for me the eternal question: Why?' The Guru raised his eyes to the sky, meditated for a bit, then looked the seeker straight in the eye and answered, with an air of sagacious profundity, 'Because!'
Capacitance. The capacitance of a capacitor is measured by this procedure: Put equal and opposite charges on its plates and then measure the potential between the plates. Then C = |Q/V|, where Q is the charge on one of the plates.
Capacitors for use in circuits consist of two conductors (plates). We speak of a capacitor as 'charged' when it has charge Q on one plate, and -Q on the other. Of course the net charge of the entire object is zero; that is, the charged capacitor hasn't had net charge added to it, but has undergone an internal separation of charge. Unfortunately this process is usually called charging the capacitor, which is misleading because it suggests adding charge to the capacitor. In fact, this process usually consists of moving charge from one plate to the other. The capacity of a single object, say an isolated sphere, is determined by considering the other plate to be an infinite sphere surrounding it. The object is given charge, by moving charge from the infinite sphere, which acts as an infinite charge reservoir ('ground'). The potential of the object is the potential between the object and the infinite sphere.
Capacitance depends only on the geometry of the capacitor's physical structure and the dielectric constant of the material medium in which the capacitor's electric field exists. The size of the capacitor's capacitance is the same whatever the charge and potential (assuming the dielectric constant doesn't change). This is true even if the charge on both plates is reduced to zero, and therefore the capacitor's potential is zero. If a capacitor with charge on its plates has a capacitance of, say, 2 microfarad, then its capacitance is also 2 microfarad when the plates have no charge. This should remind us that C = |Q/V| is not by itself the definition of capacitance, but merely a formula which allows us to relate the capacitance to the charge and potential when the capacitor plates have equal and opposite charge on them.
A common misunderstanding about electrical capacitance is to assume that capacitance represents the maximum amount of charge a capacitor can store. That is misleading because capacitors don't store charge (their total charge being zero) but their plates have equal and opposite charge. It is wrong because the maximum charge one may put on a capacitor plate is determined by the potential at which dielectric breakdown occurs. Compare: capacity.
We probably should avoid the phrase 'charged capacitor' or 'charging a capacitor'. Some have suggested the alternative expression 'energizing a capacitor' because the process is one of giving the capacitor electrical potential energy by rearranging charges in it.
Capacity. This word is used in names of quantities which express the relative amount of some quantity with respect to a another quantity upon which it depends. For example, heat capacity is dU/dT, where U is the internal energy and T is the temperature. Electrical capacity, or capacitance is another example: C = |dQ/dV|, where Q is the magnitude of charge on each capacitor plate and V is the potential diference between the plates.
Centrifugal force. When a non-inertial rotating coordinate system is used to analyze motion, Newton's law F = ma is not correct unless one adds to the real forces a fictitious force called the centrifugal force. The centrifugal force required in the non-inertial system is equal and opposite to the centripetal force calculated in the inertial system. Since the centrifugal and centripetal forces are concepts used in two different formulations of the problem, they can not in any sense be considered a pair of reaction forces. Also, they act on the same body, not different bodies. See: centripetal force, action, and inertial systems.
Centripetal force. The centripetal force is the radial component of the net force acting on a body when the problem is analyzed in an inertial system. The force is inward toward the instantaneous center of curvature of the path of the body. The size of the force is mv2/r, where r is the instantaneous radius of curvature. See: centrifugal force.
cgs. The system of units based upon the fundamental metric units: centimeter, gram and second.
Classical physics. The physics developed before about 1900, before we knew about relativity and quantum mechanics. See: modern physics.
Closed system. A physical system on which no outside influences act; closed so that nothing gets in or out of the system and nothing from outside can influence the system's observable behavior or properties.
Obviously we could never make measurements on a closed system unless we were in it†, for no information about it could get out of it! In practice we loosen up the condition a bit, and only insist that there be no interactions with the outside world which would affect those properties of the system which are being studied.
† Besides, when the experimenter is a part of the system, all sorts of other problems arise. This is a dilemma physicists must deal with: the fact that if we take measurements, we are a part of the system, and must be very certain that we carry out experiments so that fact doesn't distort or prejudice the results.
Conserved. A quantity is said to be conserved if under specified conditions it's value does not change with time.
Example: In a closed system, the charge, mass, total energy, linear momentum and angular momentum of the system are conserved. (Relativity theory allows that mass can be converted to energy and vice-versa, so we modify this to say that the mass-energy is conserved.)
Current. The time rate at which charge passes through a circuit element or through a fixed place in a conducting wire, I = dq/dt.
Misuse alert. A very common mistake found in textbooks is to speak of 'flow of current'. Current itself is a flow of charge; what, then, could 'flow of current' mean? It is either redundant, misleading, or wrong. This expression should be purged from our vocabulary. Compare a similar mistake: 'The velocity moves West.'
Data. The word data is the plural of datum. Examples of correct usage:
'The data are reasonable, considering the…'
'The data were taken over a period of three days.'
'How well do the data confirm the theory?'
Derive. To derive a result or conclusion is to show, using logic and mathematics, how a conclusion follows logically from certain given facts and principles.
Dimensions. The fundamental measurables of a unit system in physics—those which are defined through operational definitions. All other measurable quantities in physics are defined through mathematical relations to the fundamental quantities. Therefore any physical measurable may be expressed as a mathematical combination of the dimensions. See: operational definitions.
Example: In the MKSA (meter-kilogram-second-ampere) system of units, length, mass, time and current are the fundamental measurables, symbolically represented by L, M, T, and I. Therefore we say that velocity has the dimensions LT-1. Energy has the dimensions ML2T-2.
Discrepancy. (1) Any deviation or departure from the expected. (2) A difference between two measurements or results. (3) A difference between an experimental determination of a quantity and its standard or accepted value, usually called the experimental discrepancy.
Empirical law. A law strictly based on experiment, which may lack theoretical foundation.
Electricity. This word names a branch or subdivision of physics, just as other subdivisions are named ‘mechanics’, ‘thermodynamics’, ‘optics’, etc.
Misuse alert: Sometimes the word electricity is colloquially misused as if it named a physical quantity, such as 'The capacitor stores electricity,' or 'Electricity in a resistor produces heat.' Such usage should be avoided! In all such cases there's available a more specific or precise word, such as 'The capacitor stores electrical energy,' 'The resistor is heated by the electric current,' and 'The utility company charges me for the electric energy I use.' (I am not being charged based on the power, so these companies shouldn't call themselves Power companies. Some already have changed their names to something like '... Energy')
Energy. Energy is a property of a body, not a material substance. When bodies interact, the energy of one may increase at the expense of the other, and this is sometimes called a transfer of energy. This does not mean that we could intercept this energy in transit and bottle some of it. After the transfer one of the bodies may have higher energy than before, and we speak of it as having 'stored energy'. But that doesn't mean that the energy is 'contained in it' in the same sense as water in a bucket.
Misuse example: 'The earth's auroras—the northern and southern lights—illustrate how energy from the sun travels to our planet.' —Science News, 149, June 1, 1996. This sentence blurs understanding of the process by which energetic charged particles from the sun interact with the earth's magnetic field and our atmosphere to result in the aurorae.
Whenever one hears people speaking of 'energy fields', 'psychic energy', and other expressions treating energy as a 'thing' or 'substance', you know they aren't talking physics, they are talking moonshine.
In certain quack theories of oriental medicine, such as qi gong (pronounced chee gung) something called qi is believed to circulate through the body on specific, mappable pathways called meridians. This idea pervades the contrived explanations/rationalizations of acupuncture, and the qi is generally translated into English as energy. No one has ever found this so-called 'energy', nor confirmed the uniqueness of its meridian pathways, nor verified, through proper double-blind tests, that any therapy or treatment based on the theory actually works. The proponents of qi can't say whether it is a fluid, gas, charge, current, or something else, and their theory requires that it doesn't obey any of the physics of known carriers of energy. But, as soon as we hear someone talking about it as if it were a thing we know they are not talking science, but quackery.
The statement 'Energy is a property of a body' needs clarification. As with many things in physics, the size of the energy depends on the coordinate system. A body moving with speed V in one coordinate system has kinetic energy ½mV2. The same body has zero kinetic energy in a coordinate system moving along with it at speed V. Since no inertial coordinate system can be considered 'special' or 'absolute', we shouldn't say 'The kinetic energy of the body is ...' but should say 'The kinetic energy of the body moving in this reference frame is ...'
Equal. [Not all 'equals' are equal.] The word equal and the symbol '=' have many different uses. The dictionary warns that equal things are 'alike or in agreement in a specified sense with respect to specified properties.' This we must be careful about the specified sense and specified properties.
The meaning of the the mathematical symbol, '=' depends upon what stands on either side of it. When it stands between vectors it symbolizes that the vectors are equal in both size and direction.
In algebra the equal sign stands between two algebraic expressions and indicates that two expressions are related by a reflexive, symmetric and transitive relation. The mathematical expressions on either side of the '=' sign are mathematically identical and interchangeable in equations.
When the equal sign stands between two mathematical expressions with physical meaning, it means something quite different. In physics we may correctly write 12 inches = 1 foot, but to write 12 = 1 is simply wrong. In the first case, the equation tells us about physically equivalent measurements. It has physical meaning, and the units are an indispensable part of the quantity.
When we write a = dv/dt, we are defining the acceleration in terms of the time rate of change of velocity. One does not verify a definition by experiment. Experiment can, however, show that in certain cases (such as a freely falling body) the acceleration of the body is constant.
The three-lined equal sign, =, is often used to mean 'defined equal to'. Unfortunately this symbol is not part of the HTML character set, so in this document we use an underlined equal sign instead.
When we write F = ma, we are expressing a relation between measurable quantities, one which holds under specified conditions, qualifications and limitations. There's more to it than the equation. One must, for example, specify that all measurements are made in an inertial frame, for if they aren't, this relation isn't correct as it stands, and must be modified. Many physical laws, including this one, also include definitions. This equation may be considered a definition of force, if m and a are previously defined. But if F was previously defined, this may be taken as a definition of mass. But the fact that this relation can be experimentally tested, and possibly be shown to be false (under certain conditions) demonstrates that it is more than a mere definition.
Additional discussion of these points may be found in Arnold Arons' book A Guide to Introductory Physics Teaching, section 3.23, listed in the references at the end of this document.
Usage note: When reading equations aloud we often say, 'F equals m a'. This, of course, says that the two things are mathematically equal in equations, and that one may replace the other. It is not saying that F is physically the same thing as ma. Perhaps equations were not meant to be read aloud, for the spoken word does not have the subtleties of meaning necessary for the task. At least we should realize that spoken equations are at best a shorthand approximation to the meaning; a verbal description of the symbols. If we were to try to speak the physical meaning, it would be something like: 'Newton's law tells us that the net vector force acting on a body of mass m is mathematically equal to the product of its mass and its vector acceleration.' In a textbook, words like that would appear in the text near the equation, at least on the first appearance of the equation.
Error. In colloquial usage, 'a mistake'. In technical usage error is a synonym for the experimental uncertainty in a measurement or result. See: uncertainty.
Error analysis. The mathematical analysis done to show quantitatively how uncertainties in data produce uncertainty in calculated results, and to find the sizes of the uncertainty in the results. [In mathematics the word analysis is synonymous with calculus, or 'a method for mathematical calculation.' Calculus courses used to be named Analysis.]
See: uncertainty Extensive property. A measurable property of a thermodynamic system is extensive if, when two identical systems are combined into one, the value of that property of the combined system is double its original value in each system. Examples: mass, volume, number of moles. See: intensive variable and specific.
Experimental error. The uncertainty in the value of a quantity. This may be found from (1) statistical analysis of the scatter of data, or (2) mathematical analysis showing how data uncertainties affect the uncertainty of calculated results.
Misuse alert: In elementary lab manuals one often sees: experimental error = |your value - book value| /book value. This should be called the experimental discrepancy. See: discrepancy.
Factor. One of several things multiplied together.
Misuse alert: Be careful that the reader does not confuse this with the colloquial usage: 'One factor in the success of this experiment was…'
Fictitious force. See: inertial frames. Focal point. The focal point of a lens is defined by considering a parallel bundle or beam of light incident upon the lens, parallel to the optic (symmetry) axis of the lens. The focal point is that point to which the rays converge or from which they diverge. The first case is that of a converging (positive) lens. The second case is that of a diverging (negative) lens. It’s easy to tell which kind of lens you have, for converging lenses are thicker at their center than at the edges, and diverging lenses are thinner at the center than at the edges.
FPS. The system of units based on the fundamental units of the ‘English system’: foot, pound and second.
Heat. Heat, like work, is a measure of the amount of energy transferred from one body to another because of the temperature difference between those bodies. Heat is not energy possessed by a body. We should not speak of the 'heat in a body.' The energy a body possesses due to its temperature is a different thing, called internal thermal energy. The misuse of this word probably dates back to the 18th century when it was still thought that bodies undergoing thermal processes exchanged a substance, called caloric or phlogiston, a substance later called heat. We now know that heat is not a substance. Reference: Zemansky, Mark W. The Use and Misuse of the Word 'Heat' in Physics Teaching' The Physics Teacher, 8, 6 (Sept 1970) p. 295-300. See: work.
Heisenberg's Uncertainty Principle. Pairs of measurable quantities whose product has dimensions of energy×time are called conjugate quantities in quantum mechanics, and have a special relation to each other, expressed in Heisenberg's uncertainty principle. It says that the product of the uncertainties of the two quantities is no smaller than h/2greek pi. Thus if you improve the measurement precision of one quantity the precision of the other gets worse.
Misuse alert: Folks who don't pay attention to details of science, are heard to say 'Heisenberg showed that you can't be certain about anything.' We also hear some folk justifying belief in esp or psychic phenomena by appeal to the Heisenberg principle. This is wrong on several counts. (1) The precision of any measurement is never perfectly certain, and we knew that before Heisenberg. (2) The Heisenberg uncertainty principle tells us we can measure anything with arbitrarily small precision, but in the process some other measurement gets worse. (3) The uncertainties involved here affect only microscopic (atomic and molecular level phenomena) and have no applicability to the macroscopic phenomena of everyday life.
Hypothesis. An untested statement about nature; a scientific conjecture, or educated guess. Formally, a hypothesis is made prior to doing experiments designed to test it. Compare: law and theory.
Ideal-lens equation. 1/p + 1/q = 1/f, where p is the distance from object to lens, q is the distance from lens to image, and f is the focal length of the lens. This equation has important limitations, being only valid for thin lenses, and for paraxial rays. Thin lenses have thickness small compared to p, q, and f. Paraxial rays are those which make angles small enough with the optic axis that the approximation (angle in radian measure) = sin(angle) may be used. See: optical sign conventions, and image.
Inertia A descriptive term for that property of a body which resists change in its motion. Two kinds of changes of motion are recognized: changes in translational motion, and changes in rotational motion.
In modern usage, the measure of translational inertia is mass. Newton's first law of motion is sometimes called the 'Law of Inertia', a label which adds nothing to the meaning of the first law. Newton's first and second laws together are required for a full description of the consequences of a body's inertia.
The measure of a body's resistance to rotation is its Moment of Inertia.
Inertial frame. A non-accelerating coordinate system. One in which F = ma holds, where F is the sum of all real forces acting on a body of mass m whose acceleration is a. In classical mechanics, the real forces on a body are those which are due to the influence of another body. [Or, forces on a part of a body due to other parts of that body.] Contact forces, gravitational, electric, and magnetic forces are real. Fictitious forces are those which arise solely from formulating a problem in a non-inertial system, in which ma = F + (fictitious force terms)
Intensive variable. A measurable property of a thermodynamic system is intensive if when two identical systems are combined into one, the variable of the combined system is the same as the original value in each system. Examples: temperature, pressure. See: extensive variable, and specific.
Image. (Optics) A surprising number of physics glossaries omit a definition of this! No wonder. It's difficult to put in a few words, and still be comprehensive in scope. Try this. Image: A point mapping of luminous points of an object located in one region of space to points in another region of space, formed by refraction or reflection of light in a manner which causes light from each point of the object to converge to or diverge from a point somewhere else (on the image). The images which are useful generally have the character that adjacent points of the object map to adjacent points of the image without discontinuity, and is a recognizable (though perhaps somewhat distorted) mapping of the object. See: real image and virtual image.
Law. A statement, usually mathematical, which describes some physical phenomena. Compare: hypothesis and theory.
Lens. A transparent object with two refracting surfaces. Usually the surfaces are flat or spherical (spherical lenses). Sometimes, to improve image quality. Lenses are deliberately made with surfaces which depart slightly from spherical (aspheric lenses).
Kinetic energy. The energy a body has by virtue of its motion. The kinetic energy is the work done by an external force to bring the body from rest to a particular state of motion. See: work.
Common misconception: Many students think that kinetic energy is defined by ½mv2. It is not. That happens to be approximately the kinetic energy of objects moving slowly, at small fractions of the speed of light. If the body is moving at relativistic speeds, its kinetic energy is greek gammamc2, which can be expressed as ½mv2 + an infinite series of terms. greek gamma2 = 1/(1-(v/c)2), where c is the speed of light in a vacuum.
Macro-. A prefix meaning ‘large’. See: micro-
Macroscopic. A physical entity or process of large scale, the scale of ordinary human experience. Specifically, any phenomena in which the individual molecules and atoms are neither measured, nor explicitly considered in the description of the phenomena. See: microscopic.
Magnification.
Two kinds of magnification are useful to describe optical systems and they must not be confused, since they aren't synonymous. Any optical system which produces a real image from a real object is described by its linear magnification. Any system which one looks through to view a virtual image is described by its angular magnification. These have different definitions, and are based on fundamentally different concepts.
Linear Magnification is the ratio of the size of the object to the size of the image.
Angular Magnification is the ratio of the angular size of the object as seen through the instrument to the angular size of the object as seen with the 'naked eye'. The 'naked eye' view is without use of the optical instrument, but under optimal viewing conditions.
Certain 'gotchas' lurk here. What are 'optimal' conditions? Usually this means the conditions in which the object's details can be seen most clearly. For a small object held in the hand, this would be when the object is brought as close as possible and still seen clearly, that it, to the near point of the eye, about 25 cm for normal eyesight. For a distant mountain, one can't bring it close, so when determining the magnification of a telescope, we assume the object is very distant, or at infinity.
And what is the 'optimal' position of the image? For the simple magnifier, in which the magnification depends strongly on the image position, the image is best seen at the near point of the eye, 25 cm. For the telescope, the image size doesn't change much as you fiddle with the focus, so you likely will put the image at infinite distance for relaxed viewing. The microscope is an intermediate case. Always striving for greater resolution, the user may pull the image close, to the near point, even though that doesn't increase its size very much. But usually, users will place the image farther away, at the distance of a meter or two, or even at infinity. But, because the object is very near the focal point, the magnification is only weakly dependent on image position.
Some texts express angular magnification as the ratio of the angles, some express it as the ratio of the tangents of the angles. If all of the angles are small, there's negligible difference between these two definitions. However, if you examine the derivation of the formula these books give for the magnification of a telescope fo/fe, you realize that they must have been using the tangents. The tangent form of the definition is the traditionally correct one, the one used in science and industry, for nearly all optical instruments which are designed to produce images which preserve the linear geometry of the object.
Micro-. A prefix meaning ‘small’, as in ‘microscope’, ‘micrometer’, ‘micrograph’. Also, a metric prefix meaning 10-6. See: macro-
Microscopic. A physical entity or process of small scale, too small to directly experience with our senses. Specifically, any phenomena on the molecular and atomic scale, or smaller. See: macroscopic.
MKSA. The system of physical units based on the fundamental metric units: meter kilogram, second and ampere.
Modern physics. The physics developed since about 1900, which includes relativity and quantum mechanics. See: classical physics.
Mole. The term mole is short for the name gram-molar-weight; it is not a shortened form of the word molecule. (However, the word molecule does also derive from the word molar.) See: Avogadro’s constant.
Misuse alert: Many books emphasize that the mole is 'just a number,' a measure of the number of particles in a collection. They say that one can have a mole of any kind of particles, baseballs, atoms, stars, grains of sand, etc. It doesn't have to be molecules. This is misleading.
To say that the mole is 'just a number' is simply wrong, from physical, pedagogical, philosophical and historical points of view. There's no physical significance to a mole of stars or a mole of grains of sand, or a mole of people. The physical significance of the mole as a measure of quantity arises only when dealing with physical laws about matter on the molecular scale. The only physical and chemical laws which use the mole are those dealing with gases, or systems behaving like gases.
Molecular mass. The molecular mass of something is the mass of one mole of it (in cgs units), or one kilomole of it (in MKS units). The units of molecular mass are gram and kilogram, respectively. The cgs and MKS values of molecular mass are numerically equal. The molecular mass is not the mass of one molecule. Some books still call this the molecular weight.
One dictionary definition of molar is 'Pertaining to a body of matter as a whole: contrasted with molecular and atomic.' The mole is a measure appropriate for a macroscopic amount of material, as contrasted with a microscopic amount (a few atoms or molecules). See: mole, Avogadro's constant, microscopic, macroscopic.
Newton's first and second laws of motion. F = d(mv)/dt.
F is the net (total) force acting on the body of mass m. The individual forces acting on m must be summed vectorially. In the special case where the mass is constant, this becomes F = ma.
Newton's third law of motion. When body A exerts a force on body B, then B exerts and equal and opposite force on A. The two forces related by this law act on different bodies. The forces need not be net forces.
Ohm's law. V = IR, where V is the potential across a circuit element, I is the current through it, and R is its resistance. This is not a generally applicable definition of resistance. It is only applicable to ohmic resistors, those whose resistance R is constant over the range of interest and V obeys a strictly linear relation to I.
Materials are said to be ohmic when V depends linearly on R. Metals are ohmic so long as one holds their temperature constant. But changing the temperature of a metal changes R slightly. Therefore such a device as an electric light bulb increases its temperature as it warms up, which is why it glows slightly brighter for a very brief time just after it is turned on.
For non-ohmic resistors, R is a function of current and the definition R = dV/dI is far more useful. This is sometimes called the dynamic resistance. Solid state devices such as thermistors are non-ohmic, and non-linear. A thermistor's resistance decreases as it warms up, so its dynamic resistance is negative. Tunnel diodes and some electrochemical processes have a complicated I-V curve with a negative resistance region of operation.
The dependence of resistance on current is partly due to the change in the device's temperature with increasing current, but other subtle processes also contribute to change in resistance in solid state devices.
Operational definition. A definition which describes an experimental procedure by which a numeric value of the quantity may be determined. See dimensions.
Example: Length is operationally defined by specifying a procedure for subdividing a standard of length into smaller units to make a measuring stick, then laying that stick on the object to be measured, etc..
Very few quantities in physics need to be operationally defined. They are the fundamental quantities, which include length, mass and time. Other quantities are defined from these through mathematical relations.
Optical sign conventions. In introductory (freshman) courses in physics a sign convention is used for objects and images in which the lens equation must be written 1/p + 1/q = 1/f. Often the rules for this sign convention are presented in a convoluted manner. A simple and easy to remember rule is this: p is the object-to-lens distance. q is the lens to image distance. The coordinate axis along the optic axis is in the direction of passage of light through the lens, this defining the positive direction. Example: If the axis and the light direction is left-to-right (as is usually done) and the object is to the left of the lens, the object-to-lens distance is positive. if the object is to the right of the lens (virtual object), the object-to-lens distance is negative. It works the same for images.
For refractive surfaces, define the surface radius to be the directed distance from a surface to its center of curvature. Thus a surface convex to the incident light is positive, one concave to the incident light is negative. The surface equation is then n/s + n'/s' = (n'-n)/R where s and s' are the object and image distances, and n and n' the refractive index of the incident and emergent media, respectively.
For mirrors, the equation is usually written 1/s + 1/s' = 2/R = 1/f. A diverging mirror is convex to the incoming light, with negative f. From this fact we conclude that R is also negative. This form of the equation is consistent with that of the lens equation, and the interpretation of sign of focal length is the same also. But violence is done to the definition of R we used above, for refraction. One can say that the mirror folds the length axis at the mirror, so that emergent rays to a real image at the left represent a positive value of s'. We are forced also to declare that the mirror also flips the sign of the surface radius. For reflective surfaces, the radius of curvature is defined to be the directed distance from a surface to its center of curvature, measured with respect to the axis used for the emergent light. With this qualification the convention for the signs of s' and R is the same for mirrors as for refractive surfaces.
In advanced optics courses, a cartesian sign convention is used in which all things to the left of the lens are negative, all those to the right are positive. When this is used, the lens equation must be written 1/p + 1/f = 1/q. (The sign of the 1/p term is opposite that in the other sign convention). This is a particularly meaningful version, for 1/p is the measure of vergence (convergence or divergence) of the rays as they enter the lens, 1/f is the amount the lens changes the vergence, and 1/q is the vergence of the emergent rays.
Pascal's Principle of Hydrostatics. Pascal actually has three separate principles of hydrostatics. When a textbook refers to Pascal's Principle it should specify which is meant.
Pascal 1: The pressure at any point in a liquid exerts force equally in all directions. This means that an infinitessimal surface area placed at that point will experience the same force due to pressure no matter what its orientation.
Pascal 2: When pressure is changed (increased or decreased) at any point in a homogenous, incompressible fluid, all other points experience the same change of pressure.
Except for minor edits and insertion of the words 'homogenous' and 'incompressible', this is the statement of the principle given in John A. Eldridge's textbook College Physics (McGraw-Hill, 1937). Yet over half of the textbooks I've checked, including recent ones, omit the important word 'changed'. Some textbooks add the qualification 'enclosed fluid'. This gives the false impression that the fluid must be in a closed container, which isn't a necessary condition of Pascal's principle at all.
Some of these textbooks do indicate that Pascal's principle applies only to changes in pressure, but do so in the surrounding text, not in the bold, highlighted, and boxed statement of the principle. Students, of course, read the emphasized statement of the principle and not the surrounding text. Few books give any examples of the principle applied to anything other than enclosed liquids. The usual example is the hydraulic press. Too few show that Pascal's principle is derivable in one step from Bernoulli's equation. Therefore students have the false impression that these are independent laws.
Pascal 3. The hydraulic lever. The hydraulic jack is a problem in fluid equilibrium, just as a pulley system is a problem in mechanical equilibrium (no accelerations involved). It's the static situation in which a small force on a small piston balances a large force on a large piston. No change of pressure need be involved here. A constant force on one piston slowly lifts a different piston with a constant force on it. At all times during this process the fluid is in near-equilibrium. This 'principle' is no more than an application of the definition of pressure as F/A, the quotient of net force to the area over which the force acts. However, it also uses the principle that pressure in a fluid is uniform throughout the fluid at all points of the same height.
This hydraulic jack lifitng process is done at constant speed. If the two pistons are at different levels, as they usually are in real jacks used for lifting, there's a pressure difference between the two pistons due to height difference (rho)gh. In textbook examples this is generally considered small enough to neglect and may not even be mentioned.
Pascal's own discussion of the principle is not concisely stated and can be misleading if hastily read. See his On the Equilibrium of Liquids, 1663. He inroduces the principle with the example of a piston as part of an enclosed vessel and considers what happens if a force is applied to that piston. He concludes that each portion of the vessel is pressed in proportion to its area. He does mention parenthetically that he is 'excluding the weight of the water..., for I am speaking only of the piston's effect.'
Percentage. Older dictionaries suggested that percentage be used when a non-quantitative statement is being made: 'The percentage growth of the economy was encouraging.' But use percent when specifying a numerical value: 'The gross national product increased by 2 percent last year.' Though newer dictionaries are more permissive, I find the indiscriminate and unnecessary use of the ugly word percentage to be overdone and annoying, as in 'The experimental percentage uncertainty was 9%.' Much more graceful is: 'The experimental uncertainty was 9%.'
Related note: Students have the strange idea that results are better when expressed as percents. Some experimental uncertainties must not be expressed as percents. Examples: (1) temperature in Celsius or Fahrenheit measure, (2) index of refraction, (3) dielectric constants. These measurables have arbitrarily chosen ‘fixed points’. Consider a 1 degree uncertainty in a temperature of 99 degrees C. Is the uncertainty 1%? Consider the same error in a measurement of 5 degrees. Is the uncertainty now 20%? Consider how much smaller the percent would be if the temperature were expressed in degrees Kelvin. This shows that percent uncertainty of Celsius and Fahrenheit temperature measurements is meaningless. However, the absolute (Kelvin) temperature scale has a physically meaningful fixed point (absolute zero), rather than an arbitrarily chosen one, and in some situations a percent uncertainty of an absolute temperature is meaningful.
Per unit. In my opinion this expression is a barbarism best avoided. When a student is told that electric field is force per unit charge and in the MKS system one unit of charge is a coulomb (a huge amount) must we obtain that much charge to measure the field? Certainly not. In fact, one must take the limit of F/q as q goes to zero. Simply say: 'Force divided by charge' or 'F over q' or even 'force per charge'. Unfortunately there is no graceful way to say these things, other than simply writing the equation.
Per is one of those frustrating words in English. The American Heritage Dictionary definition is: 'To, for, or by each; for every.' Example: '40 cents per gallon.' We must put the blame for per unit squarely on the scientists and engineers.
Precise. Sharply or clearly defined. Having small experimental uncertainty. A precise measurement may still be inaccurate, if there were an unrecognized determinate error in the measurement (for example, a miscalibrated instrument). Compare: accurate.
Proof. A term from logic and mathematics describing an argument from premise to conclusion using strictly logical principles. In mathematics, theorems or propositions are established by logical arguments from a set of axioms, the process of establishing a theorem being called a proof.
The colloquial meaning of ‘proof’ causes lots of problems in physics discussion and is best avoided. Since mathematics is such an important part of physics, the mathematician’s meaning of proof should be the only one we use. Also, we often ask students in upper level courses to do proofs of certain theorems of mathematical physics, and we are not asking for experimental demonstration!
So, in a laboratory report, we should not say 'We proved Newton's law.' Rather say, 'Today we demonstrated (or verified) the validity of Newton's law in the particular case of…'
Radioactive material. A material whose nuclei spontaneously give off nuclear radiation. Naturally radioactive materials (found in the earth's crust) give off alpha, beta, or gamma particles. Alpha particles are Helium nuclei, beta particles are electrons, and gamma particles are high energy photons.
Radioactive. A word distinguishing radioactive materials from those which aren't. Usage: 'U-235 is radioactive; He-4 is not.'
Note: Radioactive is least misleading when used as an adjective, not as a noun. It is sometimes used in the noun form as an shortened stand-in for radioactive material, as in the example above.
Radioactivity. The process of emitting particles from the nucleus. Usage: 'Certain materials found in nature demonstrate radioactivity.'
Misuse alert: Radioactivity is a process, not a thing, and not a substance. It is just as incorrect to say 'U-235 emits radioactivity' as it is to say 'current flows.' A malfunctioning nuclear reactor does not release radioactivity, though it may release radioactive materials into the surrounding environment. A patient being treated by radiation therapy does not absorb radioactivity, but does absorb some of the radiation (alpha, beta, gamma) given off by the radioactive materials being used.
This misuse of the word radioactivity causes many people to incorrectly think of radioactivity as something one can get by being near radioactive materials. There is only one process which behaves anything like that, and it is called artificially induced radioactivity, a process mainly carried out in research laboratories. When some materials are bombarded with protons, neutrons, or other nuclear particles of appropriate energy, their nuclei may be transmuted, creating unstable isotopes which are radioactive.
Rate. A quantity of one thing compared to a quantity of another. [Dictionary definition]
In physics the comparison is generally made by taking a quotient. Thus speed is defined to be the dx/dt, the ‘time rate of change of position’.
Common misuse: We often hear non-scientists say such things as 'The car was going at a high rate of speed.' This is redundant at best, since it merely means 'The car was moving at high speed.' It is the sort of mistake made by people who don't think while they talk.
Ratio. The quotient of two similar quantities. In physics, the two quantities must have the same units to be ‘similar’. Therefore we may properly speak of the ratio of two lengths. But to say 'the ratio of charge to mass of the electron' is improper. The latter is properly called 'the specific charge of the electron.' See: specific.
Reaction. Reaction forces are those equal and opposite forces of Newton's Third Law. Though they are sometimes called an action and reaction pair, one never sees a single force referred to as an action force. See: Newton’s Third Law.
Real force. See: inertial frame.
Real image. The point(s) to which light rays converge as they emerge from a lens or mirror. See: virtual image.
Real object. The point(s) from which light rays diverge as they enter a lens or mirror. See: virtual object.
Relative. Colloquially 'compared to'. In the theory of relativity observations of moving observers are quantitatively compared. These observers obtain different values when measuring the same quantities, and these quantities are said to be relative. The theory, however, shows us how the differing measured values are precisely related to the relative velocity of the two observers. Some quantities are found to be the same for all observers, and are called invariant. One postulate of relativity theory is that the speed of light is an invariant quantity. When the theory is expressed in four dimensional form, with the appropriate choice of quantities, new invariant quantities emerge: the world-displacement (x + y + z +ict), the energy-momentum four-vector, and the electric and magnetic potentials may be combined into an invariant four-vector. Thus relativity theory might properly be called invariance theory.
Misuse alert: One hears some folks with superficial minds say 'Einstein showed that everything is relative.' In fact, special relativity shows that only certain measurable things are relative, but in a precisely and mathematically specific way, and other things are, not relative, for all observers agree on them.
Relative uncertainty. The uncertainty in a quantity compared to the quantity itself, expressed as a ratio of the absolute uncertainty to the size of the quantity. It may also be expressed as a percent uncertainty. The relative uncertainty is dimensionless and unitless. See: absolute uncertainty.
Scale-limited. A measuring instrument is said to be scale-limited if the experimental uncertainty in that instrument is smaller than the smallest division readable on its scale. Therefore the experimental uncertainty is taken to be half the smallest readable increment on the scale.
Specific. In physics and chemistry the word specific in the name of a quantity usually means ‘divided by an extensive measure that is, divided by a quantity representing an amount of material. Specific volume means volume divided by mass, which is the reciprocal of the density. Specific heat capacity is the heat capacity divided by the mass. See: extensive, and capacity.
Tele-. A prefix meaning at a distance, as in telescope, telemetry, television.
Term. One of several quantities which are added together.
Confusion can arise with another use of the word, as when one is asked to “Express the result in terms of mass and time.” This means “as a function of mass and time,” obviously it doesn’t mean that mass and time are to be added as terms.
Truth. This is a word best avoided entirely in physics except when placed in quotes, or with careful qualification. Its colloquial use has so many shades of meaning from ‘it seems to be correct’ to the absolute truths claimed by religion, that it’s use causes nothing but misunderstanding. Someone once said 'Science seeks proximate (approximate) truths.' Others speak of provisional or tentative truths. Certainly science claims no final or absolute truths.
Theoretical. Describing an idea which is part of a theory, or a consequence derived from theory.
Misuse alert: Do not call an authoritative or ‘book’ value of a physical quantity a theoretical value, as in: 'We compared our experimentally determined value of index of refraction with the theoretical value and found they differed by 0.07.' The value obtained from index of refraction tables comes not from theory, but from experiment, and therefore should not be called theoretical. The word theoretically suffers the same abuse. Only when a numeric value is a prediction from theory, can one properly refer to it as a 'theoretical value'.
Theory. A well-tested mathematical model of some part of science. In physics a theory usually takes the form of an equation or a group of equations, along with explanatory rules for their application. Theories are said to be successful if (1) they synthesize and unify a significant range of phenomena; (2) they have predictive power, either predicting new phenomena, or suggesting a direction for further research and testing. Compare: hypothesis, and law.
Uncertainty. Synonym: error. A measure of the the inherent variability of repeated measurements of a quantity. A prediction of the probable variability of a result, based on the inherent uncertainties in the data, found from a mathematical calculation of how the data uncertainties would, in combination, lead to uncertainty in the result. This calculation or process by which one predicts the size of the uncertainty in results from the uncertainties in data and procedure is called error analysis.
See: absolute uncertainty and relative uncertainty. Uncertainties are always present; the experimenter’s job is to keep them as small as required for a useful result. We recognize two kinds of uncertainties: indeterminate and determinate. Indeterminate uncertainties are those whose size and sign are unknown, and are sometimes (misleadingly) called random. Determinate uncertainties are those of definite sign, often referring to uncertainties due to instrument miscalibration, bias in reading scales, or some unknown influence on the measurement.
Units. Labels which distinguish one type of measurable quantity from other types. Length, mass and time are distinctly different physical quantities, and therefore have different unit names, meters, kilograms and seconds. We use several systems of units, including the metric (SI) units, the English (or U.S. customary units) , and a number of others of mainly historical interest.
Note: Some dimensionless quantities are assigned unit names, some are not. Specific gravity has no unit name, but density does. Angles are dimensionless, but have unit names: degree, radian, grad. Some quantities which are physically different, and have different unit names, may have the same dimensions, for example, torque and work. Compare: dimensions.
Virtual image. The point(s) from which light rays converge as they emerge from a lens or mirror. The rays do not actually pass through each image point, but diverge from it. See: real image.
Virtual object. The point(s) to which light rays converge as they enter a lens. The rays pass through each object point. See: real object.
Weight. The size of the external force required to keep a body at rest in its frame of reference.
Elementary textbooks almost universally define weight to be 'the size of the gravitational force on a body.' This would be fine if they would only consistently stick to that definition. But, no, they later speak of weightless astronauts, loss of weight of a body immersed in a liquid, etc.
This glossary is created by Donald E. Simanek, Lock Haven University and posted here with permission.
Related Books
McGraw-Hill Encyclopedia of Physics
by Sybil P. Parker
McGraw-Hill Dictionary of Physics
by Sybil P. Parker
The Penguin Dictionary of Physics
by John Cullerne
A Dictionary of Physics
by Alan Isaacs
A Dictionary of Science
by Alan Isaacs
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Science
Science (from the Latin scientia, meaning "knowledge" or "to know") is the effort to discover, and increase human understanding of how the physical world works. Through controlled methods, scientists use observable physical evidence of natural phenomena to collect data, and analyze this information to explain what and how things work. Such methods include experimentation that tries to simulate natural phenomena under controlled conditions and thought experiments. Knowledge in science is gained through research.
Etymology
DNA determines the genetic structure of all life on earth
DNA determines the genetic structure of all life on earth
The word science is derived from the Latin word scientia for knowledge, the nominal form of the verb scire, "to know". The Proto-Indo-European (PIE) root that yields scire is *skei-, meaning to "cut, separate, or discern". Other words from the same root include Sanskrit chyati, "he cuts off", Greek schizo, "I split" (hence English schism, schizophrenia), Latin scindo, "I split" (hence English rescind).[1] From the Middle Ages to the Enlightenment, science or scientia meant any systematic recorded knowledge.[2] Science therefore had the same sort of very broad meaning that philosophy had at that time. In other languages, including French, Spanish, Portuguese, Italian, Polish and Russian, the word corresponding to science also carries this meaning.
History of science
Main article: History of science
History of usage of the word science
Well into the eighteenth century, science and natural philosophy were not quite synonymous, but only became so later with the direct use of what would become known formally as the scientific method, which was earlier developed during the Middle Ages and early modern period in Europe and the Middle East (see History of scientific method). Prior to the 18th century, however, the preferred term for the study of nature was natural philosophy, while English speakers most typically referred to the study of the human mind as moral philosophy. By contrast, the word "science" in English was still used in the 17th century to refer to the Aristotelian concept of knowledge which was secure enough to be used as a sure prescription for exactly how to do something. In this differing sense of the two words, the philosopher John Locke in An Essay Concerning Human Understanding wrote that "natural philosophy [the study of nature] is not capable of being made a science".[3]
By the early 1800s, natural philosophy had begun to separate from philosophy, though it often retained a very broad meaning. In many cases, science continued to stand for reliable knowledge about any topic, in the same way it is still used in the broad sense (see the introduction to this article) in modern terms such as library science, political science, and computer science. In the more narrow sense of science, as natural philosophy became linked to an expanding set of well-defined laws (beginning with Galileo's laws, Kepler's laws, and Newton's laws for motion), it became more popular to refer to natural philosophy as natural science. Over the course of the nineteenth century, moreover, there was an increased tendency to associate science with study of the natural world (that is, the non-human world). This move sometimes left the study of human thought and society (what would come to be called social science) in a linguistic limbo by the end of the century and into the next.[4]
Through the 19th century, many English speakers were increasingly differentiating science (meaning a combination of what we now term natural and biological sciences) from all other forms of knowledge in a variety of ways. The now-familiar expression “scientific method,” which refers to the prescriptive part of how to make discoveries in natural philosophy, was almost unused during the early part of the 19th century, but became widespread after the 1870s, though there was rarely totally agreement about just what it entailed.[4] The word "scientist," meant to refer to a systematically-working natural philosopher, (as opposed to an intuitive or empirically-minded one) was coined in 1833 by William Whewell.[5] Discussion of scientists as a special group of people who did science, even if their attributes were up for debate, grew in the last half of the 19th century.[4] Whatever people actually meant by these terms at first, they ultimately depicted science, in the narrow sense of the habitual use of the scientific method and the knowledge derived from it, as something deeply distinguished from all other realms of human endeavor.
By the twentieth century, the modern notion of science as a special brand of information about the world, practiced by a distinct group and pursued through a unique method, was essentially in place. It was used to give legitimacy to a variety of fields through such titles as "scientific" medicine, engineering, advertising, or motherhood.[4] Over the 1900s, links between science and technology also grew increasingly strong.
Distinguished from technology
By the end of the century, it is arguable that technology had even begun to eclipse science as a term of public attention and praise. Scholarly studies of science have begun to refer to "technoscience" rather than science of technology separately. Meanwhile, such fields as biotechnology and nanotechnology are capturing the headlines. One author has suggested that, in the coming century, "science" may fall out of use, to be replaced by technoscience or even by some more exotic label such as "techknowledgy."[4]
Scientific method
Main article: Scientific method
The Bohr model of the atom, like many ideas in the history of science, was at first prompted by and later partially disproved by experiment.
The Bohr model of the atom, like many ideas in the history of science, was at first prompted by and later partially disproved by experiment.
The scientific method seeks to explain the events of nature in a reproducible way, and to use these reproductions to make useful predictions. It is done through observation of natural phenomena, and/or through experimentation that tries to simulate natural events under controlled conditions. It provides an objective process to find solutions to problems in a number of scientific and technological fields.[6]
Based on observations of a phenomenon, a scientist may generate a model. This is an attempt to describe or depict the phenomenon in terms of a logical physical or mathematical representation. As empirical evidence is gathered, a scientist can suggest a hypothesis to explain the phenomenon. This description can be used to make predictions that are testable by experiment or observation using the scientific method. When a hypothesis proves unsatisfactory, it is either modified or discarded.
While performing experiments, Scientists may have a preference for one outcome over another, and it is important that this tendency does not bias their interpretation.[7][8] A strict following of the scientific method attempts to minimize the influence of a scientist's bias on the outcome of an experiment. This can be achieved by correct experimental design, and a thorough peer review of the experimental results as well as conclusions of a study.[9][10] Once the experiment results are announced or published, an important cross-check can be the need to validate the results by an independent party.[11]
Once a hypothesis has survived testing, it may become adopted into the framework of a scientific theory. This is a logically reasoned, self-consistent model or framework for describing the behavior of certain natural phenomena. A theory typically describes the behavior of much broader sets of phenomena than a hypothesis—commonly, a large number of hypotheses can be logically bound together by a single theory. These broader theories may be formulated using principles such as parsimony (e.g., "Occam's Razor"). They are then repeatedly tested by analyzing how the collected evidence (facts) compares to the theory. When a theory survives a sufficiently large number of empirical observations, it then becomes a scientific generalization that can be taken as fully verified. These assume the status of a physical law or law of nature.
Despite the existence of well-tested theories, science cannot claim absolute knowledge of nature or the behavior of the subject or of the field of study due to epistemological problems that are unavoidable and preclude the discovery or establishment of absolute truth. Unlike a mathematical proof, a scientific theory is empirical, and is always open to falsification, if new evidence is presented. Even the most basic and fundamental theories may turn out to be imperfect if new observations are inconsistent with them. Critical to this process is making every relevant aspect of research publicly available, which allows ongoing review and repeating of experiments and observations by multiple researchers operating independently of one another. Only by fulfilling these expectations can it be determined how reliable the experimental results are for potential use by others.
Isaac Newton's Newtonian law of gravitation is a famous example of an established law that was later found not to be universal—it does not hold in experiments involving motion at speeds close to the speed of light or in close proximity of strong gravitational fields. Outside these conditions, Newton's Laws remain an excellent model of motion and gravity. Since general relativity accounts for all the same phenomena that Newton's Laws do and more, general relativity is now regarded as a more comprehensive theory.[12]
Mathematics
Data from the famous Michelson–Morley experiment
Data from the famous Michelson–Morley experiment
Mathematics is essential to many sciences. One important function of mathematics in science is the role it plays in the expression of scientific models. Observing and collecting measurements, as well as hypothesizing and predicting, often require extensive use of mathematics and mathematical models. Calculus may be the branch of mathematics most often used in science[citation needed], but virtually every branch of mathematics has applications in science, including "pure" areas such as number theory and topology. Mathematics is fundamental to the understanding of the natural sciences and the social sciences, many of which also rely heavily on statistics.
Statistical methods, comprised of mathematical techniques for summarizing and exploring data, allow scientists to assess the level of reliability and the range of variation in experimental results. Statistical thinking also plays a fundamental role in many areas of science.
Computational science applies computing power to simulate real-world situations, enabling a better understanding of scientific problems than formal mathematics alone can achieve. According to the Society for Industrial and Applied Mathematics, computation is now as important as theory and experiment in advancing scientific knowledge.[13]
Whether mathematics itself is properly classified as science has been a matter of some debate. Some thinkers see mathematicians as scientists, regarding physical experiments as inessential or mathematical proofs as equivalent to experiments. Others do not see mathematics as a science, since it does not require experimental test of its theories and hypotheses. In practice, mathematical theorems and formulas are obtained by logical derivations which presume axiomatic systems, rather than a combination of empirical observation and method of reasoning that has come to be known as scientific method. In general, mathematics is classified as formal science, while natural and social sciences are classified as empirical sciences.
Philosophy of science
Velocity-distribution data of a gas of rubidium atoms, confirming the discovery of a new phase of matter, the Bose–Einstein condensate.
Velocity-distribution data of a gas of rubidium atoms, confirming the discovery of a new phase of matter, the Bose–Einstein condensate.
Main article: Philosophy of science
The philosophy of science seeks to understand the nature and justification of scientific knowledge. It has proven difficult to provide a definitive account of the scientific method that can decisively serve to distinguish science from non-science. Thus there are legitimate arguments about exactly where the borders are, leading to the problem of demarcation. There is nonetheless a set of core precepts that have broad consensus among published philosophers of science and within the scientific community at large.
Science is reasoned-based analysis of sensation upon our awareness. As such, the scientific method cannot deduce anything about the realm of reality that is beyond what is observable by existing or theoretical means.[14] When a manifestation of our reality previously considered supernatural is understood in the terms of causes and consequences, it acquires a scientific explanation.[15]
Some of the findings of science can be very counter-intuitive. Atomic theory, for example, implies that a granite boulder which appears a heavy, hard, solid, grey object is actually a combination of subatomic particles with none of these properties, moving very rapidly in space where the mass is concentrated in a very small fraction of the total volume. Many of humanity's preconceived notions about the workings of the universe have been challenged by new scientific discoveries. Quantum mechanics, particularly, examines phenomena that seem to defy our most basic postulates about causality and fundamental understanding of the world around us. Science is the branch of knowledge dealing with people and the understanding we have of our environment and how it works.
There are different schools of thought in the philosophy of scientific method. Methodological naturalism maintains that scientific investigation must adhere to empirical study and independent verification as a process for properly developing and evaluating natural explanations for observable phenomena. Methodological naturalism, therefore, rejects supernatural explanations, arguments from authority and biased observational studies. Critical rationalism instead holds that unbiased observation is not possible and a demarcation between natural and supernatural explanations is arbitrary; it instead proposes falsifiability as the landmark of empirical theories and falsification as the universal empirical method. Critical rationalism argues for the ability of science to increase the scope of testable knowledge, but at the same time against its authority, by emphasizing its inherent fallibility. It proposes that science should be content with the rational elimination of errors in its theories, not in seeking for their verification (such as claiming certain or probable proof or disproof; both the proposal and falsification of a theory are only of methodological, conjectural, and tentative character in critical rationalism). Instrumentalism rejects the concept of truth and emphasizes merely the utility of theories as instruments for explaining and predicting phenomena.
Critiques
Science, pseudoscience and nonscience
Main articles: Pseudoscience and Nonscience
Any established body of knowledge which masquerades as science in an attempt to claim a legitimacy which it would not otherwise be able to achieve on its own terms is not science; it is often known as fringe- or alternative science. The most important of its defects is usually the lack of the carefully controlled and thoughtfully interpreted experiments which provide the foundation of the natural sciences and which contribute to their advancement. Another term, junk science, is often used to describe scientific theories or data which, while perhaps legitimate in themselves, are believed to be mistakenly used to support an opposing position. There is usually an element of political or ideological bias in the use of the term. Thus the arguments in favor of limiting the use of fossil fuels in order to reduce global warming are often characterized as junk science by those who do not wish to see such restrictions imposed, and who claim that other factors may well be the cause of global warming. A wide variety of commercial advertising (ranging from hype to outright fraud) would also fall into this category. Finally, there is just plain bad science, which is commonly used to describe well-intentioned but incorrect, obsolete, incomplete, or over-simplified expositions of scientific ideas.
The status of many bodies of knowledge as true sciences, has been a matter of debate. Discussion and debate abound in this topic with some fields like the social and behavioural sciences accused by critics of being unscientific. Many groups of people from academicians like Nobel Prize physicist Percy W. Bridgman,[16] or Dick Richardson, Ph.D.—Professor of Integrative Biology at the University of Texas at Austin,[17] to politicians like U.S. Senator Kay Bailey Hutchison and other co-sponsors,[18] oppose giving their support or agreeing with the use of the label "science" in some fields of study and knowledge they consider non-scientific, ambiguous, or scientifically irrelevant compared with other fields. Karl Popper denied the existence of evidence[19] and of scientific method.[20] Popper holds that there is only one universal method, the negative method of trial and error. It covers not only all products of the human mind, including science, mathematics, philosophy, art and so on, but also the evolution of life.[21] He also contributed to the Positivism dispute, a philosophical dispute between Critical rationalism (Popper, Albert) and the Frankfurt School (Adorno, Habermas) about the methodology of the social sciences.[22]
Philosophical focus
Historian Jacques Barzun termed science "a faith as fanatical as any in history" and warned against the use of scientific thought to suppress considerations of meaning as integral to human existence.[23] Many recent thinkers, such as Carolyn Merchant, Theodor Adorno and E. F. Schumacher considered that the 17th century scientific revolution shifted science from a focus on understanding nature, or wisdom, to a focus on manipulating nature, i.e. power, and that science's emphasis on manipulating nature leads it inevitably to manipulate people, as well.[24] Science's focus on quantitative measures has led to critiques that it is unable to recognize important qualitative aspects of the world.[24]
The implications of the ideological denial of ethics for the practice of science itself in terms of fraud, plagiarism, and data falsification, has been criticized by several academics. In "Science and Ethics", the philosopher Bernard Rollin examines the ideology that denies the relevance of ethics to science, and argues in favor of making education in ethics part and parcel of scientific training.[25]
The media and the scientific debate
The mass media face a number of pressures that can prevent them from accurately depicting competing scientific claims in terms of their credibility within the scientific community as a whole. Determining how much weight to give different sides in a scientific debate requires considerable expertise on the issue at hand.[26] Few journalists have real scientific knowledge, and even beat reporters who know a great deal about certain scientific issues may know little about other ones they are suddenly asked to cover.[27][28]
Epistemological inadequacies
Psychologist Carl Jung believed that though science attempted to understand all of nature, the experimental method used would pose artificial, conditional questions that evoke only partial answers.[29] Robert Anton Wilson criticized science for using instruments to ask questions that produce answers only meaningful in terms of the instrument, and that there was no such thing as a completely objective vantage point from which to view the results of science.[30]
Scientific community
Main article: Scientific community
The scientific community consists of the total body of scientists, its relationships and interactions. It is normally divided into "sub-communities" each working on a particular field within science.
Fields
Main article: Fields of science
Fields of science are commonly classified along two major lines: natural sciences, which study natural phenomena (including biological life), and social sciences, which study human behavior and societies. These groupings are empirical sciences, which means the knowledge must be based on observable phenomena and capable of being experimented for its validity by other researchers working under the same conditions.[31] There are also related disciplines that are grouped into interdisciplinary and applied sciences, such as engineering and health science. Within these categories are specialized scientific fields that can include elements of other scientific disciplines but often possess their own terminology and body of expertise.[32]
Mathematics, which is sometimes classified within a third group of science called formal science, has both similarities and differences with the natural and social sciences.[31] It is similar to empirical sciences in that it involves an objective, careful and systematic study of an area of knowledge; it is different because of its method of verifying its knowledge, using a priori rather than empirical methods.[31] Formal science, which also includes statistics and logic, is vital to the empirical sciences. Major advances in formal science have often led to major advances in the physical and biological sciences. The formal sciences are essential in the formation of hypotheses, theories, and laws,[31] both in discovering and describing how things work (natural sciences) and how people think and act (social sciences).
Institutions
Louis XIV visiting the Académie des sciences in 1671.
Louis XIV visiting the Académie des sciences in 1671.
Learned societies for the communication and promotion of scientific thought and experimentation have existed since the Renaissance period.[33] The oldest surviving institution is the Accademia dei Lincei in Italy.[34] National Academy of Sciences are distinguished institutions that exist in a number of countries, beginning with the British Royal Society in 1660[35] and the French Académie des Sciences in 1666.[36]
International scientific organizations, such as the International Council for Science, have since been formed to promote cooperation between the scientific communities of different nations. More recently, influential government agencies have been created to support scientific research, including the National Science Foundation in the U.S.
Other prominent organizations include the academies of science of many nations, CSIRO in Australia, Centre national de la recherche scientifique in France, Max Planck Society and Deutsche Forschungsgemeinschaft in Germany, and in Spain, CSIC.
Literature
Main article: Scientific literature
An enormous range of scientific literature is published.[37] Scientific journals communicate and document the results of research carried out in universities and various other research institutions, serving as an archival record of science. The first scientific journals, Journal des Sçavans followed by the Philosophical Transactions, began publication in 1665. Since that time the total number of active periodicals has steadily increased. As of 1981, one estimate for the number of scientific and technical journals in publication was 11,500.[38]
Most scientific journals cover a single scientific field and publish the research within that field; the research is normally expressed in the form of a scientific paper. Science has become so pervasive in modern societies that it is generally considered necessary to communicate the achievements, news, and ambitions of scientists to a wider populace.
Science magazines such as New Scientist, Science & Vie and Scientific American cater to the needs of a much wider readership and provide a non-technical summary of popular areas of research, including notable discoveries and advances in certain fields of research. Science books engage the interest of many more people. Tangentially, the science fiction genre, primarily fantastic in nature, engages the public imagination and transmits the ideas, if not the methods, of science.
Recent efforts to intensify or develop links between science and non-scientific disciplines such as Literature or, more specifically, Poetry, include the Creative Writing <-> Science resource developed through the Royal Literary Fu
In physiology, a smile is a facial expression formed by flexing those muscles most notably near both ends of the mouth.
The smile can also be found around the eyes (See 'Duchenne smile' below). Among humans, it is customarily an expression denoting pleasure, happiness, or amusement, but can also be an involuntary expression of anxiety, in which case it can be known as a grimace. There is much evidence that smiling is a normal reaction to certain stimuli as it occurs regardless of culture. Happiness is most often the motivating cause of a smile. Among animals, the exposure of teeth, which may bear a resemblance to a smile, is often used as a threat or warning display - known as a snarl - or a sign of submission. In chimpanzees, it can also be a sign of fear.
