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English in Use/Prepositions, Conjunctions, and Interjections

Preposition
A preposition is a word used to express some relation of different things or thoughts to each other, and is generally placed before a noun or a pronoun: as,

 * "The paper lies before me on the desk."

In that sentence, before is the preposition, me is the governed term of a preposition, "before me" is a prepositional phrase, and the verb lies is the prior term of a preposition. "On the desk" is the other prepositional phrase, and lies is its prior term.

To a preposition, the prior term may be a noun, an adjective, a pronoun, a verb, a participle, or an adverb; and the governed term may be a noun, a pronoun, a pronominal adjective, an infinitive verb, or a participle.

Although overlooked in common speech, prepositional phrases should not be placed at the end of a question: as,

 * "Who do I give this to?"
 * Say, "To whom do I give this?"

Prepositional phrases can be placed at the end of a sentence: as,

 * "She did not sign up for tennis."

See also: List of English prepositions

Some words are linked with their prepositions, e.g. compared with, similar to, and different from (possibly different than in USA).

Commonly used prepositions include:

 * About—In concern with; engaged in; intent on; on the point or verge of; in act of; concerning; with regard to; on account of.
 * Above—In or to a higher place; on or over; superior to; surpassing; beyond; higher in measure or degree.
 * Across—From side to side; athwart; crosswise; quite over.
 * After—Behind in place; below in rank; later in time; subsequent to; following; in search of; in pursuit of; concerning; in relation to; in imitation of; in conformity with; after the manner of; according to; in accordance with; in proportion to.
 * Against—Abreast; opposite to; facing; towards; in opposition to; counter to; in contrariety to; adverse to; by of before the time; in preparation for.
 * Along—By the length.
 * Amid(st)—In the midst or middle of; surrounded or encompassed by; among.
 * Among—Conjoined; associated with; making part of.
 * Around—On all sides of; encircling; encompassing; at random through; about; on another side of.
 * As—Similar of like. It can be used as conjunction and preposition.
 * At—Expresses the relations of presence, proximity to, nearness in place or time, age or order, state or condition, employment or action, point or position, rate or value, source, occasion, reason, consequence or effect, direction toward an object or end; occupied with.
 * Before—In front of; preceding in space, order, rank, right, worth, or time; ahead of; earlier than; previously to; anterior to; an advance of; farther onward; in presence or sight of; face to face with; under the jurisdiction of; open for; free of access to; in the power of.
 * Behind—At the back part; in the rear; toward the back part or rear; backward; out of sight; remaining.
 * Below—Under, or lower in place; beneath; inferior to; unworthy of; unbefitting.
 * Beneath—Lower in place; under; underneath; lower in rank, dignity, or excellence.
 * Beside(s)—Over and above; separate or distinct from; in addition to; other than; else than.
 * Between—In the space which separates; betwixt; from one place to another; shared by both; affecting mutual relation; with relation to two.
 * Beyond—On the further side of; further on or away than; at a place or time not yet reached; out of the reach or sphere of; further than; greater than; exceeding or surpassing.
 * During—In the time of; as long as the action or existence of.
 * Except—With exclusion of; leaving or left out; excepting.
 * For—In consideration of; in view of; with reference to; the cause, occasion, motive or inducement of; the reason of; in favor of; in promoting which; on account of which; indicating the object of an act; toward which; in the character of; instead of which; during; in or through the space or time of; in prevention of which.
 * From—Lessening or losing proximity to; leaving behind; by reason of; out of; by aid of; indicates the point of space or time at which the action or state is regarded as setting out or beginning; the source; the cause; the correlative of to.
 * In—With reference to space or place, circumstances or conditions, a whole, physical surrounding, personal states, reach, scope, movement or tendency, limit of time.
 * Into—To the inside of; expressing penetration beyond the outside or surface; indicating insertion, inclusion, or passing to another form or condition.
 * Like—Similar of as. It can be used as conjunction and preposition.
 * Of—Out from; proceeding from; belonging to; relating to; concerning; about; belonging to; connected with; indicating origin, source, descent, possession or ownership, relation of subject to attribute, material, part, source of a purpose or action, distance in space or time, identity or equivalence, agent, or passage from one state to another.
 * Off—Not on; away from.
 * On—At, to or against the surface; by means of; with; adjacent to; in addition to; besides; indicating dependence or reliance; at or in the time of; during; in consequence of; toward; for; at the peril of; for the safety of; by virtue of; with the pledge of; to the account of; in reference or relation to; occupied with; in the performance of; in the service of; connected with; of the number of; forward; onward; in continuance; without interruption or ceasing; adhering; not off; attached to the body; in progress; proceeding.
 * Over—Above, or higher than; across; from side to side of; on the whole surface of; throughout the whole extent of; superiority in excellence, dignity, condition, value or authority; across or during the time of; from beginning to end of; beyond; in excess of; in addition to; more than; across; crosswise.
 * Past—Beyond, in position, degree or time; further than; beyond the reach or influence of; above; exceeding; more than; by.
 * Through—From one end to the opposite; between the sides or walls of; by means of; by the agency of; over the whole extent of; among or in the midst of; to the end; to a conclusion; to the ultimate purpose.
 * To—Indicates motion, course, or tendency toward a limit; connects adjectives, nouns and verbs with their governed terms and contains less the idea of appropriation than for; a sign of the infinitive; extent; limit; degree of comprehension; inclusion as far as; effect; end; consequence; apposition; connection; antithesis; opposition; accord; adaptation; comparison; addition; union; accompaniment; character; condition of being.
 * Toward(s)—In the direction of; with respect or reference to; regarding; concerning; tending to; in behalf of; near; about; approaching to.
 * Under—Below or lower; lower than; beneath; denoting relation to some thing, condition or person that is superior, or to something that comprehends, includes or furnishes a cover.
 * Underneath—Under; beneath; below.
 * Until—To; unto; towards; up to; till; before.
 * With—Denotes relation of nearness, proximity, association, connection, opposition or hostility, connection of friendship, support, alliance, assistance, countenance, accomplishment of cause, means, instrument, simultaneous happening, immediate succession, consequence, possession or appendage; among; in the company of.
 * Without—On or at the outside of; out of; not within; out of the limits of; out of reach of; in absence of, separation from, or destitution of; not with use or employment of; independently of; exclusively of; with omission; unless; except.

A short syntax
A noun or a pronoun made the object of a preposition, is governed by it in the objective case, as "From whom."

Prepositions show the relations of words, and of the things or thoughts expressed by them, as "He came from Rome," except the following cases: the preposition to, as "To learn to die," and the preposition for, as "For us to learn."

Conjunction
A conjunction is a word used to connect words or sentences in construction, and to show the dependence of the terms so connected: as,

 * "You and he are happy, because you are good."—Murray.

Conjunctions are divided into two general classes, copulative and disjunctive; and a few of each class are particularly distinguished from the rest, as being corresponsive.

A copulative conjunction is a conjunction that denotes an addition, a cause, a consequence, or a supposition: as,

 * "He and I shall not dispute; for, if he has any choice, I shall readily grant it."

The copulatives: and, as, both, because, even, for, if, that, then, since, seeing, so.

A disjunctive conjunction is a conjunction that denotes opposition of meaning: as,

 * "Though he were dead, yet shall he live."—St. John's Gospel.
 * "Be not faithless, but believing."—Id.

The disjunctives: or, nor, either, neither, than, though, although, yet, but, except, whether, lest, unless, save, provided, notwithstanding, whereas.

The corresponsive conjunctions are those which are used in pairs, so that one refers or answers to the other: as,

 * "John came neither eating nor drinking."—Matt., xi, 18.
 * "But if I cast out devils by the spirit of God, then the kingdom of God is come to you."—Ib., xii, 28.

The corresponsives: both, and; as, as; as, so; if, then; either, or; neither, nor; whether, or; though, yet; although, yet.

A short syntax
Conjunctions connect words, sentences, or parts of sentences, as "Between me and you," except the following cases: introducing a sentence, as "That you have wronged me," corresponding conjunctions, as "Neither sun nor stars," and either and neither, as "It is not dangerous neither."

Interjection
An interjection is a word that is uttered to indicate a strong or sudden emotion. The following are the principal interjections, arranged according to the emotions which they are intended to indicate:

 * Of joy; yoo! hey! oi! yeah!
 * Of sorrow; oh! ah! hoo! alas! alack! lackaday! welladay! or welaway!
 * Of wonder; gotit! ha! strange! indeed!
 * Of wishing, earnestness, or vocative address; (often with a noun or pronoun in the nominative absolute;) O!
 * Of praise; well-done! good! bravo!
 * Of surprise with disapproval; whew! hoity-toity! really! no-way! what!
 * Of pain or fear; oh! ooh! ah! eh! O dear! Oh, no!
 * Of contempt; fudge! pugh! poh! pshaw! pish! tush! tut! humph! fine!
 * Of aversion; foh! faugh! fie! fy! foy!
 * Of expulsion; out! off! shoo! whew! begone! avaunt! aroynt!
 * Of calling aloud; oi! yo! dude! hollo! holla! hallo! halloo! hoy! ahoy! hey!
 * Of exultation; ah! aha! hazza! hey! heyday! harrah!
 * Of laughter; ha, ha, ha; he, he, he; te-hee, te-hee.(lol)
 * Of salutation; welcome! hail! all-hail!
 * Of calling to attention; ho! lo! la! law! look! see! behold! hark!
 * Of calling to silence; hush! hist! whist! 'st! aw! pst! shhh! zip it!
 * Of dread or horror; oh! ha! hah! what!
 * Of languor or weariness; heigh-ho! heigh-ho-hum!
 * Of stopping; hold! soft! avast! whoh! halt! stop! hold-on! calm!
 * Of parting; farewell! adieu! good-bye! good-day! see ya!
 * Of knowing or detecting; oho! ahah! ay-ay!
 * Of interrogating; eh? ha? hey? no?

A short syntax
Interjections are put absolute, either alone, or with other words, as "Ah Dennis!"


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Principles of Economics/What Is Economics

Economics is a social science that studies how people satisfy unlimited wants with scarce resources.
 * It involves the analysis of choice and trade through
 * The discipline is divided into two sections: microeconomics (micro) and macroeconomics (macro).

Micro and Macro
Microeconomics studies small-scale economies. That is, from the individual level on up to the industry level. Microeconomics is concerned with how consumers (buyers) and producers (sellers) come together to exchange goods and services, how much is produced, what to produce, and the going prices. It focuses on the actions of individuals and firms.

Macroeconomics is the branch that studies large-scale economies. Macroeconomics observes and analyzes how entire countries, full of many industries and consumers, function. It is not simply the sum of many "microeconomics"; many of the concepts are entirely different. Where micro will study a single consumer, a paper-clip manufacturing plant or the airline industry, macro studies the entire economy within which those three exist. Some of the elements of a large economy that macroeconomics considers include inflation, government policies, output growth, and unemployment.

Themes
Economics involves several recurring themes:

 * Trade - buying and selling goods and services
 * Models - simple representation of complex situations
 * Utility - a measure of people's happiness
 * Choices - choosing the best allocation of resources
 * Efficiency - maximizing production and profits
 * Scarcity - the premise that people only have so much to work with
 * Costs - what is lost in order to gain."there is no such thing as a free lunch"
 * Money - who has money, access to it, how it is used, etc.
 * Consumption - the buyers in the market who form the demand
 * Production - the sellers in the market who form the supply
 * Rationality - people doing things with good and logical reasoning

Human Behavior
The field of economics is a social science. This means that economics has two important attributes:
 * Economics studies human activities and constructions, and
 * Economics uses the scientific method and empirical evidence to build its base of knowledge.

Economics is a semi-concrete social science. We must study human behavior and the choices we make. The assumption that people are rational indicates that the discipline focuses heavily on thinking of what would ideally happen in models. Additionally, we have concrete data—numbers—to work with. Formally, economics is the scientific study of the way in which humans make choices about production, consumption and wealth when faced with scarce resources.

The fact that economics is in several ways an abstract science means that various economists have differing interpretations of models and the way the world works. Furthermore, it is difficult to run experiments on social situations, especially on a scale as large as an entire nation. Therefore, economists rely on extensive mathematical tools, like econometrics, to analyze real world situations that have occurred and use that to forecast future situations.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Talk:Genealogy/Software

MediaWiki?
Does anyone have any thoughts about using MediaWiki as a genealogical research platform? I think it should be listed here, with some information about how best to use it for this purpose. 150.203.2.85 01:28, 18 July 2006 (UTC) (Wikipedia:User:Samwilson)

Link to Wikipedias page on this
Should we link to Wikipedias page on this? Gioto (talk) 07:00, 20 January 2009 (UTC)

title: Talk:Genealogy/Software


text:
Intermediate Algebra/Solving Inequalities

Inequalities
As opposed to an equation, an inequality is an expression that states that two quantities are unequal or not equivalent to one another. In most cases we use inequalities in real life more than equations (i.e. this shirt costs $2 more than that one).

Given that a and b are real numbers, there are four basic inequalities:

 * a < b: a is "less than" b:
 * Example: 2 < 4 ; -3 < 0; etc.

 * a > b: a is "greater than" b:
 * Example: -2 > -4 ; 3 > 0 ; etc.

 * $$a \le b$$: a is "less than or equal to" b:
 * Example: If we know that $$x \le 7$$, then we can conclude that x is equal to any value less than 7, including 7 itself.

 * $$a \ge b$$: a is "greater than or equal to" b:
 * Example: Conversely, if $$x \ge 7$$, then x is equal to any value greater than 7, including 7 itself.

Properties of Inequalities
Just as there are four properties of equality, there are also four properties of inequality:

Addition Property of Inequality

If a, b, and c are real numbers such that a > b, then a + c > b + c. Conversely, if a < b, then a + c < b + c.

Subtraction Property of Inequality

If a, b, and c are real numbers such that a > b, then a - c > b - c. Conversely, if a < b, then a - c < b - c.

Multiplication Property of Inequality

If a, b, and c are real numbers such that a > b and c > 0, then ac (or a * c) > bc (or b * c). Conversely, if a < b and c > 0, then ac < bc. (Note that if c = 0, then both sides of the inequality are in fact equal.) We will also review cases where c is less than zero later in the lesson.

Division Property of Inequality

If a, b, and c are real numbers such that a > b, and c > 0, then $$\frac {a}{c} > \frac {b}{c}$$. Conversely under the same conditions, if a < b, then $$\frac {a} {c} < \frac {b}{c}$$. As with the Multiplication Property, there are special cases that will be discussed later when c < 0.

Note that all four properties also work with inequalities where $$a \le b$$ or $$a \ge b$$.

Trichotomy Property
The statements above form the basis of Trichotomy Property:

Given any two real numbers a and b, then only one of the following statements must hold true:  a < b a = b a > b

So, if we are given any two unknown real-number values, then any one of the three statements will hold true.

Solving Inequalities
Solving algebraic inequalities is more or less identical to solving algebraic equations. Consider the following example:

$$2x + 4 \le 3x - 7$$

Although it may be an inequality, we can use the Properties of Inequality stated above to solve. Start by subtracting 2x from both sides:

$$2x - 2x + 4 \le 3x - 2x - 7$$ $$4 \le x - 7$$

Finish by adding 7 to both sides.

$$4 + 7 \le x - 7 + 7$$ $$11 \le x$$

This can be rewritten as $$x \ge 11$$. To check, substitute any value greater than or equal to 11. However, in order to satisfy the Trichotomy Property, we'll substitute three different values: 10, 11, and 12. Ten is incorrect, whereas eleven and twelve satisfy the solution. Therefore, the solution set - the set of all answers which satisfy the original inequality - is $$x \ge 11$$. Written in set notation, the answer is {$$x | x \ge 11$$}. This is read as "the set of all x such that x is greater than or equal to 11".

Special Cases - A variable in the denominator
For example, consider the inequality
 * $$\frac{2}{x-1}<2\,$$

In this case one cannot multiply the right hand side by (x-1) because the value of x is unknown. Since x may be either positive or negative, you can't know whether to leave the inequality sign as <, or reverse it to >. The method for solving this kind of inequality involves four steps:
 * 1) Find out when the denominator is equal to 0.  In this case it's when $$x=1$$.
 * 2) Pretend the inequality sign is an = sign and solve it as such: $$\frac{2}{x-1}=2\,$$, so $$x=2$$.
 * 3) Plot the points $$x=1$$ and $$x=2$$ on a number line with an unfilled circle because the original equation included < (it would have been a filled circle if the original equation included <= or >=).  You now have three regions: $$x<1$$, $$12$$.
 * 4) Test each region independently.  in this case test if the inequality is true for 1x>2 (e.g. x=3).  In this case the original inequation holds, and so the solution for the original inequation is 1>x>2.

Practice Problems
 {Determine if the number in parentheses satisfies the given inequality:}

{$$x > 4$$ (5) +yes -no
 * type=""}

{$$2x \le 9$$ (6.5) -yes +no
 * type=""}

{$$4x - 2 > 8$$ (2.5) -yes +no
 * type=""}

Special Cases
Let us suppose that we were given this inequality to solve:

$$-3x + 8 \ge 26$$

Using the same steps as above, start by subtracting 8 from both sides.

$$-3x + 8 - 8 \ge 26 - 8$$ $$-3x \ge 18$$

Now divide both sides by -3.

$$-3x/-3 \ge 18/-3$$ $$x \ge -6$$

Check this solution by substituting three numbers. We'll use -7, -6, and -5.

Wait, what happened? -7 and -6 satisfy the inequality, yet -7 is non-inclusive in the solution set! And -5, which is greater than -6, does not satisfy the inequality!

This is a special case involved in solving inequalities. Because the coefficient of the x-term was negative, the constant on the other side (26, which became 18 and then -6) switched signs. In order to attain a valid solution if a negative number is divided, we need to switch the sign in order to make sure that the solution set is correct. Thus, $$x \ge -6$$ becomes $$x \le -6$$, or more specifically, {$$x | x \le -6$$}.

Practice Problems
 {Solve the following inequalities and check each solution set:}

{-3x - 5 > 22 x < { -9_5 }
 * type="{}"}

{4x - 2 $$\le$$ -6x - 7 x ≤ { -1/2|-0.5_5 }
 * type="{}"}

{$$\frac {-2x}{5} \ge 12 - 4x$$ x ≥ { 10/3|3 1/3_5 }
 * type="{}"}

{11 - 7x < 39 x > { -4_5 }
 * type="{}"}

Graphing Solutions
Because inequalities have multiple solutions, we need to be able to represent them graphically. In order to do so, we use the number line, depicted below:

<--|--|--|--|--|--|--|--|--|--|--|-->                          -5 -4 -3 -2 -1  0  1  2  3  4  5

There are two ways of graphing solutions; however, each one is unique depending on the nature of the inequality. If, for example, the inequality contains the sign, we use an open circle ("O") and place it on (or above) the corresponding position on the number line, then draw another line either left or right of the solution (based on the sign) to indicate the infinite number of solutions in the set. For example, if we were to graph x < 4:

<-O <--|--|--|--|--|--|--|--|--|--|--|-->                          -5 -4 -3 -2 -1  0  1  2  3  4  5

The open circle indicates that 4 is not included in the solution set; however, all values less than 4 satisfy the solution.

If an inequality contains a $$\le$$ or $$\ge$$, then a closed circle (it will be depicted here with a *) is placed on or above the corresponding position on the number line. Hence, the solution $$x \ge -2$$ is graphed as follows.

*--->                        <--|--|--|--|--|--|--|--|--|--|--|-->                           -5 -4 -3 -2 -1  0  1  2  3  4  5

The asterisk (*) indicates that -2 is inclusive in the solution set, as are all values greater than -2.

Practice Problems

Graph the following inequalities on a number line:

1. x > 4

2. $$x \le 1$$

3. -1 > x

Solutions

1.                                                                                O-> <--|--|--|--|--|--|--|--|--|--|--|-->                          -5 -4 -3 -2 -1  0  1  2  3  4  5

2.                                               <*                         <--|--|--|--|--|--|--|--|--|--|--|-->                           -5 -4 -3 -2 -1  0  1  2  3  4  5

(Note that your actual graph should have a closed circle in place of the dot. If in doubt, simply draw a circle and color it black.)

3. Be careful here; you need to rearrange the inequality first before graphing. When rewritten, the inequality becomes x < -1:

<--O <--|--|--|--|--|--|--|--|--|--|--|-->                          -5 -4 -3 -2 -1  0  1  2  3  4  5

Lesson Review
An inequality is a statement justifying that two quantities are not equal to each other. There are four cases of inequalities, two of which allow for equality ($$a \le b$$ and $$a \ge b$$). The four properties of inequality, which are more or less parallel to the properties of equality, can be used to solve simple inequalities. The only exceptions are in multiplication and division, where the signs must be reversed if both sides are multiplied or divided by a negative number. Finally, the solution set of an inequality can be graphed on the number line with either an open circle ("O") or a closed circle ("*"), depending on the original sign used.

Lesson Quiz
1. What is an inequality? List the four possible cases of inequalities.

2. State the Trichotomy Property in your own words.

3. Solve the following and graph all solutions:

a. 4x + 3 > 7                               b. $$2x - 4 \le -x + 1$$ c. $$\frac {-12c}{3} \ge -24$$ d. -x + 4 > 3x

Quiz Answers
1. An inequality states that two quantities are not equal. The four cases of inequalities: a < b, a > b, $$a \le b$$, $$a \ge b$$.

2. Answers will vary. Just make sure you didn't copy and paste the actual definition.

3a. x > 1

O--> <--|--|--|--|--|--|--|--|--|--|--|-->                          -5 -4 -3 -2 -1  0  1  2  3  4  5 3b. $$x \le \frac {5}{3}$$

<--*                        <--|--|--|--|--|--|--|--|--|--|--|-->                           -5 -4 -3 -2 -1  0  1  2  3  4  5

3c. $$x \le 6$$

<--*                     <--|--|--|--|--|--|--|--|--|--|--|--|--|-->                         -6 -5 -4 -3 -2 -1  0  1  2  3  4  5  6

3d. x < 1

                          -5 -4 -3 -2 -1  0  1  2  3  4  5


text:
Talk:Intermediate Algebra/Writing Linear Equations

Don't forget to explain Point-Slope form!


text:
Talk:Muggles' Guide to Harry Potter/Books/Philosopher's Stone/Chapter 1

Synopsis
The Synopsis of this chapter seems to be the actual text, largely, of the chapter. I'm looking to write chapter summaries... is this the sort of level of detail we're looking for? Or do we want something with a lot less potential for copyright infringement? Chazz
 * We definitely want no copyright infringement or the suggestion of such a thing. Quotations of copyrighted material should be kept professional and under the terms of fair use. Please remove text dumps, especially if they're stolen from Wikipedia. Use the Half-Blood Prince summaries as a guide since those were the first written and have the general style we want here. You're doing a lot of good work here. Keep it up! -Matt 22:48, 19 July 2006 (UTC)

 * How do we make it advanced, I have SO MUCH INFO i want to add but it woiuld amke it advanced. —The preceding unsigned comment was added by Purplerains06 (talk • contribs) on 23 June 2007.

Analysis
It is said that "if Harry was actually orphaned on 31 October, as suggested, the story actually opens with Vernon Dursley leaving for work on the morning of 1 November". Well, the way i see it October 31st, 1981, was a Saturday, November 1st was a Sunday (on which i don't quite think Mr. Vernon had to go to work); and on top of that, my (admittedly translated) book says the day was a "dull, gray Tuesday". These kind of inconsistencies should also be mentioned (if they can not be explained), IMO. -- Jokes Free4Me 02:01, 12 February 2007 (UTC)
 * As mentioned, despite many fan sites jumping on 31 October as the date when the Potter family was attacked, there is no evidence in the book to back that up; and as this is not a fan site, and as the date is not important to the understanding of the book, it will be removed. Chazz 04:06, 18 February 2007 (UTC)
 * Having found that the October 31st date is in fact canon (mentioned here, thanks to Jokes Free4Me), I have re-instated it with a comment about the days of the week being wrong, and so what anyway – trivial errors like that don't detract from the book. Chazz 00:17, 26 February 2007 (UTC)

Hagrid did see GH
You mention the following: Hagrid does say, in Chapter 4, that the house was destroyed, though we don't know whether he saw it himself or whether he is repeating what Sirius told him about the destruction.

However, what Hagrid actually says (Chapter 4, page 56, SS) is that he took Harry from the ruined house himself.

It's reasonable to assume Hagrid isn't lying, so he apparently was at the location of the Potter's destroyed home. —The preceding unsigned comment was added by 209.36.59.1 (talk • contribs) on 27 June 2007.

 * Corrected some time back now. Chazz (talk) 21:22, 17 May 2009 (UTC)

Halloween?
The article says "Hallowe'en is largely a North American custom; the more widely-celebrated autumn festival in Britain is Guy Fawkes Night on 5 November." This is simply not true, and clearly was written by an American who has made an untrue assumption about Britain, where the novel is set. I have thus changed this section. 86.128.99.136 (talk) 00:42, 24 November 2008 (UTC)
 * Guilty as charged. Chazz (talk) 18:39, 16 May 2009 (UTC)

We can also conclude that although Rowling is a good writer she like alot of her colleagues makes mistakes in further novels.

Recent questions
An editor recently asked two questions that frankly did not belong on this page... but deserve an answer anyway.

 * /i would like to ask if dursleys is such an abnormal family then why dumble dore decides to leave harry there to spend his childhood?

That is covered in significant depth later in the story. The magical protection from Voldemort that was granted to Harry by his mother's sacrifice will protect him until he reaches the age of majority, which for wizards is 17, but only so long as there is a place he calls home which is occupied by someone bearing his mother's blood -- in this case Petunia. Dumbledore is well aware of the dysfunctional nature of the Dursley family, and is worried that Harry will grow up badly distorted by that household, and in the final chapters of book 5 he finally informs us of his relief at finding Harry is unwarped by the experience. But at this point, Dumbledore feels that the risk of damage to Harry's psyche from growing up in the Dursley household is less than the risk of Voldemort's return and the chance that Harry will be murdered without the protection that he can get only from Petunia.

 * /i would also like to ask that being a magic knower he knows everything about,why not his problems and sorrows?

Not quite sure I understand this question. We don't know how much Dumbledore practices Legilimency, but I believe, at any rate, that he does not choose to wander idly through the brains of others. And whose problems and sorrows are we talking about here, exactly?

Chazz (talk) 02:43, 24 March 2013 (UTC)


text:
Talk:Special Relativity

wrong PDF
when I downloaded and opened the PDF file, though its filename is "Special_Relativity.pdf", it turned out that the PDF is on "Wikijunior Solar System"....
 * It seems that there are no problems with Special_Relativity.pdf now. Though, I found that the link captioned Part1 is actually linked to a blank file whilst the link captioned Part2 is actually linked to Special_Relativity.pdf, which is Part1:Introductory text   02:32, 15 April 2007 (UTC)
 * Thanks for noticing this. I hope it is now corrected. RobinH 08:48, 17 May 2007 (UTC)

diagrams and dimensionality
The structure of special relativity book is like this. There is a beginners part which comes first and a more advanced part which comes second. The advanced part seems to aim to use the full mathematical theory behind SR including the 4D vector spaces etc. I think SR should be easier to understand for beginners so heres my suggestion. The beginners section should only have 2D diagrams, and should only have variables x and t, no y or z except at the end of the lorentz transformations (as an aside). So the concepts of SR should be easy to tell to beginners with just 2 dimensions and easier diagrams. During the beginning section it can be hinted at that a more complete description is given in terms of 4 dimensions. Then in the advanced section, it starts out by revisting the old formulas from the beginners section but adding in the missing variables real fast. This would be a prelude to developing the whole vector space formulation of SR.

The reasoning for this is beginners need simpler diagrams to understand basic concepts in SR. Also, it is pretty much useless to have all 4 dimensions unless we are going all the way to minkowski spaces. That is not to say we totally separate it into 2D and 4D. in the beginners we should mention the extension to more dimensions somewhat, and in the advanced you start off with the 2D familiar stuff and expand it to 4 immediately.

This does mean a redrawing of many diagrams, but the current diagrams are too confusing for the most part anyway. I just wanted to see what people thought of this before I go ahead and do it. Does anyone even talk at this project? it seems dead. maybe its just new? SR's been around for 100 years! EvanR 06:33, 18 July 2006 (UTC)

 * It is very important to introduce the concept of invariance and Minkowski space as soon as possible when teaching SR. If this is not done then students get lost in the problem of how photons of light could have a constant velocity and end up missing the whole beauty of the theory. At least 90% of students who are taught SR as a subsidiary option have got absolutely no idea of what it is about because they were introduced to the subject with the old-fashioned approach. In the old-fashioned approach Einstein's postulates alone are used.

 * The SR book was produced over the last year. RobinH 08:39, 18 July 2006 (UTC)

 * if the book is targetted at undergrads in physics thats one thing. they have heard all about the nature of light and have the math background to dive right into the full theory. for others i think there should be a more down to earth explanation supported by historical anecdotes and experimental results. these 'others' probably dont have the math background to comprehend the kind of geometry that SR lives in, but you are right- it should still be emphasized that this structure is there and what mathematical form it takes. I think it is possible to do what you said, introduce invariance of spacetime intervals and other important geometry concepts, but at the same time as present it in the 'old fashioned' way. As far as confusing readers goes, there is absolutely no reason for this as long as there is a clear and precise explanation of the approach taken and the possible other approaches. If were writing a book with a problem of widespread confusing in mind, certainly there is a way to address it in the text! Obviously it would be certainly necessary to say in both sections the entire story about presentation of SR, including which is better and why. Such a thing would be necessary in any comprehensive text on SR dont you agree EvanR 20:22, 18 July 2006 (UTC)

 * Your inclusion of a historical section looks good. I am worried about the "approaches" section however and have removed this. There is only one modern special relativity theory and this is the theory of the world as a four dimensional manifold of events although there have been variations within this: see Approaches to SR. The various approaches to SR can be included in the existing section on spacetime and the misnamed "approaches" that are found in elementary textbooks can be included in a section on the applications of the theory.

 * Einstein's original (1905) approach was really a set of empirical formulae. He proposed that if c were assumed constant there were interesting relations between velocity and measurement. The modern theory of relativity is different, it has a real ontology. It proposes that if differential geometry applies to events in the world then the world is like a four dimensional manifold of signature (---+) and the physics of the world is then due to this geometry.

 * It is really important to remember that most people who are taught the Lorentz transformations using no more than algebra and the postulate that the speed of light is constant never really accept relativity theory. This is because this approach has no ontology. It has no understanding within it. It is actually not an explanation at all. When taught in this way the constancy of the speed of light appears to be an arbitrary assumption and students often believe that we are waiting for quantum theory to explain it! The introduction of elementary four dimensionalism overcomes this problem because it becomes apparent why the speed of light is constant and clear that special relativity is a geometrical theory.

 * I would propose that the existing explanation in terms of invariance and pythagoras' theorem is given pride of place and algebraical examples using people walking in trains etc. are included in a chapter containing examples of how the theory may be applied. Einstein's original approach can be included in the historical section (it was entirely superceded by 1909 although it still haunts every elementary textbook). RobinH 09:34, 19 July 2006 (UTC)

Page names
I would like to move pages to the slash convention as suggested by Naming policy. Is this alright? --hagindaz 00:16, 13 May 2007 (UTC)

Still wrong PDF
Someone wrote the comment 'Wrong PDF' a while back. The comment notes that part II of the book is unavailable (the part II link points to part I, while the part I link points to a blank file).

This is still true, so... bump! :)

Contributors, List
I removed the list of contributors from the TOC. I don't feel that lists of this sort belong in the main content areas of pages. This kind of a list certainly does warrant a place, but I dont think the TOC of the book is the correct place. Maybe a coverpage or something? --Whiteknight (Page) (Talk) 02:07, 14 August 2007 (UTC)

 * Carandol
 * EvanR
 * Flonejek
 * RobinH

Print Version
I updated all the links in the print version when i moved all the pages to the new naming convention. However, I noticed that not all of the pages from the book are included in the PV (and one page was even included twice!) I've got a script that can redo the PV in one click, and hopefully be more aesthetic and more complete. I don't want to do anything radical to the PV without getting some approval first. Maybe I could put together a demonstration? --Whiteknight (Page) (Talk) 02:15, 14 August 2007 (UTC)

Twins Paradox
Einstein's relativity is a holy grail and the establishment will go to any lengths to protect it. The standard resolution by introducing an acceleration into the argument is a fallacy. My point is this.

All attempts to resolve the paradox involve making the voyager twin follow a curved path and thus experience an acceleration which the earthbound twin does not experience. However, the Time Dilation equation does not contain an acceleration term. Therefore time dilation is independent of any acceleration. As long as two inertial frames are in relative non-accelerated motion then the effect is/should be present.

Thus, if the voyager twin sets off in a straight line at near light speed (although the actual speed is irrelevant) then after a lapse of time (again the length of time does not matter) he should be younger than his earthbound twin - or rather his clock should have ticked slower so he hasn't aged as quickly. It is not necessary for the voyager to return to earth to compare the different ages and it is not necessary to follow a curved path. I seem to remember an example I got given as an undergraduate of a cosmic ray particle(?) that did not live long enough to reach earth unless you applied the time dilation equation to extend its life! This particle did not travel in a curved path and did not suffer any acceleration - you just applied the acceleration-independent equation and got the result (the result you wanted). I didn't believe it then and I don't believe it now. However, since the equation sorted out this problem then its interpretation must be correct - obviously - no question about it. Having established that the equation is correct you then apply to the twins and get the paradox.

There is no paradox. If the only way to resolve an apparent paradox is to introduce a fictitious element like Einstein's cosmological constant - in this case an acceleration which does not appear in the original equation - then either there is something wrong with the original equation or with the interpretation of it.

So then, how should one interpret the time dilation equation? As follows. The voyager twin's clock does not actually tick slower. It's just that the earthbound twin observes that it ticks slower - rather like the way an astronomer observes a redshift. A receding galaxy doesn't actually change the colour of the light it emits but to the oberver it just looks redder. Similarly, the voyager twin doesn't actually age slower - it just looks that way to the earthling. If you want to make a round trip then the argument goes like this. On the outward journey, the clock ticks slower (redshift) and on the return journey it ticks faster (blueshift); the overall result being no gain, no loss. The same applies to the voyager twin. To him the earthbound clock just appears to run slower but actually it keeps going at the same rate. Hence no paradox. To use the astronomical analogy, if the redshift galaxy appeared on the doorstep of the Milky Way you would not see a redshift.

The whole problem is blighted by the unwillingness of the establishment to acknowledge the problem with the interpretation of the equation(s). It will go to any lengths to protect the holy grail - just like the way the religious establishment refused to accept the heliocentric solar system until it had no choice. The fallacy is self-evident (blindingly obvious) and until someone who commands sufficient authority challenges the orthodoxy then this fallacious paradox will continue to exist.

 * Modern Special Relativity is the proposal that the universe is a four dimensional spacetime in which all observers have the same physical laws. Now, it is possible, although unlikely, that this proposal is wrong.  Suppose for the moment that the proposal is correct, what physical predictions would arise?  One prediction is that the elapsed time recorded on clocks that are moved away from Earth and then returned to Earth will be less than the elapsed time measured by clocks on Earth.  The reasoning behind this prediction is given in depth in the section on the twin paradox:

 * http://en.wikibooks.org/wiki/Special_Relativity/Simultaneity%2C_time_dilation_and_length_contraction#The_twin_paradox

 * Notice that clocks do not tick slower or run faster in the twin paradox, all we can say is that the elapsed time for the whole journey is recorded as less by the travelling twin (the one who turns round).

 * Your objection about acceleration does not apply because the twin paradox can also be analysed without including any turnaround by Bill. Suppose that when Bill passes Mars he meets another traveller coming towards Earth. If the two travellers synchronise clocks as they pass each other they will obtain the same elapsed times for the whole journey to Mars and back as Bill would have recorded himself had he turned around. This shows that the "paradox" is independent of any acceleration effects at the turnaround point.

 * The reason that textbooks contain this result as an "orthodoxy" is that it is consistent with the proposal of a 4D universe. The 4D universe is the basis of modern physics, being the underpinning of Quantum Electrodynamics and QCD and hence at the bottom of all physics, chemistry and biology.  In fact, because it does not involve proposals about the constancy of physical laws, the twin paradox is solely about 4D geometry rather than relativity per se and would apply in any manifold with the signature ---+ or +++-.  The difference in elapsed times that occurs in the twin paradox is a consistent and mathematically correct result of combining time with space in a metric of the form:

 * $$\Delta s^2 = \Delta x^2 + \Delta y^2 + \Delta z^2 - (c\Delta t)^2$$ or $$\Delta s^2 = (c\Delta t)^2 - \Delta x^2 - \Delta y^2 - \Delta z^2$$

 * So if the proposals that underpin SR, QED, QCD etc are correct then the twin paradox must apply but you are obviously at liberty to maintain that this idea of a 4D universe is incorrect and to propose alternative theories. RobinH (talk) 10:15, 12 March 2008 (UTC)

I think there's a mistake in the pdf
In page 51 in the pdf (the energy section), it says $$K = \int_{u=0}^{u=u} m (\gamma du + ud\gamma) u$$

Which gives:

$$K = \int_{u=0}^{u=u} m (udu + u^2 d\gamma)$$

while it should be:

$$K = \int_{u=0}^{u=u} m (\gamma du + ud\gamma) u$$

Which gives:

$$K = \int_{u=0}^{u=u} m (u\mathbf{\gamma} du + u^2 d\gamma)$$

 * Thanks for spotting this. The PDF is getting increasingly out of step with the text. It is time for a new version. RobinH (talk) 08:26, 18 April 2008 (UTC)

"Undergraduate" reading level?
I see that one section says it is intended for readers at the "Undergraduate" level. As far as I can see, this level does not exist. The categories are red links, and it's not listed at Reading Levels. —The preceding unsigned comment was added by Gawaxay (talk • contribs) 23:49, 20 March 2009 (UTC)

 * I haven't worked much on these reading levels, but this may precede the current reading level page. Please help us update this as you see fit. You may also be interested in prerequisite. --Swift (talk) 15:38, 21 March 2009 (UTC)

PDF Corrupt
When I download the pdf file and try to open it says "not a pdf or corrupt file". —The preceding unsigned comment was added by 124.109.20.84 (talk • contribs) 21:27, 17 August 2009 (UTC)

 * I have no problems viewing the it. Can you reproduce it on another machine? --Swift (talk) 07:40, 18 August 2009 (UTC)

 * OK. Got it thru another browser. ThanX!! —The preceding unsigned comment was added by 124.109.20.84 (talk • contribs) 11:47, 18 August 2009 (UTC)

 * You're welcome. Hope you like the book. --Swift (talk) 18:01, 18 August 2009 (UTC)

Introduction
Hi. First of all I thank to everyone who have contributed to this book. Second, I would like to bring to the attention of the editorial team something that I think should be changed. One of the introductory paragraphs reads: "Special Relativity begins by re-examining the basis of Newtonian Physics and demonstrating that the Newtonian treatment of relative motion is incorrect. As a result the whole of classical physics must be rebuilt to account for this error."

I think here incorrect is not a correct word, instead inaccurate would be better. We know that the Newtonian treatment of relative motion is correct but at low speed regime. The second sentence is also somehow odd. We know that the classic physics is out there such as the classical mechanics and the classical electrodynamics. The SP Relativity wasn't "rebuilt" of those theories but their generalization, or lets say, extension to high speed regimes. Gulmammad (talk) 23:03, 25 October 2009 (UTC)

 * I agree with Gulmammad. Albert Einstein did not exactly rethink physics. He "corrected" it. I think a better way of introducing this might be "Special Relativity begins with examining inconsistencies between Newtonian Mechanics and Maxwell's EM Theory." --Pongad (talk) 12:54, 22 April 2010 (UTC)

 * I can see your point. "Incorrect" is a bit "in your face" and implies everyday error when in fact Newtonian physics is extraordinarily accurate and the departures from Newtonian predictions are almost impossible to measure except in exceptional experiments such as particle accelerators etc..   What Minkowski introduced was a new conceptual framework. RobinH (talk) 14:11, 27 April 2010 (UTC)

 * I added the phrase "conceptually flawed" because in moving from the instantaneous space of Newton to the space-time of Minkowski there was a huge conceptual leap that goes beyond a simple adjustment of formulae. I hope the combination of our edits makes it clear that something important is going on without "over-egging the pudding" as occurred in the earlier version. RobinH (talk) 14:22, 27 April 2010 (UTC)

Einstein's derivation of the Lorentz Transformation
I think that on page 14 of the PDF version, where Lorentz Transformations are reported, some preliminary words clarifying which frame is at rest and which is moving would avoid possible misunderstanding.Demaag (discuss • contribs) 16:06, 7 April 2011 (UTC)

 * Good point. Einstein used a very general derivation of the LT equations. I added: "These equations apply to any two observers in relative motion but note that the sign within the brackets changes according to the direction of the velocity - see the appendix." RobinH (discuss • contribs) 11:14, 10 April 2011 (UTC)

The Advanced Text Needs Attention
If there is anyone out there with the enthusiasm to clean up and expand the "Advanced" part of this book then please help. I have been too busy for years to take it on. RobinH (discuss • contribs) 10:09, 17 August 2012 (UTC)

Those postulates
Postulates are supposed to be used to derive the theory. The first postulate is stated as the invariance of the laws of physics but nowhere is it used in the derivation. It is poorly defined anyway. Which laws are included? Actually relativity only deals with those that have tensor form and that is a small subgroup of all physical laws. Tensor equations are invariant with respect to the Lorentz trans but also with respect to any transformation conformal to it, that is any multiple of it, such as the Voigt transformation. So the invariance of physical laws does not require the Lorentz trans and cannot be used to derive it. The postulates actually used are the invariance of the speed of light plus the requirement of symmetry between the two observers. Symmetry is stated explicitly in the derivation given in the appendix (and there is no trace of the laws of physics) but vehemently denied in the analysis of the clock paradox. Which is it?Cosmo (discuss • contribs) 22:44, 10 April 2013 (UTC)
 * No, I don't think there is any defending to the death here. Here is a suggested amendment to clarify the asymmetry question:

 * The set of objects that an observer considers to be simultaneous cannot be affected by the motion of another single object. In Special Relativity this set of simultaneous events that an observer considers to be in its present moment is a property of each individual observer and shared within a given inertial frame of reference, it does not change with the motion of single objects in the surrounding space. If the observer changes velocity the set of simultaneous events changes but if one of the events changes velocity it does not change the observer's whole simultaneous set of events.  This is shown in the diagram below:

 * Relativistic Phase in the Twin Paradox.jpeg

 * It is this asymmetry of the effect of a change of velocity on the twin's sets of simultaneous events that is the heart of the twin "paradox". Notice that, whilst the sets of simultaneous events are asymmetric between observers, length contraction and time dilation are symmetrical.

 * I will give this amendment some thought. Any comments welcome. Best wishes, RobinH (discuss • contribs) 11:58, 6 April 2013 (UTC)
 * The amendment is incorrect. I have asked for the image to be deleted.RobinH (discuss • contribs) 14:01, 15 May 2013 (UTC)
 * I have rewritten the twin "paradox" section to take account of your comment and stress the symmetry. Many thanks for drawing this to my attention. I would refer you to the Benguigui reference for the most recent academic discussion of the twin "paradox". RobinH (discuss • contribs) 20:22, 12 August 2013 (UTC)

The reality of Special Relativity
It does not require too much intellectual effort to show/see that the Special theory of relativity (STR) leads to illusory, non-real results. So, I wonder why this issue is not raised anywhere. Resolving this problem of STR would open up amazing new possibilities for research.

Equation mistake on part 2.1.2 in the PDF file
There are mistakes in the equations in part 2.1.2 Frames of reference, events and transformations on page 16 - 18 in the PDF file. They are something like $$x'^{,y'^{,z'^{t'}}}$$ and $$x'^{=x-vt}$$.

title: Talk:Special Relativity


text:
User talk:70.18.11.5

Please don't waste your time. Your ten minutes of vandalism were reverted with the click of one button. I suggest that you instead try reading some of those books. You might learn something. I wish you the best in life, hagindaz 07:57, 18 July 2006 (UTC)

title: User talk:70.18.11.5