the-french-artist/wikipedia_20220301.simple_sentence_split huggingface dataset:
The rules of the older game were changed in the West so that some of the pieces (queen, bishop) had more scope, development of the pieces was faster, and the game more exciting.
The new game formed the basis of modern international chess.
Historians of chess consider this as the most important change since the game was invented.
The rules of chess are governed by the World Chess Federation, which is known by the initials FIDE, meaning Fédération Internationale des Échecs.
The rules are in the section Laws of Chess of the FIDE Handbook.
FIDE also give rules and guidelines for chess tournaments.
Chess is played on a square board divided into eight rows of squares called ranks and eight columns called files, with a dark square in each player's lower left corner.
This is altogether 64 squares.
The colors of the squares are laid out in a checker (chequer) pattern in light and dark squares.
To make speaking and writing about chess easy, each square has a name.
Each rank has a number from 1 to 8, and each file a letter from a to h. This means that every square on the board has its own label, such as g1 or f5.
The pieces are in white and black sets.
The players are called White and Black, and at the start of a game each player has 16 pieces.
The 16 pieces are one king, one queen, two rooks, two bishops, two knights and eight pawns.
Definitions: vertical lines are files; horizontal lines are ranks; lines at 45° are diagonals.
Each piece has its own way of moving around the board.
The X marks the squares where the piece can move.
The knight is the only piece that can jump over another piece.
No piece may move to a square occupied by a piece of the same color.
All pieces capture the same way they move, except pawns.
The king (K for short) can move one square in any direction.
The king may not move to any square where it is threatened by an opposing piece.
However, the king can move to a square that is occupied by an opponent's piece and capture the piece, taking it off the board.
The queen (Q) can move any distance in any direction on the ranks, files and diagonals.
The rooks (R) move any distance on the ranks or files.
The bishops (B) move diagonally on the board.
Since a bishop can only move diagonally, it will always be on the same color square.
The knights (Kt or N) move in an "L" shape.
Each move must be either two squares along a rank and one square along a file, or two squares along a file and one square along a rank.
It is the only piece that can jump over other pieces.
Like the other pieces, it captures an opposing piece by landing on its square.
The pawns can only move up the board.
On its first move a pawn may move either one or two squares forward.
A pawn captures one square diagonally, not as it moves: see white circles on its diagram.
In some situations, pawns can capture opponent's pawns in a special way called en passant, which means in passing in French (see below).
Most pieces capture as they move.
If a piece lands on an opponent's piece, the opposing piece is taken off the board.
There are three special cases:
The king cannot be taken (see check and checkmate).
No piece can be taken while castling (see below).
Pawns take one square diagonally.
If a move is made which attacks the opposing king, that king is said to be 'in check'.
The player whose king is checked must make a move to remove the check.
The options are: moving the king, capturing the threatening piece, or moving another piece between the threatening piece and the king.
If the player whose king is in danger cannot do any of these things, it is checkmate, and the player loses the game.
Once in every game, each king can make a special move, known as castling.
When the king castles, it moves two squares to the left or right.
When this happens, the rook is moved to stand on the opposite side of the King.
Castling is only allowed if all of these rules are kept:p120
Neither piece doing the castling may have been moved during the game.
There must be no pieces between the king and the rook.
The king may not be currently in check, nor may the king pass through any square attacked by the opponent.
As with any move, castling is not allowed if it would place the king in check.
En passant ('in passing' in French) is a special capture.
It is only available when a pawn moves forward two squares past an opposing pawn on an adjacent file.
The opposing pawn must be on the 5th rank from its own side.
Then the opponent's pawn can capture the double-mover as if it had only moved one square forward.
This option is open on the next move only.
For example, if the black pawn has just moved up two squares from g7 to g5, then the white pawn on f5 can take it by en passant on g6.
The en passant rule was developed when pawns were allowed to make their double move.
The rule made it more difficult for players to avoid pawn exchanges and blockade the position.
It kept the game more open.
When a pawn moves to its eighth rank, it must be changed for a piece: a queen, rook, bishop, or knight of the same color (player's choice).
Normally, the pawn is queened, but in some advantageous cases another piece is chosen, called 'under-promotion'.
Ways a game may end
Checkmates are rare in competitive chess.
The most common ends are decisions made by one or both players.
When a king is in check, and cannot get out of it.
A player may resign at any time, usually because their position is hopeless.
A losing player is able to resign by placing their king on its side on the chessboard.
If player's clock time is over (exceeding the time control).
Strictly speaking, this is not part of the rules of the game, but part of the rules of tournament and match chess where chess clocks are used.
Draws
Draw agreed.
A game may end in a draw at any time if one player offers a draw and the other accepts.
Insufficient Material Or Dead Position .
A position where no series of legal moves could lead to a mate (example: K+B vs K).
The game is drawn.p92
If a player cannot make a move, and the player's king is not in check, this is also a draw.
This kind of draw is called a stalemate, and is rare.
50-move rule.
A game will also end in a draw if no piece is captured and no pawn has moved after fifty moves.
This is called the fifty-move rule, and happens late in the game.
Threefold repetition.
If the exactly same position is repeated three times during a game with the same player to move each time, the player next to move may claim a draw.
The game is now drawn.
This is called a draw by threefold repetition.
Competition rules
The FIDE rules for competitive chess include all the above rules, plus several others.p92 et seq
Touch and move law
If players wish to adjust a piece on the board, they must first say "J'adoube" (I adjust) or the equivalent.
Apart from that, if a piece is touched it must be moved if possible.
This is the 'touch and move' law.p425 If no legal move is possible with the touched piece, the player must make a legal move with another piece.
Section 4p90 et seq When a player's hand leaves a piece after moving it then the move is over and may not be changed (if the move was legal).
There are a few famous cases where players appeared to break this rule without being punished.
The most famous example was by the then World Champion Garry Kasparov against Judit Polgar in a top-class tournament.
Chess clocks
Competitive games of chess must be played with special chess clocks which time a player only when it is his/her turn to move.
The essence is that a player has to make a certain number of moves in a certain total time.
After moving, the player presses a button on the clock.
This stops the player's clock, and start's the opponent's clock.
Usually the clocks are mechanical, but some are electronic.
Article 6p92 et seq Electronic clocks can be set to various programs, and they can count moves made.chapter 8
Notation for recording moves
The moves of a chess game are written down by using a special chess notation.
This is compulsory for any competitive game.
Article 8 & Appendix E Usually algebraic chess notation is used.
In algebraic notation, each square has one and only one name (whether you are looking from White's side of the board or Black's).
Here, moves are written in the format of: initial of piece moved – file where it moved – rank where it moved.
For example, Qg5 means "queen moves to the g-file and 5th rank" (that is, to the square g5).
If there are two pieces of the same type that can move to the same square, one more letter or number is added to show the file or rank from which the piece moved, e.g. Ngf3 means "knight from the g-file moves to the square f3".
The letter P showing a pawn is not used, so that e4 means "pawn moves to the square e4".
If the piece makes a capture, "x" is written before the square in which the capturing piece lands on.
Example: Bxf3 means "bishop captures on f3".
When a pawn makes a capture, the file from which the pawn left is used in place of a piece initial.
For example: exd5 means "pawn captures on d5."
If a pawn moves to its eighth rank, getting a promotion, the piece chosen is written after the move, for example e1Q or e1=Q. Castling is written by the special notations 0-0 for kingside castling and 0-0-0 for queenside.
A move which places the opponent's king in check normally has the notation "+" added.
Checkmate can be written as # or ++.
At the end of the game, 1-0 means "White won", 0-1 means "Black won" and ½-½ is a draw.
In print, figurines (like those in diagrams, but smaller) are used for the pieces rather than initials.
This has the advantage of being language-free, whereas the initials of pieces are different in every language.
Typefaces which include figurines can be purchased by chess authors.
Also, basic notes can be added by using a system of well-known punctuation marks and other symbols.
For example: !
means a good move, !!
means a very good move, ?
means a bad move, ??
a very bad move (sometimes called a blunder), !?
a creative move that may be good, and ?!
a doubtful move.
The purpose of these methods is to make publications readable in a wider range of countries.
For example, one kind of a simple "trap" known as the Scholar's mate, as in the diagram to the right, may be recorded:
Qh5?!
Bc4 Nf6?? (
3...Qe7 would prevent the mate, with 4...Nf6 next move)
Qxf7# 1-0
Playing arena
Players may not smoke in the playing area, but only in areas designated by the organiser.
Mobile phones may not be used or even switched on.
Players may not use any sources of advice, and may not analyse on any device.
These and other matters are covered by the FIDE Laws on the conduct of the players.
Article 12
Stages of a game
Chess is an easy game to learn the moves, but a difficult game to master.
Strategy is an important part of the game.
First of all comes the openings, about which a great deal is now known.
The best-known move, the King's Pawn opening, is the white player moving his king's pawn on e2 forward two spaces to e4.
Black can reply to that move in various ways.
The first moves of a chess game are called the opening.
A chess opening is a name given to a series of opening moves.
Recognized patterns of opening moves are openings and have been given names such as the Ruy Lopez or Sicilian defence.
They are listed in reference works such as the Encyclopaedia of Chess Openings.
There are dozens of different openings.
They range from gambits, where a pawn, say, is offered for fast development (e.g. the King's Gambit), to slower openings which lead to a maneuvering type of game (e.g. the Réti opening).
In some opening lines, the sequence thought best for both sides has been worked out to 20–30 moves, but most players avoid such lines.
Expert players study openings throughout their chess career, as opening theory keeps on developing.
Development: to place (develop) the pieces (mostly bishops and knights) on useful squares where they will have the most powerful impact on the game.
Control of the center: the center is the most important part of the board.
The player who controls the center can move his/her pieces around freely.
His/her opponent, on the other hand, will find his/her pieces cramped, and difficult to move about.
King safety: keeping the king safe from danger.
Castling (see section above) can often do this.
Pawn structure: pawns can be used to control the center.
Players try to avoid making pawn weaknesses such as isolated, doubled or backward pawns, and pawn islands – and to force such weaknesses in the opponent's position.
Players think, and chess databases prove, that White, by virtue of the first move, begins the game with a better chance.
Black normally tries to equalise, or to get some counterplay.
The middlegame is the part of the game after most pieces have been developed.
It is where most games are won and lost.
Many games will end in resignation even before an endgame takes place.
A middlegame position has a structure.
That structure is determined by the opening.
Material: changes in the balance of material are critical.
To lose a piece for nothing is enough to lose a game.
If the players are evenly matched, then a rough material balance of pieces is normal.
Material balance is often quite static: it does not change for many moves.
Development: the opening may have left one player with a lead in development.
That player has the initiative, and may attack before the opponent can get his pieces out.
It is a temporary asset: if a lead in development is not used effectively, it will disappear.
The centre: in the centre pieces have their greatest effect, and some (such as the knight) attack more squares in the centre than at the sides.
The player who controls the centre will almost always have the advantage.
Mobility: a position is mobile if the pieces can get where they need to.
Almost all middle game positions have some limitations to mobility.
Look for open files for the rooks, and open diagonals for the bishops.
Outposts are what knights need, places where they can not easily be dislodged.
King safety: where is the king?
Ideally, a king should be castled, and kept behind a screen of pawns.
Many other things may happen in practice.
If a king is weak, it may be put under direct attack.
Pawns: they provide the skeleton of a position.
They move slowly, and may become blocked for many moves.
Everything takes place round the pawns.
Different openings produce different pawn structures.
In this way openings influence the whole game (Philidor: "Pawns are the soul of chess").
Here is an example from the borderline between opening and middlegame.
In the diagram to the left, White will operate mainly on the Q-side, and Black on the K-side.
White, to play, may wish to cope with Black playing 10...Nf4.
He can do this by playing 10.g3, or by playing 10.Re1 so that if 10...Nf4 11.Bf1 will preserve the bishop (in this position an important defensive piece).
Or maybe White will plough ahead with 10.c5, the key move on the Q-side.
10.Re1 2198
10.g3  419
10.c5  416
The data base also shows that the overall results were significantly better for 10.Re1.
What the player does is note the features on the board, and formulate a plan which takes the features into account.
Then the player works out a sequence of moves.
Of course, in practice, the opponent is interfering with the plan at every step!
The endgame (or end game or ending) is the part of the game when there are few pieces left on the board.
Pawns: during the endgame, pawns become more special.
In the endgame, one thing players try to do is to promote a pawn by advancing it to the eighth rank.
Kings: may become strong pieces in the endgame.
The king may be brought towards the center of the board.
There it can support its own pawns, attack the opponent's pawns, and oppose the opponent's king.
Draws: in the endgame, a game may be drawn because there are too few pieces on the board to allow a player to win.
This is one of the main reasons for games to be drawn.
All endgame positions can be put into two camps.
On the one hand are positions which may be won by force.
On the other hand, are positions which are drawn, or which should be drawn.
The ones that are drawn for certain may be legally drawn (mate could not happen) or drawn by chess experience (no sane defence could lose).
All endgames in master chess revolve around the borderline between winning and drawing.
Generally, once a 'textbook' drawn position is reached the players will agree a draw; otherwise they play on.
Endgames can be studied according to the types of pieces that remain on board.
For example, king and pawn endgames have only kings and pawns on one or both sides and the task of the stronger side is to promote one of the pawns.
Other endings are studied according to the pieces on board other than kings, e.g. rook and pawn versus rook endgame.
Basic checkmates
Basic checkmates are positions in which one side has only a king and the other side has one or two pieces, enough to checkmate the opponent's king.
They are usually learned at the beginner stage.
Examples are mate with K+Q v K; K+R v K; K+2B v K; K+B&N v K (this one is quite difficult).
There are two types of chess programs.
One is to play against you; the other is to help you become a better player by learning more.
The two types can be made to work together, though they have different functions.
Chess engines
Chess engines are computer systems that can play chess games against human opponents.
Quite a number have been devised; they can play at master level, though their processes are quite different from a human being.p87
Every year brings new advances, which if listed here would soon be out of date.
Best advice is to go to English Wikipedia, who keep an up-to-date chart of the leading software: .
Chess databases
Chess databases do not actually play.
They give access to the recorded history of master chess.
There are two components.
First, there is the software, which lets one search and organise the database material.
Then there is the actual database, typically one to four million games.
In practice, databases are used for two purposes.
First, for a player to train his/her ability at specific openings.
Second, to look up specific opponents to see what they play, and prepare against them beforehand.
ChessBase is the biggest database, and widely used by masters.
Although it can be used online, most users download the software and data onto their computer.
If that computer happens to be a laptop, then they might take the laptop to tournaments, to help prepare for games.
Players may not use computers or any other aid during games, but much preparation goes on behind the scenes.
ChessBase has to be purchased, and it is not cheap.
New in Chess
This is a Dutch magazine for advanced players, which runs an on-line database called NicBase as part of its services.
NicBase is free, and has over a million games.
Chessgames
Chessgames.com runs an on-line database of games.
It is partly free, but requires registration.
Full access to all its facilities is by a fairly modest subscription.
It has over half a million games on its database.
On-line playing sites
There are websites which a player can join (for a fee) and play on line.
In this case, the subscriber will play against other subscribers, not a computer.
All standards of players are amongst the members, and various events are on offer at different rates of play.
The two leaders in this market are:
Internet Chess Club
Playchess
Burgess, Graham and John Nunn 1998.
The mammoth book of the world's greatest chess games.
Carroll & Graf.
Chandler, Murray 1998.
How to beat your dad at chess.
Gambit, London.
(Improvers)
Chandler, Murray 2004.
Chess for children.
(Beginners)
Euwe, Max and Kramer H. 1994.
The middlegame, books I and II.
and  This goes further than improvers need, but might be used by chess teachers as a source of classic positions.
King, Daniel 2000.
Chess: from first moves to checkmate.
Kingfisher, London.
Illustrated, 64 pages. (
Beginners, children).
Polgar, Laszlo 2006.
Chess: 5334 problems, combinations and games.
ed, Black Dog & Leventhal.
Pritchard, David Brine 2008.
The right way to play chess.
8th ed, Right Way.
(Beginners > impovers)
Silman, Jeremy 1997.
How to reassess your chess.
3rd ed expanded, Siles.
Ward, Chris 1994.
Opening play (think like a chess master).
Batsford, London.
Wolff, Patrick 2005.
The complete idiot’s guide to chess.
3rd ed, Alpha, New York. (
Beginners > improvers)
Znosko-Borovsky, Eugene 1980.
The middle game in chess.
(Improvers > intermediate)
Flear, Glenn 2000.
Improve your endgame play.
Everyman, London.
Seirawan, Yasser 2003.
Winning chess endings.
Silman, Jeremy 2007.
Silman's complete endgame course: from beginner to master.
Siles.
Snape, Ian 2003.
Chess endings made simple.
Gold is a soft, dense, yellow metal.
It is a chemical element.
Its chemical symbol is Au.
Its atomic number is 79.
As a precious metal, it has been used for many thousands of years by people all over the world, for jewelry, and as money.
Gold is important because it is rare, but also easier to use than other rare metals.
It is also used to repair and replace teeth and in electronic equipment such as computers.
The color of this metal is also called gold.
Mining methods for gold are similar to other metals.
Gold is so valued that the discovery of a new place to mine has sometimes caused a gold rush.
The deepest workplaces for miners in the world are in South African gold mines.
Often, gold is found as a native metal.
This means it is not part of an ore, and does not need smelting.
It may be in large, pure nuggets but more often must be separated from other minerals and soil.
Most of the gold on Earth is deep inside the Earth's core because it is dense.
Nearly all discovered gold was deposited on the surface by meteorites.
In chemistry, gold is chemical element 79, a transition metal in Group 11.
It has an atomic weight of 199.966 a.m.u.
Its symbol is Au, from the Latin word for gold, aurum.
It is a "noble metal" meaning it has low chemical reactivity.
Gold is very soft.
It is malleable, meaning a goldsmith can hammer it into thin metal sheets.
It is also ductile, which means it can be pulled into wire.
When it is used in money or in jewelry, it is often alloyed with silver or some other metal to make it harder.
Most metals are gray in color.
Gold is yellow because of the way its electrons behave.
The only other metal in common use that has a non-gray color is copper.
Caesium also has a gold-like color, but it is not commonly used as a metal because it reacts with water.
Gold is a fairly good electrical conductor, better than aluminium, but not as good as copper or silver.
Copper and brass electrical connectors, especially those used with computer and audio/video equipment, are often plated with gold for corrosion resistance.
Gold can mean that something or someone is very good or has done very well.
A gold medal is often the given to the first-place winner in a race or other sports.
Something that is in some way good may be given gold status.
Metallic gold is non-toxic, which is unusual for a heavy metal.
Soluble gold compounds, however, are toxic to the liver and kidneys.
Gold is non-flammable, even in a pure oxygen environment or when finely powdered.
It does not react with most household or laboratory chemicals.
Gold is commonly processed with cyanide, which is highly toxic.
Most of the cyanide is destroyed in the production process, so it is not present in the final product, but it can be a hazard to workers in a gold processing plant.
Since gold conducts electricity, gold jewelry should never be worn when working with electricity.
Atomic Properties
Gold Institute
Gold -Citizendium
A century is a way to describe a length of time.
One century is one hundred years.
The ancient Romans used the word centuria to describe a group of about one hundred soldiers, organized into a single unit.
The Roman numeral for 100 is "C".
The word for 100 in Latin is "centum".
A centenary is a celebration of something that happened 100 years ago.
A bicentenary celebrates 200 years, a tercentenary 300 years.
The kilogram is the base unit of mass in the International System of Units (SI).
It is in widely used in science, engineering, and commerce worldwide.
The kilogram is exactly the mass of one litre of water.
There are attempts to define the kilogram in other ways.
One example specifies a number of atoms of a certain substance (at a certain temperature).
One kilogram is a little more than 2.2 pounds.
One tonne is one thousand kilograms.
One litre of water weighs almost exactly one kilogram, at , at sea level.
This was the basis of the definition of the gram in 1795.
In 1879, the piece of metal was made.
It was officially chosen to be the kilogram in 1889.
It was made of 90% platinum and 10% iridium.
Those metals were chosen because they do not rust or corrode like most metals.
It is stored in a vault at the BIPM in Sèvres, France.
From 1795 to 1799, the unit of mass was not called "kilogram" but was called "grave".
The original kilogram is kept inside bell jars.
Over time, dust can collect on it.
Before it is measured, it is cleaned to get the original size.
The kilogram is a unit of mass.
In normal language, measuring mass defines how heavy is something.
This is not scientifically correct.
Mass is an inertial property.
It measures the tendency of an object to stay at a given speed when no force acts on it.
Sir Isaac Newton's laws of motion contain an important formula: F = ma.
F is force.
m is mass.
a is acceleration.
An object with a mass (m) of one kilogram will accelerate (a) at one meter per second per second when acted upon by a force (F) of one newton.
This about one-tenth the acceleration due to earth’s gravity.
The weight of matter depends on the strength of gravity.
The mass of matter does not.
The mass of an object is the same everywhere.
Matter has invariant mass assuming it is not traveling at a relativistic speed with respect to an observer.
According to Einstein’s theory of special relativity, the relativistic mass (apparent mass with respect to an observer) of an object or particle with rest mass m0 increases with its speed as M=γm0 (where γ is the Lorentz factor).
This effect is vanishingly small at everyday speeds, which are by orders of magnitude less than the speed of light, but becomes noticeable at very high speeds.
For example, traveling at just 10% the speed of light with respect to an observer—exceedingly fast compared to everyday speeds (about )—increases an object’s relativistic mass just over 0.5%.
As regards the kilogram, relativity’s effect upon the constancy of matter’s mass is simply an interesting scientific phenomenon that has zero effect on the definition of the kilogram and its practical realizations.</ref> Objects are "weightless" for astronauts in microgravity.
However, the objects still have their mass and inertia.
Astronaut must use ten times as much force to accelerate a ten-kilogram object at the same rate as a one-kilogram object.
A common swing, as shown in the picture, can show the relationship of force, mass and acceleration.
Someone could push an adult on the swing.
The adult would accelerate slowly.
They would only swing a short distance forward before the swing would change direction.
If a child is sitting on the swing, then the child would swing forward faster and further.
General Conference on Weights and Measures (CGPM)
Grave (original name of the kilogram, its history)
International Bureau of Weights and Measures (BIPM)
International Committee for Weights and Measures (CIPM)
International System of Units (SI)
National Institute of Standards and Technology (NIST)
SI base units
Standard gravity
The second (symbol: s), is a unit of time.
There are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a day.
This tradition dates back to the Babylonian.
In science, a second is the time it takes for a caesium atom to vibrate 9,192,631,770 (around 9 billion) times.
Scientists measure the second this way because the length of a day changes all the time.
For example, when the dinosaurs lived, a day was about an hour shorter.
Vibrations of atoms on the other hand always take the same time.
This atomic second is also called the SI second.
Metric prefixes are frequently combined with the word second to denote subdivisions of the second, e.g., the millisecond (one thousandth of a second) and nanosecond (one billionth of a second).
Though SI prefixes may also be used to form multiples of the second (such as “kilosecond”, or one thousand seconds), such units are rarely used in practice.
More commonly encountered, non-SI units of time such as the minute, hour, and day increase by multiples of 60 and 24 (rather than by powers of ten as in the SI system).
International second
Under the International System of Units, the second is currently defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.
This definition refers to a caesium atom at rest at a temperature of  (absolute zero).
The ground state is defined at zero magnetic field.
The second thus defined is equivalent to the ephemeris second.
Equivalence to other units of time
1/60 minute (1 minute is equal to 60 seconds)
1/3,600 hour (1 hour is equal to 3,600 seconds)
1/86,400 day (1 day, in the sense of non-SI units accepted for use with the International System of Units, is equal to 86,400 seconds)
Historical origin
Originally, the second was known as a "second minute", meaning the second minute (i.e. small) division of an hour.
The first division was known as a "prime minute" and is equivalent to the minute we know today.
Third and fourth minutes were sometimes used in calculations.
The factor of 60 comes from the Babylonians who used a sexagesimal (base-60) numeral system.
However, the Babylonians did not subdivide their time units sexagesimally (except for the day).
The hour had been defined by the ancient Egyptians as either 1/12 of daytime or 1/12 of nighttime, hence both varied with the seasons.
Greek astronomers, for example Hipparchus and Ptolemy, defined the hour as 1/24 of a mean solar day.
Sexagesimally subdividing this mean solar hour made the second 1/86,400 of a mean solar day.
SI multiples
SI prefixes are commonly used for times shorter than one second, but rarely for multiples of a second.
Instead, certain non-SI units are permitted for use in SI: minutes, hours, days, and in astronomy Julian days.
Greek time periods, for example the mean synodic month, were usually specified quite precisely because they were calculated from carefully selected eclipses separated by hundreds of years—individual mean synodic months and similar time periods cannot be measured.
Nevertheless, with the development of pendulum clocks keeping mean time (as opposed to the apparent time displayed by sundials), the second became measurable.
The seconds pendulum was proposed as a unit of length as early as 1660 by the Royal Society of London.
The duration of a beat or half period (one swing, not back and forth) of a pendulum one metre in length on the Earth's surface is approximately one second.
In 1956 the second was defined in terms of the period of revolution of the Earth around the Sun for a particular epoch, because by then it had become recognized that the Earth's rotation on its own axis was not sufficiently uniform as a standard of time.
The Earth's motion was described in Newcomb's Tables of the Sun, which provides a formula for the motion of the Sun at the epoch 1900 based on astronomical observations made between 1750 and 1892.
The second thus defined is
the fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time.
This definition was ratified by the Eleventh General Conference on Weights and Measures in 1960.
The tropical year in the definition was not measured, but calculated from a formula describing a tropical year which decreased linearly over time, hence the curious reference to a specific instantaneous tropical year.
Because this second was the independent variable of time used in ephemerides of the Sun and Moon during most of the twentieth century (Newcomb's Tables of the Sun were used from 1900 through 1983, and Brown's Tables of the Moon were used from 1920 through 1983), it was called the ephemeris second.
Following several years of work, Louis Essen from the National Physical Laboratory (Teddington, England) and William Markowitz from the United States Naval Observatory (USNO) determined the relationship between the hyperfine transition frequency of the caesium atom and the ephemeris second.
Using a common-view measurement method based on the received signals from radio station WWV, they determined the orbital motion of the Moon about the Earth, from which the apparent motion of the Sun could be inferred, in terms of time as measured by an atomic clock.
As a result, in 1967 the Thirteenth General Conference on Weights and Measures defined the second of atomic time in the International System of Units (SI) as
the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.
This definition refers to a caesium atom at rest at a temperature of 0 K.
The revised definition would seem to imply that the ideal atomic clock would contain a single caesium atom at rest emitting a single frequency.
In practice, however, the definition means that high-precision realizations of the second should compensate for the effects of the ambient temperature (black-body radiation) within which atomic clocks operate and extrapolate accordingly to the value of the second as defined above.
The second in role-playing games
Sometimes in role-playing games a second is used to refer to a small period of time or a single turn of combat.
It is used as a standard moment of time, and does not necessarily refer to a real second, and could be shorter or longer depending on the scenario.
Until modern times, degrees and hours were divided successively by 60 in pars minuta prima, pars minuta secunda, pars minuta tertia and so on.
This evolved to the modern minute and second, but for smaller divisions we follow now the decimal division.
In some languages, dictionaries still keep the word for third for 1/60 of a second, for example Polish (tercja) and Arabic (ثالثة).
Official BIPM definition of the second
Seconds and leap seconds by the USNO
The leap second: its history and possible future
It is the combination of red and yellow.
Orange is the color of an orange fruit, which is where the name of the color comes from.
Before the orange fruit was introduced to England in the 1500s, this color was called yellow-red.
The first recorded use of orange as a color name in English was in 1512, in the court of King Henry VIII.
Meaning of orange
To the eye, orange is a very "hot" color, so it gives the sensation of fire.
But orange is not as heated a colour as red.
As a citrus color, orange is associated with healthy food and is appetising.
Orange is the color of Autumn and harvest.
Though rare in heraldry, orange is symbolic of strength and endurance.
Orange is very easy to see, so people can use it to catch attention and highlight the most important elements of a design.
Orange is very effective for promoting food products and toys.
On road signs, the color orange means there is construction work ahead.
It is used for these signs because it can easily be seen even at night.
Dark orange can mean lying or not trusting somebody.
Red-orange means desire, sexual passion, pleasure, power,  , and thirst for action.
Tones of orange color comparison chart
Seashell (web color) (Hex: #FFF5EE) (RGB: 255, 245, 238)
Old Lace (web color) (Hex: #FDF5E6) (RGB: 253, 245, 230)
Antique White (web color) (Hex: #FAEBD7) (RGB: 250, 235, 215)
Papaya Whip (web color) (Hex: #FFEFD5) (RGB: 255, 239, 213)
Blanched Almond (web color) (Hex: #FFEBCD) (RGB: 255, 235, 205)
Champagne (Hex: #F7E7CE) (RGB: 247, 231, 206)
Moccasin (web color) (Hex: #FFE4B5) (RGB: 255, 228, 182)
Bisque (web color) (Hex: #FFE4C4) (RGB: 255, 228, 196)
Navajo White (web color) (Hex: #FFDEAD) (RGB: 255, 222, 173)
Light Orange (Skin) (Crayola) (Hex: #FED8B1) (RGB: 254, 216, 177)
Melon (Crayola) (Hex: #FEBAAD) (RGB: 254, 186, 173)
Macaroni and Cheese (Crayola) (Hex: #FFDB88) (RGB: 255, 189, 136)
Sandy Brown (web color) (Hex: #F4A460) (RGB: 244, 164, 96)
Light Salmon (web color) (Hex: #FFA07A) (RGB: 255, 160, 122)
Coral (web color) (Hex: #FF7F50) (RGB: 255, 127, 80)
Bittersweet (Crayola) (Hex: #FE6F5E) (RGB: 254, 111, 94)
Terra Cotta (Hex: #E2725B) (RGB: 226, 114, 91)
Tea Rose (orange) (Hex: #F88379) (RGB: 248, 131, 121)
Vivid Tangerine (Crayola) (Tangerine Sherbet) (Hex: #FF9980) (RGB: 255, 153, 102)
Orange Peel (Hex: #FFA000) (RGB: 255, 160, 0)
Orange (web color) (Hex: #FFA500) (RGB: 255, 165, 0)
Deep Saffron (Hex: #FF9933) (RGB: 255, 153, 51)
Gamboge (Hex: #EF9B0F) (RGB: 228, 155, 18)
Carrot Orange (Hex: #ED9121) (RGB: 237, 145, 33)
Tangerine (Hex: #F28500) (RGB: 243, 132, 0)
Bright Orange (web color "Dark Orange")  (Hex: #FF8C00) (RGB: 255, 140, 0)
Corporate Orange (Hex: #FF8100) (RGB: 255, 129, 0)
Orange (Color Wheel Orange) (Hex: #FF7F00) (RGB: 255, 127, 0)
Automotive Amber (SAE/ECE Amber) (Hex: #FF7E00) (RGB: 255, 126, 0)
Medium Orange (Hex: #FF7802) (RGB: 255, 120, 2)
Pumpkin (Hex: #FF7518) (RGB: 152, 118, 54)
Carrot (Hex: #FF7700) (RGB: 255, 119, 0)
Rich Orange (Crayola Orange) (Hex: #FF681F) (RGB: 255, 104, 31)
Safety Orange (Blaze Orange) (Hex: #FF6600) (RGB: 255, 102, 0)
Persimmon (Hex: #EC5800) (RGB: 236, 88, 0)
Cadmium Orange (Xona.com Color List) (Hex: #FF6103) (RGB: 255, 97, 3)
Tangelo (Hex: #F94D00) (RGB: 249, 77, 0)
International Orange (Hex: #FF4F00) (RGB: 255, 79, 0)
Vermisse (Hex: #F34234) (RGB: 227, 66, 52)
Red-Orange (Crayola) (Hex: #FF3F34) (RGB: 255, 63, 52)
Electric Vermilion (Hex: #FF3F00) (RGB: 255, 63, 0)
Orange-Red (web color) (Hex: #FF4500) (RGB: 255, 69, 0)
Portland Orange (Hex: #FF5A36) (RGB: 255, 90, 54)
Ultra Orange (Crayola) (Outrageous Orange) (Hex: #FF6037) (RGB: 255, 96, 55)
Tomato (web color) (Hex: #FF6347) (RGB: 255, 99, 71)
Deep Carrot Orange (Hex: #E9692C) (RGB: 255, 150, 0)
Neon Carrot (Crayola) (Hex: #FFA343) (RGB: 255, 163, 67)
Ochre (Hex: #CC7722) (RGB: 204, 119, 34)
Bronze (Hex: #CD7F32) (RGB: 205, 127, 50)
Copper (Hex: #B87333) (RGB: 184, 115, 51)
Peru (web color) (Hex: #CD5700) (RGB: 205, 133, 63)
Antique Brass (Crayola) (Hex: #C88A65) (RGB: 200, 138, 101)
Café au Lait (Coffee and Milk) (Latte) (Hex: #A67B5B) (RGB: 166, 123, 91)
Pale Brown (Hex: #987654) (RGB: 152, 118, 54)
Cocoa Bean (web color Chocolate) (Hex: #D2691E) (RGB: 210, 105, 30)
Tenne (Tawny) (Hex: #CD5700) (RGB: 205, 87, 0)
Burnt Orange (Hex: #CC5500) (RGB: 204, 85, 0)
Dark Coral (Hex: #CD5B45) (RGB: 205, 91, 69)
Medium Brown (Crayola Brown) (Hex: #AF593E) (RGB: 175, 89, 67)
Sienna (web color) (Hex: #A05220) (RGB: 160, 82, 45)
Brown (Hex: #964B00) (RGB: 150, 75, 0)
Saddle Brown (web color) (Hex: #8B4513) (RGB: 139, 69, 13)
Russet (Hex: #804618) (RGB: 128, 70, 27)
Cognac brown (Xona.com Color List) (Hex: #9F381D) (RGB: 159, 56, 29)
Pullman Brown (UPS Brown) (Hex: #644117) (RGB: 100, 65, 23)
Coffee (Coffee Bean [Unroasted]) (Hex: #6F4E37) (RGB: 111, 78, 55)
Dark Brown (Hex: #654321) (RGB: 101, 67, 33)
Roast Coffee (Coffee Bean [Roasted]) (Deep Coffee) (Hex: #704241) (RGB: 112, 66, 65)
Medium Taupe (Hex: #674C47) (RGB 76, 21,71)
Cafe Noir (Black Coffee) (Hex: #4B3621) (RGB: 75, 54, 33)
Taupe (Hex: #483C32) (RGB: 72, 60, 50)
<li style = "background-color: #9ab973;"> Olivine (Hex: #9AB973) (RGB: 154, 185, 115)
It is the home of the Basque people.
It is at the western end of the Pyrenees on the Bay of Biscay.
Its boundaries are complicated, as it consists of seven districts: four within Spain and three within France.
No one knows when the Basques came to Europe.
Many say that they have been in Europe since the Neolithic period at the end of the Stone Age, but others say that they were here even earlier.
The first written information about the Basque Country is from the Roman times, when the Basque people already spoke their own language.
During the fall of the Western Roman Empire, the Basque Country was isolated from the invading Goths.
During the Muslim invasion of Southern Europe, the Basque Country split in two: the Castilian and the Navarrese lands.
A war with France later split the Navarrese zone in two.
After the Reconquista, the Castilian Basque lands and Navarre became part of the new country: Spain.
Since then, Basque people from the Spanish area of the Basque Country have had their own government and have fought to gain the northern part of the Basque Country from France.
Today, three of the Basque districts in Spain (Araba, Bizkaia, and Gipuzkoa) form the Autonomous Community of the Basque Country.
The political unit is one of 17 autonomous communities in Spain.
The entire region has a surface area of 20,664 km2 (7978 sq mi).
The Autonomous Community of the Basque Country has 7,234 km2 (2793 sq mi), and its population is about 2,000,000 - about 5% of the total population of Spain.
Basque and Spanish are spoken, and its largest city is Bilbao although the capital is Vitoria-Gasteiz.
Maurice Ravel (through his mother)
Che Guevara (through his mother)
St. Ignatius Loyola
Pío Baroja
Largest cities
Donostia
Gazteiz
Iruña
Baiona
Maule
Donibane Garazi
The official website of the Basque Autonomous Community
Geography of France
Geography of Spain
M-theory is a new idea in small-particle physics that is part of superstring theory that was initially proposed by Edward Witten.
The idea, or theory, often causes arguments among scientists, because there is no way to test it to see if it is true.
If ever proven true, M-theory and string theory would mean big progress for science.
To understand M-theory one must first have some knowledge of string theory.
For hundreds of years, scientists have thought that the simplest objects in the universe are points, like dots.
String theory says that this is wrong and that the simplest objects in the universe are shaped like pieces of string.
These strings are so small that even when looked at very closely they look like points.
Each basic particle is created by the strings vibrating in different patterns.
The reason scientists had not thought of this idea for so long is that strings are much harder to work with than points.
They seem to break such rules as causality and special relativity, which says that information cannot travel faster than the speed of light.
String theory has been developed because of a very important problem that has existed for almost 100 years.
Albert Einstein's theory that describes the universe on very large scales (it is called general relativity), and it disagrees with two theories that describe things on very small scales (they are called quantum mechanics and the standard model).
There are also problems with the Standard Model: it includes about 20 numbers that seem to have no explanation; it has too many basic particles - some scientists think it needs to have fewer; and it does not include gravity, which is needed to explain weight.
Many of these problems can be solved by thinking of basic particles as strings.
Now there is only one number with no explanation, which gives the size of the strings.
String theory includes particles that cause gravity, called gravitons; finding this out delighted the scientists who work on string theory.
So, string theory successfully brings General Relativity and Quantum Mechanics together.
But there are some problems with string theory.
Normally, we think of the universe as having 4 dimensions, or basic directions.
3 of these basic directions can be thought of as "up/down", "forward/backward" and "left/right".
The other direction is time.
String theory needs 10 basic directions.
These six other directions can be explained if they are "curled up", so they are much too small to see.
For example, by following the path of a spiral, it is possible to go a great distance along it without moving very far.
The 6 other directions can be thought of as tiny spirals - strings can move along them a great distance but not seem to move.
This can be looked at as a mathematical trick—a trick that has little to do with the real world that can  be seen and touched.
Such tricks are allowed if they give a theory that can better tell us how things work.
Another problem with string theory is that there are 5 different versions of it.
Each version allows different kinds of strings and says they work in different ways.
String theory is supposed to be a theory of everything so there should be only one version, not 5.
M-theory solves this problem.
In 1995 Edward Witten started what has been called the Second Superstring Revolution by introducing M-theory to the world.
This theory combines the 5 different string theories (along with a previously abandoned attempt to unify General Relativity and Quantum Mechanics called 11D-Supergravity) into one theory.
What Witten actually did was to predict that the fact that all these different theories were connected was a result of there being some underlying theory of  which they were all approximations.
This theory is somewhat vague in nature and has not yet been pinned down.
Additionally, it was found that the equations that required string theory to exist in 10 dimensions were actually approximations as well.
The proposed M-theory would need one extra dimension and instead be a theory that takes place in 11 dimensions.
Witten has himself compared this idea in simple terms to a general who takes up a position on a hilltop, the extra space-coordinate, to get a better view of the battlefield's two other dimensions.
The combination is accomplished by knitting together a web of relationships between each of the string theories called dualities (specifically, S-duality, T-duality, and U-duality).
Each of these dualities provides a way of converting one of the string theories into another.
T-duality is probably the most easily explained of the dualities.
It has to do with the size, written as R, of the curled up dimensions of the string theories.
It was discovered that by taking a Type IIA string theory that has a size R and changing the radius to 1/R the result will end up being what is equivalent to a Type IIB theory of size R. This duality, along with the others, creates connections between all 5 (or 6, if supergravity is counted) theories.
The fact that these dualities existed had been known before Witten came up with the idea of M-theory.
Additional amusement has come for many in guessing what the M might stand for (possibilities include Matrix, Magic, Muffin, Mystery, Mother and Membrane).
Regardless of what the M might possibly mean, M-theory has become one of the most interesting and active areas of research in theoretical physics today.
For a more technical explanation, see w:M-theory (simplified explanation).
Books and Links
Brian Greene has written a book that explains string theory and M-theory for the layman called The Elegant Universe
The Official String Theory Website has excellent references on string theory for the layman and expert
Jaguar Cars was a car manufacturer and the Jaguar marque is now owned by Jaguar Land Rover.
The original company was established in 1922 by William Lyons and was renamed Jaguar in 1935.
Jaguar is known for its luxury saloons and sportscars.
Jaguar was a private company until it merged with the British Motor Corporation in 1966.
The new company was called British Motor Holdings.
In 1968 that company joined with Leyland Motors to became British Leyland.
In 1975 British Leyland was nationalised.
In 1984 Jaguar was made private again by Margaret Thatcher.
Ford bought Jaguar in 1989.
In 1999 it was made part of Ford's "Premier Automotive Group" along with Aston Martin, Land Rover, Volvo and Lincoln.
In 2008, Ford sold Jaguar and Land Rover to Tata Motors.
Jaguar is now a brand of the merged company called Jaguar Land Rover (JLR).
The company was originally in Blackpool, but moved to Coventry.
Today Jaguar automobiles are made at the JLR factory in Castle Bromwich in Birmingham.
In late 2018 was open new plant in Slovakia.
Jaguar owns the Daimler brand (not Daimler-Benz).
Jaguar bought the British Daimler Company in 1960.
Daimler became a brand for some of Jaguar's saloon automobiles, but is not used now.
Sportscar racing
Jaguar International
Jaguar USA
Jaguar MENA
British automobile companies
A scientist gathers empirical and measurable evidence, and uses sound reasoning.
New knowledge often needs adjusting, or fitting into, previous knowledge.
What distinguishes a scientific method of inquiry is a question known as 'the criterion'.