Golf is a sport played on an a course consisting of 18 areas, called "holes." For each hole, a hard, specialized ball is hit from a starting area (the tee) towards a target section of turf (called the green) located varying distances away. Located on the green is a cup into which is set a flagstick. The flag allows the golfer to locate the cup from his/her position on the tee and, because the flag can move in the breeze, to assess the wind speed and direction. The object of the sport is to hit the ball into the cup. Depending on the distance from the tee to the cup, a set number of shots (or "strokes") is allotted to get the ball from the tee into the cup. This number of shots is referred to as "par." On shorter holes, typically ranging from 90 to 200 yd (82-110 m) in length, the par is three. Holes between 200 yd (182 m) and approximately 470 yd (430 m) are usually par four, with longer holes rated as par five. The tally of the scores for the 18 holes represents the final score (the standard is 71 or 72). If a golfer has shot a lower score, he or she is said to have shot under par. A higher score is over par.

The game of golf today is very different in character and technology from a pastime that began on the eastern coast of Scotland in the fifteenth century. Then, equipped with a stick or club, shepherds would hit a small rock at targets set on sand dunes and pathways. At that time, there were no cups to aim at and no set number of holes. Within a few decades, ground was being specifically set aside and maintained for the pastime. By the latter decades of the sixteenth century, golf had become very popular throughout the British Isles. The game spread to France when Mary Queen of Scots went to study in that country. Indeed, the origin of the word "caddie" (a person who assists the golfer in judging what shots to play and carries the golfer's equipment bag) derives from the French term cadet for members of the French military, who assisted her during her golf outings.

The first golf club was formed in 1744. The Gentlemen Golfer's of Leith even sponsored an annual tournament and awarded a trophy to the winner. The course consisted of five holes.

Golf is famous for the numerous rules that govern play. Rules include the use of the same ball on a given hole unless the ball is lost, assessing an extra shot as a penalty if a ball has to be moved from water, having to play the ball from whatever position in which it has come to rest ("play the ball where it lies"), and playing in a determined order with the person farthest from the cup playing first. Many rules have been enacted to deal with the tremendous technological changes of the game. As scientific advances have altered the game (the equipment, the playing area), the rules have attempted to maintain the importance of human skill to the outcome.

By 1552, the St. Andrews Society of Golfers had been formed. The golf game played today stems from this club. For example, the club established the par-based scoring method (it is also referred to as stroke play) and built the first 18-hole course. By the end of the nineteenth century, the club (now renamed The Royal and Ancient Golf Club of St. Andrews) had assumed control for the rules of golf. Later, in 1894, the United States Golf Association was formed and assumed some responsibility for the rules.

By the mid-1880s, golf equipment had become more specialized; proper clubs had been devised. Wood was the material of choice for the shafts, and the club head of woods (clubs whose hitting surface was nearly perpendicular to the ground, and which were intended to propel the ball at a low angle for a long distance). Other clubs were forged of iron (called, logically, irons) and had a hitting surface that was oriented at various angles to the ground to produce shots of varying heights and distances. The club grip was typically of strips of wound leather. The golf ball was a sphere of wood or tightly packed feathers wrapped in a sphere made of stitched-together pieces of horsehide or cowhide.

The modern-day golf ball is similar to the original wooden or hide-bound golf ball only in its shape. A series of technological changes have completely changed the performance of the ball and, consequently, the game of golf.

The first innovation in golf ball design occurred in 1848, when balls formed from heated sap of the sapodilla tree were introduced. Once the sap cooled, these gutta-percha-resin golf balls ("gutties") were harder than their feather-cored predecessors ("featheries"). This allowed more of the energy built up in the club face during the golf swing to be transferred to the ball. The result was a longer flight of the ball. Also, because the balls became much less expensive to produce, golf became a sport that many could afford to play.

It was soon noted that a smooth-surfaced ball did not fly as far as a ball with surface pocks. Gutta-percha balls made with minute bulges over its surface became very popular.

In 1898, a golf ball was introduced in which a core consisting of wound rubber thread was covered with gutta-percha. The core increased the amount of energy transfer from club to ball, increasing shot length yet again. As well, recognizing the improved aerodynamics produced by surface pocks, various cover patterns were tried. By 1908, the dimple pattern had been introduced.

This pattern was refined still further during the 1930s. By blowing smoke over differently pattern balls, William Taylor experimented with different dimple patterns to find those that produced the most uniform movement of air over the ball's surface. The result was a ball that would not be directed off-course during flight by irregular patterns of air flow.

England's Lee Westwood at the 2005 PGA championship. The PGA celebrated its 90th anniversary on April 10, 2006.

This consistent pattern of flight has provided another opportunity for golfers to affect the ball's flight. By imparting a clockwise or counterclockwise spin on the ball during impact with the club, a ball can be made to deliberately bend to the left or right during flight.

As golf ball design evolved, the rules of the game were revised to prescribe standards of ball weight, size, and dimple pattern. Then, as now, the intent is to standardize the technology so that human skill remains a predominant factor in scoring.

With the invention of the gutta-percha golf ball, control of the flight and distance of the ball became possible. This meant that the golf clubs then in use were outmoded. Golf club design was refined to provide this control. Shafts made of hickory and then of steel and aluminum provided more strength, making a quicker swing possible. As well, these shafts resisted the tendency to rotate during the back swing and down swing (rotational force is also called torque). More recently, shafts constructed of graphite have maintained the shaft strength while allowing clubs to become lighter and easier to swing more smoothly.

Steel, aluminum, and graphite shafts also allow the bulk of a club's weight and center of gravity to be concentrated in the club face. This permits most of the energy from a golf swing to be focused on the area of the club face that contacts the ball (called the "sweet spot").

The golfer's arsenal of clubs expanded during the mid-1880s to include club faces made of iron. Construction of differently angled club faces allowed the same swing to produce a shot that went lower and farther, or higher and shorter. This control allowed golfers to more precisely aim for the cup.

Originally, the face of an iron was smooth. Introduction of horizontal grooves in the club face and the roughening of its surface made it possible for the ball to travel up the club face during impact. As a result, the ball could spin off of the club face, rather than just flying off. Because the ball spins backward during flight, it will tend to stop more quickly on impact with the ground. This allows a golfer to shoot just beyond the cup and either to spin the ball back closer to the cup or to stop the ball almost immediately on impact. This has resulted in even more control of the ball near the cup.

Today, a golfer will carry several woods and about seven irons in their golf bag. The woods propel the ball the farthest; smaller woods offer more control if a target area is small and can be used more easily when attempting a long shot from the fairway. The designation wood is a misnomer today, since most of these clubs are made of metal. This innovation of the 1980s increased the energy transfer from club to ball. During the 1990s, introduction of composites of new materials allowed woods to be made much larger than before, while reducing the overall weight of the club. Many golfers find oversized clubs easier to control and capable of producing a longer shot.

On the green, a golfer will use a club called a putter to roll the ball over the grass and into the cup. There are literally thousands of different designs of putters.

The grips on a golf club have also changed, from leather strips to a variety of synthetic materials that cushion the hands, soak up moisture, and absorb the impact of the ball strike.

As with golf balls, the rules of golf have been revised to set standards for the construction, size, weight, and design of clubs.

Although not a necessary part of the game, golf shoes can be an aid to better golf performance. The reason is the sole of the shoe, which contains hard rubber discs that grip the grassy surface. This provides more stability for the golfer during the swing. As well, anchoring the leading foot can provide a pivot around which the golfer's weight can shift during the swing. Weight shift is another way that the energy of the swing can be efficiently transferred to the ball.

Until the 1980s, golf shoes were equipped with short metal spikes called cleats to provide the anchorage. But, spikes damaged the turf, and so were replace by the plastic discs.

The technology of golf, which is driven by science, has dramatically changed the way the sport is played since its inception. Yet, the fundamental nature of golf—to accurately control the forward progress of the ball—has remained unchanged over centuries.

SEE ALSO Golf: Why graphite-shafted clubs produce longer drives; Tennis racquet construction.