Editing Fast bowling (section)

== Swing bowling ==
{{main|Swing bowling}}
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Swing bowlers cause the ball to move laterally through the air, rather than off the pitch like seam bowlers. Normal or conventional swing bowling is encouraged by the raised seam of the ball,<ref name="Science">{{Cite web|title = The science of swing bowling|url = http://www.espncricinfo.com/magazine/content/story/258645.html|access-date = 16 July 2015}}</ref> and conventional swing is usually greatest when the ball is new and therefore has a pronounced seam. As the ball gets older, the wear makes swing more difficult to achieve, but this can be countered if the fielding team systematically polishes one side of the ball while allowing the other to become rough. When the ball has been polished highly on one side and not on the other and if the ball is bowled very fast (over {{Convert | 85 | mph | abbr = out | sigfig = 2}}), it produces a [[reverse swing]] such that the ball swings in the opposite direction as in conventional swing. Contrary to popular opinion, this [[reverse swing|swing]] is not produced by air flowing faster over the smooth or "shiny" side as compared to the rough side.

Swing is produced due to a net force acting on the ball from one side; that is, the side with the more [[turbulence|turbulent]] [[boundary layer]]. For conventional swing bowling, the raised seam and the direction it points governs the direction of swing. Due to the angled seam of the ball, air flowing over the seam produces turbulence on the side that the seam is angled toward. This causes the boundary layer to separate from the surface of the ball later (further toward the rear of the ball) than the other side where it separates earlier (further forward on the surface). The resulting net force acts so as to move or swing the ball in the direction of the angled seam. Conventional swing bowling is delivered with the seam angled such that the smooth or polished side of the ball faces forward to move the ball in the direction of the seam ''i.e.'' toward the rough side.

A swinging ball is classed as either an outswinger, which moves away from the batter, or an inswinger, which moves in toward the batter.<ref name="Science"/> In most cases the outswinger is seen as the more dangerous ball because, if the batter fails to recognise it, it catches the outside edge of the bat instead of the middle and fly up to be caught in the [[Fielding positions in cricket|slips]]. Inswingers have their place too, especially combined with the [[yorker]] as this can result in the ball either breaking the wicket (by going clean "through the gate" or getting an inside edge) or hitting the pad rather than the bat (resulting in a possible [[leg before wicket|LBW]] decision).

Swing bowling can also be roughly categorised as early swing or late swing, corresponding to when in the trajectory the ball changes direction. The later the ball swings, the less chance the batter has of adjusting to account for the swing.

Bowlers usually use the same grip and technique on swing balls as fast balls, though they usually keep the seam slightly rather than straight, and may use the slower ball grip. It is difficult to achieve swing with a cutter grip since the ball spins in flight, varying the orientation of the shiny and rough surfaces as it moves through the air. Many players, commentators on the game, and fans agree that swing is easier to achieve in humid or overcast conditions, and also that the red ball used in [[Test cricket]] swings more than the white ball used in the [[One Day International|one-day game]].

=== Reverse swing ===
[[Reverse swing]] is a phenomenon that makes the ball swing in the opposite direction to that usually produced by the orientation of the shiny and rough sides of the ball.<ref name="Science" /> When the ball is reverse swinging, the ball swings towards the shiny side. Balls that reverse swing move much later and much more sharply than those swinging conventionally, both factors increasing the difficulty the batter has in trying to hit the ball. At speeds of over 90&nbsp;mph a ball always exhibits reverse swing, but as roughness increases on the leading side, the speed at which reverse swing occurs decreases.<ref name="Science" /> This means that an older ball is more likely to be delivered with reverse swing as its surface is roughened through use.

In [[reverse swing]] the seam is angled in the same way as in conventional swing (10–20 degrees to one side) but the boundary layer on both sides is turbulent. The net effect of the seam and rough side is that the ball swings in the direction opposite to where the seam is pointing to. The turbulent boundary layer separating later is similar to the effect produced by dimples in a golf ball. In case of the golf ball, turbulence is produced on both sides of the ball and the net effect is a later separation of the boundary layer on both sides and smaller wake in the back of the ball and a lower net drag due to pressure differential between the front and the back. This enables the golf ball to travel further.

The discovery of reverse swing is credited to Pakistan's cricketers, with [[Sarfraz Nawaz]] and Farrukh Ahmed Khan, both named as originators of the delivery.<ref>{{Cite news|url = https://www.telegraph.co.uk/sport/cricket/10963855/How-Pakistan-became-the-kings-of-swing.html|title = How Pakistan became the kings of swing|last = Oborne|first = Peter|date = 12 July 2014|work = The Telegraph|access-date = 16 July 2015}}</ref>