Reverse swing in an exact opposite of conventional cricket ball
swing. It normally occurs when the ball gets a little old.
Depending on weather conditions, pitch nature and environment
around, the ball normally starts getting old after 20 to 25 overs.
In Australia and South Africa, the ball normally starts reverse
swinging around 40 to 45 overs.
While the ball starts getting old, players on the ground
(especially bowlers) try desperately to keep the shine on one side
of the ball while the other side of the ball keeps getting rougher.
Once there is a significant difference of shine and roughness on
both sides of the ball, the ball starts swinging towards the shiny
side. This is called reverse swing, however, it is not natural and
the bowlers have to really work hard to deliver reverse swing.
When the ball becomes very old - around 40 or more overs old -
it begins to swing towards the shine. This is known as reverse
swing- which means a natural outswinger will become an inswinger
and conversely, an inswinger into an outswinger.