40 yards across.
When the ball leaves the field of play completely surpassing the sideline.
It's called a cross.
the width of NFL field sideline to sideline is 53.5 yards
There is three official referees, one running on the field and one on each sideline. They do have a reserve/4th ref who is out of the field. Currently there is an experiment with an extra referee behind the goals.
Not very big but I am not positive
Is that a ? no it's not!
Whenever the ball exits the field across a touch line.