Three identical spheres of mass \( m \), are placed at the vertices of an equilateral triangle of length \( a \). When released, they interact only through gravitational force and collide after a time \( T = 4 \) seconds. If the sides of the triangle are increased to length \( 2a \) and also the masses of the spheres are made \( 2m \), then they will collide after __________ seconds.
