Function causally_connectable 

pub fn causally_connectable(dt: f64, dx: f64, dy: f64, dz: f64, c: f64) -> bool

Are two events causally connectable — within or on each other’s light cone (timelike or lightlike, s² ≤ 0)? The relativity-adjusted “could one have influenced the other?” that bounds temporal logic in 4-D space-time. Spacelike-separated events have no frame-invariant ordering.