Detect "collision" between Vector3 and GameObject

I’m new to Unity3D, and some of the concepts are still a little confusing, so this might be a dumb question.

Basically I have a bunch of dynamically-generated moving spheres in my scene. I also have a unit vector3 pointing generally in the positive-Z direction. I want to be able to detect if that unit vector, if its magnitude were extended to infinity, would intersect with any of those spheres.

Can anyone point me in the right direction (no pun intended)? Thanks in advance!

Point → Unity - Scripting API: Physics.Raycast