What happens if two Star Destroyers collide at lightspeed?

[Drakkith]

They are of course what is called vacuously true

Phinds, what did we tell you about using big words?

1) If matter can travel FTL then a collision would produce long blue tentacles on the creatures.
2) If matter can travel FTL then a collision would produce <insert statement of your choice>

I like option one. Though option two looks promising.