Question: This is about the 1980 movie *Superman II* with Reeve and Hackman.

The only information I noticed in the film itself was this line from Superman's mother:

> 
> The one danger we have considered is that the Phantom Zone might - we cannot predict - just might be cracked by a nuclear explosion in space. I cannot say I am glad you asked me that -
> 
> 
> 

This almost makes it sound like a nuke *anywhere* in space would shatter the Phantom Zone, but if that was the case it ought to only take one supernova or warring space-capable civilization anywhere in the universe to shatter it, in which case it wouldn't have lasted very long.

So what's special about the part of outer space around Earth that makes the Phantom Zone gateway nukeable from there? Did the gateway follow Superman's ~~christmas ornament~~ spaceship all the way from Krypton to Earth or something?

Answer: 
In this movie the Phantom Zone is a prison that travels through space and you could argue that the Zone was caught in Krypton's explosion and followed a similar path as Kal El's ship.
Furthermore, later in the movie, Superman grabs the nuke in Paris and disposes of it by throwing it in deep space where it just happens to explode near the wayward Phantom Zone. Yes, it's a plot contrivance but all of fiction is a contrivance.
And it's not a nuke anywhere in space; it's just that the Zone is strong, but not strong enough to survive a big enough explosion.
Well, perhaps when the rocket ship was sent from Krypton if you remember in the new version with the added scenes the ship passed by them in space so maybe, it was caught in the rockets trajectory, even though it left them behind because it was much faster letting them drift the same way the ship was going, and eventually getting to our galaxy? Maybe?