Which explanation for Superman's journey to Earth is the most convincing?
A few details:
Krypton: 50 light years away
Light-year: 9.46 trillion km
Speed of light: 300,000 km/s
Travel at light speed: 50 years
Please do not think as a fanboy, leave everything aside that might influence your opinion, such as: suspension of disbelief or "come on, it's a comic". The question is comic-independent. It's not about what sounds cool or what would be more practical, faster or easier. It's just about what sounds most believable or convincing.
Please share your views.