According to the first comic, Superman was sent with a rocket/spaceship to Earth. This happened when he was three years old. Over time, the origin story changed a little, but their core remained the same. A closer look reveals that the story has some weaknesses.
To clarify one thing: I am well aware that this is a comic. It's not about to stir things up or to make Superman implausible. In comic books everything is possible; suspension of disbelief, etc.
However, it´s never wrong to do some things more believable or realistic. Sometimes realism helps to be able to better identify with the comic book character or it helps to make the told story more interesting. But realism does not mean that everything has to work in reality. Science fiction is the main factor for good superhero stories. The main thing is that the science fiction elements are believable or logical in the fictional world.
The weaknesses of Superman's origin story
The nearest star is Proxima Centaurie, 4.2 light years away from Earth. The nearest large galaxy is Andromeda Nebula, around 2.5 million light years away. Super-Earth Gliese with the catalog number 1214b is about 40 light years away from Earth and orbits a sun in the constellation Ophiuchus. One light year is 9.46 trillion km. The speed of light is 300,000 km/s. If a spaceship could fly at the speed of light, then it would take ...
... 4.2 years to Proxima Centaurie,
... 2.5 million years to Andromeda Nebula,
... 40 years to Earth Gliese.
According to the Green Lantern Corps, Krypton is 50 light years away from Earth. With speed of light, the spaceship would take 50 years. Even at twice the speed of light, the spacecraft would take 25 years. And now calculate how much times the speed of light would be necessary to take only 3 years for this route. Besides the fact that huge amounts of energy would be needed to reach the speed of light, what about maneuvering and throttling of speed or about free-floating or flying matter in space? The spacecraft may be made of a very resistant material, but at the speed of light there is no protection. Also a spaceship with an energetic shield would require a lot of energy and would be destroyed or thrown from the trajectory. Only the enormous G-forces inside the spaceship could be avoided by a special technology.
If the child was sent to Earth at the age of three years, then his stepparent would have adopted a 53 years old man; unless one uses Einstein's time dilation, then his parents would have been dead (twin paradox), or they were either not even born at the time of the journey or still been children, depending on how long the journey took. In addition, a three year old child would already be able to speak, in this case it would be the kryptonian language. Can american parents teach an alien three year old an earthly language? O.K. the age of the child has changed. In Man of Steel, the child was a suckling. (I wanted to mention it anyway.)
The spaceship would only be drawn or brought to Earth. That would be faster and safer. But it does not sound believable.
The spaceship could appear at any point in space. A solution, but not spectacular and even more unbelievable.
Krypton´s universe would be very close. A stone's throw for the spaceship. Believable? Not at all.
The speed of the spaceship is far below the speed of light. It takes centuries or even millennia until it reaches the Earth. Before the spaceship is sent, the mankind is still in the median age or antiquity. The advanced kryptonian technology ensures that the baby can neither age nor starve. (That´s my favorite.)
What do you think?
Does Superman´s origin story need a change?
PS: Sorry if my english is faulty, I´m german.