Originally Posted by
Illusions
I think it was mainly because the plot didn't rely on the plot holes being accurate or realistic, just that the information was there. Of course its going to take longer than 3 years for Christopher to get to Andromeda, but that doesn't matter, all we need to know as an audience is that its going to take a long time, at least for Wikus, before he's even going to see help. Same thing with the black liquid, its not really essential that we know why it does what it does, just that 1) Its causing Wikus to turn into a Prawn, and 2) They need it to run the ship, weapons, etc.
This is different from movies that rely on an unrealistic or impossible explanation (within the movie's own universe) as a driving force in the plot, or requires setting logic entirely aside to the point where its uncomfortable to continue watching.