Storm Raven said:
Well, for starters: what do the alien creatures in the movie eat when there aren't any humans to munch on? The planet is otherwise devoid of all life, so what is their normal source of food when a crew of hapless humans doesn't happen to fall from the sky? (More to the point, how did creatures that die in sublight evolve on a planet with three suns?)
Since the creatures are subterranean, the sun(s) may not factor much into it. After all, whole species of fish, salamander, etc. evolve without ever seeing the light. Of course,
they don't explode in the sun, but this is a sci-fi movie, so, if we can accept that the Alien has acid blood that can eat through several feet of metal, that isn't much of a stretch.
I, too, wondered what they ate. If it wasn't for the bones on the surface, I'd argue that most of the life on the planet existed underground. Probably, most of the life does exist below the surface (the only other life forms we see are the glow worms).
On the other hand, we only see a small portion of the world. It's quite possible that these things only inhabit a small area. Sure, they come out and rampage every 22 years, but they may not exist all over the world. Think of the ants that run amuck in Africa. They lay waste to everything, but only in certain areas. Life in the rest of Africa goes on.
When one of the kids goes missing, why do they look for him in a bulidng that they have the blast the locks open to get inside? How did the characters think the kid get in to such an apparently inaccessible structure?
Two possible reasons. The kid sneaked in while Riddick was examining that building. It's possible that he either saw him or, after seeing the other kid hanging out on top of it, put two and two together.
OTOH, don't forget that Riddick wanted to get in there earlier and is also a sociopath. He may not have known or cared where the kid was. He just wanted in the room.
When they figure out that an eclipse is coming, realizing that the predatory creatures only come out at night, does anyone bother to advance the model to figure out how long it will be until the sun comes up again? No. Why not? One would think that was a pretty vital piece of information.
I didn't like or understand the model at all. It was pretty much a plot device.
And the whole ending sequence with Fry and Riddick made no sense whatsoever.
Are you talking about how she got out of the cave and to him while leaving the others behind? Yeah, that is a big problem.
Another fault I had with the film was that this colony was wiped out 22 years ago. It's a mining colony, it had to report to someone. If anyone came looking, they'd definitely find out what happened (look how long it took the crash survivors to encounter the creatures and they weren't outright investigating anything). If others knew, you'd think there'd be a big "Stay the hell away from this planet" warning that everyone would be aware of.
Lastly, the biggest problem I had was the "only works when in sunlight" solar technology. Okay, that's just stupid! They could have explained it away by saying that the battery in the car was damaged or didn't have time to recharge properly or something.
With all that out of the way...I actually enjoy the film. As far as bad science or questionable writing, this film comes out ahead of many other sci-fi action flicks (the Godzilla remake, anyone?). I even bought the DVD.
EDIT: I seem to have posted at the exact same time as Strithe. We covered most of the same points, too.