system
Given the following post, respond as if you're commenting on Reddit:
human
[Predators] How did no one figure out where they were sooner? (Spoilers)

Although it's easily guessed from the beginning, we don't find out until halfway through the film that they're on an alien planet and only then because they see the sky and spot the other planets etc... However at various points before that (like when walking across the rocks) the sky is clearly visible... Also, wouldn't an alien planet likely have a slightly different gravity unless it was close to identical to earth in size and composition?

Thanks!
gpt
If all they saw of the sky was blue with clouds, or even just a night sky with stars, they're unlikely to notice anything different. There are very few people outside of astronomers and navigators who know the stars and constellations well enough to identify them (or the lack of them) in a place they've never been to, especially if they don't know where that is (or is supposed to be). And the planet/moon that finally tips them off may not have risen in the mean time.

As for the gravity, it's highly unlikely for a planet to have exactly the same gravity as Earth, but it could well be close enough to the point that a person wouldn't be able to tell the difference. It wasn't just some random planet, after all, so surface gravity was likely a characteristic taken into account when the Predators chose that place as their game preserve.