I don't believe either answer is right. I feel there is a definative and undenyable link bewteen Fantasy and sci-fi. You merely have to look at things like Warhammer 40,000 or Japan to see this. The fact of the matter is that sci-fi, moreso than fantasy, is a genre (or sub-genre depending on your opinion) which relies heavily of immersion and "believability", for want of a better word.
In main-stream sci-fi, it is integral that the writters form a bank of rules and literary physics that will rein in their future exploits in the universe in question. This is something which has been adequately demonstrated by Star Trek which, (despite it's numberous expeditions into the ludicrous and "oh, it's a good job we found that cure" scenes to rapidly tie up various episodes) is a series dedicated to it fictional scientific and social structures.
The problem with this modern Doctor Who is that it couldn't give a cat's crap about underlying universal physics and has become little more and a moderate-budget, celebrity-guest-star whore house. Even most magical fantasies conform to a basic law structure (take the fade from Dragon Age) and I believe Terry Pratchett's works to be the perfect balance between nonsensical fantasy psychedelia and ingenious world-creation.
In main-stream sci-fi, it is integral that the writters form a bank of rules and literary physics that will rein in their future exploits in the universe in question. This is something which has been adequately demonstrated by Star Trek which, (despite it's numberous expeditions into the ludicrous and "oh, it's a good job we found that cure" scenes to rapidly tie up various episodes) is a series dedicated to it fictional scientific and social structures.
The problem with this modern Doctor Who is that it couldn't give a cat's crap about underlying universal physics and has become little more and a moderate-budget, celebrity-guest-star whore house. Even most magical fantasies conform to a basic law structure (take the fade from Dragon Age) and I believe Terry Pratchett's works to be the perfect balance between nonsensical fantasy psychedelia and ingenious world-creation.