Or it follows real world physics except where it doesn’t.
In the AD&D MM, we are told (pp 44-5) thatcloud giants
cloud giants usually reside in crude castles built atop mountains or on magical cloud islands . . . 10% of cloud giants are very intelligent. These will be the ones found dwelling on cloud islands. . . .
The most powerful and respected true giant is the storm giant. . . . Their abodes are typically cloud islands (60%), mountain peaks (30%) or underwater (l0%), and there the storm giants build their spacious castles.
The most powerful and respected true giant is the storm giant. . . . Their abodes are typically cloud islands (60%), mountain peaks (30%) or underwater (l0%), and there the storm giants build their spacious castles.
What is a "magical cloud island"? What role does it play in the water cycle? If rain falls from a cloud island, does it get smaller? If rain can't fall from cloud islands, then why are they called cloud islands at all? And does this mean that, in the D&D world, the connection between clouds and precipitation is much more arbitrary than in the real world?
At a certain point, the instances of "except when it doesn't" become so numerous that the sense in which it does becomes hard for me to grasp.
Look at it this way: if the player of a character in a standard CoC game says "I go to the physics lecture at the university", the GM can pick up an old physics textbook and start reading from it and the player will get an immersive experience. Or I could use my copy of Einstein on relativity as a prop.Which is odd, because a constantly-recurring trope of travel-based adventuring is that your transportation needs repair or needs a whole new propulsion unit built out of whatever spare parts you have on hand.
But what happens if the player in Traveller says (in character) "I go to the introductory lecture on jump drives"? The GM can spout some babble or other, but there are not actual coherent things that can be said, or equations exhibited, to generate an immersive experience, because it's all just made-up nonsense.
But whereas this sort of pressure-point can come up in a sci-fi game, I don't think it is even really an issue in a fantasy game, as there is no assumption in a fantasy game that the world is knowable by way of natural laws. The supernatural element is what makes a fantasy game fantasy.