Lyxen
Great Old One
EVERYTHING that is not magical or described by the lore as different should be assumed to work like the real world.
I disagree, taking on a fantasy world perspective can certainly lead to at least, if not more interesting gaming, and it does not have to lead to bizarro world.
Why? Because the players don't live in the D&D world. They haven't grown up in it and learned all its quirks.
So what ? It's not the players who are living there, it's their characters.
If nothing can be assumed to work the way it does in the real world, the players can become lost in a morass of uncertainty. Does wood float? Do pigs lay eggs? Are metal tipped arrows better than rubber ones? Do more coins weight more than less coins? Is ale toxic? Does the sun or the moon shed heat? Do people need food? Is time 2 dimensional? (yes, btw)
etc etc etc etc etc.
There are so many things that the players have to keep track of already (longswords do more damage than short swords. Fireball has a 20 foot radius. Acid and fire work well vs trolls. Dwarven exiles are not to be trusted. Hundreds of other things). We need a stable footing from which we can explore the wonders of the imaginary world, and to help us understand it.
The problem is that for example something like gravity does not work like in our real world, as it includes spelljammer gravity which is notably different (and in 5e, thanks to Dungeon of he Mad Mage).
Furthermore, there are good reasons to doubt fundamental physics. There is an elemental plane of air which provides the air on the worlds. It is an elemental plane of (O2 21% / N2 70% / Ar 0.9% / etc.) ? No, it's a plane full of the stuff of air, and therefore the air that adventurers breathe is the air element, which is elemental. Same when you produce a fireball, it cannot be a physical combustion, it requires no comburant and does not suck out the air to produce CO2 (as an example). It's just stuff from the elemental plane of fire personified.
I really suggest reading Brandon Sanderson's "The Stormlight Archives", you will see a fantasy world with its own physics and metaphysics, very logical, but which functions on different principles, and it's as good a basis for a fantasy world as our own.
For the sake of simplicity, you are welcome to make the hypothesis above, but please realise that it's not that simple, and that it cannot be forced upon others since there is clear evidence to the contrary.
Also, most of the questions that you are asking probably have the same answer as the real world, but they are completely trivial and unlikely to lead to interesting gaming. However, considering a completely different perspective, in particular about elements, and plane, and metaphysics can make your game more magical and interesting.