For context
One of my players is playing for the first time and has some problems with magic and how versatile it is, therefore he is attempting to make an armor to resist fire, lightning, acid and cold. Of course, he is not using any magic. He is a bit more knowledgeable than me in how physics work and likes to apply them ever since I said that in D&D you can try to do almost anything.
How it presumably works
His idea is to make a wool based gambison knee length covered in copper plates and copper wire. The idea is that he the wool would insulate from heat and cold, the copper plating would protect the wool from catching fire and would also provide protection against acid. Finally the copper wire would have a hook to stick in the ground and would serve as a lightning catcher completely protecting against the damage. All of that worn on top of a full plate armor.
That is obviously broken.
I don't want to allow him to make it without major draw backs but I don't want to say no completely either. I don't even know if it makes any sense at all, what he is trying to make.
I am new at DMing.
Is it possible to get magical elemental damage resistances through mundane means?
What would his project cost (time and money) how hard would it be to make? Should I allow it?
What are the implications?
Best Answer
No, this scheme does not work. Elemental magic is primarily magical rather than primarily elemental
For the same reason you can successfully cast Fireball underwater you can't expect wool and copper wire to mitigate a magic spell's damaging effects. It's often said that D&D is not a physics simulator, and this is one of the cases where that is relevant. This means that, for circumventing game rules, your player's knowledge of physical science is irrelevant.
Other details arguing against this idea exist but are less important than the above reason, which is decisive. You may or may not want to give some benefit for creative thinking, but full-on resistance is a pretty big deal and is generally gained by making some significant investments towards it rather than in other options.