is every material replaceable?

Question

should scientist develop new materials to replace old one, or should we focus our efforts on using existing material more effficiently?

Answer 1

Not every material is replaceable. There are some elements, chemicals, and materials that are in a finite supply.

Since scientists have a finite $$ supply, they have to prioritize their efforts on developing infinite replacements of finite materials to maximize the $$ returns of thier finite $$$.