Can first principles replace all scientific experiments?

Absolutely not. They are a collaborative relationship, not a substitute for each other.

You can think of it this way: First-principles are like the underlying logic of a recipe, such as the Maillard reaction (why seared meat smells good) or emulsification (why oil and water can mix to form a sauce). Knowing these principles allows you to better understand recipes and even create new dishes.

But what about scientific experiments? That's like actually making the dish yourself and tasting it. Can you "calculate" from theory alone that the dish will definitely be delicious? Absolutely not. You have to test the seasoning, check the heat. What if the salt you bought is saltier than expected? What if today's pan conducts heat a bit faster? These are all variables that theory cannot account for. Experimentation is the ultimate "judge."

It's the same in science. First-principles (like quantum mechanics) are the most fundamental "rules of the game" we currently understand. We can use them to calculate and predict what properties a new material "should" have. This is incredibly powerful, helping us to point in the right direction and avoid blindly experimenting like headless chickens.

However, the real world is infinitely more complex than even our most advanced computer models. A material might contain trace impurities we didn't consider, or the experimental environment might have subtle fluctuations we didn't anticipate. These can all lead to results that are completely different from theoretical calculations. That's why we must conduct experiments to verify.

More importantly, many great discoveries have seen experiments precede theory. Scientists observed an inexplicable phenomenon in experiments, and only then did they turn back to study the underlying principles, attempting to establish new theories. Superconductivity, for example, was discovered first, and it took decades for a theory to explain it reasonably well. Without experiments, we might never have known of its existence.

Therefore, first-principles and scientific experiments are like walking on two legs; neither can be missing. First-principles help you design the most reliable "map," telling you where the path might be; while scientific experiments are about you personally "walking" that path, seeing if it's truly passable, and even discovering treasures along the way that aren't on the map. One is responsible for "thinking," the other for "verification and discovery," and only by working together can they drive scientific progress.