Why are Newton’s Laws of Physics called laws and not theories?


Why are Newton’s Laws of Physics called laws and not theories?

In: Physics


There isn’t an exact answer but generally a law tells you *what* will happen. A theory tells you *why* it happens.

So Newton’s second law of motion, F = d(mv)/dt, tells you how forces relate to changes in momentum; if you push something it will accelerate. But it doesn’t tell you *why* forces lead to a change in momentum.

Similarly his Law of Universal Gravitation tells you (roughly) what will happen if you put two things with mass near each other, but won’t tell you why it does that.

Laws are observational constants. When you drop something it falls down. When you push on something an equal force is applied in the opposite direction. There is no conclusion or idea of why this happens. Its just an observable thing that happens. This is what scientific laws are. Theories on the other hand answer the far more interesting why question. Why do things fall down when i let them go. To answer this you need a theory.

Like theories, scientific laws describe phenomena that the scientific community has found to be provably true. Generally, laws describe what will happen in a given situation as demonstrable by a mathematical equation, whereas theories describe how the phenomenon happens.