# Dangerous statement Quantum mechanics is nothing but an **entirely** random theory and therefore not a good **accurate** predictive tool. # Answer / Explanation Quantum mechanics is certainly *not just* purely random, albeit pure randomness is indeed an **intrinsic aspect** of the theory. What this notion precisely entails, is that while we will certainly **not** be able to predict the outcome of one experiment. Instead, what quantum mechanics will accurately predict is the **average outcome** out of a big collection of repeated experiments! Let's have a look at a classical example first. Imagine you are throwing a coin. You know that there are only two possible outcomes, either heads or tails. While it would be indeed possible to accurately predict the outcome with a very complicated computer simulation that simply used [[Newton's Laws]], for our day to day experience it is **simpler to assume** that the coin is simply fair and treat the outcome of a coin throw as random. ![[coin_dice.excalidraw.light.svg]] We associate and accept randomness for many things like this in our everyday life: stock markets, gas prices, the lotto numbers, etc... The **logic however remains the same**, we lack a good enough predictive tool, either because a simulation would be too hard (like coins, dices or the lotto raffle) or because we simply lack all the necessary information to make one such simulation (like stock markets or gas prices, where we don´t know what other people are doing). But that does not mean that we know nothing about all the previous instances! It just means that we accept that **a single** coin throw or tomorrows stock prices will be impossible to predict. In exchange, we can instead **predict the average** of the coin throws, or the average movements of the market. ![[coins.excalidraw.light.svg]] So what is different in [[Quantum Mechanics|quantum mechanics]]? The key difference, is that we accept as a rule of quantum mechanics, that **the randomness is intrinsic** to the theory, as opposed to a simplification to make our life easier! The **predictive power of the theory lies within the ability to predict the weights of the randomness!** To exemplify it in more technical terms, we can take the principle of [[Superposition|superposition]], which is somewhat similar to the scenario of the coin. If we [[Measurement|measure]] a state which is in a [[Superposition|superposition]], we don't know into which [[quantum state]] it will collapse. However, the [[Schrödinger Equation|Schrödinger equation]] gives us a tool to precisely evaluate the probability of each state, the aforementioned weights! Thus, we will be able to predict the results we expect if we repeat a quantum experiment many times, and not as a simplification as in the previous examples. To summarize: Quantum mechanics is not deterministic by construction, i.e. we cannot predict the outcome of each experiment. However, the theory comes equipped with the tools to predict the probability of each of the different outcomes. These predictions can then be experimentally tested by repeating an experiment many times. >[!read]- Further Reading >- [[Determinism]] >- [[Measurement]] >- [[Schrödinger Equation]]