# Probability in Physics

1. Nov 23, 2006

The other day, a question popped in my head about how we use probability in physics (not limited to classical), since it is my weakest subject, and since I will be applying my math knowledge to physics, I don't want to study anything that won't be necessary.

Thanks for any replies.

2. Nov 23, 2006

### Kurdt

Staff Emeritus

3. Nov 23, 2006

### Crosson

In classical physics, probability can be used to derive useful formulae in statistical mechanics and thermodynamics.

In quantum physics, probability is central to the theory. Briefly, for each quantum observable there are infinitely many states i.e. E=1, 2, 3... , and a general quantum state can be written as a linear combination (series) of these independent state, the squares of the coefficients of which are the probability that a measurement would yield that result E=2, or something.

4. Nov 23, 2006

### quasar987

Statistical mechanics is the study of systems made up of large numbers of particles my means of probability theory.

For systems such as a gaz in an enclosure, the number of particle is of the order of 10^24. If you want to know how the system evolves in time, you must solve 3*10^24 coupled differential equations with 6*10^24 initial conditions (the initial positions and momenta of each particles). This is obviusly not feasable and even if it were, it would not be very interesting to know exactly how each particles will evolved in the gaz.

Instead, we talk about the probability of finding the system in a particular state.

5. Nov 23, 2006

### Cyrus

You're going to need statistics, if your an engineer or a physicist.