Reversible process in General Physics Usually, for christmas , I have lunch with my family and a couple of other families. Most of the people got a Phd on chemistry, or molecular biology, and are high academics (they're in they 50-70). On the other side, i'm the only one who studies physics there, and 2 years ago, in the same situation, they told me that physics only study reversible proccess (In the context that we're like, noobs). At that moment I was very young and have litle idea about physics. What's your opinion?
 A: My opinion is that you should not form an opinion about physics based on the statements of people who are not physicists!  If physics only studied reversible processes, we wouldn't have terms for irreversible processes.  Next time you see them, ask if they have heard of "entropy."  Reversible processes never change the entropy of the full system undergoing the reversible process.  So their claim is that physics only treats entropy changes equal to zero.  Now ask them if they have ever heard of the "second law of thermodynamics."  Then point out that is a law of physics.
Basically, what actually distinguishes physics from chemistry and biology is not reversibility, it is how fundamental the processes are.  All biological and chemical processes are built of physical processes, it's just a matter of whether you are interested in what is fundamentally happening, or what is the net result of those fundamental interactions.  So we can say that all chemistry and all biology is, at some level, actually physics, but we cannot say that all physics is chemistry or biology.
A: Their claim is plainly false. A good example would be radioactive decay; once the nucleus has decayed, it would be somewhat absurd to suggest that one could capture the decay products and cram them back into the nucleus, especially in the case of beta decay, which releases an antineutrino.
A: Never-the-less, there is the law of entropy, which chemical re-actions follow, which has an irreversibility of direction to it. probably that is behind the comment. A chemist might not have picked up how that law applies in other areas (or maybe I should say at other scales/levels) if they have specialised, I suppose.
A: Any inelastic deformations and ferromagnetic cycles are always irreversible processes.
