Final answer:
If the entropy of the universe changes, it suggests the process is spontaneous, where entropy typically increases, indicating an irreversible process. In contrast, reversible processes keep the entropy constant, but perfect reversibility is an idealized concept not often found in real-life scenarios.
Step-by-step explanation:
If the entropy of the universe changes, this implies that the process is spontaneous. According to the second law of thermodynamics, if a process is reversible, the entropy of the universe remains constant. During an adiabatic process, there is no heat transfer to or from the system, and if the process is reversible, the entropy of the system remains unchanged. However, most adiabatic processes in practice are irreversible and may involve changes to the system's entropy.
Despite the ideal concept of a reversible process, real processes are not perfectly reversible, and they do change the total entropy. Always, the total entropy of a system either increases or remains constant; it never decreases. This means that in real-life interactions, entropy tends to increase, making spontaneous processes generally irreversible.
Therefore, the change in entropy in an adiabatic process does not necessarily imply that the process is reversible. Additionally, it is extremely difficult for a macroscopic system to undergo a process that is precisely adiabatic due to the practical challenges of perfectly insulating the system from its environment.