I was reading H. Moysés Nussenzveig "A course in basic physics, Volume IV" and in chapter 8, he is introducing the basic ideas of quantum mechanics, where he states that:
In quantum mechanics, one thing that is important is the observation changes the system. In classical physics, there are examples of systems that also change with observation, but the change is so small and unimportant that we can ignore it.
This got me thinking. What are these examples of classical physics that also change with observation?