Time reversible systems make causality fuzzy. There’s nothing special about this example in that respect. You can’t object have ball A hit ball B. A causes B to

Time reversible systems make causality fuzzy. There’s nothing special about this example in that respect. You can’t object have ball A hit ball B. A causes B to move. You can then reverse it, end up with an equivalent but time reversed system where B hits A, and B causes A to move.