Our definition of life keeps changing as we discover living things in places we did not think life could exist. My question is how would we define life if this trend continues? As of now we believe all living things need liquid water. But we may find organism living in any kind of liquid. But is a liquid even necessary? Is solid material needed for life to anchor on? I am thinking of life in the most optimistic way and wondering how to define it. Could in theory life take hold anywhere there is a slow exchange of energy over a long period of time?