I've heard of Stephen Hawking talking about the Planck Length and how nothing could exist at a level smaller than that length. I'd like to know how we know this to be certain. It seems that history has always repeated itself in that when humans see as far as we possibly see we simply just believe that is the edge of the universe. Etc. Similarly I have to wonder if that is the case here. Are we seeing as small as we can see and deciding that's it? What if we were wrong? Say I have a glass bottle how do we know that an INFINITE number of molecules couldn't fit within that bottle so long as those molecules were scaled down to an infinitely small size somehow? Would appreciate some insight.