YES everything exists with or without humans observing and how do I know? Because I have been to a funeral and had pets grow old and eventually die, and even after they go, everything continues without them. This is how I know it's not just a figment of their mind or everything would disappear when someone dies. So, therefore, it must not be just a figment of my mind, either. However, my perception might influence how the hamster looks. To an ant, the same hamster would seem like a dinosaur but to me, it's merely a mouse. And to that same ant, the human is a mountain!