Curious about space-2

I know that astronomy is taught in schools and colleges and there is burgeoning interest in space (as evidenced by science fiction movies) but we are still stuck in what we know and trying to make the resemblances of other beings to us. We all see aliens as having hands, legs, eyes, ears and tastes with slight variations and that is the limit of our imagination. We cannot or refuse to imagine that there can be some beings that can have entirely different anatomy than ours. Our lack of knowledge and limitation of our technology cannot even know how far and wide is the space and how many galaxies and stars we have (although a wide estimate states we have 100 billion of each but this can change anytime too as we explore and discover more stars). There are stars out there brighter than sun and colder than what we have on earth or even our own galaxy. We don’t know that there are any other planets which can sustain human life or this earth is the only one for us. How far can the human being travel on oxygen when he/she has to venture into space and will we ever have the capabilities to travel for years on the oxygen that we can carry with us? Does gravity affect the earth only or do other planets have the same pull? And what about the asteroids and meteors that we encounter each other without our knowledge or who get a close call that we pray does not hit us.