What does the Bible say on why many believe Heaven doesn't exist since they can not see it with their physical?

dude look around you. do you see whats going on. nothing is beyond us.we can do what ever we think about. we are having a world wide conversation. we are gods children. yes we can understand. im sure you cant even imagine how great this world would look with a hundred more years of mankind. but you do know that its going to be outstanding