Please forgive me all for asking such an odd question, but I'm a science fiction novelist and I am currently researching for my new book. I'm attempting to create a new "fictional universe" in which it pretty much is the real universe as we know it in real life. Theres a couple of things im doing to make it unique, in addition to making the world as real as possible by the laws of science without ruing the story. Anyhow, im trying to figure something out. Remember my whole deal is realistic science fiction....so that means things are as they are in real life. Ok, so barring the debate over whether or not life exists on other planets...im assuming it doesnt for purposes of my novel.....why are there 8 other planets that cant support human life? It just doesnt make sense as to why out of 9 only 1 can support life. I know the science as to why, but what purpose do the other 8 serve? Is there any scientific reason known as to why? Do they affect the gravity of earth or anything? Someone, please help me understand this, because I need to know for the sake of my story. I really appreciate any help.