I have some questions that I have been wondering about for a while. I'm not a physicist, and I don't know the math behind anything. Just a guy who is thinking up some questions. Just think of me as a student asking some questions. I know these questions can be answered and have been thought of. Some random guy like me isn't going to shake the foundations of astronomy. Sorry if I have a lot. Why do we think entire Universe is expanding? Why can't the Big Bang/Inflation just be a big explosion/inflation in only a small part of the Universe? Why do we think space came with the Big Bang/Inflation? Is there a reason why we think space didn't exist before everything? Galaxies rotations have us think there is Dark Matter at play. Why do we think that? (Stupid question) Is it possible gravity acts different at larger scales? Do Galaxy clusters rotate, and if they do, do they show evidence of dark matter as well? You don't have to put any of your answers in Layman's terms. Speak to your hearts content.