What if someone told you the cure to all of your problems is simply urine? Plenty of people believe exactly that; it's a concept called urine therapy. But the bizarre theories believed by a significant number of people don't stop there. You may have heard of Flat Earthers, but what about Hollow Earthers? These people believe the Earth is just an empty shell, some even taking it as far as believing the center of the hollow Earth is populated by an advanced civilization. Another strange theory is breatharianism, the idea that humans do not need food and water, just sunlight.