Oct. 31, 2011, was a scary day, and not just because Frankenstein and Big Foot were running around on campus. This Halloween, the world population hit 7 billion people, a milestone that has generated increasing concern about how our world can provide the basic necessities of food, clothing, shelter and energy for more and more people. So just how fast is the world population growing? In 1900, the world had 1.6 billion people, and 99 years later, that number had grown to 6.1 billion. It is projected that by 2025, when current Notre Dame students are 32-36 years old, the world population will hit 8 billion, and that is a lot of mouths to feed.