What makes Earth able to support life?

Why is Earth the only habitable planet in the Solar System? What is the Goldilocks Zone? Are there other planets out there like Earth? Attention SmartyFamilies! To get TWO NEW episodes of WHO SMARTED? every week, plus BONUS CONTENT all AD FREE (and support Who Smarted?)... subscribe to WHO SMARTED?+ Sign up HERE! Apple users can sign up right on the Apple App. For free home activities sign-up at www.WhoSmarted.com