Athletes who push themselves in mesmerizing ways while the rest of us sit from the comfort and safety of the stands or couch will always be fascinating. They dare to achieve things that most of us couldn’t even attempt. It’s one thing to see a professional hit a home run, throw down a slam dunk or score a touchdown. It’s another to see the action-adventure athletes in HBO’s Edge of the Earth. This is as extreme as extreme sports get. You’re watching snowboarding, skiing, kayaking, free climbing, and big-wave surfing in the most remote corners of the globe. With jaw-dropping moments and beautifully shot visuals, this four-part documentary series (a…