Speculative Fact #200: Snowball Earth

Long before the modern era of global warming, Earth’s entire surface might have been covered in ice. While the “ice ages” most of us have been taught about occurred prehistorically,  (some millions of years ago), the earliest hypothesized glaciation period (Huronian) happened billions of years ago – at a time when only multicellular life existed on Earth. These glaciation periods have complex and debated origins, but have occurred repeatedly throughout Earth’s history. Something to think about this summer.