What drives the flat earth movement's unconventional view--one that disavows thousands of years of scientific research? Correspondent Mariana Van Zeller investigates their motivation and why denying science can be so dangerous. Learn more about this story and others at NatGeo.com/x | National Geographic TV

Our planet is getting warmer. Every year, NASA and NOAA calculate the average surface temperature around the globe. These annual temperature data make up the global temperature record – and it’s how scientists know that the planet is warming. Red spirals in this visualization indicate years with warmer-than-average temperatures. The visualization “turns red” after 1975, showing that most of Earth’s warming has occurred in the last several decades. Overall, the average global temperature on Earth