Another viral challenge is sweeping the social media landscape.This time it appears that people just discovered gravity. Of all the challenges, this one is the hardest to understand. It's called the "Gravity Challenge" and, basically, you just have someone dump water on your head, or dump it on your own head, to prove gravity works. The people who are posting these challenge videos on TikTok set their videos to John Mayer's song "Gravity." Now unlike the Ice Bucket Challenge a few years ago, this water dumping is not for charity. If you want to participate in the challenge, you need a lot of water and some willingness to deal with a wet carpet for days.