The forty-second annual Earth Day, in which people around the world celebrate the planet and stress the importance of environmental wisdom, is taking place all weekend with a spate of activities throughout the metropolitan area. This year’s global theme is “Mobilize the Earth” with the express purpose to emphasize that “the Earth won’t wait,” and indeed it won’t. At Grand Central Terminal on Saturday, there will be storytelling, a food and nutrition panel, a special exhibit, and concerts by the Nightmare River Band, Conveyor, Annie and the Bee Keepers, FlyinFisch, the Whispering Tree, Push Method, and Kinetics & One Love. On Saturday night at 7:45, Rooftop Films will host a free screening of Sir David Attenborough’s widely acclaimed Planet Earth series, followed by the world premiere of the documentary The Making of Planet Earth, at Solar One; be sure to RSVP in advance here. And on the High Line on Sunday, performance artist Alison Knowles will invite visitors to help her make a huge salad at the West Sixteenth St. area from 10:00 am to 1:00 pm; the High Line will also host talks with gardeners, live music by the family-friendly On the Lam Brass Band, and interactive field stations.