Tens of thousands are celebrating Earth Day by marching Saturday against President Donald Trump's ongoing attacks on science, in an unprecedented global uprising of scientists against the anti-science Trump administration.

With demonstrations on six continents, there was even a (small) march on the North Pole:

"I'm encouraged by the marches I've seen already taking place around the world," Rush Holt, a former congressman and head of the American Association for the Advancement of Science, told the Guardian on Saturday morning. "For generations scientists have been reluctant to be in the public square."

"Scientists are understanding that they have to become activists, that they have to speak up, that they have to be heard," John Holdren, a science advisor to former President Barack Obama, added to the newspaper.

As the march in Washington, D.C, kicks off, here are photos and videos of satellite science marches in the U.S. and around the world: