Bearing protest signs and many wearing lab coats, thousands of scientists from around the world began gathering to express their objections to the cutbacks in scientific research proposed by President Donald Trump.
Despite rainy weather, protesters gathered around the Washington Monument for a festive day of music, speeches and teach-ins by scientists disturbed by the rise of so-called "alternative facts" around crucial issues like climate change following Mr. Trump's election.
The rallies in more than 600 cities put scientists, who generally shy away from advocacy and whose work depends on objective experimentation, into a more public position. Photo shows protesters at a rally in Geneva.
Scientists said they were anxious about political and public rejection of established science such as climate change and the safety of vaccine immunizations. Picture shows demonstrators taking part in a rally in downtown Los Angeles
The marches put a new twist on the traditional Earth Day activities, the aim of which was to reaffirm "the vital role science plays in our democracy," according to the march's website.
People hold signs of pioneering women in science in front the U.S. Environmental Protection Agency during the March for Science in Washington.
At a time when the Earth has marked three consecutive years of record-breaking heat, and ice is melting at an unprecedented rate at the poles, risking massive sea level rise in the decades ahead, some marchers say it is more important than ever for scientists to communicate and work toward solutions to curb fossil fuel emissions.