In January 2017, what started as a subreddit thread about the new White House scrubbing all mention of climate change from its official government website became, just three months later, the single biggest pro-science demonstration in the history of humankind. On April 22, more than a million people across all seven continents took to the streets (and dirt roads and snowfields) to declare themselves, not dispassionately, for the fundamental political value of science.

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