This Earth Day, April 22, scientists and their supporters are expected to take to the streets of Washington, D.C., as part of the March for Science. It aims to celebrate science while urging government leaders to base decisions on scientific evidence and to support research.

Many marchers are dismayed that President Trump has expressed skepticism about scientific issues such as climate change. Climate scientists overwhelmingly agree that this change in global climate patterns is driven by human activity, such as the burning of fuels that release heat-trapping greenhouse gases into the atmosphere.

Not all scientists think that a march is a good idea. Some believe that science should be kept separate from politics.