An estimated 40,000 scientists and their supporters descended on Columbus Drive on Saturday to stand up for scientific research and the initiatives they feel are increasingly under siege by the policies of President Donald Trump’s administration.

It was a peaceful gathering, without the loud chanting of recent city protests needling the Trump administration, including last weekend’s Tax Day rally, which saw between 2,000 and 4,000 marchers. The March for Science Chicago had an almost cheerful quality to it; it seemed that for Earth Day, marchers wanted to celebrate the planet as well as advocate for its protection.

A brass band whose members wore white lab coats blared “You Are My Sunshine” while stilt walkers in flashy costumes towered over them. Inflatable globe beach balls waltzed through the air, and a 6-year-old girl who caught one read aloud a message someone had scribbled on it. “There is no Planet B!” she cried, showing the globe to her mother.

While organizers said the march wasn’t partisan, they said it was political, and intended to defend scientific research from attack, including proposed U.S. government budget cuts under President Donald Trump, such as a 20 percent cut from the National Institute of Health.

Charles Cappell, a 70-year-old sociologist and retired Northern Illinois University professor, waved a 3-by-5-foot flag that displayed an image of Earth from space, an image he said represented unity, because everyone belongs to the same solar system.