Ordinarily, Geoffrey Rojas doesn’t think of himself as a rabble rouser.

As a physicist, he spends his days in a University of Minnesota lab, using high-tech gadgets to analyze how surface materials interact.

But in his spare time, he’s laying the groundwork for a mass rally in St. Paul on Saturday as part of a global event called the March for Science.

So far, 13 rallies are planned across Minnesota, from New Ulm to Grand Marais, in concert with the national march in Washington, D.C., and more than 500 satellite marches around the world.

Rojas, the vice president of the Minnesota march, says the event is a grass-roots effort to protect science from what he calls an unprecedented assault — including threats to slash government funding and attempts to censor research on climate change.

“More and more people are coming to grips with the fact that they need to speak up,” he said. And that includes scientists like him, who normally might prefer to stay in the background.

As the organizers in Grand Rapids, Minn., posted on Facebook: “On April 22, 2017, we walk out of the lab and into the streets.”

Nationally, plans for the March for Science started taking shape shortly after the Jan. 20 Women’s March, which drew millions of protesters against President Donald Trump the day after his inauguration.

But science, say organizers of the April 22 event, isn’t a partisan issue, and they’re trying to keep the discussion above the political fray.

“That’s our overarching goal, to make people aware of what scientists are doing, and make it so our political climate makes informed decisions,” said Alex Steiner, a 26-year-old geologist who is helping organize the march in Duluth. “It’s not really a protest. We’re not against something, we’re for something.”

In New Ulm, organizers are even more cautious. “We’re calling this a science celebration,” said Megan Benage, a 34-year-old state ecologist who is helping to plan the event in her free time.

“New Ulm is a conservative town,” she said. “I wanted to do something that felt inclusive instead of just marching through the streets.” The plan: to gather at scenic Hermann Heights Park for speeches and a group science project to kill invasive buckthorn.

In these tense political times, she joked, “we’re going to take out that rage on some invasive species.”

Benage says she hopes people will see science as a unifying force, rather than a divisive one. “There should be some things, regardless of whatever political values we hold, that we can agree on,” she said. “My hope is that those things are as simple as clean air, clean water and healthy land.”

There’s little doubt, though, that national politics have fueled the movement. Trump has infuriated many scientists, for example, by dismissing climate change as a hoax, and placing what some describe as “gag orders” on government-funded climate research.

“We face a possible future where people not only ignore scientific evidence, but seek to eliminate it entirely,” declares the national website for the March for Science. “Staying silent is a luxury that we can no longer afford.”

Some scientists, though, have warned that the marches, which take place on Earth Day, will only drive a deeper wedge in the political landscape.

“It is a terrible idea,” wrote Robert Young, a coastal geology professor from Western Carolina University, in a Jan. 31 commentary in the New York Times. “A march by scientists, while well intentioned, will serve only to trivialize and politicize the science we care so much about [and] turn scientists into another group caught up in the culture wars.”

A number of organizations have declined to endorse the marches.

The Minnesota Academy of Sciences said it “obviously and enthusiastically” supports science and education, but generally steers clear of “politically motivated movements.”

At the University of Minnesota, the Faculty Senate also balked at an official endorsement, said Colin Campbell, the group’s chairman and an associate professor of pharmacology. While many members support the goals, he said, they thought it was too risky to put the U’s imprimatur on what could turn into a partisan rally. “I’m also concerned that we’re just going to make the people we need to work with more [likely to] dig in their heels.”

Yet dozens of other groups, from corporations to labor unions to physician associations, have signed on as partners. “It’s very important for people to recognize that this isn’t just scientists,” Rojas said. “This isn’t a liberal issue. This is really universal.”

Just how effective will the marches be? That’s still an unknown, the organizers admit.

“I look at rocks, right? So I don’t know how people are going to react to something like this,” said Steiner, the Duluth geologist. But, he says, “I would be surprised if everybody in Washington is capable of ignoring such a movement like this.”

Rojas, meanwhile, says he and his group already have begun meeting with lawmakers on both sides of the aisle.

“Marches don’t really accomplish much if all you do is march and go home,” he said. “We’re not simply marching. We’re putting together a campaign.”

In that sense, he said, “we’re just beginning.”