(CNN) Crowds massed in the US capital and around the world Saturday to support science and evidence-based research -- a protest partly fueled by opposition to President Donald Trump's threats of budget cuts to agencies funding scientists' work.

At the main March for Science , demonstrators gathered at Washington's National Mall to hear speakers laud science as the force moving humanity forward, and rail against policymakers they say are ignoring fact and research in areas including climate change.

Members of the Union for Concerned Scientists with Muppet character Beaker protest in front of The White House in Washington D.C., before heading to the National Mall for the March for Science.

Members of the Union for Concerned Scientists with Muppet character Beaker protest in front of The White House in Washington D.C., before heading to the National Mall for the March for Science.

The March for Science from around the world

Photos: The March for Science from around the world

Scientists and science enthusiasts gather prior to the start of the March for Science in central London.

Scientists and science enthusiasts gather prior to the start of the March for Science in central London.

The March for Science from around the world

Photos: The March for Science from around the world

People stand together in Martin Place, in Sydney, Australia,for the city's international March for Science.

People stand together in Martin Place, in Sydney, Australia,for the city's international March for Science.

The March for Science from around the world

Photos: The March for Science from around the world

Researchers and scientist protest against budget cuts during the March for Science in Madrid, Spain.

Researchers and scientist protest against budget cuts during the March for Science in Madrid, Spain.

The March for Science from around the world

Photos: The March for Science from around the world

A woman in Vienna, Austria,attends the March for Science there. In the US, many marchers have been galvanized by President Donald Trump's proposed cuts to scientific research, including slashing $5.8 billion from the budget of the National Institutes of Health.

A woman in Vienna, Austria,attends the March for Science there. In the US, many marchers have been galvanized by President Donald Trump's proposed cuts to scientific research, including slashing $5.8 billion from the budget of the National Institutes of Health.

The March for Science from around the world

Photos: The March for Science from around the world

Marching in support of scientific research in Berlin, Germany. Many of the marches featured music and speeches.

Marching in support of scientific research in Berlin, Germany. Many of the marches featured music and speeches.

The March for Science from around the world

Photos: The March for Science from around the world

Scientists at the Neumayer Station in Antarctica take part in the March for Science on April, 22.

Scientists at the Neumayer Station in Antarctica take part in the March for Science on April, 22.

The March for Science from around the world

Photos: The March for Science from around the world

Marchers at the Paris March for Science holding signs. In addition to Paris and Berlin, marches were schedued in Rio, Munich, San Francisco, Boston, Oklahoma City and Bratislava, Slovakia.

Marchers at the Paris March for Science holding signs. In addition to Paris and Berlin, marches were schedued in Rio, Munich, San Francisco, Boston, Oklahoma City and Bratislava, Slovakia.

The March for Science from around the world

Photos: The March for Science from around the world

Marchers gathered in front of the Brandenburg Gate in Berlin. Similar marches drew people in more than 500 cities around the world.

Marchers gathered in front of the Brandenburg Gate in Berlin. Similar marches drew people in more than 500 cities around the world.

The March for Science from around the world

Photos: The March for Science from around the world

The March for Science from around the world

Photos: The March for Science from around the world

People show support of scientific research in Berlin, Germany, residents march behind a sign that reads, "There are no alternatives to facts."

People show support of scientific research in Berlin, Germany, residents march behind a sign that reads, "There are no alternatives to facts."

The March for Science from around the world

Photos: The March for Science from around the world

A woman wears a brain beanie during the March for Science in Portland.

A woman wears a brain beanie during the March for Science in Portland.

The March for Science from around the world

Photos: The March for Science from around the world

Thousands participate in the National March for Science in Rome, Italy, on Earth Day.

Thousands participate in the National March for Science in Rome, Italy, on Earth Day.

The March for Science from around the world

Photos: The March for Science from around the world

Thousands of protesters fill Tom McCall Waterfront Park during the March for Science in Portland, Oregon, on Saturday, April 22. Protests were held in cities around the world against President Donald Trump's policies.

Thousands of protesters fill Tom McCall Waterfront Park during the March for Science in Portland, Oregon, on Saturday, April 22. Protests were held in cities around the world against President Donald Trump's policies.

The March for Science from around the world

Photos: The March for Science from around the world

"Today we have a great many lawmakers -- not just here but around the world -- deliberately ignoring and actively suppressing science," one of the event's speakers, TV host and scientist Bill Nye, told a rain-soaked crowd from a stage.

"Their inclination is misguided and in no one's best interest. Our lives are in every way improved by having clean water, reliable electricity and access to electronic global information."

Besides the Washington march, organizers said more than 600 "satellite" marches were taking place globally in a protest timed to coincide with Earth Day

'That guy over there' in the White House

The march, whose beginnings reflect the viral birth of the Women's March on Washington , was billed by its organizers as political but nonpartisan.

One speaker said the administration "tries but fails to silence scientists." Several contrasted rationality and scientific thought to "alternative facts," a phrase that's attracted popular derision since a White House aide uttered it

With the White House in view, protesters held signs with messages such as "In peer review we trust" and "It's the environment, stupid."

The crowd fended off a steady rain with umbrellas and jackets as event co-host Questlove alluded to Trump.

"That guy over there," the musician and producer said from a stage north of the Washington Monument. "It's been frustrating to watch as certain forces in our society try to squelch science or their refusal to believe in it or propose alternative realities and facts -- alternative facts, whatever that (expletive) is."

Demonstrators push forward Saturday in Chicago's March for Science.

Demonstrators marched from the National Mall to Union Square.

Joni Wright, a neurophysiology graduate student at the University of Florida, cited the Trump administration as a reason why she was in the crowd.

"Science is really important, and the current administration is making decisions that are counter to climate change, genetically modified food and vaccinations," Wright, 38, told CNN.

Slow and steady, the scientists make their way in the cold rain #marchforscience pic.twitter.com/gDO7FI9FG3 — Christina Zdanowicz (@stinaz27) April 22, 2017

Thousands of people also marched in Boston, Los Angeles, San Francisco and New York. In Chicago, throngs marched from Grant Park to the Field Museum for a science exposition, CNN affiliate WBBM-TV reported

"Science has always strived to remain nonpolitical, nonpartisan -- and we're still striving for that," Liz Homsey, a co-organizer, told the station. "Every single scientist at this event feels that it is much more pro science than anti anything."

Marches start in Australia

Demonstrators in Australia kicked off the day of protest.

In Sydney, marchers carried banners, many homemade, with slogans such as "Science makes sense," "Science-based policy = stuff that works," and "Climate change is real, clean coal is not."

Another placard displayed the message, "Governments: stop ignoring inconvenient science!"

It wasn't only major cities where scientists and their supporters came out.

Rebecca McElroy, an astrophysics doctoral student at the University of Sydney, tweeted video of a "mini march for science" around the dome of the Anglo-Australian Telescope in New South Wales.

Demonstrators also turned out in New Zealand cities, including Wellington, Auckland, Dunedin and Christchurch.

New Zealand Green Party co-leader James Shaw tweeted a popular chant from the marchers: "What do we want? Evidence-based science! When do we want it? After peer review!"

"What do we want? Evidence-based science! When do we want it? After peer review!" #marchforsciencenz pic.twitter.com/nvMbsBPAKw — James Shaw (@jamespeshaw) April 22, 2017

Marches were also held in Durban and Cape Town, South Africa, and in Tokyo.

'Broader vision'

Crowds converge Saturday in front of the Brandenburg Gate in Berlin support of scientific research.

Scientists and their supporters were urged to turn out in force in London as well as other marches in France, Ireland, Finland, Germany, Portugal and the Netherlands.

David Johnson, 35, a doctoral student in London, said he was marching because he felt climate change was being sidelined by the US administration and that science was being demonized.

PhD student David Johnson feels Climate change is being sidelined and science demonized by the new administration #MarchForScience A post shared by Meera Senthilingam (@meera_senthi) on Apr 22, 2017 at 3:42am PDT

Another London marcher, 24-year-old student Rachel Denley Bowers, said science was important and that budget cuts affected research.

Roger Morris, professor of molecular neurobiology at King's College London, said: "These marches are brilliant -- a spontaneous, global response led by young scientists empowered by social media, keenly aware of the global challenges that need to be addressed if their world is to have a civilized, sustainable future.

"Insular populist politics, which have temporarily triumphed in the US and UK, need to be balanced by the broader vision of youth."

Katherine Mathieson, chief executive of the British Science Association, said she hoped the marches would be a catalyst for people to think about the role science plays in their lives and a chance for scientists to demonstrate the public benefit of their work.

"Protecting the government's investment in science, particularly when that includes funding for public engagement, is incredibly important," she said. "Science is not just for scientists, and I believe that all of us, whether we work in a lab or not, should have a voice on its future."

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Trump's budget proposal, unveiled in March, outlined $54 billion in cuts across government programs to make way for an increase in defense spending.

US scientists said they fear such a plan would have a major impact on research and science-based policy as well as undermine the importance of science in society and limit future innovation.

"It might have been ignited by Trump, but it's not about Trump," march honorary co-chair Lydia Villa-Komaroff ahead of the event. "It's about the importance of science in society and continuing the support for the science community in keeping our edge."