A few people chanted “Science is real. It’s not how you feel,” beating a tempo on buckets, but mostly the mass of people marched through Washington quietly Saturday, letting their homemade signs show their support for empirical research.

“Let’s make America SMART again,” one sign read at the second annual March for Science, while another proclaimed: “I’d rather be finishing my dissertation!”

On the same street earlier in the day, people cheered and clapped and stretched on tiptoes along the route of the National Cherry Blossom Festival Parade, holding phones over the crowd to snap photos of motorcycles rumbling along Constitution Avenue. Toddlers on parents’ shoulders pointed as white, brown and black horses clip-clopped by.

It was a most Washington sort of day, full of sunshine and cherry blossoms and costumes and music, the streets teeming with people celebrating, protesting and enjoying the spectacles. By mid­afternoon, the clamor of snare drums on Pennsylvania Avenue signaled another march, this one honoring the emancipation of slaves in Washington. A woman wearing a “Black by popular demand” shirt watched cheerleaders shaking pompoms, and a man held a sign demanding, “STATEHOOD NOW!!”

People waved from a float, and three people held ropes as a giant balloon with a portrait of Frederick Douglass bobbed in the wind. Another balloon had a somber black-and-white portrait of the Rev. Martin Luther King Jr. A giant image of Rosa Parks followed, then one of Marion Barry Jr. — “Mayor for Life.” Dancers twirled in black fringed skirts and hot-pink sequins.

Bubbles floated on the wind as almost-4-year-old Mila Conley pumped her bubble maker. Her mother, Melinda Conley, had come with her daughter and parents from Germantown to watch the Cherry Blossom parade, and stayed to see this one, too.

With so many events in such a small space, they all melded together a bit, with scientists watching parades, and tourists happening upon scholarly discussions about fossils.

Binyam Darge came with his wife and mother from Maryland to see the Cherry Blossom parade and stumbled upon the Emancipation Day march. “I thought today was the March for Science?” he asked.

Others were a little confused by all the events, too, but happy to find a shady spot to sit and let it all unfold, like Dionne Singh, a District resident from Guyana.

Deborah Rosell, who lives in the Edgewood neighborhood of Washington, watched from a folding chair with friends. Her grandsons were in the emancipation parade with their baseball team.

She said she had only recently learned that slaves were freed in the District before they were emancipated nationally. “I was surprised to learn that.”

Four generations of Rosell’s family before her grew up in Washington, and she remembers watching parades from the steps of the National Archives as a child.

Earlier in the day, Amy Gonzalez, a scientist, had come for the March for Science. “I want to make sure that science is recognized publicly in this country,” she said, “and for my children to recognize that, as well.”

Her son Tomas Gonzalez, who’s 8, showed the signs he had drawn. They had been printed with the prompt, “I fight climate change for,” and he wrote in “animals” on one, and “the sea” on another, drawing a whale and jellyfish on it. His father, Francisco Gonzalez, asked him, “The oceans become more acidic with more CO2 in the atmosphere — what does that do to the animals?”

“Kills,” Tomas answered, then pointed with a shout — an enormous float was bobbing past in the Cherry Blossom parade.

Teenagers whizzed by on unicycles, waving to the crowd. A band rattled and thundered past, silver tubas shining in the sun. People slapped hands with performing skateboarders. More than 30 people stood in line for ice cream cones.

A woman climbed onto a wooden barricade to snap photos of people tottering by on stilts.

Behind her, Chloe Ngo took photos of her daughter under the cherry blossoms, the shutter of her camera clicking steadily as 5-year-old Celine Ngo smiled in a red kimono.

A woman walked by with a sign with an arrow pointing toward a drawing of the Earth and the words “I’m with her.”

June Song, a scientist, sat in the grass with her 5-year-old daughter, Mila Song, who was squeezing the last drops of chocolate milk from her box.

“The deniers — it’s hard to understand where they’re coming from,” she said, and why they don’t believe the data about climate change. Scientists are so skeptical and spend so long on research before drawing any conclusion, she said.

Mila had drawn the Earth on a pink sign, and written: “Do not throw trash in the ground and do not kill animals and do not kill people and do not kill chickens and don’t eat them. Do not ruin our Earth it’s everybody’s home!! Respect mother nature.”

People crowded under cherry trees, seeking patches of shade, with signs: “Positively charged and ready to react,” “E.O. Wilson for president,” and “I march because science saves soldiers’ lives” (alongside: “I march because science makes beer better.”)

They wore science-themed shirts: “Science is not a conspiracy,” and, “Forget princess — I want to be an astrophysicist,” “Stand back — I’m going to try Science,” and some with smiling cartoon test tubes and beakers. They cheered when a singer said you need chemistry to flirt.

Mary Woolley of Research­America, a nonprofit promoting research, said that while a majority of Americans when surveyed indicate support for science, only 16 percent can name a living scientist, and only one-third can name a place where medical and health research is done. Events like this — and continued engagement by scientists after it’s over — are needed to remind the public and policymakers of how essential it is to fund and support science, she said.

Part of the March for Science’s evolution over the past year has included transforming into a nonprofit with a broader mission: to support science and research policy through campaigns, outreach and marches.

And so they marched, with their signs riffing on the periodic table of elements, their beaker T-shirts and one inflatable T-Rex costume, past the cherry trees. Just to the north in the heart of Washington, the Emancipation Day parade had ended. Both performers and onlookers — and surely some scientists — crowded in close for an outside concert, smiling and dancing with their arms in the air.

Marissa J. Lang contributed to this report.