By Eliott C. McLaughlin, CNN

(CNN) -- The George Floyd police brutality protests are different -- bigger, fiercer, more sustained -- than demonstrations prior.

America rises up regularly. It's in the DNA of a country founded on dissent. Millions have forged their anger into action, from the tax revolts of the nation's earliest days, to the labor, housing and busing protests that helped shape the civil rights movement. The Me Too-fueled women's marches of 2017 and 2018 and the March for Our Lives demonstration, born of the Parkland school shooting, each drew a seven-figure attendance.

Before Floyd's killing, the highest estimate for any American protest -- the 2017 Women's March -- was 4.6 million. Polls indicate that, as of mid-June, as many as 21 million adults had attended a Black Lives Matter or police brutality protest. They continue today, more than 10 weeks after a Minneapolis policeman knelt on Floyd's neck till the life left his body.

It's not just people and protests, though. It's also policies and points of view.

"I never would've imagined I would see a day when the Washington football team would change its name," said Tyran Steward, assistant history professor at Williams College, noting demands once deemed nonstarters are now on the table.

Police accountability bills have been introduced in Congress. Americans are discussing what defunding law enforcement actually means. Corporations are recognizing Juneteenth. Mississippi is changing its flag. Tributes to Confederates and others who espoused hate are falling. Athletes kneeling during the National Anthem aren't seen as so un-American anymore.

Why now? People demanded change after Michael Brown in Ferguson, Missouri, after Freddie Gray in Baltimore, after Walter Scott and the Mother Emanuel massacre in South Carolina.

Publisher and former St. Louis Alderman Antonio French, a staple of 2014's Ferguson protests, oversees coverage of the ongoing unrest in his city. Nationally, there are "daily reminders of why they need to be out in the streets protesting and demanding change," and he's proud they've been overwhelmingly peaceful, he said, but don't take it for granted.

"What started in 2014 in the streets of Ferguson has just spread across the country," he said. "Having this kind of turmoil with that many unemployed young people, with this kind of national leadership that has zero empathy ... this is the makings of real conflict, and I think we should be really concerned."

The reaction to Floyd's killing has indeed been different, experts say, owing to the graphic nature of the video that captured it, the nation's calls for justice in other killings, a pandemic disrupting normality, widespread unemployment, a phenomenon known as "vicarious trauma" and White people joining people of color in the streets.

'Interest convergence'

Covid-19 plays a dual role in the protests' momentum, scholars say. The pandemic has kept people home, with more time to consume news of Floyd's fatal arrest and the ensuing unrest. The pandemic has also robbed Americans of popular escapes, such as bars, movie theaters and vacations.

Coronavirus also exposed the interconnectedness of human vulnerability, which provides a new lens through which Whites can view Floyd's killing, said Emory University philosophy professor George Yancy.

"It has unveiled the way in which we are all interrelated and haptic. There's a way all of our bodies are touching through Covid," he said.

It's not a new concept. Poet John Donne wrote in 1624, "Any man's death diminishes me because I am involved in mankind, and therefore never send to know for whom the bell tolls; it tolls for thee." The Rev. Martin Luther King Jr. said man is "tied in a single garment of destiny," and what affects one affects all.

Yancy and Steward also cited legal scholar Derrick Bell, whose theory of "interest convergence" posited African American advances are reliant on the dominant culture.

"The only way in which Black people will have success or the same level of equity is their interests have to converge with White interests," Yancy said. "It's not genuine equity. It conforms to the interests of White people."

Some of history's most monumental advances for African Americans didn't emerge from a sense of justice or what's right, the scholars say, but because of White leaders' ulterior motives.

The government didn't file its amicus brief in Brown v. Board of Education because desegregating schools meant better education for Blacks. Instead, discrimination jeopardized America's "moral leadership" and its commitment to democracy, while furnishing "grist for the Communist propaganda mills," according to the brief.

Likewise, President Franklin Roosevelt didn't integrate the defense industry because it suddenly became clear Blacks and Whites were equally qualified. He did it to stave off a massive march on Washington as a nation on the brink of World War II clawed its way out of the Great Depression.

"You cannot as a country have the issue of racism sort of percolating or festering at home while trying to project yourself as this paragon of virtue when it comes to democracy abroad," Steward said. "America could not look weak in that particular moment. America could not look undemocratic."

The video of George Floyd

Duchess Harris, an American studies professor at Macalester College in St. Paul, Minnesota, echoes Yancy's thoughts on vulnerability -- especially White people's vulnerability and "their relationship to illness and not being able to live life on their own terms."

It's just one in a complex collection of variables that explain the protests' duration, she said.

Early Covid-19 quarantines meant people were home with ample time to watch the Floyd video, which rapidly spread across social media and TV. It was also the eve of summer, the season of protests, she said, noting that Spike Lee's 1989 "Do the Right Thing," about racial tensions and a police violence protest in Brooklyn, opens on a stifling summer day.

The financial turmoil from the pandemic hit young people hard; they're the backbone of social movements, she explained. Summer is a time for the youth to vacation or find a summer job. Neither was an option, she said, explaining she knows a summa cum laude graduate who took a nanny job because she had no prospects. This gave people more time to take to the streets, she said.

The economic conditions also helped many empathize with Floyd, who had just lost his job and was accused of trying to pass a fake $20 bill at a grocery store, the professor said.

"Even if we acquiesce there was a fake $20 bill," Harris said, "he's dead because of that. ... Why was he using fake money? That's structural inequality."

The locale was important, too. Minnesotans have weathered dozens of police killings in recent years, including the high-profile deaths of Philando Castile and Jamar Clark, she said. Like video of Floyd's killing, Castile's went viral, but it begins after the officer shot him five times. Castile is bleeding out as his girlfriend chronicles what happened.

Floyd's death drags out over 10 minutes of footage as Floyd pleads for his life, which is snuffed out as three officers look on without physically intervening. Going back to the 1991 Rodney King beating, Americans have watched police violence, but bits are often missing or extenuating circumstances allow them to explain it away.

Not this time, scholars say. The depiction of Floyd's death was too timely, vivid and undebatable to ignore.

"The visual trauma which people were exposed to was a necessary condition to what we're seeing," Yancy said.

'I can't breathe'

White and Black interests converge today for many reasons. It can't be undersold that the delayed reaction to the Ahmaud Arbery and Breonna Taylor killings dovetailed with the anger over Floyd's death, about two weeks before an Atlanta policeman killed Rayshard Brooks. The confluence of the four killings serves to underline problems with racial and police violence, experts say.

Video of Floyd's death, however, was a clarion call, Yancy said. Viewers watched, uninterrupted, as an officer kneels on the prone, handcuffed 46-year-old for almost eight minutes as he cries, "I can't breathe" and calls out for his mother before his ability to articulate is sapped. Still, the officer continues to kneel. Bystanders protest, but they're helpless.

"I can't breathe" evokes Eric Garner's 2014 death at the hands of New York police, but it's also an existential cry, a concept that "goes back to the Middle Passage, to the hulls of those slave ships," Yancy said.

"The very breath of this Black man was being taken from his body," he said of the video. "It pricked the conscience of White people."

While the Floyd protests demonstrate a heretofore unseen endurance over a single event, Steward said protests' durations have been growing since Ferguson, where demonstrators took to the street for weeks after Michael Brown's shooting, when a grand jury declined to indict Officer Darren Wilson and again on the anniversary of Brown's death.

"Ferguson is not to be downplayed as a harbinger of this moment," the history professor said, adding that every major racial protest, going back to the anti-lynching and Red Summer demonstrations of the early 1900s, was a phase leading to today.

What's different here, Steward said, is the myriad White faces. Past police brutality protests generally have been African American affairs. With the coronavirus exposing White people to uncertainty about their health and financial well-being -- concerns more pronounced in Black communities due to systemic inequality -- "you have individuals who are facing challenges they see as part and parcel of the same system," Steward said. Others simply may be more willing to coalesce with protesters.

Credit has to go to the Black Lives Matter movement, he said, which keeps the spotlight on White supremacy, police violence "and its White supremacist tentacles," Black-on-Black crime and violence targeting LGBTQ communities.

Where BLM was for years unutterable among swaths of the White population, today protests erupt not only in cities with vibrant Black communities (Detroit, Baltimore, Atlanta, et al) but also the largely White enclaves of Prairie Village, Kansas, Northfield, Minnesota, Pullman, Washington, and notably, Portland, Oregon.

Steward's seen them in Williamstown, Massachusetts, where he teaches and where four out of five residents are White. Pew polls from 2016 and earlier this summer indicate BLM support has jumped from 43% to 67% in four years. Support among Whites has spiked 20 percentage points in that time, to 60%.

He also sees more BLM signs popping up in White people's yards, he said: "It's like grass nowadays. It's ubiquitous, right? Some of it is performative, but more people are comfortable saying it because they're more awakened to the disparities Blacks face in the country."

Steward and Yancy also point to the movement's internationality. Steward compares it to the global outcry that upended apartheid in South Africa. In recent months, Australia, France, New Zealand, Sweden, the United Kingdom and other predominantly White nations have staged their own BLM protests in solidarity.

"They all felt the sting of White supremacy within their own historical contexts," Yancy said.

Vicarious trauma

The nature of trauma is another factor in how the world reacts to Floyd's death, said Dr. Cheryl Singleton Al-Mateen, a professor of psychiatry and pediatrics at Virginia Commonwealth University.

"Watching something horrifying happen to someone else could be a criteria for (post-traumatic stress disorder)," she said. "We all had an experience criterion that could result in the development of PTSD. It happened to the entire country -- not just the country but the world because other countries reacted for us, too."

It's called vicarious trauma, and it takes many forms. Native Americans, Jewish people, African Americans, Japanese Americans and other minorities may experience historical trauma based on horrors exacted on others sharing their identity -- something Al-Mateen says amounts to a "cumulative wounding across generations even if there's no direct experience."

Al-Mateen was horrified by the Floyd video, she said, but her dismay was compounded when she joined a White Coats for Black Lives demonstration in which health care workers knelt for the eight minutes and 46 seconds the officer reportedly knelt on Floyd (the report was later revised to seven minutes, 46 seconds).

"It hits you. It hits you very hard. This man was kneeling on his neck for this long," she said.

Where Al-Mateen stops short of saying that watching the Floyd video caused varying degrees of PTSD among Americans, Janet Helms, a Boston College professor of counseling and psychology, says that's exactly what happened.

"The trauma is triggered by seeing the video over and over again," said Helms, who is also the director of the school's Institute for the Study and Promotion of Race and Culture.

Black people may not know anyone who was lynched or enslaved, but they know their parents' and grandparents' stories of life under Jim Crow, and they share their histories with slaves.

"When you see someone being treated in the way you've heard about," she explained, "you experience the trauma in the same way."

Her center provides a toolkit for those experiencing racial trauma. In it, Helms and her co-authors wrote, "Racial trauma is a cumulative experience, where every personal or vicarious encounter with racism contributes to a more insidious, chronic stress."

Whites, too, experienced trauma, and Floyd's killing helped humanize Black people in the minds of Whites, especially White women, Helms said.

"George Floyd turned Black men into human beings for White people, and he did that by calling out for his mother," she said. "Covid made White people sit and look at the murder of George Floyd. They couldn't get away from it, especially White women. ... They became aware they were allowing this to happen."

Most important to the cause, Helms said, is the broad support of White men, who have joined the recent protests as well. They are the gatekeepers to change. It must be remembered, she said, "White men wrote a whole Constitution to protect the privilege of White, heterosexual men."

Maintaining the momentum

Yancy is pessimistic about the ultimate outcome. Paraphrasing Malcolm X, he said you can't plunge a knife 9 inches into Black people's back, pull it out 6 inches and call it progress.

"There's 3 inches to go, and there's a wound," the professor said, explaining that leaving the wound open intensifies vulnerability. "We have to open up and allow ourselves to be wounded by the violence. It has to be registered as angst or deep pain."

Despite his skepticism, he said, "I would have to grant something bigger is happening here."

Past protests didn't last as long, Helms said, because White people felt "those events had nothing to do with them," but the Floyd video and uprising viscerally exposed Whites to the trauma Blacks have always experienced.

"To keep the movement going, White people have to stay in touch with that feeling," said Helms, who authored "A Race Is a Nice Thing to Have: A Guide to Being a White Person or Understanding the White Persons in Your Life."

The movement can sustain steam "as long as White people are involved in anti-racism and re-learn to think of themselves as moral humans and see others as human beings," she said.

Steward, the history professor, said White people must demand real change, rather than perpetuating an archaic system of race management that favors the symbolic and performative. Policies must have teeth. School integration doesn't work without busing, he said, and body-cam policies are worthless if police aren't prosecuted.

"You have to see more than a statue come down. You have to see more than a policy," he said. "There's a number of people willing to say, 'I agree.' Now, they have to go beyond a yard sign, go beyond rhetoric."

He, too, quotes MLK -- who said, "The arc of the moral universe is long, but it bends toward justice" -- and he emphasizes America has a considerable journey.

"The arc of history is slouching toward justice," Steward said. "It certainly is not there."