(CNN) - President Barack Obama laid a wreath of white flowers Friday at the Pentagon, where 184 people lost their lives on September 11, 2001, when a hijacked jet smashed into the military icon outside the nation's capital.
"No words can ease the ache of your hearts," Obama told a crowd of relatives and friends standing under umbrellas in a steady rain. The plane, American Airlines Flight 77, struck the Pentagon's west wall. Earlier in the day, the president and first lady Michelle Obama held a
moment of silence outside the White House to mark the eighth anniversary of the al Qaeda attacks that killed 2,752 people.
At the Pentagon, Obama was introduced by Defense Secretary Robert Gates, who spoke of the "great pinnacle of sacrifice" shown that day.
"Eight Septembers have come and gone," Obama said. "Nearly 3,000 days have passed, almost one for each one who has been taken from us."
"We recall the beauty and meaning of their lives," he said. "No passage of time, no dark skies can dull the meaning of that moment" when they died.
"Let us renew our resolve against those who perpetrated this violent act," Obama said.
The nation paused at the moments when the planes crashed into the World Trade Center and the Pentagon - twin symbols of America's financial and military might - and a field near Shanksville, Pennsylvania. Officials believe the target of the latter was either the White House or the Capitol.
There was silence at the site of the former World Trade Center at 8:46 a.m. ET, the time when the first plane struck the North Tower, followed by another at 9:03 a.m. ET, when a jet struck the South Tower.
Family members and friends of the dead read their names in solemn roll calls at each site as bells tolled. In London, England, U.S. Ambassador Louis Susman and his wife, Marjorie,
laid a wreath at the September 11 Memorial Garden in Grosvenor Square.
At ground zero in New York City, a woman whose husband worked on the 94th floor of one of the World Tower buildings recalled that day.
"The pain can still be so sharp. ... I realize how much my life has changed," she said, mentioning that her children have now grown and she has grandchildren.
Her husband left many lessons, she said, including "the courage to be kind."
Just before the first moment of silence, New York City Mayor Michael Bloomberg praised the newly established September 11 National Day of Service and Remembrance, designated by Obama.
"Appropriately, the city of New York has taken up that call. From this day forward we will guard the memories of those who died by rekindling the spirit of service and help keep us strong," Bloomberg said.
At the Web site set up for that day, people were listing their charitable acts.
One man who spoke to the crowd at ground zero remembered his brother, a partner at a law firm located near the Twin Towers and a longtime volunteer firefighter. He rushed toward the South Tower, "toward the inferno," to do what he could to help, the brother said.
"He was there when the tower collapsed." In Shanksville, a ceremony was under way to remember the 40 passengers and crew of United Airlines Flight 93, who died when the hijacked plane went down in a field there. The passengers and crew, aware of the fate of at least some of the other hijacked planes, fought the men who had taken control of their aircraft, leading to its crash.
Colin Powell, former U.S. secretary of state, was to give the keynote address. A $58 million memorial being constructed at the 2,200-acre site is to open on the 10th anniversary of the attack.
On the eighth anniversary of the attacks, the level of concern about terrorism in the United States is roughly half of what it was immediately after September 11 and is down 20 points since the five-year anniversary in 2006, according to a new CNN/Opinion Research Corporation poll. Thirty-four percent of Americans think an act of terrorism is likely in the United States over the next few weeks. More than six in 10 have confidence in the Obama administration's ability to protect the nation.