Twin towers of light beam from 'Ground Zero'

Two shafts of light near the World Trade Center site are visible from New Jersey.

NEW YORK (CNN) -- Where six months ago smoke and ashes darkened the daytime sky over New York, two shafts of bright light pierced the night sky Monday in memory of all those who lost their lives in the September 11 attacks.

The lighting of the "Tribute in Light" was one of many ceremonies held across the United States. The twin towers of light are meant to represent the fallen twin towers of the World Trade Center.

Located about a block from "Ground Zero," the banks of 44 searchlights will remain lit from dusk until 11 p.m. for 32 days and under certain conditions might be seen for up to 25 miles away. (Graphic)

Recalling the horror, heroism and haunting images of September 11, President Bush earlier implored governments across the globe to join the war against "terrorist parasites."

"Every civilized nation has a part in this struggle because every civilized nation has a stake in its outcome," Bush said during a White House ceremony marking six months since the attacks on the Pentagon and the World Trade Center. (Full story)

"There can be no peace in the world where differences and grievances become an excuse to target the innocent for murder."

More than 1,000 people, including world leaders, members of Congress, top administration officials and relatives of September 11 victims, joined the president on the White House's south lawn.

MORE STORIES  •  America remembers  •  The day the world changed  •  Unanswered questions remain  •  Hope in Kabul  •  Bush: World stirred to action  •  Giuliani looks back  EXTRA INFORMATION  •  In-Depth: September 11: A Memorial  •  In-Depth: War Against Terror  •  In-Depth: Day of Terror  •  People in the News: WTC survivors  •  TIME.com: Can we stop the next attack?  INTERACTIVES  •  Gallery: Images of September 11  •  Gallery: Remembering 9/11  •  Quotes: 9/11 remembered  •  Lighting the Towers  •  Maps and Interactives Index

"September 11 was not the beginning of global terror, but it was the beginning of the world's concerted response," Bush said.

"History will know that day not only as a day of tragedy but as a day of decision, when the civilized world was stirred to anger and to action. And the terrorists will remember September 11 as the day their reckoning began."

Later in the Oval Office, the president unveiled a new commemorative stamp. It features the famous picture of three firefighters raising an American flag in the rubble of the World Trade Center. Bush said the stamp will sell for 45 cents, of which 8 cents will go to victims' charities. (Full Story)

'Damaged, not destroyed'

The nationwide memorials began in New York at 8:46 a.m. ET, the same time the first hijacked plane crashed into the north tower of the World Trade Center.

New York Mayor Michael Bloomberg presided over the rededication Monday of a 45,000-pound sculpture called "The Sphere" in Manhattan's Battery Park.

"The sphere that rests behind me in many ways symbolizes New York," Bloomberg said of Fritz Koenig's steel-and-bronze sculpture that once stood in the fountain of the trade center plaza.

"For 30 years, it stood in the World Trade Center as a symbol for peace. On September 11, it was damaged, not destroyed."

In the Bronx, the New York Police Department paid tribute Monday to the 23 officers killed in the World Trade Center collapse.

Officers at the 40th Precinct stood at attention as names of their fallen comrades were read, then bowed their heads for a moment of silence at 8:46 a.m.

New York officials Monday rededicate "The Sphere," a sculpture that once stood in the World Trade Center plaza's fountain.

"This and each anniversary should not be remembered for the evil act of violence, but for the goodness of these officers and their tremendous spirit that they ran without hesitation in harm's way and laid down their lives for the sake of others," said Capt. Robert Boyce.

Later in the morning, Defense Secretary Donald Rumsfeld presided over a ceremony at the Pentagon, which was struck by one of the four hijacked planes.

"We have the opportunity to tear terrorism out by the roots," Rumsfeld said. "By our campaign against terrorism, we are preventing acts of terror that may well have been planned before September 11 and we would have never known until it was too late. The memory of September 11 reminds us all of the need to remain vigilant."

'They died so we could be free'

In Shanksville, Pennsylvania, a crowd gathered at the United Methodist Church for a multi-denominational service honoring the 40 victims of United Airlines Flight 93. The crew members and passengers were remembered as heroes who gave their lives to prevent an even greater tragedy.

Several passengers with phones on board the plane contacted family members and learned about the attacks on the World Trade Center and the Pentagon. They decided to try to retake the plane.

Authorities said the plane crashed into a rural Pennsylvania field possibly as passengers struggled with the hijackers.

During another ceremony Monday at the nearby crash site, red, white and blue paper angels were placed at the edge of the field and a children's choir performed.

Former Soviet leader Mikhail Gorbachev brings a wreath to the World Trade Center site.

Earlier Monday, former New York Mayor Rudy Giuliani, whose response to the terrorist attacks made him a national hero to many Americans, said he thinks about September 11 every day.

"I always think about, and did from the very beginning, the tremendous courage of all of those people -- the rescue workers, just the ordinary citizens," he said on CNN's "American Morning."

"They conducted themselves with such bravery that they lifted all of us and set a standard that we had to reach since we were the fortunate ones who got to live. They died so we could be free." (Transcript)

Also Monday, former Soviet President Mikhail Gorbachev visited Ground Zero for the first time and laid a wreath in memory of the September 11 victims.

Gorbachev praised the U.S. government in the aftermath of the attacks and called Bush a "mature" statesman and politician. He expressed some displeasure, however, with Bush's "axis of evil" comments directed at Iran, Iraq and North Korea.