If screaming at the top of your lungs could change in the world, the 18,000 students at the 2010 We Day in Vancouver Friday could collectively end global warming, AIDS and poverty, all in one shrieking go.

The second annual youth event, held at Rogers Arena, drew some of the most influential and prominent social activists of our time, including former U.S. vice-president Al Gore, civil rights leader and politician Reverend Jesse Jackson and Golden Globe-winning actor and activist Martin Sheen. Coupled with musical acts like Vancouver's own Hedley, the iconic Canadian band Barenaked Ladies and American pop singer Colbie Caillat, it was an all-out scream fest.

In Pictures: We Day in Vancouver

Event organizers and Free the Children founders, brothers Craig and Marc Kielburger, hail the event as the largest secular student event on earth. And the goal? Empowering students to use their individual actions towards a collective good, or, Me to We.  

Their hope is that the students, who volunteered for social projects and did fundraising to attend this year, will leave the event with inspiration and passion to make a difference and the tools to make this change a reality. Many this year will commit to Free the Children's We Schools in Action program, pledging to take one local and one global action within the school year.

"B.C. has to be very proud of its sons and daughters because what they've achieved for those schools is truly remarkable," Craig Kielburger told ctvbc.ca.

Kielburger, an Order of Canada winner, says when he founded Feed the Children at age 12 he was constantly told by his teachers he was too young and too naive to make a difference. Now, 15 years later and with 500 schools built, his aim is to create another generation of student leaders.

"It goes to show that young people -- this generation that has grown up with the Internet and social networking -- that they don't have to wait to grow up to make positive change."

Introduced as Canada's greatest hero, former Paralympic medallist and activist Rick Hansen told the crowd the event has special meaning to him because of his own 15-year-old daughter, who watched the show with her classmates.

"I hope I can talk to her about this, and this will inspire her to change," he said. "I want this to be a legacy for those who come after us."

Hansen talked of overcoming his own obstacles as someone with a disability, citing his own journey to scale the Great Wall of China, a journey that will soon be featured on the big screen in the film Heart of a Dragon.

"There are no walls in life too big to climb over," he said. "None."

Speaking about the vision that inspired him to make his award-winning film on climate change, An Inconvenient Truth, Al Gore told students the key to changing the world is first looking inside your own heart.

"You have heard a challenge to change the world for the better. Never give up. We have to face the danger, come over it and find the hope. We can and will prevail."

Perhaps the most motivating speech of the day came from Reverend Jesse Jackson, whose struggles in the civil rights movement 50 years ago still rang true to the youngsters, who stood and cheered through his speech.

Once jailed as a black man for entering a public library, Jackson told the audience they need to use their positions of privilege to make positive changes in their own lives, whether that means not taking drugs, being energy efficient or reaching out to those less fortunate in other countries.

"Let this day in Vancouver speak to the world. We are the world. We are the hope. We are the joy. We have the power. This world is our world. Keep hope alive. Never surrender. Keep hope alive," Jackson yelled, shaking his fist.

Since last year's We Day, which featured Mia Farrow, the Dalai Lama and Jason Mraz, Canadian students have collectively logged a million hours of community service and raised $1.5 million for local causes and $3 million for global causes.

But with a pep rally more reminiscent of a rock concert than a not-for-profit fundraiser, you have to wonder whether it takes Hollywood star power -- not simply a do-good attitude -- to inspire young people to make a difference.

Jesse Jackson insists using Hollywood to sell the ideals of social justice started in the heyday of the civil rights movement, and cites Sammy Davis Jr. and baseball great Jackie Robinson as stars who inspired him to make a difference when he was a young man.

"We learned more about African justice from Harry Belafonte than our textbooks. There's a role for celebrities. Celebrities have this gift of light, this charisma and they must use this to make things better for all of us, to fight that darkness."

Actor and activist Martin Sheen, best known for his role of the president on the television show the West Wing, says celebrities aren't just inspiring people through speaking, they're also out there in the trenches doing some of the heavy lifting.

"Look at George Clooney and Sean Penn and Bono and Angelina Jolie. It seems the most powerful and most famous are doing the most work. Sean Penn's been in Haiti since Jan. 12 of this year. He built his own camp," he told ctvbc.ca.

"When people are moved, when people connect to another person's brokenness, it doesn't matter if that comes from someone rich or poor, famous or not, it's that connection that's critical."

Organizer Craig Kielburger told ctvbc.ca the role of celebrities in modern social activism goes beyond showing young people that change is possible, it's telling them it's also cool, which may be the biggest challenge of all in getting teenagers involved in social projects.

"Now you have rockers like Hedley talking about going to Africa and the kids in the audience will never forget seeing them. You can't ask for something better for your cause."

Indeed, Hedley front man Jacob Hoggart told ctvbc.ca his life has never been the same since visiting Kenya with Free the Children to build a school.

"It's important and inspiring to see this event grow," he said. "It's rewarding to see work done as a result of the positive change you've inspired. We've been inspired."

Capitalizing on the youth audience, perhaps We Day's biggest successes is its social networking fundraising. For every person who joins the Facebook page and "likes" We Day, $1 will be donated to Free the Children from corporate sponsors. The organization had raised $239,650 of its $1 million goal by press time.

We Day's makes its final Canadian stop in Montreal Nov. 12.

CTV will be airing a special prime time showcase from the inspirational moments of We Day on Friday, Oct. 30.