How do we create peace in the world? And if we can achieve peace, how do we make sure it lasts?
Today is the United Nations International Day of Peace, and this year's theme is "Sustainable Peace for a Sustainable Future."
At this year's Rio+20 Summit, world leaders met with local authorities, representatives of civil society and the private sector to discuss sustainable development as a path to sustainable peace.
What does that mean? Well, the theory is that many of the most brutal conflicts around the world are fuelled by fighting over valuable natural resources like diamonds, gold, oil, timber and water.
If we can figure out a better way of managing and sharing natural resources, we can help reduce conflict and restore the economy in post-conflict countries.
And that's not just a job for the world's governments and corporations. Today, the UN is asking people around the world to "think about how, individually, they can contribute to ensuring that natural resources are managed in a sustainable manner."
Here's a statement from UN Secretary General Ban Ki-moon:
Rallies are also taking place in various cities. Ghent, Belgium held a peace event where they set a new record by unveiling the world's largest peace flag.
It's a rainbow flag measuring 164 feet long. That's a lot of peace. Check it out below:
A peace rally in Yangon, capital of Burma, featured hundreds of people marching in the streets, even though authorities refused to grant permits for the event.
The rally was organized by 19 civil society groups, including the Kachin, who are engaged in combat with the government in the country's north.
Marchers sang songs, listened to speeches, observed five minutes of silence and called on the president and the parliament to end civil war in the country.
In Lebanon, meanwhile, UN Interim Forces (UNIFIL) held a ceremony at their headquarters in the southern city of Naqoura. Soldiers laid wreaths in memory of the peacekeepers who have died in the line of duty in southern Lebanon.
Speaking at the event, Maj. Gen. Paolo Serra (UNIFIL Head of Mission in southern Lebanon), echoed the theme of the day: "we cannot possibly think about building a sustainable future if there is no sustainable peace, as armed conflicts attack the very pillars of sustainable development."
So while the world marks a day of peace, this is a perfect opportunity to list some of the great songs that have been written on the subject.
Here are ten we like. They highlight the many different visions of peace, from the warmth of being with someone you love ('Home') to the questionable nature of some promises of peace ('The Waiting Song'). We left out maybe the most obvious choice - 'Give Peace A Chance' by the Plastic Ono Band - but you know that one already, right?
What would you add to this list?
Elvis Costello - '(What's So Funny About) Peace, Love And Understanding'
Sam Cooke - 'A Change Is Gonna Come'
Melanie Safka - 'Peace Will Come'
Bob Marley - 'One Love'
Dixie Chicks - 'I Hope'
Aretha Franklin - 'Border Song (Holy Moses)'
Edward Sharpe & The Magnetic Zeros - 'Home'
Ani DiFranco - 'The Waiting Song'
Marvin Gaye - 'What's Going On/What's Happening Brother'
Tina Turner - 'Sarvesham Svastir Bhavatu'
Tina Turner's 'Sarvesham Svastir Bhavatu' from the 2011 album 'Children Beyond.' The mantra of this song means "May well-being, peace, wholeness and tranquility, happiness and prosperity be achieved by all".
The album was a follow-up to the 2009 album 'Beyond', which was Turner's first involvement in a spiritual project. The albums have raised hundreds of thousands of dollars for several charity projects.
For 'Children Beyond', a wider range of prayers and songs from different religions was chosen. It includes songs from Christianity, Islam, Judaism, Buddhism, Hinduism and Sikhism.
The goal is to get children and adults to learn different religious traditions, to help promote respect and tolerance. The album contains lyrics for each song, so it is easy to sing along. And the message of each song is explained.
There is also a 'Children Beyond' documentary directed by Xaver Walser.