TED.com

What should a community do with its unused land? Plant food, of course. With energy and humor, Pam Warhurst tells at the TEDSalon the story of how she and a growing team of volunteers came together to turn plots of unused land into communal vegetable gardens, and to change the narrative of food in their community.

Afghan-American artist Aman Mojadidi calls himself “Afghan by blood, redneck by the grace of god.” Playing off his two identities, the TED Fellow's bold, funny, thought-provoking artwork explores jihad, gangsterism, consumers and corruption in modern Afghanistan.

Parkinson’s disease affects 6.3 million people worldwide, causing weakness and tremors, but there's no objective way to detect it early on. Yet. Applied mathematician and TED Fellow Max Little is testing a simple, cheap tool that in trials is able to detect Parkinson's with 99 percent accuracy -- in a 30-second phone call.

Most people instinctively avoid conflict, but as Margaret Heffernan shows us, good disagreement is central to progress. She illustrates (sometimes counterintuitively) how the best partners aren’t echo chambers -- and how great research teams, relationships and businesses allow people to deeply disagree.

How do you deal with a bully without becoming a thug? In this wise and soulful talk, peace activist Scilla Elworthy maps out the skills we need -- as nations and individuals -- to fight extreme force without using force in return. To answer the question of why and how non-violence works, she evokes historical heroes -- Aung San Suu Kyi, Mahatma Gandhi, Nelson Mandela -- and the personal philosophies that powered their peaceful protests. (Filmed at TEDxExeter.)

Mark Applebaum writes music that breaks the rules in fantastic ways, composing a concerto for a florist and crafting a musical instrument from junk and found objects. This quirky talk might just inspire you to shake up the “rules” of your own creative work. (Filmed at TEDxStanford.)

In the wake of the 2011 Japanese earthquake and tsunami, mixed into the wreckage were lost and damaged photos of families and loved ones. Photo retoucher Becci Manson, together with local volunteers and a global group of colleagues she recruited online, helped clean and fix them, restoring those memories to their owners.

Daphne Koller is enticing top universities to put their most intriguing courses online for free -- not just as a service, but as a way to research how people learn. With Coursera (cofounded by Andrew Ng), each keystroke, quiz, peer-to-peer discussion and self-graded assignment builds an unprecedented pool of data on how knowledge is processed.

A whirlwind of energy and ideas, Stephen Ritz is a teacher in New York's tough South Bronx, where he and his kids grow lush gardens for food, greenery -- and jobs. Just try to keep up with this New York treasure as he spins through the many, many ways there are to grow hope in a neighborhood many have written off, or in your own. (Filmed at TEDxManhattan.)

Michael Anti (aka Jing Zhao) has been blogging from China for 12 years. Despite the control the central government has over the Internet -- "All the servers are in Beijing" -- he says that hundreds of millions of microbloggers are in fact creating the first national public sphere in the country's history, and shifting the balance of power in unexpected ways.

Bees have been rapidly and mysteriously disappearing from rural areas, with grave implications for agriculture. But bees seem to flourish in urban environments -- and cities need their help, too. Noah Wilson-Rich suggests that urban beekeeping might play a role in revitalizing both a city and a species. (Filmed at TEDxBoston.)

Inspired by cell division, Michael Hansmeyer writes algorithms that design outrageously fascinating shapes and forms with millions of facets. No person could draft them by hand, but they're buildable -- and they could revolutionize the way we think of architectural form.

Ramesh Raskar presents femto-photography, a new type of imaging so fast it visualizes the world one trillion frames per second, so detailed it shows light itself in motion. This technology may someday be used to build cameras that can look “around” corners or see inside the body without X-rays.

When Tracy Chevalier looks at paintings, she imagines the stories behind them: How did the painter meet his model? What would explain that look in her eye? Why is that man … blushing? She shares three stories inspired by portraits, including the one that led to her best-selling novel "Girl With a Pearl Earring."

What kind of data is your cell phone company collecting? Malte Spitz wasn’t too worried when he asked his operator in Germany to share information stored about him. Multiple unanswered requests and a lawsuit later, Spitz received 35,830 lines of code -- a detailed, nearly minute-by-minute account of half a year of his life.

Imagine global security driven by collaboration -- among agencies, government, the private sector and the public. That's not just the distant hope of open-source fans, it's the vision of James Stavridis, a highly accomplished Navy Admiral. Stavridis shares vivid moments from recent military history to explain why security of the future should be built with bridges rather than walls.

Two-thirds of the world may not have access to the latest smartphone, but local electronic shops are adept at fixing older tech using low-cost parts. Vinay Venkatraman explains his work in "technology crafts," through which a mobile phone, a lunchbox and a flashlight can become a digital projector for a village school, or an alarm clock and a mouse can be melded into a medical device for local triage.

Computer science began in the '30s ... the 1830s. John Graham-Cumming tells the story of Charles Babbage's mechanical, steam-powered "analytical engine" and how Ada Lovelace, mathematician and daughter of Lord Byron, saw beyond its simple computational abilities to imagine the future of computers. (Filmed at TEDxImperialCollege.)

Artist Neil Harbisson was born completely color blind, but these days a device attached to his head turns color into audible frequencies. Instead of seeing a world in grayscale, Harbisson can hear a symphony of color -- and yes, even listen to faces and paintings.

Matt Mills and Tamara Roukaerts demonstrate Aurasma, a new augmented reality tool that can seamlessly animate the world as seen through a smartphone. Going beyond previous augmented reality, their "auras" can do everything from making a painting talk to overlaying live news onto a printed newspaper.