The Vikings were among the fiercest warriors of all time. Yet only a select few carried the ultimate weapon of their era: the feared Ulfberht sword. Fashioned using a process that would remain unknown to the Vikings’ rivals for centuries, the Ulfberht was a revolutionary high-tech tool as well as a work of art. Considered one of the greatest swords ever made, it remains a fearsome weapon more than a millennium after it last saw battle. But how did Viking sword makers design and build the Ulfberht, and what was its role in history? Now, NOVA uses cutting edge science and old-fashioned detective work to reconstruct the Ulfberht and finally unravel the "Secrets of the Viking Sword."

The episode was rated 7.75 from 16 votes.

Was Hurricane Sandy a freak combination of weather systems? Or are hurricanes increasing in intensity due to a warming climate? How did this perfect storm make search and rescue so dangerous? "Inside the Megastorm" takes viewers moment by moment through Hurricane Sandy, its impacts, and the future of storm protection. Through first person accounts from those who survived, and from experts and scientists, "Inside the Megastorm" gives scientific context to a new breed of storms.

The episode was rated 7.78 from 18 votes.

In 1943 a squadron of Lancaster bombers staged one of the most audacious raids in military history: destroying two gigantic dams in Germany’s industrial heartland and cutting the water supply to arms factories. Their secret weapon? A revolutionary bouncing bomb invented by British engineer Barnes Wallis. Wallis and the pilots of 617 Squadron—a lively mix of Britons, Australians, Americans, and Canadians—were hailed as heroes who dealt a mighty blow to the German war machine. Now, NOVA recreates the extreme engineering challenges faced by Wallis and the pilots. A crack team of experts, including dam engineers, explosives specialists, mechanics, and aircrew, steps into the shoes of the "dambusters" and attempts to overcome each of the obstacles the original team faced. They must adapt a vintage World War II DC-4 to carry a bomb the size of an oil drum, train to drop it from a dangerously low altitude in pitch darkness, and get it to bounce over obstacles and onto the target, a scale model the German dam struck by the original dambusters. Can they succeed in destroying the dam and unraveling the mysteries of the one-of-a-kind bouncing bomb?

The episode was rated 7.87 from 15 votes.

There is a startling gap between the glamorous television world of “CSI” and the gritty reality of the forensic crime lab. With few established scientific standards, no central oversight, and poor regulation of examiners, forensics in the U.S. is in a state of crisis. In "Forensics on Trial", NOVA investigates how modern forensics, including the analysis of fingerprints, bite marks, ballistics, hair, and tool marks, can send innocent men and women to prison—and sometimes even to death row. Shockingly, of more than 250 inmates exonerated by DNA testing over the last decade, more than 50 percent of the wrongful convictions stemmed from invalid or improperly handled forensic science. With the help of vivid recreations of actual trials and cases, NOVA will investigate today’s shaky state of crime science as well as cutting-edge solutions that could help investigators put the real criminals behind bars.

The episode was rated 7.89 from 18 votes.

A remote, bleak speck of rock in the middle of the Pacific, Easter Island, or Rapa Nui, has mystified the world ever since the first Europeans arrived in 1722. How and why did the ancient islanders build and move nearly 900 giant statues or moai, weighing up to 86 tons? And how did they transform a presumed paradise into a treeless wasteland, bringing ruin upon their island and themselves? NOVA explores controversial recent claims that challenge decades of previous thinking about the islanders, who have been accused of everything from ecocide to cannibalism. Among the radical new theories is that the islanders used ropes to "walk" the statues upright, like moving a fridge. With the help of an accurate 15-ton replica statue, a NOVA team sets out to test this high-risk, seemingly unlikely theory—serving up plenty of action and surprises in this fresh investigation of one of the ancient world's most intriguing enigmas.

The episode was rated 7.90 from 10 votes.

Twenty million passengers embark on cruises each year, vacationing in deluxe "floating cities" that offer everything from swimming pools to shopping malls to ice skating rinks. And the ships just keep getting bigger: The average cruise ship has doubled in size in just the last ten years. Some engineers fear that these towering behemoths are dangerously unstable, and the recent tragedy of the Costa Concordia has raised new questions about their safety. Now, NOVA brings together marine engineering and safety experts to reconstruct the events that led up to famous cruise disasters, including the ill-fated Concordia, the Sea Diamond, and the Oceans.

The episode was rated 8.11 from 18 votes.

It contains 99.9 percent of all the matter in our solar system and sheds hot plasma at nearly a million miles an hour. The temperature at its core is a staggering 27 million degrees Fahrenheit. It convulses, it blazes, it sings. You know it as the sun. Scientists know it as one of the most amazing physics laboratories in the universe. Now, with the help of new spacecraft and Earth-based telescopes, scientists are seeing the sun as they never have before and even recreating what happens at its very center in labs here on Earth. Their work will help us understand aspects of the sun that have puzzled scientists for decades. But more critically, it may help us predict and track solar storms that have the power to zap our power grid, shut down telecommunications, and ground global air travel for days, weeks, or even longer. Such storms have happened before—but never in the modern era of satellite communication. "Secrets of the Sun" reveals a bright new dawn in our understanding of our nearest star—one that might help keep our planet from going dark.

The episode was rated 8.17 from 24 votes.

In April 2011, the worst tornado outbreak in decades left a trail of destruction across the U.S., killing more than 360 people. Why was there such an extreme outbreak? How do such outbreaks form? With modern warning systems, why did so many die? Is our weather getting more extreme—and, if so, how bad will it get? In this NOVA special, we meet scientists striving to understand the forces at work behind last year's outbreak. Could their work improve tornado prediction in the future? We also meet people whose lives have been upended by these extreme weather events and learn how we all can protect ourselves and our communities for the future.

The episode was rated 8.18 from 17 votes.

What will it mean when most of us can afford to have the information in our DNA—all three billion chemical letters of it—read, stored, and available for analysis? In "Cracking Your Genetic Code," NOVA reveals that we stand on the verge of a revolution. We meet cancer patients returned to robust health and a cystic fibrosis sufferer breathing easily because scientists have been able to pinpoint and neutralize the genetic abnormalities underlying their conditions. What are the moral dilemmas raised by the new technology? Will it help or hurt us to know our genetic destiny? What if such information falls into the hands of insurance companies, employers, and prospective mates? One thing is for certain: The new era of personalized, gene-based medicine is relevant to everyone. Soon, all of us may be deciding whether to join the ranks of the DNA generation.

The episode was rated 8.21 from 24 votes.

In a race against developers in the Rocky Mountains, archaeologists uncover a unique fossil site packed with astonishingly well-preserved bones of mammoths, mastodons, and other giant extinct beasts. The discovery opens a highly focused window on the vanished world of the Ice Age in North America.

The episode was rated 8.52 from 27 votes.

Why go back to Mars? Far from dead, Mars holds untold potential. Nearly half a century of Mars exploration has yielded tantalizing clues that Mars may once have harbored life—and may harbor it still. The extraordinary landing of a revolutionary rover named Curiosity—which successfully touched down inside the Gale Crater—means we have wheels down on the planet once again, in the form of the most sophisticated robot ever to rove the Mars surface. Will NASA's bold mission and this marvel of technology answer some of our biggest questions and usher in a new golden age of exploration? NOVA goes behind the scenes on NASA’s quest to solve the riddles of the red planet.

The episode was rated 8.52 from 23 votes.

During World War II, Hitler’s scientists developed terrifying new weapons of mass destruction. Alarmed by rumors of advanced rockets and missiles, Allied intelligence recruited a team of brilliant minds from British universities and Hollywood studios to a country house near London. Here, they secretly pored over millions of air photos shot at great risk over German territory by specially converted, high-flying Spitfires. Peering at the photos through 3D stereoscopes, the team spotted telltale clues that revealed hidden Nazi rocket bases. The photos led to devastating Allied bombing raids that dealt crucial setbacks to the German rocket program and helped ensure the success of the D-Day landings. With 3D graphics that recreate exactly what the photo spies saw, NOVA tells the suspenseful, previously untold story of air photo intelligence that played a vital role in defeating the Nazis.

The episode was rated 8.60 from 15 votes.

Witness the extraordinary surgery that will allow twin girls, born joined at the head, to live separate lives.

The episode was rated 8.67 from 33 votes.

It contains 99.9 percent of all the matter in our solar system and sheds hot plasma at nearly a million miles an hour. The temperature at its core is a staggering 27 million degrees Fahrenheit. It convulses, it blazes, it sings. You know it as the sun. Scientists know it as one of the most amazing physics laboratories in the universe. Now, with the help of new spacecraft and Earth-based telescopes, scientists are seeing the sun as they never have before and even recreating what happens at its very center in labs here on Earth. Their work will help us understand aspects of the sun that have puzzled scientists for decades. But more critically, it may help us predict and track solar storms that have the power to zap our power grid, shut down telecommunications, and ground global air travel for days, weeks, or even longer. Such storms have happened before—but never in the modern era of satellite communication. "Secrets of the Sun" reveals a bright new dawn in our understanding of our nearest star—one that might help keep our planet from going dark.

The episode was rated 8.75 from 16 votes.

Where do nature’s building blocks, called the elements, come from? They’re the hidden ingredients of everything in our world, from the carbon in our bodies to the metals in our smartphones. To unlock their secrets, David Pogue, the lively host of NOVA’s popular "Making Stuff" series and technology correspondent of The New York Times, spins viewers through the world of weird, extreme chemistry: the strongest acids, the deadliest poisons, the universe’s most abundant elements, and the rarest of the rare—substances cooked up in atom smashers that flicker into existence for only fractions of a second.

The episode was rated 8.77 from 22 votes.