NOVA — Season 49

Skyscrapers are gleaming symbols of prestige and an ingenious way to save space in dense urban areas. But as buildings rise ever higher, what are the risks of these architectural behemoths? Do we truly know how they will hold up in earthquakes, fires, and other potential disasters? What have--or haven't—we learned from past tragedies?

The hidden scientific secrets of butterflies reveal them to be more inventive and resilient than we ever imagined. Follow their extraordinary life cycle and migrations to tropical rainforests, windswept prairies, and even inside a chrysalis as it's being spun. Discover how butterfly science inspires groundbreaking technology, including more efficient solar power cells and bulletproof vests stronger than Kevlar.

A team of intrepid paleontologists discovers that dinosaurs thrived in the unlikeliest of places—the cold and dark of winter in the Arctic Circle. How did they survive year-round and raise their young in frigid and dark winter conditions? A dinosaur expedition explores a remote, treacherous, and stormy terrain where the team knows that every bone they find there will likely be a first, adding up to a unique picture of a lost northern world.

The ancient ancestors of today's Maya people thrived in large, sophisticated cities across Central America for centuries. Why, around 750 CE, did they begin to abandon many of their major cities? Archaeologists investigate dramatic new evidence of the catastrophic droughts and instability that pushed cities beyond their limits. The evidence also testifies to the survival and resilience of the Maya people, whose traditions and creativity continue to enrich the world today.

Colossal explosions shake a remote corner of the Siberian tundra, leaving behind massive craters. In Alaska, a huge lake erupts with bubbles of inflammable gas. Scientists are discovering that these mystifying phenomena add up to a ticking time bomb, as long-frozen permafrost melts and releases vast amounts of methane, a potent greenhouse gas. What are the implications of these dramatic developments in the Arctic? Scientists and local communities alike are struggling to grasp the scale of the methane threat and what it means for our climate future.

Scott Burnett is "Scatman"—an Australian ecologist on the trail of the secrets of poop. By identifying and analyzing animal scat for DNA and hormones, he discovers essential details of their behavior, how they fit in the ecosystem, and even how to protect them. From the mysterious cubic poop of wombats to the precious pink waste of whales, join scientists as they explore nature's smelliest secrets.

Sir David Attenborough investigates a unique site in southern England where amateur fossil hunters uncovered giant mammoth bones and evidence of Neanderthals. A team of paleontologists and archaeologists soon discover that the site preserves rare evidence of the extinct beasts and early human inhabitants of Britain dating to over 200,000 years ago. What skills did the early humans have to help them survive during the Ice Age? How did they hunt and protect themselves against formidable creatures such as mammoths? With hands-on experiments with replicas of Neanderthal-era spears and stone tools, the world of prehistoric Britain comes to life.

Follow the dramatic personal journey of Hugh Herr, a biophysicist working to create brain-controlled robotic limbs. At age 17, Herr's legs were amputated after a climbing accident. Frustrated by the crude prosthetic limbs he was given, Herr set out to remedy their design, leading him to a career as an inventor of innovative prosthetic devices. Now, Herr is teaming up with Jim Ewing, an injured climber and friend, and Dr. Matthew Carty, a surgeon at a leading Boston hospital, to test a new approach to surgical amputation that allows prosthetic limbs to move and feel like the real thing. Herr's journey is a powerful tale of innovation and the inspiring story of a personal tragedy transformed into a life-long quest to help others.

In 2005, filmmaker Jason DaSilva was diagnosed with primary progressive multiple sclerosis, a rare type of MS with no known cure that inflicts a host of progressively debilitating symptoms. In this moving personal film, DaSilva looks back on the challenges he's faced, delves into the science behind MS, and investigates the potential risk factors that may–or may not–have contributed to his rare diagnosis. Refusing to be labeled a "tragic" case, he continues to advocate for people with disabilities and pursue his career as an artist and filmmaker.

Three women at risk of developing Alzheimer's join a groundbreaking study to prevent the disease while sharing their ups and downs, anxiously watching for symptoms, and hoping they can make a difference. Barb, Sigrid, and Karen all had mothers with Alzheimer's and witnessed firsthand the devastation wrought by the disease, not only on the mind and body but on patients' families. Now, they are all participating in a major study that tracks the health and memory of thousands of people over many years, as researchers hunt for lifestyle changes and medicines that could improve all our chances and ultimately protect the brain and body from one of the world's deadliest diseases.

In the Badlands of North Dakota, scientists think they might have found the fossilized remains of animals killed on the day an asteroid struck Earth 66 million years ago. The evidence points to a catastrophic event, with a jumble of rare fossils, including a pterosaur embryo still in its shell and a well-preserved patch of triceratops skin mixed in with tiny spheres of clay and glass that could be the fallout from the massive asteroid impact. Sir David Attenborough guides us on a search for clues that could give an unprecedented snapshot of what happened in the dinosaurs' final moments on Earth.

In the second episode of this two-part series, the search continues for signs of what happened on the day the dinosaurs died. Scientists uncover extremely rare fossils and more evidence that could link the dig site in North Dakota to the asteroid that wiped out the dinosaurs 66 million years ago. Among the fossils are tiny spheres of glass locked in amber. Inside one of the spheres is a speck of rock that appears to be a chemical match to the killer asteroid itself. And scientists uncover one of the most spectacular finds of all: an almost perfectly preserved dinosaur leg. Sir David Attenborough guides us on a search for clues that could provide an unprecedented snapshot of what happened in the dinosaurs' final moments on Earth.

When the bow of the colossal Ever Given container ship plowed into the bank of the Suez Canal on March 23, 2021, international supply chains ground to a halt. What went wrong? Follow the dramatic efforts to free the ship and the investigation into one of the most expensive shipping disasters ever. Maritime experts analyze other recent accidents and try to figure out how such devastating crashes could be prevented.

Thousands of ancient footprints stretch for miles across New Mexico's White Sands National Park, capturing moments when Ice Age humans encountered now-extinct beasts, including mammoths and enormous ground sloths. These footprints tell an intimate story about what life was like during the Ice Age and reveal surprising new evidence about when humans arrived in North America.

How did NASA engineers build and launch the most ambitious telescope of all time? Follow the dramatic story of the James Webb Space Telescope—the most complex machine ever launched into space. If it works, scientists believe that this new eye on the universe will peer deeper back in time and space than ever before to the birth of galaxies, and may even be able to "sniff" the atmospheres of exoplanets as we search for signs of life beyond Earth. But getting it to work is no easy task. The telescope is far bigger than its predecessor, the famous Hubble Space Telescope, and it needs to make its observations a million miles away from Earth—so there will be no chance to go out and fix it. That means there's no room for error; the most ambitious telescope ever built needs to work perfectly. Meet the engineers making it happen and join them on their high stakes journey to uncover new secrets of the universe.

Rising sea levels and sinking land threaten to destroy Venice. Leading scientists and engineers are racing against the clock and battling the forces of nature to try to save this historic city for future generations. Discover the innovative projects and feats of engineering currently underway, including a hi-tech flood barrier, eco-projects to conserve the lagoon, and new efforts to investigate erosion beneath the city. This is Venice as never seen before, at a critical moment in its rich history.

Almost 40 years after the discovery of HIV, could we be on the verge of ending the AIDS epidemic in America? As of 2019, in the US, there were only 34,000 new cases of the disease––a feat that once seemed near-impossible to achieve. How did scientists and the public health community tackle one of the most elusive deadly viruses to ever infect humans? Can innovative drugs and therapies bring new infections to zero? This is the story of an incredible scientific achievement and the public health work that still needs to be done to end HIV in America.

In police departments and courts across the country, artificial intelligence is being used to help decide who is policed, who gets bail, how offenders should be sentenced, and who gets parole. But is it actually making our law enforcement and court systems fairer and more just? This timely investigation digs into the hidden biases, privacy risks, and design flaws of this controversial technology.

Hallucinogenic drugs—popularly called psychedelics—have been used by human societies for thousands of years. Today, scientists are taking a second look at many of these mind-altering substances–both natural and synthetic–and discovering that they can have profoundly positive clinical impacts, helping patients struggling with a range of afflictions from addiction to depression and PTSD.

Lionfish – long prized in home aquariums – have invaded the Atlantic and are now one of the ocean's most successful invasive species, wreaking havoc in waters across the globe. Join ocean explorer Danni Washington on a journey to discover how they took over, why they're doing so much damage, and what can be done about it. These fascinating creatures are a window into the impacts of invasive species in a globalized world where human activity is an increasingly powerful evolutionary force.

One of the world's greatest ancient enigmas, the Nazca lines are a dense network of crisscrossing lines, geometric shapes, and animal figures etched across 200 square miles of Peruvian desert. Who created them and why? Ever since they were rediscovered in the 1920s, scholars and enthusiasts have raised countless theories about their purpose. Now, archaeologists have discovered hundreds of long-hidden lines and figures as well as evidence of ancient rituals, offering new clues to the origins and motivations behind the giant desert symbols.

From Bitcoin to NFTs, crypto is making headlines. But what exactly is it, and how does it work? Experts go beyond the hype and skepticism to unravel crypto's social and technological underpinnings – exploring how it came to be and why this new technology may change more than just money.

Zero and infinity. These seemingly opposite, obvious, and indispensable concepts are relatively recent human inventions. Discover the surprising story of how these key concepts that revolutionized mathematics came to be – not just once, but over and over again as different cultures invented and re-invented them across thousands of years.

Following the April 2019 fire that almost destroyed Paris's iconic Notre Dame Cathedral, a team of engineers, masons, and timber workers set out on the daunting challenge of restoring France's historic landmark. The program traces the dramatic human and technical challenges of the project's first three years, going behind the scenes with carpenters shaping lumber for the new roof and spire, stone masons repairing gaping holes in the vault, and artisans who use traditional techniques to restore stained glass windows. A symbol of the nation's identity and resilience, Notre Dame gradually rises from the ashes, thanks to a restoration project like no other.