For animals in Mozambique’s Gorongosa National Park, the normal balance of competition and predation was upended when a war wiped out the top predators. The remaining animals didn’t simply grow in numbers—they began behaving in unusual ways, veering outside their typical territories and feeding patterns. Could it be that it’s not just predators’ kills that keep other populations in check, but also the fear they inspire? NOVA joins a team of scientists as they reintroduce wild dogs to Gorongosa to find out if restoring the park’s “landscape of fear” can restore balance to an entire ecosystem.

The episode was rated 6.79 from 14 votes.

As global temperatures continue to rise, scientists are wondering if we need solutions beyond reducing emissions. Enter geoengineering. From sucking carbon straight out of the air to physically blocking out sunlight, the options may seem far-fetched. But as time runs out on conventional solutions to climate change, scientists are asking the hard questions: Can geoengineering really work? How much would it cost? And what are the risks of engineering Earth's climate?

The episode was rated 6.91 from 11 votes.

The coronavirus SARS-CoV-2 has upended life as we know it in a matter of mere months. But at the same time, an unprecedented global effort to understand and contain the virus—and find a treatment for the disease it causes—is underway. Join the doctors on the front lines of the fight against COVID-19 as they strategize to stop the spread, and meet the researchers racing to develop treatments and vaccines. Along the way, discover how this devastating disease emerged, what it does to the human body, and why it exploded into a pandemic.

The episode was rated 6.95 from 20 votes.

If spacecraft OSIRIS-REx can grab a piece of an asteroid and bring it back to Earth, scientists could gain great insight into our planet's origins, and even how to defend against rogue asteroids. But NASA only gets three shots at collecting a sample.

The episode was rated 7.18 from 17 votes.

Where would we be without the world’s alphabets? Writing has played a vital role in the expansion and domination of cultures throughout history. But researchers are only now uncovering the origin story to our own alphabet, which may have gotten its beginnings in a turquoise mine 4,000 years ago. From the shape of the letter A to the role of writing in trade and storytelling, discover how the written word shaped civilization itself.

The episode was rated 7.50 from 12 votes.

Cuban scientists develop their own biotech industry, including lung cancer vaccines that may give new hope to patients around the world.

The episode was rated 7.53 from 17 votes.

The mysteries of fat and its role in hormone production, hunger and pregnancy.

The episode was rated 7.54 from 35 votes.

Dogs have long been dependable companions by our sides. But it wasn’t always that way, and a look at their closest living relative, the wolf, makes it clear why. Research into dog domestication and intelligence offers clues into what the human-dog relationship is all about. And analyzing dogs’ brain activity and genes may even help answer the question of whether dogs are in it for the food—or if they really love us.

The episode was rated 7.65 from 40 votes.

Worshipped as a goddess, condemned as satanic, and spun into a stunning array of breeds, cats have long fascinated humans. But did we ever really domesticate them? And what can science tell us about our most mysterious companions?

The episode was rated 7.76 from 38 votes.

The coronavirus SARS-CoV-2 has upended life as we know it in a matter of mere months. But at the same time, an unprecedented global effort to understand and contain the virus—and find a treatment for the disease it causes—is underway. Join the doctors on the front lines of the fight against COVID-19 as they strategize to stop the spread, and meet the researchers racing to develop treatments and vaccines. Along the way, discover how this devastating disease emerged, what it does to the human body, and why it exploded into a pandemic.

The episode was rated 7.88 from 17 votes.

Just as writing changed the course of human history, the evolution of paper and printing revolutionized the spread of information. The printing press kicked off the Industrial Revolution that fast-tracked us to the current digital age. But as the 4,000-year-old tradition of penmanship falls out of favor, should we consider what might be lost in this pursuit of ever more efficient communication?

The episode was rated 7.91 from 11 votes.

From fruit flies to whales, virtually every animal sleeps. But why? Why do we need to spend nearly a third of our lives in such a defenseless state? Scientists are peering more deeply into the sleeping brain than ever before, discovering just how powerful sleep can be, playing a role in everything from memory retention and emotional regulation to removing waste from our brains. So why are we getting so little of it?

The episode was rated 7.91 from 34 votes.

In this two-hour special, renowned paleontologist Kirk Johnson takes us on an epic adventure through time at the polar extremes of our planet. Following a trail of strange fossils found in all the wrong places—beech trees in Antarctica, hippo-like mammals in the Arctic—Johnson uncovers the bizarre history of the poles, from miles-high ice sheets to warm polar forests teeming with life. What caused such dramatic changes at the ends of the Earth? And what can the past reveal about our planet’s climate today—and in the future?

The episode was rated 7.98 from 41 votes.

Who says you need brains to be smart? Extremely primitive life-forms called slime molds can navigate mazes, choose between foods, and create efficient networks—no brain required. New research on these organisms, which are neither plant nor animal, could help reveal the fundamental rules underlying all decision making.

The episode was rated 8.08 from 12 votes.

Eagles dominate the skies. But what makes these predators so special? Researchers study one special bird—and stunning up-close footage reveals her exceptional strength, eyesight, and flying skills. With intimate access to a new bald eagle family, NOVA takes you into the nest to witness the drama of chicks struggling to survive.

The episode was rated 8.35 from 26 votes.