NOVA

Examine the science behind vaccinations, the return of preventable diseases and the risks of opting out.

Meet the new global geek squad racing to stay one step ahead of the hackers.

Get the inside story of the search for Flight MH370 and meet those who looked for the lost plane.

Watch the re-creation of an 18th-century hot air balloon, using period tools and materials.

Uncover secrets of some colorful and deadly early flying machines and explore their role in WWI.

Almost a century ago, paleontologists found the first tantalizing hints of a monster even bigger than Tyrannosaurusrex, perhaps the largest predator ever to roam the Earth: spectacular fossil bones from a dinosaur dubbed Spinosaurus. But the fossils were completely destroyed during a World War II Allied bombing raid, leaving only drawings, questions, and a mystery: What was Spinosaurus? Now, the discovery of new bones in a Moroccan cliff face is reopening the investigation into this epic beast. What did it feed on, and how? Why did it grow so big? We follow the paleontologists who are reconstructing this terrifying carnivore, revealing a 53-foot-long behemoth with a huge dorsal sail, enormous, scimitar-like claws, and massive jaws tapered toward the front like a crocodile. Bringing together experts in paleontology, geology, climatology, and paleobotany, this NOVA/National Geographic special brings to life the lost world over which Spinosaurus reigned more than 65 million years ago.

In central China, a vast underground mausoleum conceals a life-size terracotta army of cavalry, infantry, horses, chariots, weapons, administrators, acrobats, and musicians, all built to serve China's first emperor, Qin Shi Huang Di, in the afterlife. Lost and forgotten for over 2,200 years, this clay army, 8,000-strong, stands poised to help the First Emperor rule again beyond the grave. Now, a new archaeological campaign is probing the thousands of figures entombed in the mausoleum. With exclusive access to pioneering research, "Emperor's Ghost Army" explores how the Emperor directed the manufacture of the tens of thousands of bronze weapons carried by the clay soldiers. NOVA tests the power of these weapons with high-action experiments and reports on revolutionary 3D computer modeling techniques that are providing new insights into how the clay figures were made, revealing in the process the secrets of one of archaeology's greatest discoveries.

Scientists investigate the specific local geological and climatic factors behind the 2014 collapse of a hillside in Oso, Washington. Learn what triggered the deadliest U.S. landslide in decades.

A profile of Neil Armstrong (1930-2012), the first person to set food on the moon, featuring remarks from his family and friends.

On July 4, 2012, scientists at the giant atom-smashing facility at CERN announced the discovery of a subatomic particle that seems like a tantalizingly close match to the elusive Higgs Boson, thought to be responsible for giving all the stuff in the universe its mass. Since it was first proposed nearly fifty years ago, the Higgs has been the holy grail of particle physicists: in finding it they validate the "standard model" that underlies all of modern physics and open the door to new discoveries when CERN's Large Hadron Collider switches on at higher power in 2015.

Follow the epic operation to secure, raise, and salvage the Costa Concordia cruise ship, which ran aground and tragically capsized off the coast of Italy on January 13, 2012, killing 32 people. The massive wreck—with a 160-foot-long hole in its hull—stretches the length of three football fields, weighs 45,000 tons, and was half submerged on the site of a protected reef. Moving it from its precarious perch on the edge of an underwater cliff turned into a technical and logistical challenge of staggering proportions. Join NOVA as we follow a team of more than 500 divers and engineers working around the clock as they attempt the biggest ship recovery project in history.

Investigate what it's like to have your world vanish beneath your feet. http://pressroom.pbs.org/Programs/n/NOVA.aspx.

One of the ancient world's most iconic buildings, the Colosseum is a monument to Roman imperial power and cruelty. Its graceful lines and harmonious proportions concealed a highly efficient design and advanced construction methods that made hundreds of arches out of 100,000 tons of stone. In its elliptical arena, tens of thousands of gladiators, slaves, prisoners, and wild animals met their deaths. Ancient texts report lions and elephants emerging from beneath the floor as if by magic to ravage gladiators and people condemned to death. Then, just as quickly, the Colosseum could be flooded with so much water that ships could engage in sea battles to the delight of the crowd. Now, archaeologists and engineers are teaming up to recreate a 25-foot lifting machine and trap door system capable of releasing a wolf into the Colosseum's arena for the first time in 1,500 years. Do they have what it takes to replicate the innovation and ingenuity of the Romans?

More than 2,000 years ago, the thriving city of Petra rose up in the bone-dry desert of what is now Jordan. An oasis of culture and abundance, the city was built by wealthy merchants whose camel caravans transported incense and spices from the Arabian Gulf. They carved spectacular temple-tombs into its soaring cliffs, raised a monumental Great Temple at its heart, and devised an ingenious system that channeled water to vineyards, bathhouses, fountains, and pools. But following a catastrophic earthquake and a slump in its desert trade routes, Petra's unique culture faded and was lost to most of the world for nearly a thousand years. Now, in a daring experiment, an archaeologist and sculptors team up to carve an iconic temple-tomb to find out how the ancient people of Petra built their city of stone. Meanwhile, scientists using remote sensors and hydraulic flumes uncover the vast city and its sophisticated water system. The race is on to discover how these nomads created this oasis of culture in one of the harshest climates on Earth.

Whether serving as a Christian church, Islamic mosque, or secular museum, Hagia Sophia and its soaring dome have inspired reverence and awe. For 800 years, it was the largest enclosed building in the world—the Statue of Liberty can fit beneath its dome with room to spare. How has it survived its location on one of the world's most active seismic faults, which has inflicted a dozen devastating earthquakes since it was built in 537? As Istanbul braces for the next big quake, a team of architects and engineers is urgently investigating Hagia Sophia's seismic secrets. Follow engineers as they build a massive 8-ton model of the building's core structure, place it on a motorized shake table, and hit it with a series of simulated quakes, pushing it to collapse—a fate that the team is determined to avoid with the real building.

Join NOVA on a mathematical mystery tour—a provocative exploration of math's astonishing power across the centuries. We discover math's signature in the swirl of a nautilus shell, the whirlpool of a galaxy, and the spiral in the center of a sunflower. Math was essential to everything from the first wireless radio transmissions to the prediction and discovery of the Higgs boson and the successful landing of rovers on Mars. Astrophysicist and writer Mario Livio, along with a colorful cast of mathematicians, physicists, and engineers, follow math from Pythagoras to Einstein and beyond. It all leads to the ultimate riddle: Is math a human invention or the discovery of the language of the universe?

The Hubble Space Telescope's discoveries over past 25 years.

Learn about a little-known attack from the ocean depths that claimed 5,000 American lives.

A deadly recipe is brewing that threatens the survival of countless creatures throughout Earth's oceans. For years, we've known that the oceans absorb about a quarter of the carbon dioxide in our atmosphere. But with high carbon emissions worldwide, this silent killer is entering our seas at a staggering rate, raising the ocean's acidity. It's eating away at the skeletons and shells of marine creatures that are the foundation of the web of life. NOVA follows the scientists making breakthrough discoveries and seeking solutions. Visit a unique coral garden in Papua New Guinea that offers a glimpse of what the seas could be like a half-century from now. Can our experts crack the code of a rapidly changing ocean before it's too late?

View New Horizon's historic capture of the first-ever detailed images of Pluto's icy world.

Follow the minute-by-minute story of the Fukushima nuclear crisis and its aftermath.