Robots that cook, a sea that's vanishing, and the love story behind the Taj Mahal

Robot arms already work in a few restaurant kitchens. Some fast-food chains have tested machines that fry fries and flip burgers, and a few cafés use robots to make coffee or salads. They never get tired and they never forget the recipe.

Home cooking is much harder. A robot has to tell when an onion is golden, crack an egg without crushing it, and cope with a messy kitchen it has never seen before.

New robots learn the way people do: by watching. Engineers record people cooking, then train AI models on thousands of hours of video and practice. The robot slowly learns which movements work, a bit like an apprentice in a busy kitchen.

The hardest dish for a robot is not a fancy one. It is scrambled eggs.

In a vertical farm, lettuce, herbs and strawberries grow on shelves stacked to the ceiling inside a warehouse. There is no soil and no sun. Roots sit in water rich in nutrients, and pink-purple LED lights give plants exactly the colors they use most.

Because the water is recycled, these farms can use up to about 90 percent less water than a field. They grow all year, with no pesticides needed, right next to the cities that eat the food.

For now, vertical farms work best for fast, light crops like leafy greens. Wheat and corn still need real fields.

Sunlight looks white, but it is a mix of every color of the rainbow. When it hits the air, tiny gas molecules bounce some of it around. Short, blue waves get scattered much more than long, red ones.

So when you look anywhere in the sky, blue light is coming at you from every direction. That is why the sky looks blue. This effect is called Rayleigh scattering.

At sunset, sunlight travels through far more air to reach you. Most of the blue is scattered away before it arrives, leaving the reds, oranges and pinks.

Your immune system is like a security team that has to recognize an invader before it can fight it. The first time a new germ shows up, that takes time, and you may get sick while your body catches up.

A vaccine is a practice drill. It shows your immune system a harmless version or piece of a germ, or instructions to make that piece. Your body learns what the invader looks like without having to fight the real disease.

During the drill, your body makes antibodies, proteins that latch onto the germ, and "memory cells" that can last for years. If the real germ shows up later, the team recognizes it and responds fast.

Wombat poop is cube-shaped. The cubes stack neatly, which helps wombats mark their territory without them rolling away.

Sea otters hold hands while they sleep, so they don't drift apart.

There are more trees on Earth than stars in our galaxy. Scientists estimate about 3 trillion trees, versus a few hundred billion stars in the Milky Way.

Oxford University is older than the Aztec Empire. Teaching at Oxford began by 1096. The Aztec capital was founded in 1325.

The Eiffel Tower grows up to about 15 cm taller in summer, as the iron expands in the heat.

A group of flamingos is called a flamboyance.

In 1631, Mumtaz Mahal, the beloved wife of Mughal emperor Shah Jahan, died while giving birth to their 14th child. Heartbroken, the emperor ordered a tomb unlike anything the world had seen, beside the Yamuna River in Agra.

About 20,000 workers spent roughly two decades building it. They used white marble from Makrana in Rajasthan and set precious stones into it in flower patterns, a craft called pietra dura.

The four minarets lean very slightly outward. If an earthquake ever toppled them, they would fall away from the tomb instead of onto it.

Late in life, Shah Jahan was locked in Agra Fort by his own son. He could see the Taj from his window.

On December 17, 1903, near Kitty Hawk, North Carolina, Orville Wright lay flat on the lower wing of a wood-and-fabric airplane and took off into a freezing wind. The flight lasted 12 seconds and covered about 120 feet (37 m), shorter than the wingspan of a modern jumbo jet.

It was the first time a powered, controlled airplane carried a person. The brothers flew three more times that day, and Wilbur's last flight lasted 59 seconds.

Orville and Wilbur had no college degrees. They ran a bicycle shop in Dayton, Ohio, and paid for their experiments with bike sales. They built their own wind tunnel to test wing shapes, and figured out how to steer by twisting the wings, an idea borrowed from watching birds.

66 years later, a piece of their airplane's fabric traveled to the Moon on Apollo 11.

The Dead Sea, between Jordan, Israel and the West Bank, sits more than 430 meters below sea level. Its shore is the lowest land on Earth. Its water is about ten times saltier than the ocean, so salty that people float without trying, and almost nothing can live in it.

But the sea is disappearing. Its surface is falling by roughly a meter every year.

The main reason is people. For decades, much of the water that once flowed in from the Jordan River has been taken for farms and cities. Mineral companies also pump seawater into evaporation ponds. With little fresh water coming in, the hot desert sun wins.

Iceland is a country built by volcanoes and ice. You can drive its Ring Road, about 1,300 km around the whole island, past glaciers, black sand beaches, waterfalls and steaming hot springs.

At Thingvellir National Park, the North American and Eurasian tectonic plates are slowly pulling apart. In the clear water of the Silfra fissure, divers and snorkelers float in the gap between two continents.

Fun fact: Iceland is one of the few places in the world with no mosquitoes.

The tallest living tree on Earth is a coast redwood in northern California nicknamed Hyperion. It stands about 116 meters (380 feet), taller than the Statue of Liberty with its base. Its exact location is kept secret to protect it from visitors.

Its cousin, the giant sequoia, wins on size. General Sherman, in Sequoia National Park, is the largest single tree by volume and is estimated to be over 2,000 years old.

These trees are built to survive fire. Their bark can be up to about 60 cm (2 feet) thick and full of water instead of sap. Fire even helps: heat dries the sequoia's cones so they open and drop seeds onto fresh, cleared ground.

Some giant sequoias alive today were already seedlings when the Roman Empire was young.

Beavers build dams of sticks, stones and mud to create calm ponds where they are safe from predators. The largest known beaver dam, in Wood Buffalo National Park in Canada, stretches about 850 meters and can be spotted in satellite images.

Termites in Africa build mounds that can tower taller than a giraffe. Tunnels inside let air flow through to keep the colony cool. Architects copied the idea for an office building in Harare, Zimbabwe, that stays cool with very little air conditioning.

Sociable weaver birds in southern Africa build giant shared nests of grass in trees and on telephone poles. One nest can house a hundred or more birds and last for decades.

Male bowerbirds in Australia build little stages of sticks and decorate them with colorful objects to impress females. The satin bowerbird especially loves anything blue, from berries to bottle caps.

On Monday, August 21, 1911, the Louvre in Paris was closed for cleaning. A former museum handyman named Vincenzo Peruggia walked in wearing a worker's smock, lifted Leonardo da Vinci's Mona Lisa off the wall, hid it under his clothes and walked out.

Nobody noticed until the next day. Police even questioned the young artist Pablo Picasso. The painting had vanished.

For more than two years, the world's most famous painting sat in a trunk in Peruggia's small Paris apartment. In 1913 he took it to Florence and tried to sell it to an art dealer, who called the police.

Before the theft, the Mona Lisa was admired. After it, she was world famous.

The painting is surprisingly small, about 77 by 53 cm, and today sits behind bulletproof glass.

Most sounds you hear in a movie were not recorded on set. Microphones on set focus on the actors' voices, so footsteps, rustling coats and clinking cups are added later by Foley artists, named after Jack Foley, a sound pioneer at Universal Pictures from the late 1920s.

Foley artists watch the film on a big screen and perform the sounds live in a studio, matching every step and movement.

Studios keep "Foley pits" filled with gravel, sand and wood, so artists can walk on any surface a scene needs.