Why rainbows bend, how owls hunt in the dark, and the copper giant of New York Harbor

Ordinary computers work with bits, tiny switches that are either 0 or 1. Everything your phone does, from photos to email, comes down to billions of those switches flipping on and off.

Quantum computers use qubits instead. Under the strange rules of quantum physics, a qubit can be in a blend of 0 and 1 at the same time, a state called superposition. Qubits can also be linked, or entangled, so that measuring one tells you something about another.

That lets a quantum computer tackle certain problems in ways ordinary computers cannot. Scientists hope to use them to design new medicines and materials by simulating molecules atom by atom.

Many quantum computers run colder than outer space.

The catch is that qubits are fragile. Heat, vibration or stray signals can scramble them, so many machines hang inside gold-colored refrigerators chilled to a whisker above absolute zero. Taming those errors is the big challenge before quantum computers become everyday tools.

For most of the space age, rockets were used once. After launch, their big lower stages fell into the ocean or burned up, and every flight needed a brand-new rocket. Imagine throwing away an airliner after a single trip.

The Space Shuttle, which flew from 1981 to 2011, was partly reusable. The orbiter glided home to a runway, and its two side boosters parachuted into the sea to be fished out and refurbished.

In December 2015, a rocket booster that had just helped send satellites toward orbit flew itself back and landed upright on a pad in Florida. It was the first time the booster of an orbital rocket had done that.

The booster steers home with small fins, re-lights its engines and touches down on legs.

Since then, some boosters have flown more than 20 times. Reusing hardware cuts the cost of reaching space, and engineers are now working on rockets where every part comes back.

A rainbow needs two things: sunshine and raindrops, with the Sun behind you and the rain in front of you. That is why rainbows often appear in the late afternoon, just after a passing shower.

Sunlight looks white, but it is really a mix of colors. When it enters a raindrop, it bends, an effect called refraction. Each color bends by a slightly different amount, so the colors begin to spread apart.

The light bounces off the back of the drop and bends again on the way out, fanning the colors further. Red light leaves at an angle of about 42 degrees and violet at about 40, so red sits on the outside of the bow.

Everyone sees their own rainbow, made by a different set of raindrops.

When light bounces twice inside the drops, a fainter second rainbow appears above the first, with its colors in reverse order. And from an airplane, you can sometimes see that a rainbow is really a full circle.

Goosebumps can pop up when you step into cold air, hear a stirring piece of music or get a sudden fright. The tiny bumps get their name from the skin of a plucked goose.

Each hair on your body grows from a pocket in the skin called a follicle. Attached to most follicles is a tiny muscle, the arrector pili. When it tightens, it tugs the hair upright and pushes up a little mound of skin around it.

The signal comes from the sympathetic nervous system, the same fight-or-flight system that releases adrenaline. That is why both a chill and a strong emotion can set it off.

In furry animals, raised hair traps warm air or makes them look bigger.

A frightened cat puffs up its fur, and a porcupine raises its quills. Humans have far less body hair, so for us goosebumps are mostly a leftover reflex from our ancestors. The medical name is piloerection.

General information, not medical advice. Talk to a doctor about your own health.

The Pacific Ocean is bigger than all of Earth's land put together. It covers about a third of the planet's surface.

Some kinds of bamboo can grow almost a meter (about 3 feet) in a single day, making them among the fastest-growing plants on Earth.

An ostrich's eye is bigger than its brain. Those huge eyes help it spot danger far across open plains.

Russia stretches across 11 time zones. When it is morning on its Pacific coast, it is still the evening before in Moscow.

Lobsters have blue blood. It carries oxygen using copper instead of the iron in our red blood.

Sound travels about four times faster in water than in air, which is one reason whales can hear each other over long distances.

The Statue of Liberty was a gift from the people of France to the United States, a symbol of friendship and freedom. It was dedicated in New York Harbor on October 28, 1886, 140 years ago this week.

French sculptor Frédéric Auguste Bartholdi designed the statue. Its hidden iron skeleton was engineered by Gustave Eiffel, the man behind the Eiffel Tower in Paris.

The statue was built in France, taken apart and shipped across the Atlantic in hundreds of pieces packed into crates. Americans raised money for the granite pedestal, helped along by a fundraising drive in Joseph Pulitzer's newspaper.

Lady Liberty was not always green. She started out the shiny brown of a new copper penny.

Her copper skin is only about as thick as two pennies. Within a few decades, air and rain turned it blue-green, a coating called patina that actually protects the metal. The tablet in her left hand reads JULY IV MDCCLXXVI, the date of the Declaration of Independence.

In the year 79 AD, Mount Vesuvius erupted above the Bay of Naples in southern Italy. Pompeii, a busy Roman town, lay just a few miles from the volcano.

Ash and pumice rained down for hours. Then scorching avalanches of hot gas and rock, called pyroclastic flows, swept through the streets and buried the town under several meters of volcanic debris.

A young Roman writer, Pliny the Younger, watched from across the bay and later described the eruption in letters. They are among the earliest eyewitness accounts of a volcanic eruption.

The ash that destroyed Pompeii also preserved it.

Organized digging began in 1748. Archaeologists found streets, bakeries, painted walls and even graffiti, a snapshot of everyday Roman life. In the 1860s they began pouring plaster into hollows left in the hardened ash, capturing the final poses of the people who died there. Excavations continue today.

The Grand Canyon in northern Arizona is about 277 miles (446 km) long, up to 18 miles wide and more than a mile deep in places. It is one of the most famous landscapes on Earth.

The Colorado River carved it, cutting downward over roughly the last five to six million years while the land around it slowly rose. Rain, ice and landslides widened it further.

The canyon's striped walls read like a giant history book. The rocks near the bottom are close to two billion years old, while the layers along the rim are about 270 million years old.

Hike down into the canyon, and every step takes you further back in time.

It became a national park in 1919 and now draws millions of visitors a year, most of them to the South Rim. The North Rim, higher and cooler, closes to cars in winter.

In northern Cambodia stands Angkor Wat, the largest religious monument in the world. It was built in the early 1100s for the Khmer king Suryavarman II and first dedicated to the Hindu god Vishnu. It later became a Buddhist temple, which it remains today.

A wide moat surrounds the temple, and five towers shaped like lotus buds rise from its center. The tallest stands about 65 meters (213 feet) high.

Its walls are covered with long stone carvings of gods, battles and daily life. Angkor Wat sits in a vast area that was once the heart of the Khmer Empire, with many other temples close by.

Angkor Wat is so important to Cambodia that it appears on the national flag.

Pumpkins are fruits, not vegetables. Like cucumbers, melons and zucchini, they belong to the gourd family: they grow from flowers and carry their seeds inside.

Pumpkins and other squash are native to the Americas. People in what is now Mexico were growing squash thousands of years ago, and it became a staple food across the continent.

Carving jack-o'-lanterns began in Ireland and Britain, where people carved faces into turnips and other root vegetables. Immigrants brought the custom to America, where big, soft pumpkins were far easier to carve.

The biggest pumpkins today weigh more than a ton.

Giant-pumpkin growers pamper a single fruit all summer, and at their peak the champions can gain dozens of pounds in a day. For pies, cooks prefer small, sweet sugar pumpkins.

Owls are built for night hunting. Their huge eyes gather what little light there is, but they are shaped like tubes rather than balls, so they cannot roll in their sockets. To look around, an owl turns its whole head, as far as about 270 degrees.

Hearing matters even more. The flat, dish-shaped face of an owl such as the barn owl works like a satellite dish, funneling sound toward its ears.

In some owls, one ear opening sits higher than the other. A sound reaches each ear at slightly different times and loudness, which lets the owl pinpoint its prey up, down, left and right. Barn owls can catch a mouse in total darkness by sound alone.

An owl's feathers have soft, comb-like edges that hush its wingbeats.

That near-silent flight means the mouse rarely hears it coming, and the owl's own hearing is not drowned out by the sound of flapping.

Few paintings are as recognizable as The Scream by the Norwegian artist Edvard Munch. A figure with a skull-like face clutches its head on a bridge beneath a blazing, swirling orange-red sky.

Munch made the first painted version in 1893. He returned to the image several times, making versions in paint and pastel, plus a black-and-white print so the picture could be reproduced.

Munch described the idea as coming to him on a walk at sunset near the city now called Oslo, when the sky turned red and he sensed a scream passing through nature.

The figure is not screaming. In Munch's telling, it is hearing one.

The Scream became a symbol of modern worry and anxiety. In 2012, one of the pastel versions sold at auction for about $120 million, a record at the time. Two other versions belong to museums in Oslo.

On June 6, 1933, Richard Hollingshead opened the first patented drive-in movie theater, in Camden, New Jersey. Families could watch a film from their own car, with no need to dress up or find a babysitter.

Early drive-ins used big speakers beside the screen. Later, each parking spot got a small speaker that hung on the car window, and today most drive-ins send the soundtrack to your car radio.

Drive-ins boomed after World War II, as more families owned cars and moved to the suburbs. By the late 1950s there were roughly 4,000 across the United States.

At a drive-in, the show can't start until the sun goes down.

Rising land prices, color TV and home video thinned their numbers, and only a few hundred remain today. Many still show double features, and some open just for the warm months.