What was the Challenger disaster?

Seven astronauts were aboard Challenger flight STS-51L when it exploded during liftoff on January 28, 1986. Christa McAuliffe was a Concord, New Hampshire, high school social studies teacher. She and the other six crew members were killed when a solid-fuel booster rocket leak led to a massive fuel tank explosion during liftoff from its launch pad.

NASA’s next flight was Discovery, which was launched on September 28, 1988. After the Challenger disaster, NASA’s three remaining shuttles— Atlantis, Discovery, and Columbia—were rebuilt, each with more than 250 modifications improving safety and performance.

What is high-definition television?

High-definition television (HDTV) is a digital television broadcasting system with higher resolution than traditional television systems. The amount of detail shown in a television picture is limited by the number of lines that make it up and by the number of picture elements on each line.

The latter is mostly determined by the width of the electron beam. To obtain pictures closer to the quality of 35-millimeter photography, HDTV has more than twice the number of scan lines with a much smaller picture element. American and Japanese HDTVs have 525 scanning lines, and Europe has 625 scanning lines.

Are all flowers fragrant?

Unlike the fragrant blossoms that attract bees, carrion flowers simulate the odor of a rotting animal carcass and attract carrion beetles and different types of flies, including blowflies, flesh flies, and midges. The stapelia flower, which is shaped like a starfish and grows in Africa, has fine hairs around its petals, perhaps to imitate the appearance of a small dead animal. When the bloom opens it gives off a rotting smell, imitating dead animal meat.

The smell attracts flies, which collect pollen before they fly away. Some carrion flowers, such as the European and Brazilian Dutchman’s pipe, lure insects into dark openings that lead to the foul-smelling interior where they become trapped. When the flower “releases” the insect, it is coated with fresh pollen to be taken to a different plant. The lantern stinkhorn, a fungus that releases a feces-like odor, attracts green bottle flies to spread its spores.

Why does my cat purr?

Animal specialists believe that cats purr to show contentment. Cats are born with the ability to purr; kittens make tiny rumbling sounds when they are nursing. Scientists think that purring starts out as a form of communication between a mother cat and her kittens. The purr lets the mother cat know that her babies are happy and feeding well, and she may purr back in response. Later, cats continue to purr when they are in a contented mood or as a friendly greeting. But scientists aren’t really sure how cats purr. Many think that it comes from the vibration of blood in a large vein in the cat’s chest, caused when surrounding muscles repeatedly squeeze and release the blood vessel.

Air in a cat’s lungs and windpipe increase the sound of the vibrations that can be heard (although sometimes the purring is silent and can only be felt). Other scientists think that cats purr when membranes called false vocal chords, located in a cat’s throat near the real ones, start to vibrate.

Why is the Statue of Liberty such an important symbol of the United States?

The Statue of Liberty stands for many of the nation’s most cherished ideals: freedom, equality, and democracy. Perhaps most importantly to the millions of immigrants for whom the statue was one of their first sights of the United States, it stands for the ideal of opportunity—the chance to begin a new life, in a new land. While their lives in the United States were frequently difficult, for millions of immigrants America offered the chance to escape from grinding poverty and abusive governments in other lands. Standing in the midst of New York Harbor, the point of entry into the United States for so many immigrants arriving on ships from other countries, the Statue of Liberty has been a powerful symbol of opportunity for more than 100 years.

 

A poem called “The New Colossus,” written by Emma Lazarus, was mounted on the statue’s pedestal in the early 1900s. Its famous lines include these words that Lazarus imagined Lady Liberty to be saying: Give me your tired, your poor, Your huddled masses yearning to breathe free, The wretched refuse of your teeming shore; Send these, the homeless, tempest-tost to me, I lift my lamp beside the golden door!

Why do baby boys wear blue and girls wear pink?

The custom of dressing baby boys in blue clothes began around 1400. Blue was the colour of the sky and therefore Heaven, so it was believed that the colour warded off evil spirits. Male children were considered a greater blessing than females, so it was assumed that demons had no interest in girls.

It was another hundred years before girls were given red as a colour, which was later softened to pink.

Why do we call the perfect world “Utopia”?

The word Utopia was created by the English philosopher Sir Thomas More in 1516 and was the title of his book that compared the state of life in Europe at the time with an imaginary ideal society. Utopia is from Greek meaning nowhere.

The thrust of More’s message was that an ideal world, or Utopia, will never exist, and that our only choice is to improve the standards of our existing society.

Is it true that parts of Earth are always covered in ice?

About one-tenth of Earth’s surface is always under the cover of ice. And almost 90 percent of that ice is found in the continent of Antarctica. The remaining 10 percent is found on the mountains in the form of glaciers.

The ice sheet that covers Antarctica is almost one-and-a-half times the size of the United States.

How old is Earth?

Scientists estimate that Earth—born out of a swirling cloud of gas and dust—is about 4.6 billion years old. They have reached this conclusion by studying Moon rocks and meteorites (rocks that have fallen from space to Earth) that they believe were formed at the same time as our planet.

How does an ear thermometer read body temperature?

An ear thermometer reads the spectrum of thermal radiation given off by the inner surfaces of a person’s ear. All objects give off thermal radiation (including the light emitted by a glowing incandescent light bulb) and that radiation is characteristic of their temperatures. The hotter an object is, the brighter its thermal radiation and the more that radiation shifts toward shorter wavelengths.

The thermal radiation from a person’s ear is in the invisible infrared portion of the light spectrum, which is why you can’t see people glow. But the ear thermometer can see this infrared light and it uses the light to determine the ear’s temperature. The thermometer’s thermal radiation sensor is very fast, so it can measure a person’s body temperature in just 168 a few minutes.