Babies are born with about 300 to 350 bones, but many of these fuse together between birth and maturity to produce an average adult total of 206. Bone counts vary according to the method used to count them, because a structure may be treated as either multiple bones or as a single bone with multiple parts. There are four major types of bones: long bones, short bones, flat bones, and irregular bones. The name of each type of bone reflects the shape of the bone. The shape of the bone also tells about its mechanical function. Bones that do not fall into any of these categories are sesamoid bones and accessory bones.
A virus is a malicious software program that infects computer files or hard disk drives and then makes copies of itself. Many activities that kids do online can leave computers vulnerable to viruses. E-mail attachments are a common means of distributing viruses, but viruses can also be downloaded when you share files and open instant message attachments. In order to keep your computer safe, never open an e-mail attachment you haven’t requested.
Send an e-mail to friends to confirm that they meant to send you an attachment. Also, you can configure your instant messaging program so you can’t receive files from other users. Never download any program without checking with a parent first. You can protect your computer by always running up-to-date firewall software, by running antivirus software regularly, and by periodically scanning your computer for spyware or other unwanted software and immediately removing it.
Cellular, or cell, phones first became available to consumers in the early 1980s, but the technology that made them small and truly portable evolved gradually over the next 10 years or so. By the beginning of the twenty-first century, millions and millions of people in countries all over the world were using cell phones on a daily basis. And it isn’t just adults who enjoy the benefits of completely mobile phone capabilities: in the United States alone, more than 20 percent of teenagers have a cell phone. That translates to at least one in five American teens. The cellular system divides each city into many small cells (a large city can have hundreds). Each cell has its own tower (which contains an antenna as well as transmitters and receivers that send and receive signals). Each tower can handle numerous callers at a given time, and their small size and weaker signal (compared to the radio antennae) means that their signals don’t interfere with those of nearby towers. When you call someone using a cellular phone, your phone is sending and receiving signals via radio waves, invisible bands of energy that work like light rays. In other words, your cell phone is a fancy, high-tech radio. After you dial a friend’s number, your phone must find the closest tower by searching for the strongest signal. Once that signal is located, your phone transmits certain information—like your cell phone number and serial number—that help your service provider make sure you are one of their customers.
Then the mobile telephone switching office (MTSO) finds an available channel where your conversation can take place. The MTSO then completes the connection (all of this happening in a few short seconds) and you are chatting with your friend, without wires or cords to hold you down. If you are sitting in the back seat of the car while talking, and your mom is driving you from one end of town to the other, your call will be switched automatically from one cell tower to the next without any pause in your conversation.
Dogs bark to communicate with other dogs and with humans. Dogs are descendants of wolves, which are social animals that live in packs, and they share many of the behaviors that define the complex relationships that exist within such animal groups. Few domestic dogs live together in packs (though they often consider their human family their group), but they still use complicated behaviors that involve smell, sight, and hearing to communicate. A dog has many scent-producing glands that it uses to communicate. The scent that a dog leaves behind (in its urine, feces, and paw prints) can reveal its sex, age, and even its mood to other dogs that come sniffing by.
A dog uses its posture, facial expression, and ear and tail position to communicate with other dogs, too. And it uses its voice to communicate by whining, growling, howling, or barking. A dog usually whines or whimpers when it is in distress: when it is hungry, cold, or in pain. Growls indicate that a dog is angry and ready to fight. Barks usually show excitement.
Both bravery and courage are acts of valour and imply a certain strength and fearlessness. There is, however, a subtle difference in meaning between the two words. Courage comes from the French word coeur, meaning heart. It is a quality of character that allows someone to carry through with a difficult premeditated plan of action.
Bravery, on the other hand, comes from the Spanish word bravado, meaning a single or spontaneous act of valour. It is not planned, but rather a kneejerk reaction that often occurs within a crisis.
The expression dates back to the English Crown’s first efforts to control the Irish by outlawing their language and customs. But the unruly Irish were just that, and by the fifteenth century the English still controlled only a small area around Dublin, protected by a fortification called “The Pale,” meaning sharp sticks (i.e., impaled). To the British, to go “beyond The Pale” meant that you were entering the uncivilized realm of the wild Irish.
“Hanging out” usually means getting together for no particular reason other than to pass time and see what’s happening. The expression comes from a time before commercial signs, when English shopkeepers set up poles in front of their stores from which they would hang flags describing their goods. These flags were called hangouts, and they became a place where people would stop to linger and gossip with their friends.
The blue whale, who swims all of the world’s oceans, in the largest mammal. The largest blue whale cited was at least 110 feet (33.5 meters) long and weighed 209 tons (189,604 kilograms). The average length is about 82 feet (25 meters) for the males, and 85 feet (26 meters) for the females. A newborn blue whale can weigh anywhere from 2.5 to 4 tons (2,268 to 3,628 kilograms), and can reach 100 to 120 tons in adulthood. Whale calves drink 50 to 150 gallons of its mother’s milk per day, adding about 8 pounds (3.6 kilograms) of weight per hour, or 200 pounds (90.7 kilograms) per day.
At about eight months of age, when the calf is weaned, it measures close to 50 feet (15.2 meters) long and weighs about 25 tons (22,679 kilograms). Blue whales do not have teeth. Instead, in their upper jaw they have rows of hundreds of baleen plates—flat, flexible plates with frayed edges, arranged in two parallel rows that look like combs of thick hair. The blue whale feeds on a small shrimp-like animal called krill. Scientists believe that large marine mammals, like whales and dolphins, have brains much like those of humans. They are able to communicate, follow instructions, and adapt to new environments. Throughout history, these gentle giants have been hunted for their baleen and blubber (fat), and are today considered an endangered species. Scientists believe there are about 4,000 or so of them left in the world.
When the time came to honour the patron saint of Ireland’s birthday, church officials gathered solemnly to choose a day, then realized that most of St. Patrick’s life was a mystery. They finally narrowed his birthdate down to either March 8 or 9, but because they couldn’t agree which was correct, they decided to add the two together and declared March 17 to be St. Patrick’s Day.
In the early days of theatre, the players were lit by gas lamps hidden across the front of the stage. Early in the twentieth century, it was discovered that if a stick of lime was added to the gas, the light became more intense, and so they began to use the “limelight” to illuminate the spot on stage where the most important part of the play took place. Later called the “spotlight,” the “limelight” was where all actors fought to be.