The Japanese word tsunami (pronounced soo-NAH-mee) means “harbor wave.” It is a huge volume of moving seawater—kind of like a giant wave—that can travel for thousands of miles across the sea and then approach the shoreline with the strength to destroy buildings, trees, wildlife, and people. Tsunamis can be triggered by an undersea earthquake, landslide, or volcanic eruption. The most frequent tsunami-maker is an undersea earthquake, which buckles the seafloor and displaces large volumes of seawater, creating a tsunami. This unique ocean event is not related to tides, although it is sometimes mistakenly called a tidal wave.
In 1823, the English mathematician originated the concept of a programmable computer. At this time, he persuaded the British government to finance what he called an “analytical engine.” This would have been a machine that could undertake any kind of calculation. It would have been driven by steam, but the most important innovation was that the entire program of operations was stored on a punched tape (a long strip of paper in which holes are punched to store data).
Babbage’s machine was not completed in his lifetime because the technology available to him was not sufficient to support his design. However, in 1991 a team lead by Doron Swade at London’s Science Museum built the analytical engine (sometimes called a “difference engine”) based on Babbage’s work. Measuring 10 feet (3 meters) wide by 6.5 feet (2 meters) tall, it weighed three tons and could calculate equations down to 31 digits. The feat proved that Babbage was way ahead of his time, even though the device was impractical because one had to a turn a crank hundreds of times in order to generate a single calculation. Modern computers use electrons, which travel at the speed of light.
A rainbow is an arc that shows all the colors, with their different wavelengths, that make up visible light. Seven colors make up a rainbow, and they always appear in the same order: red, with the longest wavelength, is on the top, followed by orange, yellow, green, blue, indigo (a deep reddish-blue that is often difficult to see), and violet, which has the shortest wavelength. A good way to remember the order of those colors is by taking the first letter of each to spell “ROYGBIV,” pronounced “roy-jee-biv.” A rainbow occurs when sunlight passes through water droplets and is refracted or bent by their rounded shape into separate wavelengths.
Rainbows can sometimes be spotted in the spray of lawn sprinklers, in the mist of waterfalls, and—most spectacularly—in the sky during a rain shower when the Sun is still shining. A rainbow appears in the part of the sky opposite the Sun. Because the Sun must also be low in the sky, near the horizon, late afternoon is the best time to look for a rainbow if the day has been sunny with a few short rain showers or thunderstorms.
Farmers and state governments use chemical pesticides to protect their crops from insect pests, weeds, and fungal diseases while they are growing. They also spray their crops with pesticides to prevent rats, mice, and insects from contaminating foods while they are being stored.
While these actions are meant to benefit human health and bring a wide variety of fruits and vegetables to the supermarket, they can also harm people, wildlife, and the environment. This is why there are strict controls in place over their sale and use.
The Joshua tree is a desert tree that grows in southwestern North America, in California, Arizona, Utah, and Nevada. A native of the Mojave Desert, these droughttolerant trees thrive in the open grasslands of California’s Joshua Tree National Park. The Mormon pioneers named this tree after the prophet Joshua, because its extended branches resembled the outstretched arm of Joshua as he pointed with his spear to the ancient city of Ai. The trees are twisted and spiky, with tough leaves, and look a little bit like a tree from a Dr. Seuss book. Joshua trees can grow from seed or from an underground rhizome of another Joshua tree. They grow very slowly, sometimes 3.9 to 7.8 inches (10 to 20 centimeters) in their first few years.
The tallest trees reach about 49 feet (15 meters) tall. The trunk of a Joshua tree is made of thousands of small fibers and does not have yearly growth rings, Which makes it hard for scientists to tell the tree’s age. Although the fragile tree has shallow roots, if it survives the harsh desert environment, it can live hundreds— even thousands—of years.
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.
Frogs are able to make their croaking noises because they have simple vocal cords that have two slits in the bottom of the mouth. These slits open into what is called a vocal pouch. When air passes from the lungs through the vocal cords, a sound is produced. The inflating and deflating vocal pouch makes the sound louder or quieter.
That sound changes depending on the kind of frog there are as many different kinds of croaks as there are frogs! Frogs croak for the same reasons that many animals make noises: to track down and then select a mate, and to protect their territory from other male frogs.
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.
Most people think that Mercury is the hottest planet because it is nearest to the Sun. However, Venus, the second nearest planet, is the hottest because it has an atmosphere. Its atmosphere is primarily composed of carbon dioxide, which acts like a greenhouse.
The solar heat enters Venus’s atmosphere, but it cannot leave, heating the planet’s surface to about 900 degrees Fahrenheit (482 degrees Celsius). This temperature is hot enough to melt several metals, including lead, tin, and zinc.
Quickly gobbling up cold ice cream may result in “brain freeze,” also know as an ice cream headache. When the cold object touches the roof of your mouth, the blood vessels contract in order to prevent loss of body heat. As the coldness stops, the blood vessels relax again, quickly increasing blood flow to the brain.
This sudden release is What causes the intense headache sensation. You can relieve brain freeze by quickly warming the roof of your mouth: Touch your tongue to the top of your mouth or, if you can roll your tongue in a ball, press the underside of your tongue (which is warmer) to the roof of your mouth. Slowly sipping room-temperature water or pressing a warm thumb against the roof of the mouth also works for some people.