Guglielmo Marconi, of Bologna, Italy, was the first to prove that radio signals could be sent over long distances. Radio is the radiation and detection of signals spread through space as electromagnetic waves to convey information.
It was first called wireless telegraphy because it duplicated the effect of telegraphy without using wires. On December 21, 1901, Marconi successfully sent Morse code signals from Newfoundland to England.
The good thing about fission-generated nuclear energy is that very little fuel is needed to produce huge amounts of energy. (Two pounds of nuclear fuel could produce as much energy as 6.5 million pounds of coal, for instance!) The challenging part is that the process must be very carefully controlled. (In a nuclear reactor, control rods that absorb neutrons are moved in and out of the core to control the process.) If it isn’t controlled, the result could be a build up of pressure within the reactor. If this continues, radioactive gases might be released along with steam. It was a situation like this that happened at the Chernobyl plant in the Soviet Union in 1986, resulting in radioactive pollution that still exists today. An uncontrolled nuclear reaction can cause harmful radioactive materials (such as iodine isotopes that can cause thyroid cancer) to be released into the environment. This by-product of nuclear fission is a problem connected with nuclear power. Nuclear reactors are encased in thick layers of steel and concrete to keep radiation from escaping.
And because leftover nuclear fuel is highly radioactive, it must be carefully stored far away from people for decades or even centuries before it is safe again. Transporting and disposing of dangerous waste is another challenge presented by nuclear power; at present, used fuel is sealed in safety containers and buried deep underground. The nuclear process that we get our power from is called fission, where atomic nuclei that break apart produce great energy and heat. But nuclear power can also be created by a process called fusion, where atomic nuclei join together. Scientists are still working on creating a satisfactory fusion reactor. The Sun produces its great energy and heat through the nuclear fusion of its hydrogen gases.
1. We should never put anything in or near our eyes, unless we have a reason to use eye drops. We would only do that if our doctor or parent told us to use them.
2. If the lens in our eye doesn’t work quite right, we can get glasses to help us see. Glasses have lenses in them that work with our eye’s own lens to help us see better.
3. Just behind the pupil is a lens. It is round and flat. It is thicker toward the middle.
4. Over the front of our eye is a clear covering called the “conjunctiva.”
5. Blinking helps to wash tears over our eyeballs. That keeps them clean and moist. Also, if something is about to hit our eye, we will blink automatically.
6. Some people start to sneeze if they are exposed to sunlight or have a light shined into their eye.
7. The highest recorded speed of a sneeze is 165 km per hour.
8. Our eyes have many parts. The black part on the front of our eye is called the “pupil.” It is really a little hole that opens into the back part of our eyes.
9. Our body has some natural protection for our eyes. Our eyelashes help to keep dirt out of our eyes. Our eyebrows are made to keep sweat from running into our eyes.
10. The most common injury caused by cosmetics is to the eye by a mascara wand.
11. It is impossible to sneeze with your eyes open.
12. Around the pupil is a colored muscle called the “iris.” Our eyes may be BLUE, BROWN, GREEN, GRAY OR BLACK, because that is the color of the iris.
13. Our eyes are very important to us, and we must protect them. We don’t want dirt, sand, splinters or even fingers to get in our eyes.
14. The reason why your nose gets runny when you are crying is because the tears from the eyes drain into the nose.
15. The space between your eyebrows is called the Glabella.
16. The white part of our eye is called the “sclera.” At the front, the sclera becomes clear and is called the “cornea.”
17. We don’t want our eyes to get scratched or poked. That could damage our sight!
18. Babies’ eyes do not produce tears until the baby is approximately six to eight weeks old.
19. Inside our eye, at the back, is a part called the “retina.” On the retina are cells called “rods” and “cones.” These rods and cones help us to see colors and light.
20. Your eyes blinks over 10,000,000 times a year!
21. The study of the iris of the eye is called iridology.
22. The shark cornea has been used in eye surgery, since its cornea is similar to a human cornea.
23. The number one cause of blindness in adults in the United States is diabetes.
24. The eyeball of a human weighs approximately 28 grams.
25. The eye of a human can distinguish 500 shades of the gray.
26. The cornea is the only living tissue in the human body that does not contain any blood vessels.
27. The conjunctiva is a membrane that covers the human eye.
28. Sailors once thought that wearing a gold earring would improve their eyesight.
29. Research has indicated that a tie that is on too tight cam increase the risk of glaucoma in men.
30. People generally read 25% slower from a computer screen compared to paper.
31. Men are able to read fine print better than women can.
32. In the United States, approximately 25,000 eye injuries occur that result in the person becoming totally blind.
33. All babies are colour blind when they are born.
34. A human eyeball weighs an ounce.
Air is a mixture of gases that circle Earth, kept in place by gravity. Air makes up Earth’s atmosphere. The air we breathe is 78 percent nitrogen gas, 21 percent oxygen, 0.9 percent argon, and 0.03 percent carbon dioxide, along with water vapor (floating molecules of water).
Also present are traces of other gases and tiny bits of dust, pollen grains from plants, and other solid particles. As our atmosphere extends higher and higher above Earth, toward outer space, air becomes thinner and the combination of gases in the air changes.
Green plants get nourishment through a chemical process called photosynthesis, Which uses sunlight, carbon dioxide, and water to make simple sugars. Those simple sugars are then changed into starches, proteins, or fats, which give a plant all the energy it needs to perform life processes and to grow. Generally, sunlight (along with carbon dioxide) enters through the surface of a plant’s leaves. The sunlight and carbon dioxide travel to special food-making cells (palisade) deeper in the leaves. Each of these cells contain a green substance called chlorophyll.
Chlorophyll gives plants their green color and traps light energy, allowing food making to take place. Also located in the middle layer of leaves are special cells that make up a plant’s “transportation” systems. Tubelike bundles of cells called xylem tissue carry water and minerals throughout a plant, from its roots to its outermost leaves. Phloem cells, on the other hand, transport the plant’s food supply sugar dissolved in water—from its manufacturing site in leaves to all other cells.
Although a helicopter doesn’t have wings like an airplane, it uses the same principle of lift to rise and maneuver in the air. The blades of a helicopter’s propeller-like top rotor are shaped just like a plane’s wings—flat on the bottom and rounded on the top—and are likewise adjustable. Instead of rushing forward through the air like a plane does to gather enough lift to fly, a helicopter moves only its (three to six) rotor blades, which are attached to a central shaft driven by an engine.
The rotor blades slice through enough air—creating the changes in surrounding air pressure that produce lift—to achieve flight. Adjusting the angle at which the rotor blades are set helps control a helicopter’s lift and manner of flight. Because the angle of the rotor is adjustable, too, a helicopter has far greater maneuverability than an airplane: besides moving up, down, and forward, it can fly backward and hover in the air.
According to many religions based on Judaism and Christianity, heaven is a state of existence where a person’s spirit is at last united with God forever. In a number of Christian religions, heaven is believed to be the reward for people who have lived good lives according to certain rules of thought and behavior that God has made known through scriptures (sacred writings, like the Bible) and through the teachings of churches and religious leaders. (Those who have not followed these rules, it is believed by many, go to a place of punishment known as hell.) Many Christians believe that at the end of the world their human forms will be resurrected in a perfect state—just as the body of Jesus Christ was, when he arose from the dead on Easter morning—and join their souls or spirits in heaven for eternity.
This idea has led to the concept that heaven is an actual place—located above—with physical characteristics. Over the centuries, through pictures and writings, people have tried to create images of heaven, imagining a place of perfect happiness perched atop fluffy white clouds. It has often been portrayed as a place full of things that would bring happiness on Earth, possessing, for instance, pearly gates and streets of gold.
Jupiter, Saturn, Uranus, and Neptune have rings—or thin belts of rocks—around them. Jupiter’s ring is thin and dark, and cannot be seen from Earth. Saturn’s rings are bright, wide, and colorful. Uranus has nine dark rings around it, and Neptune’s rings are also dark, but contain a few bright arcs.
At one time all of the planets, Earth included, had rings. These rings were unstable and the material was either lost in space or collected into the satellites of these planets.
On a clear, dark night in your backyard, you can see about 2,000 or so stars in the sky, a small fraction of the 100,000 or so stars that make up our galaxy. They seem to twinkle, or change their brightness. In reality, most of the stars are shining with a steady light. The movement of air (sometimes called turbulence) in the atmosphere of Earth causes the starlight to get slightly bent as it travels from the distant star through the atmosphere down to the ground.
This means that some of the light reaches us directly and some gets bent slightly away. To the human eye, this makes the star seem to twinkle.
Rain forests—thick forests of trees and other plants found in the lowland areas of the Tropics around the world—exist in parts of Australia, Indochina, India, the Malay Peninsula, the East Indies, in central and western Africa, and in Central and South America. Unlike forests in many other parts of the world, which have been affected by global climate changes like the Ice Age, tropical rain forests have been growing uninterrupted in some places for millions of years. During that time an unimaginable number of different types of plants and animals have evolved to use every food source and live in every spot there. Tropical rain forests have more plant and animal species than the rest of the world combined, and scientists continue to discover new species. Because tropical rain forests are located near the equator, their climate is warm.
The name “rain forest” comes from the fact that they receive a lot of rain—between 160 and 400 inches (4 and 10 meters)—throughout the year. Plants grow very quickly under such ideal conditions. In order to get the sunlight that they need for photosynthesis (the process by which they and other green plants make their own food), rain forest trees grow very tall, up to 130 feet (40 meters) high. Their tops form a huge canopy that shades most of the ground, protecting plants on the ground from excessive sunshine as well as wind. Rain forest trees have very shallow roots, for the soil in which they grow is poor, having long been depleted of nutrients by the needs of thick plant life over millions of years. But the abundant life all around contributes organic matter (the decomposed remains of plants and animals) to the surface of the soil, which is enough to nourish these grand, ancient forests.