An eclipse happens when one object in space blocks another from view. For example, during a solar eclipse the Moon comes between Earth and the sun. The Moon blocks the sun for a time so that people on Earth cannot see it.
Solar eclipse is one of nature’s most breathtaking eclipses. It happens when the Moon moves in front of the Sun for a few minutes, blocking its light and underneath the Moon’s shadow darkness falls. There are three types of solar eclipses: total, partial, and annular. Total solar eclipses are rare.
Unlike a solar eclipse, where the Sun is hidden, we can still see the Moon during a total lunar eclipse. This is because there is enough scattered light from the Earth to illuminate the lunar surface, but in a deep blood red.
Eclipses are very short, with totality lasting just a couple of minutes. Others can last six or seven minutes. You can see the planets during an eclipse.
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Water is the most important liquid on Earth. It covers almost 75 percent of Earth’s surface in the form of oceans, rivers, and lakes. All plants and animals need water to live.
Water is made of tiny units called molecules, which are combinations of even smaller units called atoms. A molecule of water is made of two hydrogen atoms and one oxygen atom. The scientific formula for water is H2O.
Water can be found in three physical states: liquid, solid (ice), or gas (steam or vapor). Freshwater boils when it reaches 100° C and freezes at 0° C.
Most of Earth’s water is in the oceans. But water is constantly being recycled. Through a process called evaporation, water moves from Earth’s surface into the air as water vapor. The vapor can form clouds, which make rain and snow. Rain and snow bring water back to the ground again and into lakes, streams, and oceans. Some of the water seeps underground, where it is called groundwater.
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Rain is the liquid form of water that falls from the sky in drops. Rain fills lakes, ponds, rivers, and streams. It provides the freshwater needed by humans, animals, and plants. Rain is a part of Earth’s endless water cycle.
It may sound a paradox, but it is actually rain that keeps the earth dry. If the moisture was not taken out of the air and formed into clouds, it would condense on every solid surface. We would feel as if we were in a steam bath.
Rain falls almost everywhere on Earth. One of the world’s rainiest places is Mount Waialeale in Hawaii. It rains about 350 days a year there. One of the driest places on Earth is the Atacama Desert in Chile.
The Sahara desert in Africa is very dry. Rain never falls on some parts of it. It is true that clouds pass over those areas and actually drop rain but the rain never touches the ground. The heat of the desert air evaporates the moisture as it falls.
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Clouds are made of water—thousands of gallons of water, floating high in the air. It’s easier to believe this when you know that cloud water takes the form of tiny droplets. The droplets are so tiny that you couldn’t see one if it was separated from all the others. If all these water droplets in a cloud meet a mass of warm air they evaporate – and the cloud disappears! This is why clouds are constantly changing shape.
Sometimes the water droplets join together around tiny pieces of dust in the air. These drops get bigger and bigger as more droplets collect. When they become too heavy to float, they fall.
There are three main kinds of clouds. “Cumulus” refers to the small puffballs or great wooly-looking clouds that are flat on the bottom. “Stratus” are low clouds, usually streaky or without much shape. And “cirrus” are light feathery clouds, like the ones in the photo. Sometimes cirrus clouds are so high, where the air is very cold, that the whole cloud is made of ice.
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Cotton is the most important and widely used natural fiber in the world. It is primarily an agricultural crop, but it can also be found growing wild.
Cotton was one of the first cultivated plants. There is evidence that the cotton plant was cultivated in India as long as 5,000 years ago.
The cotton plant is cone or pyramid shaped and grows to a height of 0.9–1.8 m. The fruit of the cotton plant is called the boll. Different kinds of cotton plant produce fibers of different lengths. The longest fibers may be 6.5 centimeters long.
Cotton plants grow in warm areas in many parts of the world. Some of the top cotton-growing countries are the United States, Pakistan, India, and Uzbekistan. China is the world’s biggest producer of cotton.
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About 10,000 BC, man first started eating flat bread — a baked combination of flour and water. Ancient Egyptians were the first to have baked leavened bread. About 3,000 BC, they started fermenting a flour and water mixture by using wild yeast. Since wheat is the only grain with sufficient gluten content to make a raised or leavened loaf, wheat quickly became favored over other grains grown at the time, such as oats, millet, rice, and barley.
In 150 BC, the first bakers’ guilds were formed in Rome. Wealthy Romans insisted on the more exclusive and expensive white bread. Roman bakeries produced a variety of breads and distributed free bread to the poor in times of need.
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Bees are four-winged stinging social insects producing wax and honey. They live all over the world except Antarctica. There are more than 20,000 species, or types, of bee. The best-known kinds are honeybees and bumblebees. Like all insects, bees have six legs. They have two pairs of wings and five eyes. They also have mouth parts that act like a long tongue.
We can distinguish among them queens, workers and drones.
Some people are afraid of bees, for they think that the bees will sting them, but unless a bee is frightened it does not sting. So the bee flying from flower to flower to collect honey and pollen is not dangerous.
There are thousands of bees in a hive, but only one queen, who spends all her time laying eggs. The queen bee is the biggest bee in the hive.
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