The Proccess of Photosynthesis

Plants need sunlight. Houseplants lean toward the Sun, and if they do not get enough light they wither and die. Plants use sunlight to make their food. This process is called photosynthesis.

 Photosynthesis is a scientific word made up from Greek words. These words mean “putting things together using light.” Inside plants’ leaves, light causes air and water to combine to make new chemicals. These chemicals are food for the plants.

DNA, Genes, and Heredity

Have you ever heard a news reporter talk about DNA? Reporters talk about DNA found at the scene of a crime. They talk about police finding DNA “fingerprints.” Police sometimes use DNA as a clue to find out who committed the crime.

DNA (deoxyribonucleic acid) is a substance that makes up genes. Everything alive has genes. Plants have genes. Animals have genes. You have genes.

Gregor Mendel

Gregor Mendel (1822-1884), Austrian monk, whose experimental work became the basis of modern hereditary theory.

Mendel was born on July 22, 1822, to a peasant family in Heinzendorf (now Hynčice, Czech Republic). He entered the Augustinian monastery at Brünn (now Brno, Czech Republic), which was known as a center of learning and scientific endeavor. He later became a substitute teacher at the technical school in Brünn. There Mendel became actively engaged in investigating variation, heredity, and evolution in plants at the monastery's experimental garden. Between 1856 and 1863 he cultivated and tested at least 28,000 pea plants, carefully analyzing seven pairs of seed and plant characteristics. His tedious experiments resulted in the enunciation of two generalizations that later became known as the laws of heredity. His observations also led him to coin two terms still used in present-day genetics: dominance, for a trait that shows up in an offspring; and recessiveness, for a trait masked by a dominant gene.

The Water Cycle (Rain Cycle)

Maybe you recycle cans, glass, and paper. Did you know that nature recycles, too? One of the things nature recycles is water. Water goes from the ocean, lakes, and rivers into the air. Water falls from the air as rain or snow. Rain or snow eventually find their way back to the ocean. Nature’s recycling program for water is called the water cycle.

The water cycle has four stages: storage, evaporation, precipitation, and runoff. Most of the water on Earth is in the first stage, storage. Water on Earth gets stored in oceans, lakes, rivers, ice, and even underground. The oceans store the majority of this water.

Will the Universe end?

 Look up at the sky on a clear, starry night. What you see is part of the universe. You could never see all of the universe. No one even knows whether the universe has an edge or if it goes on forever. The universe contains all matter and energy. The universe holds all space and time. You are a part of the universe. The universe includes everything there is.

Earth and all the planets in our solar system make up just a tiny part of the universe. Billions of other stars like our Sun all form a group called the Milky Way Galaxy. With telescopes we can see billions of other galaxies. Galaxies are in turn clumped together in enormous groups called clusters and superclusters. There are at least 100 billion that’s 100,000,000,000 galaxies in the universe. The universe is a big place!

The universe holds many strange things, such as exploding stars. It holds great clouds of gas and dust where new stars form. It also holds black holes. Black holes have a pulling force called gravity. Gravity is the force that holds you to the ground and makes things fall when you drop them. Black holes suck in all the matter around them. The gravity of black holes is so strong that nothing, not even light, can escape.

Astronomers think there is even more matter in the universe than we can see. The matter we see makes up gas, dust, galaxies, stars, and planets. Astronomers think there is a type of invisible matter that they call dark matter. They think there may be a lot more of this mysterious dark matter in the universe than there is regular matter that we can see.

Astronomers also think the universe holds a strange substance that they call dark energy. They don’t know much about dark energy except that it seems to make the universe expand.

Many astronomers think the universe began about 14 billion years ago. They think it suddenly exploded into being. They call this beginning the big bang. All space and time began with the big bang. With a special telescope, astronomers can see radiation left over from the big bang. They call this cosmic background radiation.

The big bang theory says that the universe was hotter than you can even imagine at the moment it began. The universe started to fly outward, or expand. As it expanded, it started to cool. Tiny particles that would make up matter started to form. All of this happened in just a few minutes.

When the universe was about 1 million years old, it had cooled to about 5900° Fahrenheit (3300° Celsius). This temperature was still scorching, but it was cool enough that tiny bits of matter called atoms started to form. All the objects around you the computer, the floor, the air are made of atoms. The hot atoms gave off rays of light. The universe was like a huge, hot fireball.

Over millions of years, the force of gravity pulled gas and dust together. Stars and galaxies formed from clumps of gas and dust. The stars began to shine. Our Sun and our solar system formed about 4.6 billions years ago.

Rays of light travel across the universe. Even though light travels extremely quickly, it takes light millions or billions of years to travel from galaxies far away. When astronomers see light from the most distant galaxies they know the light is “old.” They know they are seeing the galaxies as they were billions of years ago.

Astronomers want to know what will happen to the universe. They think it is still expanding. In fact, the universe seems to be expanding faster and faster as time goes on. Many astronomers think the universe will go on expanding forever. If it keeps on expanding, everything in the universe will eventually grow cold. Billions of years in the future even the stars will stop shining.

Why is Gold valuable?

“Gold! Gold! Gold!” screamed the newspaper headlines. “Gold discovered in California!” That was in 1848. The news brought 100,000 people rushing to California. They came seeking the yellow metal that could make them rich.

People since ancient times have used gold for jewelry and money. They used it in religious objects and works of art. Wars have been fought over gold. And sometimes, as in California, gold changed the course of history.

Gold is unusual among metals. It does not rust or tarnish (grow dull and discolored). Gold coins recovered from sunken treasures are still as shiny as when they sank.

Gold is soft enough to be easily shaped into jewelry and other items. An ounce (31 grams) of gold can be hammered into a sheet 16 feet (5 meters) on each side. It can be stretched into a wire 62 miles (100 kilometers) long.

People find gold beautiful. And it is rare. All the gold in the world would fit in a cube 65 feet (20 meters) on each side. Because it is so rare, its value doesn’t change much from one year to the next. In ancient times, people could easily carry a lot of wealth in the form of a small bag of gold.


The easiest way to mine gold is with a pan. You fill the pan with sand or gravel that contains tiny bits of gold. Then you swirl the pan under a gentle stream of water. The lighter gravel or sand gradually washes out with the water. The heavier gold particles collect at the bottom of the pan. Gold is so heavy that it doesn’t take many tiny flakes to make an ounce.

Today, gold is most often mined by digging underground with machines. Rock that contains gold is treated with chemicals to separate out the gold. Nuggets of solid gold are quite rare. The largest nugget ever found weighed about 130 pounds (59 kilograms). It was found in Australia in 1869. About two-thirds of all gold mined today comes from South Africa.

Gold is used for many things besides coins, decorations, and jewelry. Gold conducts electricity very well. It is used in tiny electrical circuits. There are very small amounts of gold in your computer.

Gold is also used to protect tall buildings and spaceships from the Sun’s heat. The Sun's rays bounce off even a thin coating of gold. Gold-coated mirrors are used in telescopes. Dentists use gold for tooth fillings. Gold is even used in medicine, to treat cancer and arthritis.

Gold has always made people who controlled it wealthy. Folktales of many peoples tell of greed for gold. The ancient tale of King Midas tells of a greedy king. Midas wished that everything he touched would turn to gold. But he was sorry when his wish was granted. He could not eat because his food and water also turned to gold.

In the 1500s, the Spanish conquered Mexico and Peru while searching for gold. They brought back tons of gold looted from native peoples. The peoples of those regions had never considered gold very valuable.

The discovery of gold in parts of western America and Australia brought in thousands of people seeking quick fortunes. Many stayed on and settled those regions.

How do Crystal form?

Look closely at some table salt through a magnifying glass. You’ll see that the bits of salt are made up of tiny cubes. Each cube is a salt crystal. The salt crystals within the particles can be different sizes, but they always have this shape.

A crystal contains identical particles that are arranged in a particular pattern such as a cube, rectangle, or hexagon. As a crystal grows in size, this pattern is repeated over and over.

Salt is made up of the elements sodium and chlorine. Extremely tiny particles of sodium and chlorine, called atoms, form a repeating cubic pattern in a crystal of table salt. The more times the pattern is repeated, the bigger the crystal that forms.

Crystals form when some liquids turn into solids. A liquid may freeze into a crystal. Snow, for example, is made of tiny crystals of frozen water. Crystals can also be left behind when a liquid dries out. When seawater in a rock pool dries out, tiny crystals of salt remain.

Most of the rocks and minerals in Earth’s crust are crystals. Some crystals were formed from melted rock when it cooled and became solid. Others were left behind by the waters of a sea, lake, or river that dried up long ago.

Many crystals are beautiful. Diamonds, rubies, and emeralds are crystals that are made into attractive jewelry. Crystals also have many practical uses. Quartz crystals are used in clocks, radios, and sonar, the system that allows ships and submarines to see things underwater. Quartz crystals can also be pressed or heated to make electricity.

Who discovered gravity?

Try to jump as high as you can. Bend your knees. Now jump! No matter how hard you try, or how high you jump, you always come back down again.

Something called gravity pulls you back down. Gravity holds you down on Earth. Without gravity, you would fly off into space. You would jump up and just keep on going. That might sound like fun, but you could not live very high up. For one thing, you need to breathe air. The higher you go, the less air there is. You need gravity to keep you down on Earth.