Place to Live

A Place to Live

People must have shelter to survive. They will die without protection from the sun, rain, wind and cold. Today, people can live in almost every part of the world because they have learned to build walls and to put a roof over their heads. For centuries, people had no tools to cut or move trees and large stones, so the first houses were built from materials that were hard rocks with sharp edges could cut trees and other rocks, and these became the first building tools. Many centuries later, people melted metals from rocks to make stronger, sharper tools. In places with little stone or wood, people made sun-dried bricks out of mud to build their houses. Some of the earliest cultures in history were the first to discover and use many of the basic building materials still used today.

Did you know?

The basic methods used to support the roofs of many great buildings were first developed in ancient villages to hold up the roofs of huts.

The Roof

A waterproof roof is made from grass by thatching. Bundles of swamp grass are tied to a wooden frame so that each bundle overlaps the ones next yo it and below it.

Stone Hut

Walls of stone shaped with tools surround clusters of houses in many ancient villages. Each house has several rooms and each room has its own dome. Some even have a second story. Smoke from fires used for cooking escapes through holes in the roof.

A perfect place to live. Photo by Elena.

Making Bricks

Sun-dried mud bricks were perhaps the first synthetic building material ever made. A mixture of mud and straw is pressed into molds then laid out in the sun to dry. The straw holds the bricks together so they do not crumble. As rain will dissolve sun-dried bricks, a coating of lime is added or a wide roof is built to protect the walls.

Beehive Hut

A hut on Dingle Peninsula in Ireland looks like a beehive. It was built centuries ago. It was built centuries ago by a monk who piled up small flat stones cleared from his fields. He stacked each circle of stones on top of the circle below and made each stone slope downwards slightly towards the outside, so rain could not get in (as well in the village of Haaran on the Turkish-Syrian border).

The Walls

A man in weaving mats from palm fronds or leaves, which will become the walls of his hut. Weaving stiffens the fronds.

South Pacific Woven Huts

On the Trobriand Island of Papua New Guinea, houses are still built from small trees cut with stone tools. The pieces of wood are tied together with vines to form the frame of each house. The island people use plant material to complete the house. Grass and leaves vend easily and people thought they seemed too weak to use for building until they discovered how hard it was to pull them apart.

War and Peace

Today and Tomorrow

War and Peace

Technological progress is faster in times of war. Each side tries to make weapons and machines that are bigger and better than those of the enemy. At the beginning of the First World War, for example, the typical flying speed of an airplane was 70 miles per hour. By the end of the war this speed had doubled. In the Second World War, the Germans introduced two inventions that later transformed flight – the turbojet, which became the basis of modern aircraft, and the ballistic missile, which took aviation from the skies into space.

Some wartime inventions, such as the tank, are only suited to war, but many have other uses. The antibiotic penicillin, which saves many lives, was invented in 1941 to cure the infected wounds of soldiers. It is impossible to say whether more good has come from wartime inventions than bad. But one thing is certain, many things were invented because of war.

Radio Detection and Ranging

In 1935, the scientist Robert Watson-Watt was asked by the British army to invent a radio death ray for warfare. Instead, he invented radio which detects enemy aircraft using radio waves.

Guided Missiles 

All modern strategic missiles and space rockets were developed from the work of a team of Second World War German scientists, who created more than 20 types of missiles. Air-to-air guided missiles, such as this one, are used for aerial combat. 

Red Floppy. Photo by Elena.

Armored Tank

The tank lurched onto First World War battlefields in 1916, thanks to the combined efforts of a number of inventors and British army officers. This modern United Nations tank has a swiveling gun turret and lookout post.

Modern Armor

Heavy steel armor plating was first used in America in 1862 to strengthen warships. Today's tanks are encased in lightweight but strong metal alloys, plastics and even ceramics.

Stealth Fighters

Difficult to detect because of their shape and a radar absorbent coating, F-117 fighter bombers are designed for precision attack. They were used by the United States in the Gulf War in 1991.

Lethal Weapons

Grenades have been around for more than 500 years. In the 1600s, French soldiers, called greanadiers, were trained specially as throwers. Plastic explosives, once unwrapped from their sausagelike skins, can be molded into position. They were used in military operations to shatter parts of bridges and buildings.

Caterpillar Tracks

In 1904, Benjamin Holt built a tractor that laid down its own track under the rear wheels to travel over mud. A continuous track enables it to break through fences and go over deepgullies.

Night Vision

Since the 1950s, scientists have been working on devices to make it possible for soldiers to fight in the dark. The night-vision goggles shown below are sensitive to low levels of light, such as reflected straight or moonlight. The goggle intensify this light and allow soldiers to see, move and shoot at night as well as they can during the day. In theory, 24-hour war is now possible.

Time-line

• 1861 : Sea Mine – USA
• 1862 : Machine Gun – Richard Gatling, USA.
• 1883: Automatic Machine Gun – Hiram Maxim, USA.
• 1902: Exploding Bullet – John Pomeroy, New Zealand.
• 1915: Sonar – Paul Langevin, France.
• 1944: V2 Rocket Bomb – Wernher von Braun and Walter Dornberger, Germany.
• 1945: Atomic Fission Bomb – Project Manhattan scientists, USA.
• 1952: Hydrogen Bomb, USA.
• 1984: Stun Gun, USA.
• 1985: Flashball Gun – François Richet, France.

War and Peace. Illustration by Elena.

Biotechnology

Biotechnology

We use biotechnology to alter living things. It gives us the power to create new animals, plants, foods, medicines, materials and even machines. People have used biotechnology for thousands of years to slowly breed new plants, animals and the microorganisms that make cheese, bread, beer, yogurt and wine.

In 1987, geneticist Truda Straede of Australia created spotted cats after breeding toroiseshell cats with Burmese and Abyssinian cats for ten years. Today, modern biotechnology could speed up this breeding process by altering the genetic material deep inside the cells. Scientists have already created bright blue carnations, and tomatoes that ripen on the vine without getting mushy. Biotechnology's potential is enormous. We can even use bacteria grown in laboratories to digest oil to clean up oil spills. The next hundred years will be an age of exciting ”bio-inventions”.

Spot the Difference

In the future, the spot-making genes from a leopard could be mixed in with the genes of a domestic cat to produce a spotted animal.

Killer Cotton

In 1992, an American company altered the genes in some cotton plants so that their leaves became poisonous to caterpillars but nothing else. This reduced the need for harmful insecticides.

Two cats, Jamaica. Photo by Elena.

Strange but True

In 1994, scientists in Australia invented a way of removing fleece from sheep without shearing. They injected sheep with a special hormone then wrapped them in lightweight hairnets. Three weeks later, the fleece could be peeled off the sheep by hand.

Transgenic Pigs

The heart of a pig is similar in shape and size to the human heart. People and pigs, however, have very different genes. Scientists in England have developed a virus that carries human genes into pigs. This makes it possible for the human body to accept the heart of a pig in a transplant.

Changing Genes

Every living cell has spiral-shaped deoxyribonucleic acid (DNA), discovered in 1953 by Francis Crick and James Watson at Cambridge in England. The DNA is made up of genes that control how the cell works. Biotechnhologists have learned how to alter the genes and change living cells.

• 6000 BC: Beer – Mesopotamia.
• 1000 BC: Cheese – Nomad tribes, Middle East.
•  1972: Oil-digesting microbes – Dr. Ananda M. Charkabarty, USA.
• 1975: Monoclonal Antibody – George Kohier and Cesar Milstein, England.
• 1984: Transgenic plant – University of Ghent, Belgium.
• 1986: Black Tulip, Geert Hageman, Netherlands.
• 1989: Gene Shears – James Haseloff and Wayne Gerlach, Australia.
• 1990: Crown Gall Bactericide – Dr. Alan Kerr, Australia.
• 1991: Long-life Tomato, USA.

On a Farm

On a farm

The plow and irrigation have tamed more farmland than any other farming inventions. People first grew crops in the Middle East about 10,000 years ago, but planting, harvesting and watering them by hand was a slow process.

In Egypt and India, nearly 4,500 years later, farmers prepared the ground for planting with wooden plows pulled by oxen. The Egyptians invented a machine called a shaduf, which helped them take water from the River Nile to irrigate or water their crops. Barbed wire was another great farming invention. Farmers used it to divide huge areas of Africa, North America and Australia into separate wheat, cattle and sheep farms in the 1800s. These enormous new farms revolutionized farming. Farmers now needed faster ways of harvesting grain, wool, meat and milk. The old methods were soon replaced by machines that did the work of hundreds of people.

Spade

Wooden spades with iron blades were invented by the Romans about 2,000 years ago.

Barbed wire

In 1867, American Lucien Smith invented barbed wire and made it possible for farmers to fence off their lands.

Cows and barbed wire. Photo by Elena.

Four jobs in one

In 1884, Australian Hugh McKay invented the horse-drawn harvester. It combined cutting, threshing, winnowing and bagging wheat grain into one operation. Combine harvesters with gasoline or diesel engines are now used 24 hours a day, with lights at night, to harvest the crops.

Watering the Crops

The Egyptian shaduf is a little like a seesaw. A long wooden pole, balanced on a crossbeam, has a rope and bucket at one end, and a heavy stone weight to counterbalance it at the other. The weight of the rock makes it easier to lift a heavy bucket of water.

Did you Know?

Superphosphates – aftificial chemicals that enrich the soil – were invented by Sir John Bennett Lawes in England in 1842. But fertilizers often run into the rivers and oceans, killing fish and making algae grow,

Plow

Plows made from wood and stag antlers were invented in Egypt and India about 5,500 years ago. Simple ox-drawn plows are still used on family farms in many countries.

Tractor

Three-wheeled steam tractors, built by the Case company of America in 1829, were very heavy and often became stuck in the soft soil. Modern tractors were pioneered by Henry Ford in 1907.

Time-line

• 1794: Cotton Gin (separator) – Catherine Green and Eli Whitney, USA.
• 1831: Grain Reaper (Cutter) - Cyrus McCormick, USA.
• 1833: Steel Plow – John Lane, USA.
• 1860: Nutriculture – Julius vos Sachs, Germany.
• 1868: Granny Smith Apple – Maria Smith, Australia.
• 1889: Modern Milking Machine, William Murchland, Scottland.
• 1924: Aerial Crop Dusting, USA.
• 1939: Dot Pesticide: Paul Muller, Switzerland.
• 1975: Axial Combine Harvester – International Harvester, New Holland, USA.

The Ways of Water

The Ways of Water

Water covers more than two-thirds of the Earth's surface and is constantly on the move. It rushes along rivers and streams ; it flows into oceans.

This endless movement of water creates energy that can be harnessed. For centuries, people have channeled flowing water into waterwheels that turn to grind grain. Hydroelectric power stations use water in a similar way, but to generate electricity. These enormous concrete constructions are usually found in mountainous regions where there is a high rainfall. Engineers build huge dams across steep-sided valleys. Turbines (modern versions of ancient wooden waterwheels) are placed in the path of the water that gushes with force through the dam. This torrent of water strikes the angled blades of the turbines, which begin to spin and extract an incredible amount of energy from the water. The process of producing hydroelectric power is set in motion.

Control room

The operation of the entire power plant is directed from the control room.

Watering the land

The water for this insectlike irrigation system is coming from the dam of a hydroelectric power station.

Transmission lines

Strengthened electric cables called transmission lines carry electricity away from the power plant.

Way of Water. Photo by Elena.

Spillway

The spillway gates are opened to release water when the level of water behind the dam is too high.

Reservoir

The deep lake that forms behind the dam wall is called a reservoir. The reservoir is built to make sure there is always enough water to operate the generators.

Dam Walls

There are usually curved to withstand the enormous force of water pressing against them. The walls are thicker at the base than the top.

Transformers

Transformers boost the electrical force from the generators to more than 200,000 volts.

Penstock

This channels water from the reservoir through the dam to the turbines

Generators

The spinning turbines are connected by shafts to electricity generators. When the turbines spin, the generators make electricity.

Turbines

Water flowing through tunnels in the dam makes the turbines spin at high speed. Once the energy has been removed, the water flows away through the center of the turbines.

Make Your Own Waterwheel

Cut four pieces of cardboard 1 ½ in x ¾ in and collect an empty thread spool and drinking straw (Step 1) to Glue each piece of cardboard to the thread spool (Step 2) and push the drinking straw through the middle so that your waterwheel can spin easily. Hold the wheel under a running faucet. When water hits the card paddles, the wheel will turn (Step 3).

A Daily Grind

Water-powered hammers are used in Laos in Southeast Asia to grind rice. When the paddles are turned by the flow of the river, the crossbeam at the end of the axle raises the hammer, then releases it to fall on the rice below.