"Machines Then And Now"
1. The First Machines
A long time ago. They were simple tools made of stone, wood, or bone. About two million years ago people made stone axes with wooden handles. They used these tools to cut wood. People also used stone and animal bone to make knives and arrows.
About 7,000 years ago people started farming for food. They invented new machines, like plows, and used animals to make work easier
2. Round and Round
About 5,500 yeas ago potters used the first wheels to make clay pots. Before people ad wheels to move heavy objects, they used rollers. The rollers were made from tree trunks.
Today there are lots of machines with wheels. We can see wheels on cars, bicycles, and skateboards.
3. Ramps and Cranes
Ramps are useful because thy help us lift object more easily. More than 5,000 years ago the Ancient Egyptians used ramps to build pyramids.
The Egyptians used rollers to move large blocks of stone up the ramps. They needed lots of workers because the blocks were very heavy.
About 2,500 years ago the Ancient Egyptians Greeks used big cranes to build temples. The cranes were made of wood, and they had many ropes and little wheels called pulleys.
4. Water and Wind
Watermills use energy from flowing water. Thousands of years ago people built watermills next to rivers. They used the watermills to make flour from grain. Watermills have a big wheel on the outside. The river turns the wheel. then the wheel turns an axle inside the watermill.
Windmills use energy from the wind. Hundreds of years ago people started using windmills to make flour. Windmills have long arms with big sails. The wind pushes the sails and turns the arms. Inside the mill, an axle turns all a millstone.
5. Telling the Time
Thousand or years ago people used sundials. Sundials had a pointer that made a shadow to tell the time. A sundial only worked on sunny days!
Some people also used water clocks. Simple water clocks had two pots. Water flowed from the top pot to the bottom pot to tell the time. Later, people used sand clocks. These clocks had two glass bubbles with sand in side them.
About 1,000 years ago people invented mechanical clocks with metal gears. Some mechanical clocks have a pendulum to move the parts.
Today many clocks are digital. They show the time with only numbers. Digital clocks work with electricity.
6. Engines and Energy
For thousands of years people used animals to do work. Then inventors built steam engines. People used steam engines to power vehicles like trains and boats. This was the beginning of modern industry.
Then people invented new engines that used fuels like oil, gasoline, and diesel.
Now we use these engines for vehicles like cars, buses, planes, or helicopters. They can carry enough fuel to travel long distances.
7. Communications
For a long time, people sent messages on paper. Then people invented new machines to communicate more quickly and easily.
In 1876 Alexander Graham Bell invented the telephone. It transmitted sounds through wires.
In 1895 Guglielmo Marconi invented the radio. It transmitted sounds with no wires.
Communications today are very different. We walk on cell phones that transmit sounds with no wires. We can send text messages, photo, and videos. Many cell phones are also music players, and they can connect to the Internet!
8. Computer
One of the first computer was called ENIAC. It was built in about 1946. ENIAC was big and heavy.
Over the next 40 years computers became smaller and cheaper. From about 1980 people started using computers at home. then in 1989 Tim Berners-Lee invented the World Wide Web, or the Web.
Computers today are very useful. You see images on a monitor and you use a keyboard to type words. You use a mouse to move the cursor and click on buttons. To connect to the Internet you use a modem.
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