Can you imagine a world without cameras? There would be no photographs in newspapers, books, and magazines, or even on your computer. There would be no school pictures, no snapshots of your summer vacation, no television, and no movies.
It’s hard to imagine, but that’s what the world was like until the mid-1800s. That’s when the first cameras were made.
BANG! Light and color burst overhead against a dark sky. Sparkles shower down like giant spider legs or twist and shoot into the night. Fireworks have delighted people for centuries.
WHAT ARE FIREWORKS MADE FROM?
Fireworks are small rockets filled with substances that burn brightly. Most are made from powdered chemicals packed into a stiff paper case.
Tiny flecks of metals give fireworks their color. A little bit of the metal copper, for instance, can make an explosion bright blue.
Radar was once a secret military weapon. In 1940 and 1941, radar helped Britain defend itself against German bombers during World War II. Today, radar has many uses. It prevents airplanes from colliding in midair. Radar is even found in many kitchens. Microwave ovens use radar technology to heat food.
WHAT IS RADAR?
Radar uses radio waves to locate airplanes, ships, storm clouds, and other large objects. A radar system sends out radio waves. These invisible waves move at the speed of light—about 186,000 miles (300,000 kilometers) a second. When the waves strike an airplane or other object, some of the waves bounce back.
Lasers are powerful enough to cut through steel. Lasers are delicate enough to use in eye surgery. Lasers “read” the information coded on compact discs (CDs). These are just a few things that lasers do.
WHAT IS A LASER?
A laser is a device that produces a beam of light and makes the beam more intense. A laser beam is very exact. It can travel a long distance without spreading out and losing its power.
Laser light is unlike sunlight or light from a light bulb. To understand the difference, think of a crowded city street.
ou hear a rumble and a roar. A blast of fire shoots out of a big rocket. The rocket heads up into the air. Maybe the rocket is carrying a satellite into orbit around Earth. Maybe the rocket is carrying a space probe to another planet!
Only a big rocket can make it into outer space. No other machine is as powerful as a rocket.
WHAT DO ROCKETS LOOK LIKE?
A rocket looks like a long tube. Most rockets have fins on the back end to help them fly straight.
Rockets that carry fireworks can be short, only a few inches long. They are usually made of cardboard.
Rockets that go into space are huge. They are made mostly of metal.