Scientists do not know exactly why people need sleep, but studies show that sleep is necessary for survival. Sleep appears to be necessary for the nervous system to work properly. While too little sleep one night may leave us feeling drowsy and unable to concentrate the next day, a long period of too little sleep leads to poor memory and physical performance.
Hallucinations (seeing things that aren’t really there), vision problems, and mood swings may develop if sleep deprivation continues.
Television works through a series of complicated processes. It starts with a television camera, which takes pictures of scenes. Photo cells inside the camera change the pictures to electrical signals. At the same time, a microphone records sounds that are occurring during the scenes. A vibrating magnet in the microphone changes these sounds into electrical signals, too. Some television shows, like news reports, are recorded live, which means that they are broadcast to homes as they occur. But most of the television programs that we watch are recorded, which means that they are put on videotape and sent out later. The electrical signals of sound and pictures are stored as magnetic signals on videotape, which are converted back to electrical signals when played. Before a program is broadcast, its electrical picture and sound signals are run through a device called a television transmitter. With the help of strong magnets, the transformer turns the electrical signals into invisible bands of energy called radio waves (similar to visible light waves), which can travel great distances through the air. They can travel directly to outdoor television antennae, which catch the waves and send them to television sets that change them into pictures and sounds again.
Cable companies send electrical picture and sound signals through cables directly to homes. When broadcasting to distant places, communication satellites that orbit Earth are used to bounce or return the waves back to Earth, extending their travel distance. Satellites are necessary because radio waves move in straight lines and cannot bend around the world. When an antenna or satellite dish receives radio waves, it changes them back into electrical signals. A speaker in a television set changes some of the signals back into sound. The pictures are reproduced by special guns at the back of a television set that shoot electron beams at the screen, causing it to glow with tiny dots of different colors. Viewed together, the dots look like a regular picture. The individual pictures that make up a scene are broadcast and received, one after another, at a pace so quick that it looks like continuous action is occurring on the screen. The entire process happens very fast because television stations and broadcast towers are all around and because radio waves travel very quickly, at the speed of light. Radio programs broadcast talk and music across the airwaves using the same technology.
Yes. The air inside your home might be filled with toxins from tobacco smoke, cleaning products, ceiling tiles, and upholstery. Scientists have discovered that many types of houseplants absorb airborne pollutants as part of their normal “breathing” process—they take carbon dioxide in through their leaves, and let oxygen out. The plant transports these toxins to their roots, where microbes feed on and detoxify them.
Although scientists disagree about how many—and what types of—houseplants it takes to clean the air, they suggest using a mix of plants. Bill Wolverton, a former NASA scientist and environmental engineer, studies the effects that plants have on air quality and has rated the areca palm, lady palm, bamboo palm, rubber plant, and dracaena as highly effective at clearing pollutants from the air.
On the outside, most electric cars look exactly like gas-powered cars. An electric car does not have a tailpipe or a gas tank, but the overall structure is basically the same. Instead of a huge engine, an electric car uses an electric motor to convert electric energy stored in batteries into mechanical energy.
Different combinations of generating mechanisms—solar panels, generative braking, internal combustion engines driving a generator, fuel cells— and storage mechanisms are used in electric vehicles.
Technically, no. While it is responsible for receiving and transmitting all messages of pain for the whole body, the brain itself does not have pain receptors.
That means that, if you could somehow gain access to another person’s brain, you could poke it or pinch it and that person would not feel the pain.
The deepest hole ever made by humans is in Kola Peninsula in Russia, where in 1989 geologists dug a hole 7.6 miles (12.2 kilometers) deep. The Kola Superdeep Borehole began in the 1970s.
Russian teams used special drilling techniques to dig into the Baltic continental crust, presumed to be about 22 miles (35 kilometers) thick, exposing rocks 2.7 billion years old at the bottom.
A roller coaster works the same way as a bicycle coasting down a hill. When you ride your bike to the top of a hill, you pedal to get there. Then, to coast down the hill, you take your feet off the pedals and glide down the other side. If the slope is steep enough, you can go very fast. Similarly, a roller coaster is only powered at the beginning of the ride, when the coaster, or train, is pulled up the first hill. When it goes over the top of the hill, the weight of the train itself, pulled downward by gravity, is what keeps the entire unit moving.
There are no cables that pull the train around the track. This conversion of potential energy (stored energy) to kinetic energy (the energy of motion) is What drives the roller coaster, which often reaches 60 miles (96.5 kilometers) per hour. Running wheels guide the train on the track, and friction wheels control the train’s movement to either side of the track. A final set of wheels keeps the train on the track even if it is upside down. Air brakes stop the car as the ride ends.
The phrase charley horse has its roots in baseball. At the beginning of the twentieth century, groundskeepers often used old and lame horses to pull the equipment used to keep the playing field in top condition.
The Baltimore Orioles had a player named Charley Esper, who, after years of injuries, walked with pain. Because his limp reminded his teammates of the groundskeeper’s lame horse, they called Esper “Charley Horse.”
1. On average, a man spends about five months of his life shaving.
2. On average, a hair strand’s life span is five and a half years.
3. On average redheads have 90,000 hairs. People with black hair have about 110,000 hairs.
4. Next to bone marrow, hair is the fastest growing tissue in the human body.
5. In a lifetime, an average man will shave 20,000 times.
6. Humans have about the same number of hair follicles as a chimpanzee has.
7. Hair will fall out faster on a person that is on a crash diet.
8. The longest human beard on record is 17.5 feet, held by Hans N. Langseth who was born in Norway in 1846.
9. The average human head weighs about eight pounds.
10. The reason why some people get a cowlick is because the growth of their hair is in a spiral pattern, which causes the hair to either stand straight up, or goes to a certain angle.
11. The reason why hair turns gray as we age is because the pigment cells in the hair follicle start to die, which is responsible for producing “melanin” which gives the hair colour.
12. The fastest growing tissue in the human body is hair.
13. A lifespan of an eyelash is approximately 150 days.
14. A survey done by Clairol 10 years ago came up with 46% of men stating that it was okay to color their hair. Now 66% of men admit to coloring their hair.
15. The big toe is the foot reflexology pressure point for the head.
16. The average human scalp has 100,000 hairs.
17. The first hair dryer was a vacuum cleaner that was used for drying hair.
18. Ancient Egyptians used to think having facial hair was an indication of personal neglect.
19. The loss of eyelashes is referred to as madarosis.
20. Hair and fingernails are made from the same substance, keratin.
21. Eyebrow hair lasts between 3-5 months before it sheds.
22. A Russian man who wore a beard during the time of Peter the Great had to pay a special tax.
23. Everyday approximately 35 meters of hair fiber is produced on the scalp of an adult.
24. Hair is made from the same substance as fingernails.
25. Brylcreem, which was created in 1929, was the first man’s hair product.
People usually read newspapers to get information about current events, things that are happening at the present time or have just occurred. When a good news story breaks, reporters are immediately sent out to gather as much information about the situation as possible and photographers take pictures that add visual information. When they return to the newspaper office, the reporters type their story into a computer, and camera film is developed into photos in a darkroom. The photographs are put into the computer with a device called a scanner. Increasing numbers of photographers use digital cameras, which means their photos do not have to be first developed on paper. They are automatically in digital, or computer-ready, format and can be transmitted over phone lines or via satellites just like e-mail or other electronic files. Once the photos are in digital format, the printed story and the pictures that illustrate it are arranged together. The story may take up part of a newspaper page or may extend for a few pages. Designers arrange all the stories and photos that make up a newspaper into visually appealing, easy-to-read pages on the computer screen. They are then printed out on pieces of clear film. Next, the film print of each newspaper page is laid on a light-sensitive metal plate. When it is exposed to a flash of bright light, shadows of the film’s letters and pictures are left on the plate. The shadows are permanently etched or marked into the plate when it is soaked in acid, which eats some of the metal away. What is left is a perfect copy of the film print of the newspaper page, with its words and pictures appearing as grooves in the metal.
The newspaper page is now ready to be printed on paper. The metal plate is first wrapped around a roller on a motor-driven printing press and coated with ink. After being wiped clean, ink still stays in the grooves. When paper (in big rolls) is passed under the roller, it is pressed into the grooves, and perfectly printed pages appear. This process is repeated for each newspaper page. As you can imagine, printing plants are enormous, with some presses standing three stories tall. These expensive machines (costing tens of millions of dollars) can print and sort up to 70,000 copies of a newspaper per hour. Once the press is done printing and sorting, the newspapers are bundled for delivery the next day to homes and newsstands.