Study starters
- 2. Electricity Lightning Fast Facts Fifty to one hundred lightning bolts hit the ground every second all over the earth. Lightning strikes discharge 100 million volts of electricity, and heat the air in their paths to over 60,000 degrees F (33,000 Cº). An ordinary piece of steel will turn into a magnet if it is struck by lightning.
- 3. Forces & Gravity Weighty Calculations? The world's first calculator weighed at least a ton and had more than 2,000 levers and gears. It was invented by British mathematician Charles Babbage in 1832. He called the Difference Engine.
- 4. Sound Taking a Bite Out of Music Toward the end of his life, the great composer Ludwig von Beethoven was totally deaf. To compose music, he would clench one end of a wooden stick between his teeth and place the other end against the piano's soundboard. When he hit a note, the vibrations traveled up the stick into his jaw. He used the vibrations of sound to create his compositions.
- 5. Sound Bark Beetles Beware During periods of extreme drought, many trees will let out ultrasonic chirps too high to be heard by humans, but right in the range of bark beetles and other insects. The beetles know the tree is stressed when they hear this sound, so that's when they usually attack. To protect the trees, the U.S. Forest Service is designing beetle traps that set off ultrasonic sounds to attract the beetles elsewhere, far away from the trees.
- 6. Sound Using Their Heads When Native American hunters wanted to track a herd of bison, they would put their ears to the ground and listen to the sound of the hooves pounding. They could detect the sound more than a mile away. Train robbers in the Old West did the same thing. They put their ears on the train tracks and listened for an approaching train.
- 7. LIGHT It's in the Stars Scientists have discovered that every chemical element produces its own characteristic spectrum when it burns. Astronomers use devices called spectroscopes to measure these "light fingerprints," enabling them to determine what chemicals are present in distant stars.
- 8. Light Crystal Clear In ancient Rome, citizens with poor vision used crystals to help view the gladiatorial games. These "natural lenses" were the first attempts to correct vision and eventually led to the development of eyeglasses.
- 9. States of Matter In Hot Water After boiled water is cooled to room temperature, it will freeze faster than a container of room temperature water. Boiling drives out some of the air bubbles in water. Air bubbles reduce thermal conductivity and can inhibit or slow the freezing process. Fewer air bubbles results in faster freezing. Previously heated water forms denser ice than unheated water. That's why hot water pipes tend to burst in very cold weather!
- 10. States of Matter Gel-O Jell-O™ is an example of a gel, as is butter. Making a gel is a chemical process that "traps" a liquid in a solid. But once it is made, it is considered a solid. Gels are considered solids because they fit the classic definition of a solid: "the state of matter that holds its own shape." But these solids sure can change back into liquids easily! Butter and Jell-O both change back into liquids at a temperature common in many kitchens.
- 11. Magnetism And a Magnet Shall Guide Them... The bacterium Aquaspirillum magnetotacticum uses the Earth's magnetic field to navigate its way to its food source deep with in the muck of saltwater marshes. Scientists have discovered that this species has a tiny chain of magnetite, a kind of magnetic rock, inside them that detects the direction of Earth's magnetic field. Not only do these bacteria know which direction is north, but they also use the magnetic inclination to figure out which way is down — the direction of their food source.
- 12. Magnetism Magnetic Personality Did you know that you are just a little bit magnetic? Magnetism comes from the spin of an atom's electrons. Since we are all made up of atoms with spinning electrons, all of our atoms are little potential magnets. Paired electrons usually cancel out one another's magnetic fields, but very powerful magnets can force some atoms to align even if their orbiting electrons are paired. MRI (magnetic resonance imaging) machines, used in hospitals, are an example of this. Using superconducting magnets that are about 20,000 times more powerful than Earth's magnetic field, MRI machines create a magnetic field capable of aligning a small percentage of the atoms in your body. This makes you a living magnet! In fact, only three atoms in a million become aligned. But that's enough to create small magnets in your body. Computers then detect slight variations in these fields and arrange them to form an image.
- 13. Magnetism It's Magic! Jean-Eugene Robert-Houdin (1805-1871), whom many consider the father of modern magic, used electromagnets to deprive the most powerful of their strength. He would place a tiny metal box onstage and hide a powerful electromagnet under the stage. When the magnet was turned on, no one could pick up the box. When the electric current was turned off, Robert-Houdin would then embarrass muscle-bound men by lifting the box with little effort. It was the magic of magnetism!