A few weeks ago I wrote a school report on Australian boomerangs—those curved objects that return to you when you throw them. I told my mother some of what Line I’d learned: that the Aborigines who first settled Australia thousands of  years ago used boomerangs only for sport; that they used a similar tool—a throwing  stick, which doesn’t return to the thrower—for hunting birds and other animals; and  also that there is a boomerang club right here in our town that gives lessons and  holds competitions. All of this was in preparation for my asking for a boomerang, which I did, but at  first, she didn’t like the idea. “David, how do you know you can even throw one?” she asked.  “I don’t,” I said. “But I’ll never find out unless I get one!” “I’ll tell you what,” she said. “Why don’t we check out this boomerang club and you can  try it.” I agreed, and a week later we were at the club’s monthly gathering at a local football  field. A man named Ben greeted us warmly and told us how the day would go: after some  practice time and a lesson for beginners, there would be a competition.   And then he handed me a wooden boomerang. “You can use this one today, David,” he said. “I made it myself.” I could hardly  believe I was finally holding a boomerang in my own hands. Ben went to talk with  another club member. I waited a few minutes, but my eagerness got the best of me—I  decided to try throwing the boomerang before anyone showed me how. I threw it sideways,  releasing it at waist level. To my surprise it curved straight upward, then came  crashing down to the ground, nearly hitting me. “A typical beginner!” Ben yelled from a distance, laughing.  Then he gave me a lesson. He threw the boomerang overhand, the same way you’d throw a  ball, releasing it at eye level. He also told me to throw it into the wind.  I copied his motion and threw it, and to my surprise, the boomerang curved around and  came toward me. I ran a bit, then caught it. I could hardly believe it!  “Hooray, David!” my mother yelled. “It looks like you’ll be getting that boomerang  tomorrow!” 

 Vicuna, a small town in the north of Chile, is a great place for watching the stars.  Although the town is near the ocean, the cold, moist air from the coast does not bring  clouds. Instead, dry winds blowing from the desert keep the clouds away at night. In  Line fact, the sky is so clear in Vicuna that it is possible to see many stars that can  be seen only with advanced instruments in other parts of the world.   In Vicuna, distant star systems such as the Magellanic Clouds are visible without the  help of a telescope. This is why the town was chosen as the home of a number of sky  observatories. One of them, the Mamalluca, is quite different from the typical  observatories used by astronomers and other scientists. This observatory was designed  for tourists who like to look at the stars. Throughout the year, Vicuna’s hotels  accommodate thousands of tourists who come from all over the world to see the night sky  as they have only seen it in books. The cloudless sky is clearly a moneymaker for the  town, which plans to erect even more observatories. It was recently decided that the  construction of additional observatories will continue for another few years.   At one point, however, the town faced a serious problem. As the town grew, more  streetlights were added, making it more and more difficult to see the stars at night.  The town saved the night sky by investing in a new system of lamps that lit up the  streets without ruining the view of the sky. 

 The zipper today is a very common item. Used to join two pieces of fabric  along the edges, it serves an important function for many types of clothing  as well as other things people use, such as bags or tents. Yet a look at its  early history reveals that the zipper was, in fact, an unlikely success.   Toward the end of the nineteenth century, when the first zippers were being  developed, people were generally satisfied with the way they were already  fastening their clothing. Simple buttons were considered sufficient, and few  people complained that something better was needed. It is therefore puzzling  that companies invested money in the development of a product that few people  thought necessary.   Remarkable dedication was also required on the part of the  zipper’s inventor because the device took a long time to perfect. The  Swedish-born designer, Gideon Sundback, who is considered the father of the  zipper, needed twenty years to arrive at a design reliable enough for  everyday use. His first zippers either did not last very long or had the  tendency to open unexpectedly. They were also very expensive to make. After  so many years of difficulty, many other inventors most likely would have  admitted their failure. It took someone as tireless and persistent as  Sundback to keep trying despite the many setbacks.   Even after he finally managed to develop a functional zipper, Sundback still  had reason to feel discouraged because when his zipper became available for  purchase, few people wanted to buy it. Many more years had to pass for people  to realize how convenient his invention actually was.   An important breakthrough in the zipper’s marketability came when England’s  Duke of Windsor ordered that his clothes be made with zippers. It was because  of the Duke’s fame and popularity that people became interested in zippers.  Nowadays, zippers are everywhere, and it is hard to imagine clothes—or change  purses, sleeping bags, etc.—without them. Even the progress of technology,  which often replaces old inventions with more advanced ones, does not seem to  be a threat to the zipper. It is safe to say that the zipper will be around  for a long time to come.  

 As its name suggests, the acacia ant lives in acacia trees, and it chooses the most inaccessible places in the tree to build its nest. When an ant finds itself on a  tree, it will start making a hole beneath one of the thorns, the sharp needle-like  structures growing une on the branches. When the hole is big enough, the ant will  start a family there. That 5 family soon grows very large, and when it is a few  hundred strong, it will protect the whole tree, from the roots up to the leaves  and flowers, by defending against invaders.   Acacia ants ward off not only small animals, like sugar gliders, but also large  ones, like goats or giraffes. As soon as the ants detect an intruder near the tree,  they quickly rush toward it and bite it, injecting a toxic substance into the  animal’s skin. The io substance is not life threatening, but it creates enough pain  to make the intruder look for another tree whose tasty leaves are not so well  guarded.   The ants protect the tree because it is in their interest to do so. If a giraffe  were to destroy the tree, it would also mean the demise of the ants’ home. Such  animals are thus a threat to the ant. But acacia ants do not frighten away all  animals that come near them. 15 Scale insects, for example, are quite welcome,  because they produce a sweet juice the ants enjoy. Some of the ants’ food also  comes from the acacia tree itself. Acacia trees provide a kind of oil that is  collected by the ants and taken to their nests. It is one of the favorite foods of  baby ants.