gre写作涉及的话题实例:科学的含义

　　During scientific investigations, scientists put together and compare new discoveries and existing knowledge. In most cases, new discoveries extend what is currently accepted, providing further evidence that existing ideas are correct. For example, in 1676 the English physicist Robert Hooke discovered that elastic objects, such as metal springs, stretch in proportion to the force that acts on them. Despite all the advances that have been made in physics since 1676, this simple law still holds true. Scientists utilize existing knowledge in new scientific investigations to predict how things will behave. For example, a scientist who knows the exact dimensions of a lens can predict how the lens will focus a beam of light. In the same way, by knowing the exact makeup and properties of two chemicals, a researcher can predict what will happen when they combine. Sometimes scientific predictions go much further by describing objects or events that are not yet known. An outstanding instance occurred in 1869, when the Russian chemist Dmitry Mendeleyev drew up a periodic table of the elements arranged to illustrate patterns of recurring chemical and physical properties. Mendeleyev used this table to predict the existence and describe the properties of several elements unknown in his day, and when the elements were discovered several years later, his predictions proved to be correct.In science, important advances can also be made when current ideas are shown to be wrong. A classic case of this occurred early in the 20th century, when the German geologist Alfred Wegener suggested that the continents were at one time connected, a theory known as continental drift. At the time, most geologists discounted Wegeners ideas, because the Earths crust seemed to be fixed. But following the discovery of plate tectonics in the 1960s, in which scientists found that the Earths crust is actually made of moving plates, continental drift became an important part of geology.Through advances like these, scientific knowledge is constantly added to and refined. As a result, science gives us an ever more detailed insight into the way the world around us.