This infrared echo travels towards Earth, though it lags behind the original flash (which got a head start) and will arrive later. The cloud, which was too cold to detect directly, begins warmly emitting infrared light. Downward-pointing arrows in this figure indicate light rays that are headed toward Earth and the telescopes of astronomers.In panel B, light from the flash reaches the first, closest dust cloud, heating it up. This flash travels out in all directions, but will still take years before it reaches the nearest dust cloud. The sequence of events associated with one such astronomical light echo are sketched out in this illustration.The stage is set in panel A, where a neutron star surrounded by dark, cold clouds of dust emits a brilliant burst of light. For example, if a flash bulb goes off in even the largest hangar, only the most sensitive scientific instruments could detect the tiny delay, or light echo.In deep space, where distances between objects are measured in light-years, astronomers can directly observe echoes from cosmic flashes of light. However, since the speed of light is fantastically greater than the speed of sound, spaces as tiny as an aircraft hangar would not give rise to a noticeable light delay. Because the sound reflects off of walls at different distances, returning at different times, a listener will often hear many echoes.Light possesses the same properties as sound and thus can also produce echoes. As a result, a listener will hear a delay. In the case of an aircraft hangar, the walls are far enough away that a clapping sound will take some time to reach the walls, reflect, then return. These sound echoes are very much like a phenomenon astronomers have dubbed "light echoes."A sound echo occurs because of two basic properties of sound: it travels at a limited speed, and it will reflect off of many surfaces. If you clap your hands, you will be rewarded with a series of echoes reverberating through the building. Imagine yourself standing in a large open chamber like an aircraft hangar.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |