Earth Sciences 1086F/G Chapter Notes - Chapter 2: Parallax, Microsoft Onenote, Local Group
21 Sep 2016
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Scientists use light-years to measure distances in space. A light-year is the distance that light travels in one year. Light travels at about 300,000 km per second; there are 31,500,000 seconds in a year. Multiply that and you will see that light travels 9. 4608 1012 km per year. Di erent measurement techniques are needed for di erent distance ranges, and the middle range work (500 to 500 million light years distant) is the most complex. To gauge near distances, astronomers use the same method as we do (unthinkingly) every time we take a walk. A nearby tree, viewed against a more distant eld, appears to move slowly behind you as you pass it by. This phenomenon, called trigonometric parallax, relies on an object appearing to be at a di erent place relative to the background, depending on your viewpoint. As earth rotates around the sun, the nearby star appears to "wobble" relative to the distant stars.
