| [ garbages ] in KIDS 글 쓴 이(By): limelite (a drifter) 날 짜 (Date): 2012년 01월 18일 (수) 오전 11시 10분 25초 제 목(Title): Re: 요 며칠 이해가 안 가는 얘기 -_-; >너무 당연한거 아닌가요? >멀어지고 있으면 주기가 길게 관측 되는게.. >도플러효과.. 저도 도플러 효과를 떠올렸는데 위키 글에 따르면 아니라네요. 도플러효과에 대해서 잘못 이해하고 있는 건지... 도플러효과는 빛이나 음파 같은 파동에만 적용해야 하고, 목성 위성이 깜빡이는 주기에 적용하면 안 되는 건지... 슬슬 물리 기본도 헷갈리는 -_-;;; http://en.wikipedia.org/wiki/R%C3%B8mer%27s_determination_of_the_speed_of_light It has also been suggested that Rømer was measuring a Doppler effect, and this 166 years before Christian Doppler's 1842 discovery. The Doppler effect is the change in observed frequency of an oscillator (in this case, Io orbiting around Jupiter) when the observer (in this case, on Earth's surface) is moving: the frequency is higher when the observer is moving towards the oscillator and lower when the observer is moving away from the oscillator. This apparently anachronistic analysis implies that Rømer was measuring the ratio c/v, where c is the speed of light and v is the Earth's orbital velocity (strictly, the component of the Earth's orbital velocity parallel to the Earth- Jupiter vector), and indicates that the major inaccuracy of Rømer's calculations was his poor knowledge of the orbit of Jupiter. There is no evidence that Rømer thought that he was measuring c/v: he gives his result as the time of 22 minutes for light to travel a distance equal to the diameter of Earth's orbit or, equivalently, 11 minutes for light to travel from the Sun to Earth. It can be readily shown that the two measurements are equivalent: if we give τ as the time taken for light to cross the radius of an orbit (e.g. from the Sun to Earth) and P as the orbital period (the time for one complete rotation), then c / v = P / 2πτ Bradley, who was measuring c/v in his studies of aberration in 1729, was well aware of this relation as he converts his results for c/v into a value for τ without any comment. ............................................................................... a drifter off to see the world there's such a lot of world to see |