How light years are measured. Once i remember the distance between earth and moon are measured by light which travels and comeback and by the delay the distance is calculated.. But how light years are calculated
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We don't directly measure distances to anything light years away by timing light. "Light year" is just a unit of distance like a mile or kilometer. We know how fast light goes in 1 second, we know how many seconds in a year and so we know how many meters (or miles) are in a light year. To learn how we actually measure distances to stars see How do you measure distance to stars within the galaxy? edit A light year is now defined as 9,460,730,472,580,800 m = 299 792 458 m / s * 365.25 * 24 * 60 * 60s (http://www.iau.org/public/measuring/) Since the speed of light is constant and we are able to measure time very accurately we now actually define the meter in terms of the distance light travels in a fraction of a second - so as measurements of the speed of light improve it's actually the length of a meter that changes. |
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