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The distance between stars is measured by the time it takes light to travel between them correct? How do you measure the time it takes?
for example from CNN "It is 12.7 billion light-years away, meaning the light just recorded -- by NASA's Chandra X-ray Observatory -- took 12.7 billion years to reach the vicinity of Earth."
How do they figure out how long it took this light to reach us?
for example from CNN "It is 12.7 billion light-years away, meaning the light just recorded -- by NASA's Chandra X-ray Observatory -- took 12.7 billion years to reach the vicinity of Earth."
How do they figure out how long it took this light to reach us?