Ignoring cosmic expansion and relative motion, what does it mean to receive light today from an object 1,000 light-years away?
Answer & explanation
It was emitted about 1,000 years ago.
A signal cannot transmit an event instantaneously. In the stated approximation, a distance measured in light-years gives the corresponding years of light travel. The approximation should not be applied uncritically to cosmological distance definitions.
Cosmos
Chapter 1 · The Shores of the Cosmic Ocean
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