Monday, 27 March 2017

cosmology - Seeing cosmic activity now, really means it happens millions/billions of years ago?


A Recent report about a cosmic burst 3.8 billion light years away. It is written as though it is happening now. However, my question is, if the event is 3.8 billion light years away, doesn't that mean we are continuously looking at history, or is it possible to detect activity in "realtime" despite the distance?



Answer



You are absolutely correct. The event happened 3.8 billion years ago, but it gets tedious and confusing to write in the past tense. For example, which one of the following statements do you find easier to understand?



The high-energy radiation continued to brighten and fade for at least a week after the burst 3.8 billion years ago



or




More than a week later, high-energy radiation continues to brighten and fade from its location



As an example, see this article about writing in astronomy, under Miscellaneous Sticky Points:



Remember that statements about astronomical objects should always be in present tense ("the galaxy has a strong color gradient") unless you are specifically talking about a past event or an object that no longer exists ("the supernova progenitor star was a type O supergiant").



Hope that helps.


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