Monday, 4 June 2012

units - Is the Earth-Sun distance 1.012 AU?

As of this moment (2016 May 18, 13:15 UTC), the Earth is 1.0116 astronomical units from the Sun. WA is smart enough to know that "Sun Earth distance in AU" is a time-dependent question.



Update: The stricken text that follows from my original answer is incorrect. I am leaving it present (but stricken) for the sake of humility.



It interpreted your query to mean Sun Earth distance today in AU, and because today is 2016 May 18 and because you didn't specify a time of day, it picked noon (UTC), it in turn interpreted your query to mean Sun Earth distance on 2016 May 18 at noon UTC in AU.



The correct answer: I happened to ask WA the very question posed in the OP a couple of minutes apart and got two different answers (1.014 and 1.015 AU), and this did not occur across a day boundary. WA apparently interpreted your query to mean the current distance between the Sun and the Earth.



You have to be very careful of what you ask WA.



A better query is to ask WA What is the mean distance between the earth and the sun in AU? That query will give you an answer of 1.0000010178 au. An even better question is What is the semimajor axis of Earth's orbit? That will give you an answer of 1.00000011 au. Note the extra zero, but also note that for some reason, the precision is reduced.

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