[seqfan] Re: Value of A248424 in the OEIS

M. F. Hasler oeis at hasler.fr
Mon Sep 18 18:16:32 CEST 2017


On Mon, Sep 18, 2017 at 10:57 AM, Felix Fröhlich <felix.froe at gmail.com>
wrote:

> Dear SeqFans,
>
> A248424 gives the decimal expansion of the value of 1 Parsec in meters.
> According to Wikipedia, (https://en.wikipedia.org/wiki/Parsec), since
> 2005,
>

no : since August 2015 !


> 1 Parsec is defined to be exactly (648000 / Pi) astronomical units (AU).
> The AU itself is defined to be exactly 149597870700 meters. With this, I
> get
> 1 Parsec = (648000/Pi) * 149597870700 =
> 30856775814913672.789139379577964716107319211604092.... meters.
>
> Why does this value differ from the value given in A248424? Why does
> A248424 give a different definition (see for example the comment by M. F.
> Hasler)? Who is correct?
>

This was done in 2014 when the 2012 definition was in vigor.

Now I have amended the definition of the sequence (proposed) to clarify
this.
Wikipedia was incorrect in so far as it still wrote in the first line (I
just fixed this, too)

 " A parsec is the distance at which one astronomical unit subtends an
> angle of one arcsecond."


although it is now defined to be exactly (648000 / Pi) astronomical units
(AU),
which is* not * the distance at which one astronomical unit subtends an
angle of one arcsecond."

I suggested the new value as the new sequence A292525.
(I think the sequence data should not be changed as this was done e.g. for
A163103, cf.
https://oeis.org/history?seq=A163103&start=10
in so far more as in the present case, it would lose interesting nontrivial
properties inherent to the former definition.

--Maximilian


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