[LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1

[Zefram]

Tony Finch wrote:

>                        As we have seen there are a lot of intricate

>details whose necessity people can legitimately disagree about and no way

>to determine an official consensus. Which is why I say that astronomical

>GMT doesn't exist.


Interesting argument.  I disagree with your central point: I don't
think an official realisation of GMT is required in order for GMT to
meaningfully exist.  The details that need to be sorted out are indeed
problems in defining GMT, but we don't need an official decision about
which definition is the proper one.  We can perfectly well decide
for ourselves which version of GMT we are interested in, and realise
that version of GMT.  If interoperability with the historical official
realisation is important, we would want to take care to define GMT as
closely as possible to the de facto definition behind that realisation.

I think ultimately I'm perceiving GMT (or each flavour of GMT) as
a Platonic time scale, akin to TT, whereas (despite your choice of
terminology) you're perceiving it more as a realisation of a time scale,
akin to TT(TAI).  The historical official realisation of GMT no longer
exists.  You see this as meaning that GMT no longer exists, whereas I
am open to new realisations of GMT.  Making a clear distinction between
ideal and realisation smells like modern behaviour; considering the many
different meanings of "GMT" that have already been identified, I would
not be surprised at it being irretrievably ambiguous in this respect.
Does anyone have relevant historical documentation on the philosophical
definition of GMT?

-zefram