On 5 Aug 2005 at 10:16, Mark Calabretta wrote:
> The fiction that there are 86400 "seconds" in a solar day is part of
> the problem - noone uses the word "second" in this context. Currently
> there are about 86400.003 seconds in a mean solar day but we use leap
> seconds so that we can carry on pretending that there are only 86400.
> Eventually when there are 86401 seconds in a mean solar day, or
> probably well before, we'll simply have to stop pretending.
Actually, I'd say that more people use the word "second" in this
context than do in the scientifically accurate context of the SI
definition. To the "man/woman on the street", a second is 1/60 of a
minute, a minute is 1/60 of an hour, and an hour is 1/24 of a day,
just as these units were originally defined before scientists got
more precise about it. And a day is defined in terms of the
relationship of the Sun and the Earth; even if this mythical non-
scientific member of the public doesn't know the technical
astronomical details of "mean solar time" and so on, he/she knows
that the sun rises and sets exactly once within this time unit. So
the solar definition of "second" is actually more in line with how
the average person regards the unit than the SI definition.
--
== Dan ==
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Received on Thu Aug 04 2005 - 17:46:13 PDT