The
beauty and fundamental benefit of the metric system is its ease of use, which is
largely due to it being decimal. Within the system, it is simple to compare
the measurements of objects. For example, it takes very little effort to convert or compare a centimetre to a kilometre – much less than comparing an inch to a furlong.
For the
most part, metric measures are based on an SI base unit, with sub units which are either
a multiple or a fraction of ten of that SI unit. A simple example of this is
the metre. It is the SI unit for length. A millimetre is 1/1000 of a metre and
a kilometre being 1000 metres. However there are some exceptions. With
mass, the kilogram is the SI unit, rather than the gram, but still, all
measurements of mass are still based on ten around the gram. I am sure
none of this is new, but I will get to the point eventually.
The SI
unit for time is the second. It is common for SI prefixes to be used for times
shorter than a second (millisecond, nanosecond, etc), but any similar use for
measurements over a second is only likely to raise eyebrows. Have you ever heard of a kilosecond? Instead, for units
above the second, non-SU units are used, such as minutes, hours,
days.
What would time look like if we had fully SI-compliant system for measuring time?
The first
experiment with metric time took place during the French Revolution - after
all, there is no better opportunity to change the system of time than when the streets are
littered with severed heads. The French Revolutionary Time consisted of 10 days
in a week, 10 hours in a day, 100 minutes in an hour, and 100 seconds in a
minute. The system came into force on 24 November 1793.
Converting this to the regular time, we get:
1 metric
hour = 2.4 hours
1 metric
minute = 1.44 minutes
1 metric
second = 0.864 seconds
This
system lasted a mere 17 months. People had limited practical reason to change
how they told the time. Unlike the metric system, which standardised
measurements and hence many aspects of life commerce, metric time offered no benefit of homogenisation. A minute in Paris was a minute in Marseille. It was the same minute in Spain and the same minute in England.
Moreover, the Catholic Church also had a
strong say the demise of French Revolutionary Time. The Church used the
Gregorian calendar, which was incompatible with the new Revolutionary Time
(which also redefined months and years).
Ultimately
it meant that both forms of time had to be used. Given the costs of replacing
clocks at the time, and the fact that people more or less still had to use regular time anyway, it is a no-brainer that few
clocks were replaced. Those which were replaced were typically dual-unit and
terribly confusing. With no discernible benefit to using French Revolutionary
time, its use was eventually abandoned.
Image by DeFacto - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=64816687
While
this was the only time some form of 'metric' time was actually implemented, it
is by no means the only possible form of metric time. The French system is
based on the central unit being the second.
1
centiday = 1/100 day
1
milliday = 1/1000 day
An
alternative idea for creating metric time was based on using the solar
day as the base unit of time, rather than redefining hours, seconds and minutes.
1 deciday
= 1/10 day
While
this neatly frames the day in terms of the standard conventions of the metric
system, it also offers no practical benefit. It was also hardly different to the French Revolutionary Time and so subject to all of the same failings.
One of
the key constraints of measuring time is that its major elements are fixed. A day
is one rotation of the earth, a year is one revolution around the sun. The fact
that we have 60-second minutes and 60-minute hours are a legacy of the
Sumerians and their use of a sexagesimal number base. While not perfect, it
is universally used and understood.
Universality
is central to metre (the cornerstone of the entire metric system) both as a
word and as a measurement. It came from John Wilkins' concept of a "universal
measure", which then became the "metro
cattolico" and later the “mètre” – and hence the metre. It is the
universality of our current system of time which makes it work.
While
there is merit to the saying, “If at
first, you don't succeed, try, try again”, some things fail because they
replace a problem with problems. Attempts to create a decimal system of time
did just that. It was simply change for the sake of change and should remain a mere curiosity in history books.
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