Calendars and Timekeeping in the Terragen Sphere
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Calendars and Timekeeping in the Terragen Sphere |
At the start of the Information
Age there were a number of
calendars in use on Old Earth, but the one most commonly used for
commerce and
science was the Common Era calendar (c.e.), based on the ancient
Gregorian
Christian calendar. This calendar was used in conjunction with the
Coordinated
Universal Time standard (UTC) to give a single value for timekeeping
all over
the planet. UTC was adopted throughout the Solar System at first, but
once
permanent colonies were established on the Moon
and Mars
new calendars were
established for those worlds. The Martian calendar was adopted in 2185
c.e and is
based around the ‘sol’ or Martian Day, having a
start date of 14 November 2031
when the first manned landing occurred. The Lunar calendar known as the
‘After Tranquility
Calendar’ (a.t. or A.T.) was established soon after, and
takes the first manned
landing on the Moon in 1969 c.e. as its starting date. However the
Lunar day
was considered too long to be useful, so the new calendar retained UTC
to count
the time of the new colony. By 391 a.t. the majority of the Solar
System (apart
from Earth and Mars) was using the a.t./UTC standard.
After the Great
Expulsion several billion refugees from
Earth crowded on to the Moon and onto habitats in Cislunar space,
waiting for a
chance to escape to the roomier colonies of Mars and the Outer Solar
System or
onto the great Arkships that were being built to carry them to the
nearest
stars. During this time the Lunar calendar became the common
measurement of
time for most of the former inhabitants of Earth. The refugees almost
always
took the ‘After Tranquility’ calendar with them to
their new homes among the
stars. Later Luna became the capital of the First
Federation in the early years
of its formation, and attempted to regularize the measurement of time
on an
interstellar scale; this of course proved to be impossible.
In a universe governed by special
relativity it is
impossible to say in an absolute
sense whether two events occur at the same time if they are separated
in space.
Time dilation changes the rate at which time passes for any moving
object when
observed from another moving object; so no common frame of reference
can be
found to measure the passing of time. On the surface of a planet, or
even
within a single solar system, it is possible to disregard simultaneity
effects
for almost all purposes; but once the Terragen Expansion spread from
Sol to
other planetary systems these effects became very much more important.
Interstellar
spacecraft and their crews traveling at an appreciable fraction of the
speed of
light will experience time dilation to a greater or lesser extent
according to
their velocity; a journey of 6 light years at 0.6 c will take ten years
as seen
from an observer on the world it left from, but will only take 8 years
from the
point of view of the crew. Once the ship arrives, the colonists have a
number
of choices if they want to establish an accurate calendar. They can
keep the
calendar of the original world, and if they left that world in the year
1000
a.t. for instance they would count a date of 1008 a.t. as their date of
arrival. However when they compare notes with the original world (a
process
which would involve an exchange of messages at light speed, and which
would
take twelve years) they would find that ten years had passed on the
home world,
and the calendars would be out of synch.
What
is worse,
the two stars concerned would be so far apart and moving so fast with
respect
to each other (because of their so-called proper motion) that there is
no way
to coordinate the rate at which their respective measures of time pass;
the two
calendars are essentially independent from each other and can never be
reconciled. The proper motion of one star with respect to another
changes
constantly because of the gravitational effects of the rest of the
universe, so
the effects of time dilation on the measurement of time on each world
when
compared to the other cannot be measured accurately.
So
when the First
Federation attempted to standardise the After Tranquility calendar
across
interstellar space they found it was literally impossible’ by
the end of that
period the Terragen Sphere was several hundred light years in radius,
and the
uncertainty in the calendar date from one side of the volume to the
other was
as much as two or three years.
When wormhole communication began to spread throughout this expanding sphere there was the chance to establish a new standard. A signal could be sent from any particular world to the centre of the Wormhole Nexus, which has a basically tree-like structure to this day, and at first was centred upon the earliest holes in the Vega system but later found a centre at the so-called Root of the Eye, Aksijaha, in an unknown location somewhere in the Inner Sphere. This signal could be datestamped at the centre of the Nexus and returned to the originating world, and the date at that world could be established as being the time on the datestamp plus half the traveling time to and from the centre.
The
Second
Federation
was particularly keen on establishing a common time in this way, and
they
continued to use the After Tranquility standard. Following on from the
Second
Federation, the Sephirotic Empires generally use the a.t. calendar to
record
significant events, and this is the calendar used at the department of
History
in Verlibcon Arcology on Ken Ferjik for
the Encyclopedia
Galactica.
On the
other hand,
most worlds and habitats and even separate countries or polities within
those
worlds maintain their own separate calendars, often based on the
orbital
characteristics of their world and or the date of the foundation of the
colony
or other momentous events. Mars still uses its original calendar, and
the few
inhabitants of Earth still use the Gregorian measure; the oldest
calendars in
use are those of the alien xenosophonts on To’ul’h
and Muuhhome,
which date
back to long before human civilization.
However
the value of
Common time is subject to many effects of simultaneity which makes it
an
arbitrary measure of time; wormhole
linelayers move at considerable fractions of the speed of
light, and the
ends of the hole can therefore have quite different local time values
on
arrival. This effect can be modified by the judicious use of
gravitational
fields at one, or both ends. Also the passage of information through a
wormhole
can happen at different rates according to exact geometry of the hole.
A message
from a distant world may need to pass through dozens, or even hundreds,
of
wormholes, and the transit time can vary considerably over time. So for
the
outlying worlds Common time, or Empire time as it is sometimes known,
is a very
variable measure of time, and in no way establishes a single frame of
reference
for the whole Orion’s Arm Civilisation.
In any case there are countless worlds in the Outer Volumes and elsewhere which are not linked to the Nexus, so are subject to the same relativistic uncertainties that plagued the First Federation. As the Nexus expands to link with new systems, very often the calendars of the new worlds are very much out of synch with Common Time. For instance the Refugium Empire was almost sixty years adrift when it was finally rediscovered, despite having consistently and accurately used the old Lunar Calendar (although without any attempt at adjusting for relativity). And relativistic polities such as the Deeper Covenant which ply the space between the Sephirotic worlds are accustomed to recalibrating their calendars on arrival, whilst maintaining accurate ship time as the most important and relevant measure.
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