The definition of time seems so easy and not
worth a thought but we may want look at its concept first in order
to settle this case. Time in general is not a
constant and can only be measured among two objects in gravitational
reference. The physically defined unit of time is the second, which
is officially defined as "the duration of 9,192,631,770 periods of
the radiation corresponding to the transition between the two
hyperfine levels of the ground state of the cesium 133 atom."
Time on Earth
The earth day at this point is 23 hours 56
minutes and 4 seconds long. Expanding a minute within each 3.3
million years based on a constant slowing rotation of earth.
Earth is traveling with various speeds pending on distance to the
Sun around it making a full circle in 365.2422 days in reference to
the eclipse varying only within the length of seasons within
(precession). The all over extending distance between earth
and Sun is at a rate of 15cm per year which extends the year
mathematically speaking by 30 seconds within each 1 million years.
So the time we live by is a simplified construct based on
observation mainly focused on the day night pattern in order to
allow a smooth connectivity within and among society.
Natural time patters are more various and show a
high volume of differences matching among each other creating a
complex system of interaction.
The idea of relativistic time is a direct result
of Albert Einstein’s Theory of Relativity.
It was Einstein’s genius to realize that the
speed of light is absolute, invariable and cannot be exceeded (and
indeed that the speed of light is actually more fundamental than
either time or space). In relativity, time is certainly an integral
part of the very fabric of the universe and cannot exist apart from
the universe, but, if the speed of light is invariable and absolute,
Einstein realized, both space and time must be flexible and relative
to accommodate this.
Although much of Einstein’s work is often
considered “difficult” or “counter-intuitive”, his theories have
proved (both in laboratory experiments and in astronomical
observations) to be a remarkably accurate model of reality, indeed
much more accurate than Newtonian physics, and applicable in a much
wider range of circumstances and conditions.
One aspect of Einstein’s Special Theory of
Relativity is that we now understand that space and time are merged
inextricably into four-dimensional space-time, rather than the three
dimensions of space and a totally separate time dimension envisaged
by Descartes in the 17th Century and taken for granted by all
classical physicists after him. With this insight, time effectively
becomes just part of a coordinate specifying an object’s position in
Hermann Minkowski, Einstein’s one-time teacher
introduced the relativity concept of proper time, the actual elapsed
time between two events as measured by a clock that passes through
both events. Proper time therefore depends not only on the events
themselves but also on the motion of the clock between the events.
By contrast, what Minkowski called coordinate time is the apparent
time between two events as measured by a distant observer using that
observer’s own method of assigning a time to an event.
An event is both a place and a time, and can be
represented by a particular point in space-time, i.e. a point in
space at a particular moment in time. Space-time as a whole can
therefore be thought of as a collection of an infinite number of
events. The complete history of a particular point in space is
represented by a line in space-time and the past, present and future
accessible to a particular object at a particular time can be
represented by a three dimensional light cone which is defined by
the limiting value of the speed of light, which intersects at the
here-and-now, and through which the object’s world line runs its
Modern physicists therefore do not regard time as
“passing” or “flowing” in the old-fashioned sense, nor is time just
a sequence of events which happen: both the past and the future are
simply “there”, laid out as part of four-dimensional space-time,
some of which we have already visited and some not yet. So, just as
we are accustomed to thinking of all parts of space as existing even
if we are not there to experience them, all of time (past, present
and future) are also constantly in existence even if we are not able
to witness them. Time does not “flow”, then, it just “is”.
According to relativity, the perception of a
“now”, and particularly of a “now” that moves along in time so that
time appears to “flow”, therefore arises purely as a result of human
consciousness and the way our brains are wired, perhaps as an
evolutionary tool to help us deal with the world around us, even if
it does not actually reflect the reality. As Einstein himself
remarked, “People like us, who believe in physics, know that the
distinction between past, present and future is only a stubbornly
Arrow of time
However, if time is a dimension, it does not
appear to be the same kind of dimension as the three dimensions of
space. For example, we can choose to move through space or not, but
our movement through time is inevitable, and happens whether we like
it or not. In fact, we do not really move though time at all, at
least not in the same way as we move through space. Also, space does
not have any fundamental directionality (i.e. there is no “arrow of
space”, other than the downward pull of gravity, which is actually
variable in absolute terms, depending on where on Earth we are
located, or whether we are out in space with no gravitational
effects at all), whereas time clearly does.
Time appears to have a direction, to be inherently directional: the
past lies behind us and is fixed and immutable, and accessible by
memory or written documentation; the future, on the other hand, lies
ahead and is not necessarily fixed, and, although we can perhaps
predict it to some extent, we have no firm evidence or proof of it.
Most of the events we experience are irreversible: for example, it
is easy for us to break an egg, and hard, if not impossible, to
un-break an already broken egg. It appears inconceivable to us that
that this progression could go in any other direction. This one-way
direction or asymmetry of time is often referred to as the arrow of
time, and it is what gives us an impression of time passing, of our
progressing through different moments. The arrow of time, then, is
the uniform and unique direction associated with the apparent
inevitable “flow of time” into the future.
~Christian Hoffmann 12/2018