This is a rather long contribution. It will deal with our sense of time
and memorising. I will try to create parallels of our sense of history,
our personal memory, the relationship between this and the environment,
and finally I will try to connect this with entropy production and
emergencies. It will hopefully trigger some thoughts with you about the
relationship between learning and time and some questions are raised about
the frequency of emergencies with growing age. Although it seems a bit
far from the primary goal of this list, all the mentioned items are
frequently mentioned in our collective contributions. So I hope that you
will find the patience and time to think and learn further.
I have given some examples from the Earth sciences, since the record of
memory of our planet is so rich and long. However, I can imagine that this
stuf is for some of you too much out of scope. In that case you may stick
on the Introduction and to the Epilogue.
INTRODUCTION
Time is a subject that regularly is discussed on this list. It is
interesting to look in detail what the relation is of our daily life and
historical phenomena in respect to the dimension of time. In several
discussions the presumable regularity of time has put forward. Time was
also mentioned in relation with emergencies and entropy production. In
learning organisations time plays also an important role as is mentioned
earlier. Sometimes patience is required and time seems to be stretched;
sometimes events and emergencies develop so quickly that time seems to be
compressed.
We all know that if we have to wait for something, time seems to pass by
very slowly; on the other hand, if we are very busy, time seems to run
fast.
So the relation between time and hapenings in the environment is not
always parallel.
If we look in the past, we may be able to study these relationships. We
could study the memories of our environment and we may study our personal
memories. If we do so, we soon got the feeling that these memories are
anchored around certain hapenings with gaps inbetween. These hapenings are
emergencies, deviations which are different from the regular. If nothing
happens, time seems to run parallel and no anchor places are created in
the memory. If we like to define the positions of these anchorplaces, we
should refer to a reference frame, which usually is our calender. Without
this calender framework, we only could reconstruct the relative positions
of the anchorplaces: some are older than others. The gaps between are of
unknown length.
The calender is mainly defined by the regularity of celestial movements
and on Earth this results in yearly seasons. If there are no seasons, it
will be much harder to construct the reference frame work. I guess that in
countries with well defined four seasons, the memory of people living in
these areas is better framed. In tropical countries with only two or even
only one season, memories will be badly anchored. So even the regularity
of time, should be printed by deviations from the 'normal'.
I now will give some examples from the geological sciences to study the
memory of the evolution of the Earth. We will see how the relationship of
environment and time could be difficult. But we also will see some clues
of patterns of emergencies and the gaps inbetween.
DIACHRONICITY
An important aspect in geology is the unravelling of space-time
relationships. It is a constant challenge in 4-dimensional thinking.
Diachronicity (through the time) is a phenomenon which hits the space-time
relationship in the heart.
Imagine a sandy beach. It is the place where land and sea meet eachother
and the shore is the result of a very complex dynamic equilibrium. The
sand package is say, 25 metres thick and 100 metres wide and it stretches
along the coast for probably several 100 kilometres. Sand particles are
permanently washed and sorted by the waves of the sea. A situation which
may last for several thousands of years. During this time hardly anything
happens that could generate an anchor place in the memory of the Earth. We
do not have any clue how long this period of dynamic equilibrium exactly
lasted because no emergency occurred.
There are at least two mechanisms that could influence the geographic
position of the coast: sealevel fluctuations, and vertical movements of
the landmass. We know that during the ice ages (10.000 - 100.000 years
ago) there were periods that the sealevel was over 150 metres lower than
the present level. This was because of the enormous mass of water in the
form of landice (not floating in the sea). So from that period onwards to
the present the beach migrated land inward because of the rise of the
sealevel, and assuming that the landmass was stable during that period. So
the sandy beach stretches over a much broader area than the present 100
metres into the sea. The precise broadness of the sand deposit depends on
the flatness of the whole coastal area.
Sedimentological conditions before and after the beachsand deposit,
migrated as well, resulting in constant layers of probably other material,
for instance clay above the beach sand and gravel below. The final result
will be a sequence of (from bottom to top) gravel, sand, clay. This
complete sequence is developed at present off the coast, below the present
sealevel. On the present beach the top layer of clay is missing (but could
be deposited in the future with further sealevel rise), and on land we
will discover the gravel layer on the surface which stretches underneath
the sand towards the sea.
But now comes something difficult: we are going to study the ages of the
various layers. The complete sequence of gravel, sand clay (from bottom to
top) which lies off the coast is easy to interpret: the gravel layer is
the oldest, the clayt layer at the top is the youngest, the most recent
layer. This reasoning is true for every individual place. On the present
beach, the beachsand is younger than the underlying gravel. However, if we
study the ages of these layers not vertically, but laterally, we come to
other conclusions. The present sand on the beach is probably of the same
age as the top clay at present deposited in the sea. The sand underneath
this clay off shore, although it looks the saem sand as the sand of the
present beach, is some 100.000 years older. We have here a complicated
space-time relationship, and we call the sand layer diachronous.
Such sequences are common, also of much older ages, millions of years.
When studying these sedimentological sequences in the field, we should
realise that the age of a layer with the same composition and structure,
say a sandstone, could differ in age at different places. Despite the look
alike of the complete sequence. In some place the sandstone could be of
the same age as the shale in another place.
You may realise that lots of other complications may occur: simultaneous
movements of sealevel and landmass, differences in sedimentation rates,
periods of nonsedimentation, or short intervals of erosion, etc. Untill
the beginning of the 20th century, it was generally only possible to work
with relative ages: something is older, or younger than some other thing.
This is like the memory without the reference frame of a calender, like
our own memory. Only in very rare circumstances, absolute ages were
possible to establish during that time.
SEASONAL AGES
One of thses rare circumstances were the very fine grained sediments
deposited as a result of seasonal melting of ice. Each year a fine clay
layer was deposited and a sequence of such fine layers gives the
possibility to count the layers, and thus counting the years. However, the
age of the sequence itself was still not exactly known.
Treerings are another possibility. The growth of a tree during the seasons
of a year results in rings. Each season has its specific growing
conditions, and thus each resulting ring will have its own
characteristics. It is possible to correlate sequences of rings in trees
of the same species. It is like correlating barcodes. If overlap of
barcode patterns is recognised, one is able to extend the time (barcodes
are added). Thus with treerings it is possible to go back in time, each
specific year with its own characteristic ring pattern. There is a
competition between American and European scientists to go as far back in
time as possible. In Europe the oak tree is used. Over 10.000 years back
in time has been established on both sides of the Atlantic Ocean. In fact
scientists have intered in the last ice age. Further backward is probably
impossible, because of the severely different climatic conditions. These
results are of great importance for paleoclimatic studies, for archeology,
and for standardising the C14-method of absolute dating.
ABSOLUTE AGES
In 1905 radioactivity was discovered. And soon one realised that
radioactivity is the most regular clockwork: during precisely the same
number of years, the same proportion of the radioactive mother atoms are
transformed in one or more daughter atoms.
Only a couple of years later, it was Rutherford who measured the age of a
single chrystal and it was dated about 500 million years old. This age
must have generated an incredable shock in the scientific comunity.
Before this historical outcome, the age of the Earth was 'calculated' as
somewhere between 20 and 100 million years (my), based on thicknesses of
sedimentary deposits and rate of sedimentation; and on the time required
to change a sweet water ocean into an ocean with its present salinity.
Already around 1910, ages of 1000 to 1600 my were radiometrically dated!
At present the age of the Earth has been determined as ca. 4800 my.
VISIONS OF THE PAST
Sediment sequences and fossils have been used to establish the
stratigraphy and the relative ages of sediments on the Earth's surface.
Also ideas of the evolution of life were developed. This has resulted in
the geological time table. With radiometric dating techniques one is now
able to add to this table the absolute ages. Interestingly, these absolute
ages indicate a logarythmic framework: in the far past time seems to run
slower than at present. In other words: the memory of the Earth indicates
a gradual increase of emergencies towards the present. Hardly nothing
seems to have happened in the far past, but in the more recent periods
lots of things happened and are recorded on this table. The number of
emergencies (anchorplaces of the memory) during 1000 my in the past seems
to be the same as the number during 1 my in recent times. So are the
lengths of the gaps in between.
I will return to this phenomenon later in this contribution. The
evolution of life is represented by fossils. Interpretation however, is
difficult and lots of complications create a lot of pitfalls. Living
organisms have their specific habitats. Different habitats during the same
geological period could result in different fossils of the same age.
Fossilification is a very delicate process, only possible under
exceptional circumstances. So fissils usually are remnants of
circumstances that were not normal. They are the result of deviations from
the ordinary. Treerings indicate variations. As radiometric dating is only
possible on rocks and minerals which resulted from exceptional
circumstances (igneous rocks intruded, or extruded). If history of the
Earth was smooth and regular, no ages (no memories) could be established.
In such case even no mountains would occur. Deviations from the 'normal'
could be relative differences in time and space, chemical disturbances,
differences in physical conditions (temperature, pressure, magnetic field,
etc.).
So anomalies give us the time reference. I like to mention two anomalies;
the first discovered in the sixties, the second only one year ago.
MAGENTIC REVERSALS
The magnetic field of the Earth influences the orientation of certain
magnetic sensitive minerals in e melt. During crystallization the mineral
will be oriented according to the magnetic filed that is active at that
time. After the molten rock (magma) is fully crystallized, the orientation
of magnetic minerals is 'frozen' and fixed. If the crystallized rock
changed its relative orientation to the magnetic pole, the deviation could
be measured afterwards, and the relative translation could be
reconstructed. In this way, the relative motions of the continents
(continental drift) could also be reconstructed.
The ocean floors are composed of igneous rocks (basalt) and are completely
different from the general composition of the rocks on the continents. In
the sixties it became clear that the formation of ocean floors happened in
a specific way: along a huge fault in the ocean crust permanetly basalt
magma extruded, while the fault opens itself constently. Through the
opening fissure, fresh magma rises from the depth and crystallizes on both
sides of this fault. The most famous example is the so-called Mid-Atlantic
Ridge. An opening fault which runs from north to south, symmetrically
between North and South America on one side and Europe and Africa on the
other side.
The most remarkable outcome of detailed studies of ocean floors (triggered
by the International Geophysical Year, 1956) was that the magnetic
orientation of minerals in the ocean basalts show a peculiar pattern. For
yet not completely proven reasons, the magnetic field of the Earth
reverses its orientation now and than. Magnetic north pole becomes the
south pole, and visa versa. These reverses occur irregular in time, but
they do occur in geological terms fairly often. The reversal itself takes
little time, followed by a period of several million years of fixed
polarisation. So periods of 'normal'(as the present situation, that is
magnetic south pole in the south), and periods of reversed orientation
(magnetic south pole in the north) could be recognised. All these
orientations are fixed in the crystallized minerals of the basaltic rocks.
Since spreading and growth of the ocean on both sides of the fissure is
symmetrical, the patterns of magnetic reversals shows a symmetrical
pattern as well. The magnetic patterns could easily be mapped and the
resulting map proves that this is the mechanism. Geologists have numbered
these reversals, dated them by means of radiometric dating, and all the
ocean floors are mapped in this way. Again, anomalies give insight of
space and time.
Since paleomagnetism is much easier to measure than radiometric dating, it
was much easier to date all the oceans. The oldest parts of the Atlantic
Ocean are roughly 150 my old and lie on both sides of the ocean nearest to
the continents. The youngest ocean floor (with normal magnetic
orientation) is along the Mid Atlantic Ridge. In the non-symmetrical
Pacific Ocean the oldest parts are found in the north west, in the
'corner' of the island arcs of the Aleoutes and Japan.
>From these patterns and the radiometric dating it could be calculated that
the average speed of spreading in the Atlantic Ocean is about 10-12
cm/year, in some parts in the Pacific Ocean spreading rates of 18 cm/year
have been found.
SEISMIC TOMOGRAPHY
A very recent discovery in the earth sciences is the unravelling of the
very deep structure of our planet.
It was already known for a long time that the globe is composed of a
number of concentric shells: the core, the lower mantle, the upper mantle
and a relatively thin crust. This architecture was established by studying
the way seismic waves - triggered by earthquakes - traveled through the
Earth. The type of wave (longitudal or tranversal), travel time and travel
path (detected by a world wide network of seismographs) were the base of
interpretation of density and phase (liquid or crystalline) of the
interior. These data have given insight in the occurrence of some main
discontinueties due to a main phase transition and/or a fairly sharp
density difference.
These data gave us a 'ideal' picture of the interior of the Earth.
In recent years thousands of earthquake data were re-analised. Scientists
became focussed on the deviations from the ideal picture. So, they
predicted the travel time and travel path of waves according the ideal
picture, and than they studied the deviations from the prediction. In this
detail, some sytematic deviations seem to occur. And they interpreted
these deviations as a result of temperature differences in the Earth's
interiors. If the wave passed a relatively cold area, the wave arrive
earlier at the seismograph, of it passed a hotter place, the travel time
was longer. In this way, studying all the historical data and after a lot
of computer work, maps were made of the internal structure of the Earth.
>From earthquake data it was known that the deepest earthquakes ever
detected occur at a depth of ca. 600 km. No data were available from
deeper positions. These very deep earthquakes were caused by decending
oceanic crust underneath island arcs and mountain ranges such as the
Andes. Probably at even deeper sites the rheological differences between
the oceanic crust and the deep mantle were nihil, so no friction and
earthquakes could be generated.
With the seismic tomography as described above, it became clear that the
slabs of oceanic crust continue towards much deeper regions. Although no
earthquakes are detected at these depths, still temperature differences
could be detected. The relatively cold slab of the decending ocean plate
continues to depths of over 2000 km. Now even remnants of oceanic plates
have been detected at places were the ocean at the Earth's surface has
disappeared. The former ocean north of India which is now completely
vanished underneath the Himalya mountains, is still recognisable with
seismic tomography. But also oceanic plates underneath central Asia (below
Mongolia) have been recognised, This is a remnant of an ocean which
disappeared already 200 my ago.
These discoveries will generate a complete new set of data which will
emerge into new interpretations of the history and topography of the Earth
at times that other data will fail. It is another example that memory is
defined by phenomena that deviate from the normal.
EPILOGUE
As is regularly mentioned in contributions of this list, learning is
creating. And a creation is the result of entropy production. If I may
refer again to the experiments of Reynolds, one could see how an emergence
develops. A initial laminar flow in a tube, will after a while and given a
number of certain conditions, turbulences. The laminar flow strats with
some deviations from the regular path shown by initial meandering. And
these meanders develop further into vorteces or turbulences. A new order
has been developed after reaching gradually the edge of chaos. It is
simmilar to the smoke of a cigaret; if the atmosphere is quiet the smoke
shows a linear rising line, but at a certain moment the smoke starts
crinkling in meanders.
The laminar flow runs parallel with time and no memory will develop. This
is the period of the gap. As soon as a deviation from the laminar flow
occurs, meandering or turbulences occur, and this emergence will cause a
memory. Maybe we could compare this with the tale of the boiled frog. If
the water is slowly heated, no emergency will happen; it is like the
laminar flow. However if a emergency happens by increasing the heat
amount, something will be memorised.
And if we project this picture to our thinking and our memories, at are
the emergencies that are the anchorplaces for our thoughts. If life was
constantly normal and regular, we were not able to memorise and no
knowledge and creativity will develop in our brains. Luckily, life is not
regular. The environment is changing and we react on that. And this will
thus generate memories and thoughts and knowledge. And by this we got a
feeling of time. But the lengths of the gaps are unknown. We only could
get a grip on these gaps, if we think with our brains of the calender and
if we then create the anchorplaces.
>From the geological time table we got the impression that the gaps become
smaller or shorter towards recent times. Does that mean that the laminar
flow in the beginning of our history runs slow and that it took a long
time before an emergence happened? Does it mean that with ongoing entropy
production the number and frequency of emergencies increase? Is it true
that our own memory shows more anchorplaces in the recent past than longer
ago?
If this is so, are the increasing number of shortly after each other
occurring emergencies finally reach a state of total and final order with
such an amount of internal complexity that it looks like chaos?
Or is the memory of the Earth and our own memory selective. Are gaps and
emergencies irregular but in the long run frequently occurring? Is our
sence of time (which is a good indicator if compered with watch and
calender) not the perfect instrument to unravel this problem? Do we feel
that time is running faster when we become older? Is our next birthday in
childhood a seemingly endless wait, whereas in adulthood each year seems
shorter than the former?
I am expecting in a moment the next emergency, so I stop.
Best wishes,
dr. Leo D. Minnigh
minnigh@library.tudelft.nl
Library Technical University Delft
PO BOX 98, 2600 MG Delft, The Netherlands
Tel.: 31 15 2782226
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Let your thoughts meander towards a sea of ideas.
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--Leo Minnigh <L.D.Minnigh@library.tudelft.nl>
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