I have chosen the title of this piece to describe the deltas created by rivers such as the Amazon, the Nile, the Mississippi and the Ganges-Brahmaputra-Meghna (GBM) river systems, each of which debouches into the coastal ocean. The purpose is to distinguish this type of delta from its cousins – the land deltas such as the Okavango Delta in Botswana, the lake deltas, and flood and ebb tidal deltas we see at coastal inlets along alluvial shores. All deltas have one common feature though. Deltas are a net sediment depositional geomorphic area, and are built when the sediment carrying capacity of a constricted flow is lost in relatively wide open water. They are the typical planform areas where a flow forks outward into multiple distributary channels, cut through the fresh deposits of shoals and islands. Large river deltas are important for at least two important reasons. The first is their capacities to support many unique aquatic creatures, and flora and fauna that call deltas their homes. The second is the delta processes that bury dying plants and creatures. Through geologic time, this second process is responsible for accumulation and trapping of hydrocarbons released by decaying lives in sedimentary basins. . . . A delta is the topic of studies by at least four different disciplines of physical and applied sciences. There are the geologists in search of finding the clues to understand ancient deltaic hydrocarbon deposits – in attempts to connect the present to the past; and the geographers in search of characterizing the patterns of processes – the present and the past. The oceanographers primarily focus on hydrodynamics with some attentions paid to sediments as far as the bed-resistance to flow is concerned. In the process they discover and propose many easily understandable behavioral models coining and defining different terms to describe a delta. They mainly conduct field works far and wide, and with supporting laboratory experiments, try to connect dots to help us understand the delta processes better – not only with the behavioral models but also with the continuing progress on process-based models. The first two of the above disciplines delve into the long scales of space and time, while the oceanographers mainly focus on contemporaneous processes. The applied scientists or civil/hydraulic engineers primarily concentrate on short engineering time-scale in the order of 100 years or less. Standing on the foundations created by geologists, geographers and oceanographers, but with the safety, stability and effects of structures/interventions in mind, engineers’ methods are mostly based on investigations and scale modeling to derive process-based models in the controlled and manageable conditions of a laboratory. Supported by field works, they focus on hydrodynamics as well as on the processes of sediment transport and morphology. While the above generalizations and differences hold in general, there are considerable overlaps among the disciplines cross-fertilizing one another. This is especially true in advanced studies – where it is difficult to distinguish a certain work belonging to one discipline or the other, if the authors’ affiliations are not revealed. My professional involvement with studying coastal dynamics in a deltaic environment started with my works at the Land Reclamation Project – a Dutch project in the GBM coastal delta of Bangladesh – tasked to develop engineering plans to promote accretion, and for reclamation of the new delta landmasses. The involvement led to my Masters degree in coastal/hydraulic engineering at the UNESCO-IHE, Delft, the Netherlands; and later to my Ph.D. at the University of South Carolina (USC). Some of my works are published in journal and conference proceeding titles like, Elsevier, Taylor & Francis, Springer, Journal of Coastal Research (JCR), American Shore and Beach Preservation Association (ASBPA) and American Society of Civil Engineers (ASCE). The USC academic program gave me the opportunity to participate in a field trip to have a bird’s eye view by flying over the unique form of the Mississippi Delta. . . . With this little background, let us now try to have a glimpse of the processes that lead to the formation of deltas at a coastal river mouth. Some of the materials I will cover are taken from one of my discussion articles {Discussion of ‘Development and Geometric Similarity of Alluvial Deltas’, ASCE Journal of Hydraulic Engineering, 2002}. From the perspectives of delta building, two distinct processes can be identified at the very outset – these are the relative magnitudes of constructive and the destructive processes. Let us first try to see them by highlighting some examples. One can say that the ideal or the most recognizable delta morphology of the Mississippi and the Nile rivers shows more of constructive influences than the less recognizable delta of the GBM system. The Mississippi and the Nile flows face very low tidal forcings from the Gulf of Mexico and the Mediterranean Sea, respectively. However, since the commissioning of the Aswan Dam in July 1970, and because of several works on the Mississippi River basin (see the 2012 USGS report: A Brief History and Summary of the Effects of River Engineering Dams on the Mississippi River System and Delta), the delta morphologies of these two rivers have been increasingly getting more exposed to the destructive processes than the constructive ones. Although I have mentioned these two examples, all the major river systems and their deltas have been getting affected by increasing interventions – like the Farakka Barrage constructed on the Ganges River in 1975. . . . What are the constructive and destructive forces exactly? First let us try to see the types of the constructive processes. In simple terms these are the amount of sediment loads per a unit volume of flowing water, and the type of sediments a river transports – the larger the sediment load, the higher is its chance of forming a delta. And the rivers carrying higher percentage of sand than the fine fractions of silt and clay contribute more to the delta building processes. The destructive processes are the adverse ambient coastal environments, within which a river debouches – the submarine topography, tide, wave, and most importantly the episodic events such as tectonic activity, flood and storm surge. When a river debouches at a steep coast or a submarine canyon, the chances are that the river will only be able to build a submarine delta. A submarine delta or fan develops quietly without the disturbing effects of tide, wave and storm surge. The half-day oscillating tidal forcing erodes and resuspends the river-deposited sediments and transports them back and forth. The tidal processes align the sand shoals and islets with the prevailing current direction, and winnow the sediments to make the residual transport of the fines in preferential landward directions. The GBM delta is the typical example of a tide-dominated delta. Pounding waves work in a similar fashion in time scales in the order of 10 seconds – they winnow the deposits and transport the sand fraction in cross-shore and downdrift longshore directions to form depositional features like barrier islands. But the least understood episodes of tectonics, river flood and storm surge affect the delta evolution, perhaps more than any other. Tectonic uplift or subsidence either in secular trend or in episodes, shifts the epicenter of the delta deposits from one location to another – in the process, flow-shares of distributaries are changed. And the effects of flood? Let us try to see them. When a distributary becomes too long, its flow becomes sluggish [the Common Sense Hydraulics piece on the SCIENCE & TECHNOLOGY page indicates how delta progradation causes reduction of flow velocity], and the river looks for opportunities to find a steeper slope to the sea. A river flood comes with the help, and when the conditions are right, it cuts through the shoals or moribund channels giving a new life to the delta flow-distribution dynamics. Similar episodes happen when a storm surge forcing occurs on a delta landscape. Its power can erode and sweep away sand deposits out to the sea or could cut new channels redefining the delta dynamics. The historic Mississippi delta sequence during a portion of the Holocene Transgression period, shown in the image (credit: anon) gives an impression how deltas change their depo-centers over time. Similar shift happened in the GBM delta when the Ganges River shifted to the east to meet the Brahmaputra and the Meghna rivers, to reach out to the sea as a combined flow. . . . Delta building processes go through three major hydraulic phases – the first two primarily represent the sequences of constructive forces, but the third phase is a vigorous showcase of interactions between the constructive and destructive forces. The first phase processes are better understood through a jet theory. This theory in simple terms, explains how a jet emanating from a river, a diffuser outlet or a ship propeller, expands into the wide-open water. The expansion decelerates the flow velocity, and the river has no option other than to depositing its sediment load – the coarser fraction within the immediate vicinity, and the finer fractions further into the sea. Geologists have termed the depositional features as the seaward bottomset bed of the fines, and the coarse deposits of the topset bed. Like the submarine delta, the bottomset bed develops quietly with minimal disturbance from tide and wave. An episodic storm surge may affect the bottomset processes to some extent though. The topset bed or the delta proper, progrades forward into the sea through the avalanching of sand on the inclined foreset bed. In some instances when the foreset delta front becomes too steep, a sudden rapid submarine slope failure occurs causing tsunami. There are many examples of this type of tsunamis; some are often triggered by tectonic activities. Such a tsunami occurred in 1975 – in a little known delta of the Kitimat Arm at the head of the Douglas Channel fjord in British Columbia. The second phase occurs when the decelerated jet faces further frictional resistance from the built-up deposits of the topset bed. The result is the erratic channel and depositional patterns occurring in lateral expansions. Scientists try to understand this phase by describing and formulating the processes mostly through behavioral morphometric models. The third phase represents the most complex processes of delta evolution through time, showcasing the intensive actions and reactions of constructive and destructive forces. In this phase, delta deposits have already anchored themselves through colonization by plants and trees – therefore flows encounter more resistance. The destructive forces of tide and wave, and the episodes of extreme events when dominant, can completely redefine the delta planform evolution. Understanding delta dynamics as complicated as they are, has been made much easier with increasing applications of numerical computational models – by the advanced models dynamically coupling hydrodynamics, wave mechanics and sediment-morphology modules. Let us try to talk about this important topic at some other time. . . . Here is an anecdote to ponder: The disciple asked the master, “Sir, what do the delta processes tell us?” The master smiled, “Umm! Let me see. A river matures on its journey to the sea overcoming resistances and obstacles, meeting something different and overwhelming in the end. The loads it carries on its shoulder appear burdensome. It finds the comfort to be in right place to unload to build something new – the delta. Now, you figure out what it says to life and social living of humans.” . . . . . - by Dr. Dilip K. Barua, 15 September 2016
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The changing climate (In a later article Warming Climate and Entropy, posted in December 2019 – I have tried to throw some lights on the climate change processes of the interactive Fluid, Solid and Life Systems on Earth – the past, the present and the future) with its consequent effect on sea level is the most du jour topic of our time. It is not surprising – because there are many reasons for such popular attentions and human concerns. Some two-thirds of world’s seven billion people live within 100 miles of the coastline with the economic activities ranging from recreation to exploitation of sea resources to waterfront living, to gateways catering trade and commerce through many port and harbor infrastructure. . . . There is a caveat however – that we should watch ourselves not to lose the voice of reason by yielding in to the mob mentality of bullying and accepting whatever floats around. The fluctuation of sea level with the consequent transgression and regression of the shoreline is a complex phenomenon – and as we will try to have a glimpse – it would appear that it is a complicated response to many forcings of various scales and magnitudes – both terrestrial and extra-terrestrial. In this piece I will mainly focus on the science of sea level rise (SLR), and intend to cover the consequences and adaptive responses to SLR on the SCIENCE & TECHNOLOGY page at some other time. During the past four decades considerable amounts of works have been conducted by multiple national and international organizations on SLR and implications. It is only possible to have a glimpse of it in this piece. My discussions are primarily based on knowledge gleaned from such resources as: UN entity IPCC (Intergovernmental Panel on Climate Change), US CCSP (Climate Change Science Program), US NOAA (National Oceanic and Atmospheric Administration), US NRC (National Research Council), US EPA (Environmental Protection Agency), USGS (United States Geological Survey), USACE (United States Army Corps of Engineers) and the Canadian National Research Council (CNRC). Some of the US works are published by the National Academies Press (NAP). To give a little background, I got interested in SLR in the 1990s, not so much as part of my professional responsibilities at that time, but as an effort of self-educating myself. The effort resulted in an article I published in 1990 in a Bangladesh national weekly. The article must have caught attention of some, because it was translated to Bengali subsequently. The concern about the effects of SLR on Bangladesh has begun to get global attention because most of the country’s territories are low lying deltaic coastal landscape. Dutch Government initiated some of the studies, and I was fortunate to officially review some of their projects. I was also involved in another project in vulnerability assessments of SLR. Some other subsequent involvements in USA and Canada were mostly in the scopes of side-line responsibilities. . . . Perhaps it is helpful to know a little bit of geologic history to understand the phenomenon of SLR. Long-term studies of scientific data indicate that the present sea level, stands on the geologic interglacial period, perhaps at its peak. Geologic history tells us that there have been four major cycles of glacial-interglacial periods with the corresponding low and high sea level stands in the 400,000 years before present (BP). The last lowest sea level at -120 meter occurred about 18,000 years BP. Try to imagine the scenario of that time when our shoreline was at the edge of the present continental shelf. During that time many landmasses separated by shallow seas were connected together. We still see the remnants of the past shoreline as river mouth scars or submarine canyons. What are the causes of these past sea level fluctuations? As pointed out, these fluctuations in sea level are due to many glacial and interglacial periods, or ice age sequences. Scientists have identified some eight causes for ice age sequences: (1) change in the Earth’s atmosphere or climate; (2) relative positions of the continents or change in the volumes of ocean basins; (3) fluctuations of ocean currents; (4) uplift of the roof of the world – the Tibetan Plateau; (5) variations in Earth’s orbit (known as Milankovitch Cycles); (6) variations in Sun’s energy radiation; (7) volcanisms; and (8) fluctuations in dust-ice albedo. So the real reasons for sea level fluctuations are much more complex than we tend to think. They vary from extra-terrestrial factors to the Earth’s atmospheric, topographic and oceanic controls, to volcanism and albedo change. . . . Now let us try to attempt to look at its behavior in the recent geologic past. From 18,000 years BP sea level has been rising – but not at a constant rate, rather at variable rates – sometimes faster than other times. This process is known as Flandarian Transgression or Holocene Transgression. On average, the SLR rate slowed down onward from 5000 years BP when the sea level stand was at –10 meter. We can generalize the rates in orders of magnitude like this: from 18,000 to 5,000 years BP, SLR rate was on average +10.0 millimeter per year, and the slowed rate from 5,000 years BP was about +1.5 millimeter per year. Well, if SLR rate has really slowed down to such an extent, why should there be so much concern? The answers to the question can be found in at least three important considerations. First, humans have encroached into the domain of sea at an alarming manner. Therefore, our SLR tolerance threshold has very little room for accommodation. We have built coastal cities, human habitation and port infrastructure by advancing into the sea redefining the shoreline. Scientists had very little idea about the phenomenon of sea level fluctuations until recent time – therefore they were not in a position to warn of the consequences of our appetite and adventure for more of the sea; even if they did, it fell into deaf ears of the decision makers. The second is the narrow window of tolerance within which all plants and living creatures including humans can survive. As we have seen in the Natural Equilibrium blog on this page, system of things remains in a state of delicate balance in Nature, in quests to attain dynamic equilibrium. The narrow tolerance threshold of humans and other flora and fauna means that they cannot afford to live when the adaptation or equilibrium time is long. In addition, the narrow tolerance levels make life and habitat vulnerable to the effects of rather minor changes. Because of the complexity of processes, these effects in stresses and disruptions of normal ways of lives and livelihoods are not always easy to address. The third, and perhaps the most important one is the disturbing findings of scientists that the recent SLR rate is highly correlated with global Warming Climate change. If one breaks down the recent past, within the past 1000 years CE, SLR rate was 0.0 millimeter per year, after that the rate rose to +0.6 millimeter per year, then declined to -0.1 millimeter per year for a short period of time. Starting roughly at the middle of the 20th century, the SLR rate has been rising at +2.1 millimeter per year. Scientists have found that this accelerated rate is positively correlated with the increasing greenhouse gas emissions, rise in atmospheric, land and oceanic temperatures, and the retreats of glaciers in the Polar Regions. The conclusion is that human activities are responsible for such an accelerated rate, and scientists have coined a new term, the Anthropocene Epoch starting in 1950 to mark the human footprints on the environment. . . . So far we have discussed the global SLR rate over time. How about the rates over space? Local SLR rates are highly variable from region to region. Let us try to see how SLR is defined in space. The first is often termed as Eustatic SLR, which refers to global change in the ocean volume – evidently when the basin becomes large, sea level falls, and vice versa. Overall, some other major factors contributing to SLR include: melting of continental and Polar ice masses, reduction in ocean water density and resulting expansion, ocean circulation responsible for distributing the heat and dissolved substances, isostatic rebound of the coastal landmass resulting from melting and regression of glaciers, uplift or subsidence due to tectonic activity, soft sediment consolidation and subsidence, and ocean-atmosphere interaction. Regional uplift or subsidence adds local flavor to SLR - for a subsiding coast SLR is more than an uplifting or rebounding coast. The subsidence can overwhelm the global SLR; for example, at the Mississippi River delta, the present SLR rates vary from +9 to +12 millimeters per year, far higher than the global average. The opposite happens at an uplifting coast. The phenomenon of regional variability - the enhanced SLR on subsiding coasts and the decreased SLR on uplifting coasts - is captured by a new term, the relative SLR. . . . Let us now turn our attention to the most difficult part of the SLR problem – and this is the problem with predicting the future change in sea level. The crust of the problem lies with the predictability of soft models employed by various investigators. We have discussed the typical nature of this modeling problem in the Natural Equilibrium blog on this page as well as in the Water Modeling and Uncertainty and Risk pieces on the SCIENCE & TECHNOLOGY page. To demonstrate it, I have included an image taken from USACE. The USACE has compiled the 2100 SLR predictions conducted by most involved organizations. Looking into the image, two striking feature should attract everybody’s attention. The first is the lack of agreements among the organizations. The second is the large difference between the maximum and minimum of individual predictions. The highest predicted SLR in 2100 is +2.0 m, compared with the lowest prediction of +0.58 m. Accepting one or the other comes with huge environmental risks and financial consequences. One may dare to ask whether the scientific correlation between the SLRs and the global warming is just another anomaly or uncertainty. The chances are that such a suggestion is highly unlikely; even if likely, it is important that humanity tries to minimize its footprint on the environment impacting lives of plants and other creatures. Because an unsustainable approach impacting others has only one door open – that is the door of compromising the future well-being of all. But one thing is sure, that the uncertainties associated with predictions make it hard for decision makers to conceive and develop adaptation strategies. Let us try to address this issue more in the SCIENCE & TECHNOLOGY page at some other time - posted in the Sea Level Rise - the Consequences and Adaptation. . . . Perhaps it is helpful to note what the 2021 IPCC – AR6 says about the reality of SLR. In its WGI Technical Summary – enhanced sea level rise – has been spelled out in different confidence scales. The assessments and predictions are based on field observations/evidences and climate modeling efforts of different sorts (see modeling basics in Water Modeling). And three other WIDECANVAS articles: Warming Climate and Entropy, Uncertainty and Risk and The World of Numbers and Chances can help understanding the IPCC scale. This qualitative scale is defined in a matrix of evidence vs agreement – with the agreement indicating the degree of conformity between observations and the results of analytical tools or models. When an assessment is rated up to a sufficiently defensible scale – it is subjected to quantification in a way to define the probability of occurrence and labeling it in likelihood terms. Here is a gist of IPCC findings: Global mean sea level (GMSL) rose faster in the 20th century than in any prior century over the last three millennia (high confidence), with a 0.20 [0.15 to 0.25] m rise over the period 1901–2018 (high confidence). GMSL rise has accelerated since the late 1960s, with an average rate of 2.3 [1.6 to 3.1] mm yr –1 over the period 1971–2018 increasing to 3.7 [3.2 to 4.2] mm yr–1 over the period 2006–2018 (high confidence). New observation-based estimates published since SROCC lead to an assessed sea level rise over the period 1901–2018 that is consistent with the sum of individual components. Ocean thermal expansion (38%) and mass loss from glaciers (41%) dominate the total change from 1901 to 2018. The contribution of Greenland and Antarctica to GMSL rise was four times larger during 2010–2019 than during 1992–1999 (high confidence). Because of the increased ice-sheet mass loss, the total loss of land ice (glaciers and ice sheets) was the largest contributor to global mean sea level rise over the period 2006–2018 (high confidence) . . . At the basin scale, sea levels rose fastest in the Western Pacific and slowest in the Eastern Pacific over the period 1993–2018 (medium confidence). Regional differences in sea level arise from: ocean dynamics; changes in Earth gravity, rotation and deformation due to land ice and land-water changes; and vertical land motion. Temporal variability in ocean dynamics dominates regional patterns on annual to decadal time scales (high confidence). The anthropogenic signal in regional sea level change will emerge in most regions by 2100 (medium confidence) . . . Regional sea level change has been the main driver of changes in extreme still water levels across the quasi-global tide gauge network over the 20th century (high confidence) and will be the main driver of a substantial increase in the frequency of extreme still water levels over the next century (medium confidence). Observations show that high-tide flooding events that occurred five times per year during the period 1960–1980 occurred, on average, more than eight times per year during the period 1995–2014 (high confidence). Under the assumption that other contributors to extreme sea levels remain constant (e.g., stationary tides, storm-surge, and wave climate), extreme sea levels that occurred once per century in the recent past will occur annually or more frequently at about 19–31% of tide gauges by 2050 and at about 60% (SSP1-2.6) to 82% (SSP5-8.5) of tide gauges by 2100 (medium confidence). In total, such extreme sea levels will occur about 20 to 30 times more frequently by 2050 and 160 to 530 times more frequently by 2100 compared to the recent past, as inferred from the median amplification factors for SSP1-2.6, SSP2-4.5, and SSP5-8.5 (medium confidence). Over the 21st century, the majority of coastal locations will experience a median projected regional sea level rise within ±20% of the median projected GMSL change (medium confidence) . . . It is virtually certain that GMSL will continue to rise until at least 2100, because all assessed contributors to GMSL are likely to virtually certain to continue contributing throughout this century. Considering only processes for which projections can be made with at least medium confidence, relative to the period 1995–2014, GMSL will rise by 2050 between 0.18 [0.15 to 0.23, likely range] m (SSP1-1.9) and 0.23 [0.20 to 0.29, likely range] m (SSP5-8.5), and by 2100 between 0.38 [0.28 to 0.55, likely range] m (SSP1-1.9) and 0.77 [0.63 to 1.01, likely range] m (SSP5-8.5). This GMSL rise is primarily caused by thermal expansion and mass loss from glaciers and ice sheets, with minor contributions from changes in land-water storage. These likely range projections do not include those ice-sheet-related processes that are characterized by deep uncertainty . . . Higher amounts of GMSL rise before 2100 could be caused by earlier-than-projected disintegration of marine ice shelves, the abrupt, widespread onset of marine ice sheet instability and marine ice cliff instability around Antarctica, and faster than-projected changes in the surface mass balance and discharge from Greenland. These processes are characterized by deep uncertainty arising from limited process understanding, limited availability of evaluation data, uncertainties in their external forcing and high sensitivity to uncertain boundary conditions and parameters. In a low-likelihood, high-impact storyline, under high emissions such processes could in combination contribute more than one additional metre of sea level rise by 2100 . . . Beyond 2100, GMSL will continue to rise for centuries due to continuing deep-ocean heat uptake and mass loss of the Greenland and Antarctic ice sheets, and will remain elevated for thousands of years (high confidence). Considering only processes for which projections can be made with at least medium confidence and assuming no increase in ice-mass flux after 2100, relative to the period 1995–2014, by 2150, GMSL will rise between 0.6 [0.4 to 0.9, likely range] m (SSP1-1.9) and 1.4 [1.0 to 1.9, likely range] m (SSP5-8.5). By 2300, GMSL will rise between 0.3 m and 3.1 m under SSP1-2.6, between 1.7 m and 6.8 m under SSP5-8.5 in the absence of marine ice cliff instability, and by up to 16 m under SSP5-8.5 considering marine ice cliff instability (low confidence) . . SROCC and SSP stand for IPCC Special Report on the Ocean and Cryosphere in a Changing Climate; and Shared Socio-economic Pathways, respectively. . . . Here is an anecdote to ponder: The disciple asked the master, “Sir, because global temperature and sea level stand have changed so many times in the past, I am wondering what would happen if instead of warming, we come across cooling of Earth.” The master looked at him and smiled, “Good Lord, this is not happening in our lifetime! But you have pointed out an important issue – that may haunt humanity at some time in the distant future in the human-scale of thinking. There is no doubt that such a scenario would cause absolute havoc in people’s mind. Perhaps everyone would cry for burning more and more fossil fuels to keep things warm. Or perhaps with lowering of sea level stand with glaciations, people will go further into the sea to build – the human appetite for exploitation will never cease. There may occur a reverse flow of refugees from colder countries to warmer ones – or war may break out.” “Human destiny in the hand of climate change!” “Yes, climate is the ultimate arbiter. Inevitability of such a scenario indicates the necessity of managing the Earth’s resources in a sensible manner for common well-being. The effort of sensible management is no easy task, however – because it would require real commitments from all nations by melting down vicious differences we see now.” “How about artificial creation of energy-emitting sun or suns. I have heard that such high level researches have been sponsored by many countries.” “It is encouraging that this and many other cutting edge researches are being initiated around the world, albeit at a high cost. Scientific leaders are thinking ahead than most of us realize. But practical outcomes of such endeavors usually take very long time – and there are considerable uncertainties in such efforts, even tangible benefits may never materialize. I guess though that the efforts result in gaining and perfection of knowledge in various supporting activities.” . . . . . - by Dr. Dilip K. Barua, 8 Septermber 2016 We have discussed TIME in The Fluidity of Nature essay on this page as one of the important elements of Natural transformation. Transient and impermanent, the nature of things evolves through the mysteries of uncertainties to the future – yet in the order of duality and multiplicity. The process supports webs of activities to support each other and carry things forward. Forward? There lies the mystery – the fear of the unknowns – the fear that the established dynamic equilibrium pursuits could be dislodged. Let us first try to have a glimpse of the views of philosophers and religious leaders on time (image credit: anon). Eastern thoughts had been fascinated with time since ancient times. Time was visualized as the mysterious deities and gods – as Kala and Yama with the powers to oversee, arbiter and grasp everything. Some say, Kala metamorphosed into the Hindu goddess Kali in the ancient matriarchal Indian South. With time there was no arguing – only the consequences defined by karma – the principle of dependent-origination of things – the universality of cause and effect, action and reaction. The concept of karma is a fascinating underlying idea in Buddhism and Hinduism. The after-life extrapolation of the principle – reincarnation is a message of both hope and caution – more so in Buddhism than in Hinduism. Hinduism invites divine intervention in the process of karma. Buddhist Law (see Buddha - the Tathagata) of Impermanence - laid down the first insight on the nature of time - how it applies to the evolving canvas of Nature and Social Interactions, and what it implies. We all experience these aspects of the Law in our lifetime. Tibetan Kalachakra (The Wheel of Time) Sand Mandala - is a spectacular depiction of Impermanence created by Buddhist monks. Depending on the size, the meticulous colored sand creation of the wheel takes 8 hours or 8 eight days - with its destruction in 8 seconds or 8 minutes (again depending on the size). The number 8 is auspicious in Buddhism - emphasizing the significance of the Way of Noble Eightfold Path to attain Enlightenment. Ancient Western thoughts were not so much steeped with the futuristic view associated with time – rather with the near-sighted view of things. The good aspect of it is that social energy can be directed toward immediate gains. The undesirable aspect is that the notion can induce lackluster view of future consequences. However, the ancient beliefs of heaven and hell, representing in a sense karmic interpretations associated with time – as a message of hope and fear, have crept into all religions. Real or fictitious visualizations, religious thinkers found the belief system very useful to include it in the scriptures in one form or another. The purpose was to convince people and convey the massage of reward for performing good deeds, and consequences or fears for performing otherwise. . . . How do the physicists look at time? Let us try to see it briefly. Until the ground breaking proposition of the Special and General Theories of Relativity by Albert Einstein (1879-1955), time constituted a rudimentary yet important element in the dynamic equilibrium of things, and in motions of speeding objects – in velocities (distance over time) and in accelerations (velocity over time). How about time in waves? The wave form – the fundamental mechanism of transporting energy looks exactly the same whether portrayed in terms of wave-length or wave-period. These two wave parameters, length and time, are related to each other through the celerity or the speed of propagating energy. Time is also implicitly included in the dynamic pressure or kinetic energy of fluid flows. We have discussed the pioneering theory of Daniel Bernoulli (1700 – 1782) in the Common Sense Hydraulics blog on the SCIENCE & TECHNOLOGY page (links in Widecanvas Home Page). Bernoulli has shown that in a frictionless flow, dynamic pressure is given by the product of fluid mass and the speed or velocity squired, V^2. Perhaps this basic understanding paved the way for Einstein to formulate his famous mass-energy equivalence in the very high-speed domain of the electromagnetic and gravitational radiations, E = mC^2, with E being the energy, m being the mass and C being the speed of light (671 million miles per hour). Einstein’s theory deals with the macro-understanding of physical laws – in areas of motions dominated by the accelerations of heavy masses in the vast curved space-time field – time being the 4th dimension. The mass or its equivalent energy causes the space-time fabric to curve – the curvature in turn accelerates the motions of masses. Here again, we can take the help from Bernoulli theorem to understand Einstein. Unsteady Bernoulli theorem says that fluid accelerations can be a local phenomenon as a function of time only, or can be generated when a fluid motion is subjected to change direction in a curved field such as in a river bend. Therefore, any change in the direction of fluid motion due to curvature results in the convective acceleration of its speed – this reality is in fact nothing but the Newton’s (Isaac Newton, 1643 – 1727) First Law of Motion. Einstein’s brilliance lies in seeing this underlying physics of motion through the wave processes of electromagnetic and gravitational radiations to explain how very heavy masses or very high energies can warp the space-time frame. Einsteinian concept of acceleration is able to explain the processes that happen in space and replaced Newtonian theory of gravity. Einstein’s General Theory of Relativity has predicted the existence of gravitational cosmic waves that travel at the speed of light to transfer energy. These waves are created on the curved space-time field in the cosmos by gravitational energy radiated from heavy accelerating masses like black holes, or what happens in those masses. The existence of gravitational waves has been confirmed by experimentation in Laser Interferometer Gravitational-wave Observatory or Ligo on February 11, 2016. . . . More on time? Perhaps its mystery can better be appreciated by seeing it through the eyes of a poet. TIME See time in everyday experience It is like an arrow – heading to infinity Each moment gone forever With no turning back – only the forward motion to the future. Past is nothing but memories, experience and knowledge Future is uncertain and lies in visions and plans Time is nothing but the continuous forward translation of the present. Present – we have only the fleeting present Live in the present to the fullest with wisdom To build and to continuously refine yourself To minimize regrets To create a pleasant tomorrow. See time as a recurrent realization In changing days and nights In seasons of weather change. Time appears circular In birth, growth, decay, death and birth again In wave’s rise, fall and rise again In emotions – rise and decay and rise again In the duality of all existence – light and dark, long and short, high and low The wheel of time rolls on to the unknown. Time is the making of mind In the relativity of our consciousness and judgment Short to the fast and restless Long to the slow and steady Some equates time with money Yet others like to see quality in it. To those who has gone through a tragedy time is a healer To those who wait and wait time is a killer We warp time to meet our needs Yet time is nobody’s and is merciless Everything is transient in time – do not get attached to it. Time is like a justice overseeing everything that happens It does not discriminate – all are equal in the eyes of time. Time is the lasting witness To the transformation of Nature, life and society To the dynamic equilibrium of all existence To the translation of space – frames after frames. Time is a reference to define the beginning and foresee an end, Travel long distance – time translates to change in space Travel deep into space – time melts into the vastness of space – into the void, Where reality is unreal The realm of no time no space – only the infinite expanse of emptiness. . . . Here is an anecdote to ponder: The disciple said, “Sir, tell me something different. I am feeling very low today.” The master looked at his disciple and smiled, “Take it easy, my dear. Don’t think that low feeling only happens to you. It happens to all. A superman does not exist in a real world. High and low feelings are part of the duality – one cannot exist independent of the other.” “Are you sure, Sir? I think people are having more lows than highs.” “As unfortunate as it may sound – it is right. Lows are becoming more recurrent than highs – we are seeing and hearing the symptoms almost every single day. Regrettably, economic progress is not translating to people’s happiness. It seems our governing systems are screwing up the social system and life. Who knows what human destiny is in the making?” “Why do lows happen?” “Well, there could be many reasons – worries, disappointments, hopelessness, and rude and inhuman encounters are some of them. Therefore, it is important to be strong both physically and mentally.” “But Sir, what shall I do.” “Think of taking a stroll. Tell something nice to someone. You will be surprised to see how words can make a difference, and find out that you can gain a lot by giving a little gift of kind words.” “Any other alternative?” “There are many others you can try. But try not to get bogged down doing the same thing again and again. There is something called fatigue that affects us all. Be creative to find something different. May be you can practice relaxation and compassion meditations now and then.” . . . . . - by Dr. Dilip K. Barua, 1 September 2016 |