We begin the week by watching Voyage of Time: An IMAX Documentary directed by Terrence Malick.

Here is the trailer. The full documentary can be seen in MUBI.com.

Here are some key thoughts raised by the documentary:

1. Human mind is infinite, and the birth of a human being is similar to the birth of a whole universe. The birth of a baby from the womb is similar to the birth of light from darkness, or birth of order from chaos.
2. When there was no life, there was no death. The origin of life is essentially connected to the origin of death.
3. Time flows forward like a river.
4. One of the crucial moments in the history of humanity was the moment when a human looked at the surface of a river and saw his/her image reflected on the semi-transparent water. The water flowed, but the image did not. The image was floating on the river. If the river was like the stream of consciousness than the image was like the illusion of self or the person who is conscious.
5. The dinosaurs went extinct almost 65 million years ago due to the impact of a huge asteroid. We know about the dinosaurs because of the footprints they left behind.

We know that time dictates the evolution of the universe. But what is time and what is evolution? We do not know the answers. But let us take one step at a time and try to have a feeling for time first, and then come up with a working definition of evolution.

Time is mysterious, but it at least has a direction or arrow, it always goes forward like a river. There is something else in physics which also always goes forward. We call it entropy, which is a measure of disorder within a system or object.

We need the two laws of thermodynamics for further clarification. These are the two most fundamental laws in physics and they are:

First law: total energy within the universe never changes,

Second law: usable energy within the universe always decreases.

We can use the first law to write

$$ \text{Total Energy } = \text{Usable Energy } + \text{ Unusable Energy}. $$

Total Energy is a constant, it is the same now as it was at the moment of the big bang. However, as the universe expanded and cooled, this usable energy was transformed into many other forms of energy and matter.

Food is a form of usable energy. We take usable energy in the form of food and convert it to unusable energy in the form heat and various wastes. Here, usable energy is decreasing and unusable energy is increasing. The same is happening in the universe as a whole.

More and more energy is getting used, so usable energy is decreasing. Waste energy is produced after any use of energy. This waste is unusable. So after an use or transformation of energy, usable energy decreases and unusable energy increases. This is just the second law. The formal quantity that quantifies the total amount of unusable energy in the universe is called entropy. As usable energy is always decreasing, entropy (unusable energy) is always increasing.

The increase of entropy and the forward flow of time might be related to each other, but we do not know exactly how. Let us employ the flow of a river for relating time and entropy allegorically.

Let us assume, metaphorically, water in a river is time. River flows from a mountain to an ocean. The mountain is the symbol of the big bang and the ocean is the symbol of the future. The mouth of the river represents the present time. Time flows from the big bang to the present as the water flows from its source in a glacier to its mouth near an ocean. The analogy between time and water is complete.

But now carefully observe the flow of the Brahmaputra river in this youtube video (also embedded below) and in the diagram above. You will see that the river is narrow near its source and gets wider and wider as it approaches its mouth in the ocean. If you observe a real river, you will also understand that the water gets more and more murky, dirty and sediment-rich as it gets closer to the ocean. Getting dirtier is equivalent to getting disorderly (having more entropy). As the dirt and murk in the river water (metaphor of time) increases so the entropy of the universe increases. If the flow of a river is a metaphor of time, the width and dirtiness of the river could almost be a metaphor of entropy.

We can establish one further analogy. River water flows faster near its source in the mountains and there more of it can be used to produce electricity. But the water near the mouth is very slow, it almost stagnates. So near the mouth, water is less usable. As river flows toward the ocean its usability decreases. And indeed usable energy in the universe is also always decreasing with the flow of time.

The second law, stated in the previous section, clearly says that the entropy (disorder or unusable energy) in the universe as a whole always increases. But we see many examples of local exceptions to this case. For example, throughout the history of the universe a lot of ordered structures have emerged from comparatively disordered things. Organic life is more structured than inorganic matter, your mind is much more structured and ordered than the table in front you. Does not this emergence of order from disorder violate the second law?

The short answer is, no. The long answer involves another analogy. Let us go back to the river as a metaphor of time and entropy. A river normally flows from a mountain to an ocean, always downward. But in some localized parts of the river the flow might be opposite. Take the example of a whirlpool.

Whirlpools form near river rapids, parts of the river where water flows at high speed. And around a whirlpool, water sometimes flows downstream, sometimes upstream—the flow changes direction. However, this is only a local phenomena; the downstream flow wins in the end because whirlpools are temporary. Moreover, downstream speed of water is high near whirlpools; they form only near rapids. Therefore it seems, the temporary and local upstream flow of water in a whirlpool is strengthening the permanent and global downstream flow of the river.

In the same way, metaphorically speaking, the local and temporary decrease in entropy supports the global and permanent increase in entropy. When complex things emerge from relatively simpler things, order increases and entropy decreases. But this complex entity needs a lot of energy in order to survive. During the temporary lifespan of the complex entity, it uses a lot of energy and converts them to unusable energy thereby increasing the entropy of its surroundings. And the entity itself reduces to simpler disordered things after its death.

So emergence of complexity is allowed within the second law. And the process of this gradual increase in local and temporary complexity is evolution. We can define evolution as change governed by chance and necessity. If I jump from the 10-th floor roof, I will necessarily fall and die; this is necessity. But if I die in a road accident, my death will be only due to chance.

Within the eternal upstream flow of entropy, there are pockets of downstream (or negative) entropy. And within these pockets chance and necessity play there part to form complex structures. During the upstream flow a lot of new forms and things emerge by chance, and some of these chance events are selected by the laws of nature, that is by necessity. Through this feedback loop of chance occurrences and necessary selections more and more complex things emerge in the universe.

The universe is 14 billion years (giga years: Gy) old. Eric Chaisson has divided the history of the universe into seven epochs; we are calling them ages. The seven ages are shown below along with a characteristic symbol for each age drawn by Mrs. Chaisson. [My: mega (million) years, Gya: giga (billion) years ago]

Any history can be divided into arbitrary number of ages. History of the Western Christian World is usually divided into three main ages: ancient, medieval and modern. Indian or Islamic history could be divided into other ages or epochs. The number of divisions and the name of each division largely depend on the taste and preferences of the community who are adopting that division. So the seven ages we are dealing with here are not written in stone like the Ten Commandments. You could prefer a different taxonomy. I like the seven ages, personally, because it is poetic. It reminds me of the seven ages of human life described by Shakespeare and the seven heavens mentioned in many religious texts. And I could also divide the course of the Brahmaputra river in exactly seven stages using a reasonable dose of wishful thinking.

It is difficult to characterize the seven ages of the universe and even more difficult to delineate one from the other. The division, first of all, is anthropocentric because the history culminates in the emergence of human culture. But maybe millions of other intelligent cultures emerged and got extinct in the past and maybe there are many other cultures like us right now around other stars and in other galaxies. We do not know. The point of this division is not to say that this is the only history of the universe, all we are saying is that this is our history.

This history is a story of evolution, that is the history of the emergence of more and more complex structures and entities in the last 14 Gy. Initially there were only particles in a gaseous conglomeration during the Particle Age. The gas clouds condensed here and there to give rise to the first galaxies during the Galactic Age. Within each galaxy many more condensations of clouds gave rise to countless stars during the Stellar Age. And the molecular gas and dust leftover from the formation of each star created planetary systems around almost every star during the Planetary Age.

Note that the galactic, stellar and planetary ages make sense only in the context of our history, that is the history of human beings. Our galaxy formed 13 Gy ago, our sun formed around 5 Gy ago, our planet formed around 4.5 Gy ago. One age is coming after another. But of course many more galaxies formed before or after the formation of our galaxy. And countless stars and planets are forming even as we speak.

These three ages are shown in the context of the whole universe in this figure. Trillions of galaxies formed from the particles within the first few billion years of the universe. The galaxies are arranged in a cosmic web. The nodes of the web have many more galaxies than the filaments. Only one such galaxy is our galaxy located in a supercluster of galaxies. The first inset is thus representative of the Galactic age. The second inset shows only our galaxy with the position of the sun specified. Finally the third inset shows a close-up of our planetary system.

Our earth is the third distant planet from the sun. Complex chemical processes took shape on the surface and oceans of this planet between 4–5 Gya during the Chemical Age. Life emerged from complex chemistry around 3.5 Gya during the biological age. Finally , the Cultural Age begins with the emergence of human-like animals around 1 Mya, although anatomically modern humans emerged only around 300 ky ago.

Try to relate these seven ages with the concept of entropy and evolution. One age is more complex than the preceding age. Galaxies are more complex (ordered) than random particles, stars more complex than galaxies, planets more complex than stars, chemical processes more complex than geological processes, biological processes even more complex and, finally, cultures are the most complex of all. The evolution of local and temporary complexities in the universe supports the global and permanent increase of entropy.

The seven ages span an almost unfathomable period of time, 14 billion years, 1400 crore years. We can try to fathom unfathomable concepts in physics using metaphors and allegories. Let us go back to our river of time and entropy and try to relate the seven ages with the seven stages of a river.

And I have taken the Brahmaputra river as an example because it has seven interesting stages. Of course the stages are my own creation. One can divide the course of this rivers in other ways, just as any history can also divided in many different ways depending on the overarching concept behind the division. All this is just a game of poetry in any case.

The seven stages of the international and trans-boundary Brahmaputra river is shown above. Each stage could be metaphorically related to its particular age (of the universe) using a bit of poetic acrobatics.

The Brahmaputra river is born from a mysterious glacier in the northern slopes of the Himalayas near the Manas Lake of Tibet, China. The lake and the river are both famous entities in Indian mythology. ‘Brahmaputra’ literally means ‘the son of Brahman’ and Brahman is the name of the ultimate source of everything in reality in the Advaita tradition of Hinduism. If river is a metaphor of time, our time also begins here with the big bang. It is fitting that the big bang is related to the source of the Brahmaputra where Brahman gives birth to her child, the universe.

A river of course has many sources and Brahmaputra is no exception. But I have to choose one source for the sake of beauty. So I name the first part of the river the Angsi which is related to the Particle Age of the universe. The next stage is called Tsangpo (Yarlung Tsangpo in Tibetan) and is related to the galactic age. Galaxies instill in us a sense of vastness akin to the snowy mountains and vast deserts on either banks of Tsangpo. Tsangpo then enters into the deepest gorge in the world and cuts through the Himalayas; this part I am naming Siang following some indigenous communities in the Arunachal province of India and it is related to the stellar age. This stage is as turbulent and spectacular as the birth of a star from a gigantic molecular cloud. The planetary stage is related to the next stage called the Brahmaputra in the Assam province of India which creates a sense of liquid awe akin to the surface of a planet. Brahmaputra is as lush and liquid as a planet while Tsangpo was as barren and inanimate as a galaxy.

The chemical, biological and cultural ages are related to the three stages of the Brahmaputra after it enters Bangladesh: Jamuna, Padma and Meghna, respectively. The very word Jamuna has chemical connotations because the Indian Jamuna symbolizes the divine love between Radha and Krishna. Padma is perfect as an allegory of the biological age because it is born through the confluence of two great rivers, the god Brahmaputra (named Jamuna now) and the goddess Ganga (Ganges). And finally Meghna is related to the cultural age because all the rivers meet here to finally meet and greet the Bay of Bengal. Meghna symbolizes the individuality of cultures and the globalization of societies at the same time.

The video shows the course of the Brahmaputra river using the satellite view of Google Maps.

The mouth of Brahmaputra is our present era and Bay of Bengal is a symbol of the future. If river is related to the past, ocean is indeed a fitting metaphor of the future. The past has already happened, so it is very narrow similar to a river. The future is as uncertain and vast as an ocean. There is no end to the possibilities and you should jump into the ocean of right now as time is running fast and your life is emptying out like a leaky water-bottle. Detach from the narrow and dark alleys of the past to bathe in the light, salt and water of the future.