Scientific
Understanding of Heavenly Phenomena
(A lecture delivered in Berhampur University, Berhampur, Odissa)
(Receiving Sri Ganesha from the Vice Chancellor of Berhampur University)
Debi
Prasad Choudhary
Professor,
Department of Physics and Astronomy
California
State University Northridge
Associate
Director
San
Fernando Observatory
Profound
scientific discoveries are made by following this simple method.
Finding the common properties of
similar phenomena under different situations and understanding them with a
simple predictive model is central to scientific method. Over centuries,
man asks questions about its surroundings, some of which are easy and some
difficult. Attempting to answer them through generalization of observed results
and extending their scope through creative imagination is a vital aspect of
scientific method that resulted in a series of discoveries enriching our lives
and brought us from caves to modern comfort. The important thing is that any
new scientific theory or model must be able to explain the already observed
phenomena and predict new results that can be used to test them. The latter is
an important aspect, absence of which makes a theory unscientific. I have been
working in physics of the sun for past three decade. I shall illustrate these
statements using the understanding of “The Sun”, our closest life supporting
star over past century.
Earth
goes around the sun like other planets in the solar system. Our universe
contains billions and billions of galaxies in an expanding space time fabric. Enormous
amount of energy can be generated by breaking heavier elements or combining lighter
ones. These are some of the profound discoveries made in past 100 years alone
that changed our lives. By using some of these results, we can travel to faraway
lands in few hours, light-up an entire city and remove darkness, communicate
our loved ones live. These effects clearly enriched our living standards
continuously, especially in past few decades or so. And you will be surprised
to know that all these started with simple questions like “Is it true?”, “How
does it happen?”. Each one of these discoveries has a fascinating grand story
behind. I shall illustrate this process using one such story that lead us
understanding our life supporting closest star – The Sun. I selected this
story, because, I have been working for past quarter century to understand some
aspects of this object.
The
sun is a huge nuclear huge Furness, at the center of which 4.21 million tons of
hydrogen is converted to helium every second producing 3.78 x 1026 Joules of energy that takes about 4 to 40 thousand years to
come out, making the sun shine. As shown in the figure, the energy is produced
in the core, flows in “radiative” manner in Radiative Zone, and convectively in
Convective Zone. You might imagine heat
flow on a solid object in radiative zone and boiling water in convective zone.
The core and the radiative zone, which is 70% of the sun, rotate like a rigid
body, while different parts of the convective zone rotate with different speed,
that is called differential rotation. The interface between these two zones is
known as techocline, where magnetic field in the sun is supposed to be created.
As the energy escapes the sun, there are many complex physical processes occur
on its surface, since it suddenly encounters low dense atmosphere. If you see
through telescope, you will notice granule structures in the bottom of solar
atmosphere, called photosphere, above which you will notice a highly structured
(in form of for example prominences) chromosphere and transition zone leading
to super-hot corona. The chromosphere and corona can only be seen from earth
during total solar eclipse, whereas on ordinary day, you see only the
photosphere, that produce most of the energy. In photosphere, occasionally you
will notice sunspots, that are cooler regions, due to the isolation of solar
material by intense magnetic field. Such regions appear more every 11 years,
which is called a solar cycle. Complex sunspots support an entangled and highly
unstable electric current system, that produce flare as a result of breakdown. Many
times, the flares lead to events called Coronal Mass Ejections, that dump about
a billion tom of hot material in to the space with tremendous speed of 1000
km/s. As the material hit earth, they cause polar lights and potentially might
damage communication satellites and commercial flights over polar regions. So,
understanding the cause of these events are important. When such events are not
there, still material constantly flow from the sun in the form of solar wind,
at a speed of about 400 km/s. Briefly, this the story of the sun, you take 20
years to learn!!
Figure 1: Structure of the sun. The size of the earth would be smaller than the size of "o".
Now,
the question is how do you know these are the facts, or that is possibly the
real story of the sun? If you listen to a priest, or a scholar, who advocate
the ancient wisdom, he might say a different story, that most of us might have heard
in our childhood. In my childhood, my grandmother
told me that the Sun God, comes everyday on a chariot that has seven horses as
shown in the picture 2. Depending on who makes the story, often the chariot is
driven by a driver called Arun, who might possess a mustache or not. Every day,
the sun god comes from east and goes in the west, and according to various
versions distribute light on earth to sustain life and occasionally take
interest on earthly affairs, especially when the supreme God like Sri Rama or
Sri Krishna appear on earth. My mother worship sun god on a grand scale once in
a year in winter. As a Brahmin, I often recite prayers called Gayatri Mantri,
basically a prayer to the sun god. You would encounter similar and some times
more exciting narrations in different societies. These are simpler and romantic
than my story often told by people, who are considered to be closer to God that
govern your lives. So, why should you believe me not them? You don’t have any
way of verifying the two stories to ascertain, which is correct. You cannot now
go through all the physics and mathematics that I learnt in past 40 years to
appreciate my story. The only way to decide for yourself is to be doubtful of everything
and ask simple questions and
aim for simple answers. Doubtful of what I am saying and what they are saying.
Follow the logic skeptically, verify them with evidences and decide. Blind
believe is ok, but that should come in the end when you exhaust all your
intellectual power. Take for example, a god-man or god-women producing a stuff
(a gold ring) from nothing by waiving the hand. The simplest explanation is
that he or she played a magical trick. The complex explanation is that he or she created
the stuff from nothing by violating all known scientific principles. The other
example is who created the universe, and why, like an excellent designer, where
the fundamental particles are so uniform in size? These are the questions dealt
in great Indian scriptures called Upanisheds. Answer is not straightforward and
simple. You might get compiled to accept the grand creator. Anyway, let us
continue with my story.
Each of
the statements that I made in the third paragraph, were obtained by this
process. The process is extensive, takes years of hard work by many scientists
to come to these conclusions through a serious of rigorous experimentation and
calculations. Hundreds of PhD thesis are written for each of these conclusions.
Here, I shall illustrate the process that led us to know that sun is a huge
nuclear Furness.
Figure 2: The sun God according to Hindu mythology.
Understanding the solar luminosity was central
to the discovery of nuclear fusion, which is a perfect example of how a simple
quest to understand a glaring phenomenon can also lead to vast engineering
enterprise. In 19th century, astronomers were convinced that
gravity is the dominant force in the universe, so they conjectured that sun is
shining by releasing energy by “gravitational collapse” that last for few tens
of millions of years. By last 19th century, geologists were
confident that earth is much older, as we know today at least 4.5 billion
years. There was a need to explain the source of energy in the sun. In 1920,
Sir Arthur Edington, a brilliant British astrophysicist, presented to the
British Association for the Advancement of Science by using the measurement of
mass difference of hydrogen and helium that sun could shine for 100 billion
years by converting 0.7% of mass equivalent energy in accordance with
Einstein’s mass-energy relationship.
In 1939 two astrophysicists, Subrahmanyan
Chandrasekhar and Hans Bethe, working independently, quantitatively showed the
processes of gravitational collapse and nuclear fusion as the source of energy
in the sun and stars. After this great achievement of intellectual
gratification, the question was if we can use this physical process in earth.
When so much energy is released in a tiny volume, that can be used as weapon
and source of useful energy. Following the second world war and success of atom
bomb, Edward Taylor of Manhattan Project worked on the problem and designed
hydrogen bomb that is several times more destructive than atom bomb. This
design required achieving the fusion reaction by bringing the deuterium nuclei
very close to each other in a small volume unlike in the sun and stars, where
this happens due to gravitational force. The conventional atom bomb is used to
implode a container with deuterium to achieve this condition where energy is
released in an uncontrolled fashion. The next step is to achieve controlled
thermonuclear fusion that would be the source of useful energy for our daily
application. This is not straight forward and needs several engineering
research along with understanding the behavior of high temperature hydrogen
plasma in a container. This is one of the hot research topics of contemporary
physics and engineering at several leading centers around the world.
The difference between the two stories is
that, my story gives you ways to verify and leads discoveries that can directly
be used in our daily life. The other story does not have that scope, it can
only entertain some times and collapse when simple questions are asked. So, in
conclusion, I must say that be skeptical of everything, especially when people
with “uncommon robe” speak. It is better to live in doubt than living with ideas that are false. Great Indian Scriptures like Srimad Bhagabat Gita
promotes questioning and arguing. Sri Krishna says, you acquire knowledge by
questioning, “Pariprasanan Sevaya1”. He declares Himself as “Badaha
Prabadatam Aham2 – I am argument among discussion”.
1तद्विद्धि प्रनिपादेन परिप्रश्नेन सेवया । उपदेखयन्ति ते ज्ञानं ज्ञानिनः तत्व दर्शिनः ॥
Chapter 4, Verse 43
2अध्यात्म विद्या विद्यानाम , बादः प्रबदत।म अहम् ॥
Chapter 10 Verse 3
