Life - Is Physics Real?

Life in the Universe

Debi Prasad Choudhary

Los Angeles

11/5/2014

I think I am the most important person in the universe. While walking to my car, if a speck of dust falls in my eye, removing them is the most important task at that time for me. Yet, I know that every thing will go on as usual, when I am gone. I do not know this directly, but deduce from the fact that although some of my colleagues are no more with us, the world is going on in the same way, the trees are there, most of the building are standing as before. So the biggest quarry for me is: how was my grandfather like, whom I have never seen, and his grandfather, and the first human, and before that the first living entity.  When did it happen? How we came to the present state? These are big questions that were asked by all civilizations by thinking persons and tried to give an answer to best of their knowledge. There is no need for mocking the ancient answers that might sound primitive in present standards.

Life consists of complex molecules of hydrogen, carbon and oxygen. The life begins when a combination of ordinary molecules have strong urge to survive and start reproducing. Although, we do not know at what stage and how this transition takes place, it may be logical to think that life can start if sufficient complex molecules are available. In 1952, Harold Urey and Stanley Miller of University of California, San Diego conducted an experiment to show that complex molecules like amino acids can be produced by mixing carbon dioxide (CO₂), nitrogen (N₂), hydrogen sulfide (H₂S), and sulfur dioxide (SO₂) for a long time near electrical spark, similar to lightening. Amino acids being the predominant life ingredient, Urey-Miller experiment could be the process of early life formation at the early stages of earth, where such extreme conditions prevailed. However, the yield of amino acid by this process being slow, it would take a very long time to make sufficient molecules for life.

The life ingredients are made in such harsh conditions but to sustain them, an ultraviolet free friendly environment is necessary, which existed on earth only after about 1.7 billion year of its formation. Fossil records show that advanced form of life was already present on earth about 3.55 billion years ago. Since, there is a short window in which life must exist on earth after its formation, it is likely that they originated inside the comets and transported on earth while colliding. Inside the comets also conditions that create life molecules in Urey-Miller experiment can exist. Since there are 100 billion comets existing for millions of years in our solar system, even the poor yield of Urey-Miller experiment can produce enough molecule for life on earth.

If comets are the sites for seeds of life, there could be billions of them circling other earths around other stars, where life might originate and flourish. There are about 2000 confirmed exoplanets until today and the number is growing. Are there lives in any of them? Are they intelligent enough or more intelligent than us? Are they trying to contact us? These are modern question many of us are interested.

This reminds me of a conversation with my graduate school buddy, who died early after discovering the OJ287 (an active galaxy) changed its light output in about an hours, that was published in the prestigious journal Nature. We were considering, what will we gain after countering extraterrestrial intelligence? Our conclusion was that we can verify if Physics is real, the truth. He was of opinion that our physics is based on our observations and perceptions. It is a working model, a very good and powerful one that predicts phenomena, which can be verified in the laboratory. It is both valuable and useful. But, there is no way to find out if this is ultimate truth. When we meet Extraterrestrial Intelligent being, we shall ask if they have theories like Quantum Physics, General Theory of Relativity, do they know the fundamental constants of nature such as velocity of light and Plancks Constant, do they know that galaxies recede from each other? These are the profound things we know. If they also know these things, than our knowledge is verified. They are ultimate truth. My friend died in 1986. The question still remains unanswered.

The Grand Creation - Universe

The Universe

Debi Prasad Choudhary

Los Angeles

11/4/2014

The priest in our village used claim that the temple in which he worshiped the Goddess for all of us is the center of the universe. When, I started thinking on my own, I started doubting, since in our neighboring village also there was a temple with Goddess, which was better built!! After taking a modern cosmology course, I realized how correct he was, since every point in the universe can claim to be the center.

The story of the universe starts with a simple, innocent looking question: Why the night sky is dark? The answer is because the universe was created at some point of time in the past and expanding ever since. I know the language of the previous sentence is loaded with words like “created”, “point of time”, but let us keep it that way for the time being. If the universe existed forever, extend to infinity and not expanding the entire sky would be glowing due to dense stars and galaxies heating up the interstellar matter over past infinity time. We can think it of as looking the continuous trees of a thick forest. Since the universe was created and expanding, lot of light has not reached us yet. As the universe expands, the light waves are stretched such that the luminosity due to them is diminished.

There are four robust observational results that clearly show that the universe began with an extreme hot state and expanding for past 13.6 billion years.  In 1920s, Edwin Hubble measured the speed of far away galaxies and found that they move away from us. The distant galaxies move faster than the nearer ones. This is a direct consequence of the expanding universe, which was predicted by intellectual ingenuity of Albert Einstein, who considered the mass of matter and energy that moves them are manifestation of the same stuff.

In 1976, Penzias and Wilson from Bell laboratories discovered that all the empty space in the sky is uniformly cooled to about -455 F (or 2.3 K). The expanding universe means in the distant past it was compact, dense and hot. The relative amount of light elements such as hydrogen, Helium and Lithium suggest such as condition of the life of the universe. Most type of hydrogen with and without a neutron, helium with 3 and 4 neutrons and lithium with seven neutrons in their nucleus were produced when the universe was very hot and dense, in first few minutes after its existence.

Se we know that the universe came to exist as an compact, dense and hot object about 13.6 billion years back, where the space was created and time started. Intense fire produced matter and suddenly extinguished as the light clumped and converted into matter. The clouds of matter collapsed become stars and galaxies and illuminated the universe again.  We can actually trace the distribution of galaxies into groups and mega groups that correspond to the lumpiness of radiation in early stage of the universe.

This is the story of the universe told by the modern scientists who has access to large telescopes, sophisticate instruments and powerful computers. They think, measure, verify and conclude. The questions are the same, so ancient wise man without such privilege of modern professors and scientists tried to answer that “God said let there be light”¹, and others mysticism² of this sacred knowledge.

¹"In the beginning God created the heavens and the earth" And God said, “Let there be light,” and there was light. (Genesis 1 and 3:1).

²“No body can know how the creation came to exist, and if he has or has not produced this." (Rig Veda 10. 129)

Galaxies – Thousand times brighter than Milky Way

Galaxies – Thousand times brighter than Milky Way

Debi Prasad Choudhary

Los Angeles

11/3/2014

Throughout my college and school career, I used to perform a ritual on the night before the examination to please Ganesha by reciting a prayer that described him as radiating light equivalent to billions of sun and place the pen, pencil and eraser below his picture that would be used next day!! My son also continued for some time. It was just a praise to the God to do well in examination, never realized that such objects can exist, although far far away from us.

Our Milky way galaxy is as bright as about 20 billion suns. We live in a normal galaxy, the type of which may some time be 10 times brighter. There are active galaxies many of them are 5000 times brighter called active galaxies.  Our Milky way galaxy is illuminated by the stars that produce energy by nuclear fusion similar to our sun. What makes the active galaxies so bright? How do they produce light?

The brightness of these objects change rapidly in about one hour. The polarization state of the light change in similar time scale indicating that the source of light must be a tiny region, since the light would take several thousand years to reach from one end to the other. We estimate that about 100 suns must be destroyed every year and converted into energy to keep it bright. It has to be done in a very small space. This is possible only if matter continuously flow into super massive black holes of one billion times as massive as the sun. The matter is directly burned and produces gravitational energy, no nuclear fusion.

The violent motion of matter near the center of the galaxy, ejection of high-energy particles from the energy source regions in the form of large massive jets that extend several light year and visible in radio wavelengths seems to be consistent with the energy production mechanism from huge black holes.

These objects are very far away, so we actually probe the universe, what it was many years back. The universe was a violent place in the past. What is store in future? Our fate, our destiny – the common destiny is intertwined with the universe we live in.

We know so much about various objects of the universe, in such great details that was never possible in human history. Let no body claim this knowledge as their heritage. We are now able to ask the very big question of all “How did all this happen?”

Man Finds Galaxies

Man Finds Galaxies

Debi Prasad Choudhary

11/2/2014

In pursuit of knowledge, I reached a stage where none of my childhood experience related. The creation is vast beyond what we can see with our naked eye and comprehend with a single mind. The only thing relevant from my early learning that made sense is that my father’s teaching, “the creation is beyond our imagination, it contains smaller than the smallest and bigger than the biggest”, adopted from Hindu scripture Bhagabat Gita.

In first two decades of twentieth century, long exposure photographs of the sky with larger telescopes showed nebulous, fuzzy objects apart from stars. Some of them were spiral, some elliptical and some irregular shape. When such images of galaxies were put together, it seemed that there is a systematic transition from one shape to the other. The classification could be made from galaxies with tighter spiral arms, more dust and gas to the ones that had loose elliptical shape with less dust and gas. Most galaxies are found in groups bound by gravitational attraction. The spiral galaxies are loosely bound with members of few dozens. The elliptical galaxy groups contain hundreds and thousands of galaxies making huge groups. As the galaxies move around they collide and the interaction distorts their shape.

In the beginning, it was not clear if these nebulous objects resided inside the Milky Way or out side.  There was a great debate on April 26, 1920 between two famous astronomers Shapley and Curtis, who took opposite side and declared victory!! The key to answer this question is to measure distance to these objects. Several methods have been devised to determine the distance to the galaxies; they are based on the fact that when a candle is located at twice the distance it appears four times fainter. It is called “inverse square law”. There are many objects in the sky for which we know their brightness precisely. For example, the stars that are illuminated due to nuclear fusion at their center (called main-sequence stars), the supernova of white dwarf stars and Cepheid variable stars. Two astronomers, Tully and Fisher found that the brighter galaxies rotate faster. So, if we can identify a star of a particular type in a galaxy or determine the rotation speed of a galaxy, we can measure its brightness. The distances to these galaxies are measured by comparing its measured brightness with the expected brightness.

The distances to the galaxies are so large that light takes several million, in many case billions of years to reach us. There is no way to know what is happening to these galaxies now. Further away the galaxy is, we see what it was in the deep past. So, actually we see the history of the universe by studying the galaxies of the past. We now know that the spiral galaxies are made only in past 5 billion years, before which there were mostly irregular shaped galaxies. In the past, galaxies were colliding and merging into each other frequently, and producing much more stars in bursts.

Measuring the distance to the galaxies and the speed at which they move relative to us, Edwin Hubble made a fantastic discovery in 1929. He found that all the galaxies, except four are moving away from us. The galaxies that are located at greater distance move faster away from us. The four galaxies that are coming towards us are in a local group that moves randomly.  He measured the recession velocity of the galaxies by determining the difference of wavelength of spectral lines emitted by an atom in the galaxy and a similar atom on earth. This is known as Hubble’s law that describes the expansion of the universe. The universe, in which we are living, is expanding, all galaxies are moving away from each other!!!!

This is fantastic. Because, this means there was beginning when all were together. When was that? How close were they? How did it happen and why? These are profound questions. All that we know now is that all these happened at least about 13.6 billion years ago if the universe is always expanding at the present rate. 

The Home Galaxy

The Home Galaxy

Debi Prasad Choudhary

Los Angeles, 11/2/2014

The river Ganges that flows from Himalayas to Bay of Bengal, actually originate in heaven. After washing the feet of the God, she descends on earth, using the head of another powerful god Siva as launching pad. The band of light that is spectacularly visible in rural sky is the heavenly portion of this sacred river called “Akas Ganga” “Ganges in the sky”. Without asking too many questions as to how is it sustained or will it fall down etc., I looked at this band of light in my childhood with great curiosity. Much civilization from ancient time looked at this band of light with utter amazement and constructed stories extending their local culture. The Greeks called it “milky circle” and Romans “milky road” or “milky way”.  It is interesting to note that in India, the heavenly portion of the imaginary river contained milk!!

From a rural dark sky the Milky Way looks like a long stretch of light with a dark band in the middle. It was disappointing to see through a small telescope that this part of the sky is just crowded with stars, which shattered my imagination of heavenly river. Later in my astronomy class I learnt that the Milky Way is one of the arm of our galaxy, which has a spiral shape. The dark lane in the middle is due to the presence of huge dark clouds with dust that obscures the view.

In early 19^th century, Sir William Herschel and his sister counted stars in 683 directions to figure out the structure of this object, but only after about one hundred years, Dutch astronomer Jacobus Kapteyn could determine its size and thickness. In early 20^th century, Harlow Shapley using the telescope in Mt. Wilson observatory in Los Angeles worked for his PhD thesis to figure out the size of the galaxy and locate its center. He used the star clusters in our galaxy to locate the center. There are two types of star clusters in our galaxy. In one of them stars are loosely scattered, called open clusters, which are mostly found along the Milky Way. The others are more compact, looks like “meat ball” in the galaxy, located mostly in the direction of Sagittarius constellation. The open clusters contain younger stars and some gas, while globular clusters are old and devoid of gas. The globular clusters are as old as the galaxy, some of which are also located above and below the galactic plane.

The distance to the globular clusters are measured by using variable stars, which become dim periodically depending on their original brightness. These are Cepheid variable stars, which expand and contract due to build up of heat by electrons from ionized helium. The heating results the outer envelop of the star expands leading to cooling and contraction. As the star expands the bigger star becomes more bright compared to the smaller star. The period of maximum to minimum brightness depend precisely on the original or initial brightness of the star. So, by detecting the variable period, which is easier, it is possible to measure the absolute brightness accurately. By comparing the absolute or real brightness and apparent brightness, the distance to the star is determined. This is so because the star becomes dimmer by the square of the distance. If a candle is placed at twice the distance, it looks dimmer by four times. This technique of determining the distance was found to be correct when it was applied to the stars located at known nearby distance that could be measured by simple parallax method.

Now, we know the size and structure of this galaxy in which we reside. The Milkyway Galaxy is  a “dinner plate” like flat disk with a central budge and a halo that surrounds the structure. The disk is so big that the light takes 80,000 years to travel from one side to the other. The sun, and the planets around it, is located at about two third of the radius of the galaxy from its enter and revolves around it once in about 250 million years. The galaxy does not rotate like a single rigid body. The stars at different distance from the center go around with different speeds, such that the stars nearer move faster than the ones situated at greater distance. While going around the center of the galaxy, the sun also swings up and down of the plane of the disk with a period of about 60 million years. As the sun passes the disk, the reservoir of ice cloud (a comet cloud known as Oort’s cloud) gets disturbed. This results a shower comets on earth leading to massive loss of life called “mass extinction”. The dinosaurs are believed to have extinct due to such an event about 65 million years ago!

The stars are continuously formed from huge clouds of dust and gas, which are constantly disturbed by the pattern of rotation. The stars evolve and die and produce new material. New stars are born from ashes of old stars. This is going on for past 10 to 13 billion years and perhaps will go on forever, until the existence of the universe.

The motion of stars around the center of our galaxy gives vital information about the distribution of matter. As the gravitational force governs the motion of stars around the galaxy, they should follow the pattern similar as the planets move around the sun. This pattern of motion is called Keplerian motion that follows the Kepler’s Laws. The measurements show that the stars very close to the center move as if they are attached rigidly and the ones far away move faster. This type of motion is possible only if the center harbors a very massive object and the galaxy is surrounded by enormous amount of matter. But, neither in the center nor around the galaxy such matter is observed. We do not see the matter in the galactic center, because it is confined in a very small space resulting a super massive black hole. The invisibility of the matter around the galaxy is even a bigger puzzle. Astronomers think that this invisible matter is indeed dark matter, which interact with visible matter through gravitational force. Almost 85% of the matter in our galaxy is dark matter, the properties of which are unknown at this time.

How exactly our galaxy formed? Did the stars got together to form the galaxy or they were born in the galaxy? What will happen in the end? These and may other similar questions students of astrophysics constantly ask. They make ever-bigger telescopes in space and on the ground to search the clues and test their ideas. One thing is clear. Most of these questions can be answered using modern physics. All our knowledge about our home galaxy is gathered only in past 50 to 60 years. If we do not know some thing today, we will know them soon.