ANOTHER ARTICLE ON COSMOLOGY : --- Dr. Bibhash Chakravorty.
Preface : I wrote this article as a letter about 20 years ago addressed to the editor of The Statesman newspaper. However the letter was not published and it remained as a sheaf of notes ever since until I edited the contents of the article in 2013 March as many newer concepts, discoveries, breakthroughs and inventions had been made in the field of astrophysics and cosmology over a period of 16 years prior to 2013. I have decided to present this article as a letter as was written before and hope that my friends and readers enjoy going through it !
To,
The Editor.
The Statesman.
Dear Sir,
Being a regular reader of The Statesman and having an intense interest in cosmology I find many curious topics in your esteemed newspaper.
A few days ago the article, " Is the universe really flat "?, and the following letter by Mr. Ranen Roy made interesting reading. However I was intrigued by the fact that the discovery of this flatness was projected as a very recent breakthrough in science ! Infact it is not.
It was as early as 1980 that Allan Guth, then a young researcher at Cornell university, USA, came up with the idea of cosmic inflation !
In very simple terms this means a superfast ( many times the speed of light ) expansion of the space time continuum or fabric ( non tangible and hence it's superfast speed is not in contradiction with Einstein's speed limit of light ) of the universe in the first split second of the BIG BANG !!!
This inflationary model has been extensively developed since Guth made his proposal in 1980 and this accounts for the uniformity ( isotropic and homogenous ) and flatness of the universe we see today !
The flatness actually refers to the curvature of space and not exactly to a two dimensional flatness like the surface of this cell phone.
We owe our recent understanding of the origin, evolution and fate of the universe to cosmologists like Stephen Hawking, Leonard Suskind along with mathematicians like Roger Penrose.
Notwithstanding the above fact it was Albert Einstein, Max Planck, Heisenberg, Neils Bohr and many other past stalwarts of science who made it possible for Hawking, Penrose and Suskind etc to derive at their present day theories after a lifetime of pure research.
If a single handed contribution has to be mentioned it is obviously Einstein's. Einstein's theory of relativity, quantum electrodynamics and quantum gravity and particle physics have led to the present day theories although many domains remain unexplored !
It would also be a shame if the names of scientists like Satyendra Nath Bose ( FRS, Bengali theoretical quantum physicist, Bose Einstein condensate and elementary particle Boson named after him by Paul Dirac ), Abdus Salam, Jayant V. Narlikar, Fred Hoyle, Arthur Eddington, George Gamow, Steven Weinberg, Subramanyam Chandrasekhar and Edwin Hubble etc are not uttered in the same breath along with Hawking, Guth, Penrose and Suskind. Infact it is not possible to pinpoint a single scientist perhaps apart from Einstein, Max Planck ( father of the quantum theory ) and Edwin Hubble who have revolutionised our perceptions on cosmology and astrophysics !
Hawking's and Penrose's works have shown that black holes ( A region of space time continuum containing superdense matter and completely cut off from the outside due to it's supergravity not letting even light to escape from it ) can under special circumstances interact with external objects and can explode ! ------- White holes !
BLACK HOLES are precursors to space time singularity a point with infinite density and zero volume, a concept that astrophysicists and cosmologists try to avoid as all laws of physics break down at this point !
Roger Penrose's work on singularity and black holes inspired Hawking to apply that idea to the whole universe using quantum mechanics, quantum gravity and relativity.
Until now, many evidences like cosmic background microwave radiation, expansion of the universe etc; overwhelmingly support the theory of a ' BIG BANG ', model of the origin of the universe where the universe was supposedly created due to the explosion or expansion of a super massive black hole !
In this respect we are living in a black hole universe which seems to be delicately balanced on the dividing line between closed and open so that it is expanding !
Hubble's observation and red shift of the light from distant galaxies show that they are receding from each other. ( Please see my previous post, " An article on cosmology ")
The velocity with which they are receding is directly proportional to the distance between them. Therefore it can be assumed, given a sufficient distance the velocity of recession ultimately reaches the speed of light and might go beyond it ! Is this possible ? The answer is no because in this times of so called slow inflation the Hubble's red shift ( Doppler effect of light which is proportional to the distance between galaxies ) and recession velocity of galaxies has a non-linear relationship. This means at red shift 2 a galaxy may be moving at 50% the speed of light but at red shift 4 the recession velocity will not be 100% the speed of light but about 92% and it would require a red shift of infinity for the recession velocity to become 100% the speed of light which is therefore impossible !
However in the first split second of the big bang the space time fabric moved at many times the speed of light.( Inflation or superfast expansion ) This was possible because unfathomable amounts of radiation and energy was released at that time due to a process called phase transition ( Like latent heat released when water becomes steam ) and also because nothing was moving through space but it was the fabric of space time itself which was expanding and creating space at the same time !
The Hubble's non-linearity law now puts a restriction to the velocity of the space time continuum as extra energy is not available to speed up the expansion. All these processes can be deduced from Einstein's general theory of relativity.
The expansion of the universe and separation of the intergalactic distances can be very well understood by the analogy of a inflating balloon with polka dots printed on its surface. As you inflate the balloon ( Compared to the expansion of the universe ) the polka dots ( Compared to the galaxies ) move further away from each other. However the polka dots are not moving through the fabric of the balloon, rather it is the fabric of the balloon which is expanding carrying the polka dots with it. I hope this analogy will suffice it to explain what we are trying to say here.
Calculations have shown the age of our universe to be between 15 to 20 billion years and Hubble's law ( constant ) proves that at almost the edge of our universe ( 15 to 20 billion light years away from us ) the galaxies and other objects like quasars ( Stellar material from a whole galaxy accreting and falling in a supermassive black hole producing unthinkable amount of energy ! ) or supernovas ( stellar explosion ) are stretching at almost the speed of light.( but slightly slower )
You are also looking at these celestial objects as they were 15 to 20 billion years ago because light, radio waves and other kind of radiation from these objects took 15 to 20 billion years to reach our eyes !
It is as if you are seeing them very close to the BIG BANG !
These observations have been possible due to the Hubble space telescope and other satellite borne telescopes receiving different types of electromagnetic radiations from these distant objects.
Do these facts set a limit to our universe since the edge of the universe is being defined ?
Could the quasars ( quasi stellar objects ) be sentinels to another universe with a different reference frame ?
Actually there are too many questions than answers and the story of cosmology is the biggest story that there is to know because our very own existence depends on it !
However it is a different story altogether dealt with by, Anthropic Cosmology ! ( Please see my previous post on the Anthropic Principle )
The recent research on dark energy ( anti-gravity Lambda field ) and the ubiquitous dark matter would certainly reveal a lot about the fate of the universe we live in.
If the universe is still flat ( even though recent researches show that distant galaxies have accelerated recession speed ------ due to dark energy constant ? ) the density of our universe should be very close to the critical density ( density above which the universe will ultimately contract ) and the expansion of the space time continuum should balance at the knife edge between an open and closed system and will someday halt the expansion and the universe will neither RIP nor CRUNCH ! The other possibilities are, THE BIG RIP and THE BIG CRUNCH depending on the cosmic mass density. It may also be an oscillating universe like the rhythmic harmony of an accordion played by a musician !
Those who question the utility of spending vast amount of money for cosmological research, may I humbly remind them that most of the recent investigative and therapeutic techniques in medical sciences are spin-offs from space research ! ( Not to mention industrial gadgets and technologies )
Someone once said, " Of what use is a newborn child to the society " ?
The answer is, Child is the father of Man !
NOTES and EXPLANATIONS :
CRITICAL DENSITY; The minimum present cosmic mass density above which the expansion of the universe is eventually to cease and be succeded by a contraction ---- BIG CRUNCH!
The universe is spatially finite if the cosmic density is either above or equal to the CRITICAL DENSITY.
For a cosmic density below the critical density the universe is open or; it will continue to expand forever------ BIG RIP !
In other words the space time curvature at the edge of our universe will be like a saddle !
This space time curvature for a closed universe ( cosmic density above the critical density ) will fall back on itself like the surface of a sphere or, finite but unbounded.
For a flat universe ( cosmic density equals critical density ) the expansion will eventually stop and it will neither expand nor contract !
The critical density is about 3 to 5 hydrogen atoms per cubic meters of space !
ULTIMATE FREE LUNCH :
This is a term coined by Allan Guth in order to explain the origin of our universe in a lighter mood !
It is said that quantum fluctuations causing massive energy density may occur in vacuum ( energy of the vacuum ) almost out of nothing which may give origin to the total mass and energy of our universe !
It is also known that a black hole ( precursors of space time singularity ) may interact with it's surroundings or external objects to create virtual particles which give origin to a radiation known as Hawking radiation the intensity of which depends on the total mass of the black hole. In the primordial quantum universe the radiation of gravitation was so high that it could create particles anti-particles pairs which on collision would produce unfathomable amounts of blast energy. You always need money to have food or lunch but in this case the universe may originate out of nothing -------- hence the term, Ultimate Free Lunch !
HUBBLE'S CONSTANT : ( Original )
Recession velocity of galaxies: 15.3 km/sec/million light years. ( megaparsec )
HUBBLE'S RED SHIFT :
Stretchening of the frequency of light waves towards the red end of the spectrum as an object moves away from you ----- the Doppler effect of light which happens for most of the distant galaxies. Please go through my previous article on cosmology.
The opposite ---- Blue shift, occurs when a light from an object moves towards you as is the case with our local group of galaxies including Andromeda galaxy. Our Milky Way home galaxy and the Andromeda galaxy are on a head on collision course which will occur after 2 million years!
POINTS TO PONDER :
If gravity is the effect of space time distortion produced by a mass and if mass is imparted to an elementary particle by the Higgs field with the field quanta Higgs Boson particle ( so called GOD particle ), shouldn't there be a close relationship between a graviton and the Higgs Boson particle ?
I don't want to get technical but the answer is NO !
An amusing fact :
Peter Higgs got very angry to the Higgs Boson particle being coined by the papparatzi ( press media ) as , " The GOD Particle ". He exclaimed, " Inappropriate Sensationalism "! Ho, ho, ha !!!
Is the Cosmological Constant of Einstein back with a big bang ?
The Cosmological constant was first used by Einstein in his equations of general theory of relativity and later rejected by he himself 10 years later when Edwin Hubble proved that the universe is expanding, a fact which can be deduced from Einstein's equations itself. Is this constant back with a big bang, the constant being small and now referred to as the anti-gravity Lambda field produced by dark energy ?
If the universe is really open ( cosmic density less than critical density ) then a time may come when not even the galaxies and our solar system as many others but even the atoms and molecules and the fundamental elementary particles themselves would be ripped apart from each other and vanish into the oblivion -------- a very grim state of affairs, isn't it ?
And all this due to the Lambda anti-gravity force taking the upper hand over gravity and remaining as the most undisputed and most powerful force of this doomed universe !!!
There is a definite logic behind this BIG RIP ! When the universe was small and primordial and even when it was say half the size of the present universe, the Lambda constant was small with the gravity taking the upper hand. And now since the universe has expanded the gravity has become weaker while the Lambda anti-gravity force is still that constant, however small it may be and now perhaps taking the upper hand over gravity !!!
Questions often asked :
What is the universe expanding into ? OR Where did the BIG BANG bang into ? What was outside the space time singularity from where the Big Bang originated ? What was there before the Big Bang ?
The universe is expanding into nothing at all. Space is being created by stretching of the space time continuum itself the force causing the expansion having originated from the BIG BANG ! The BIG BANG was not like a bomb which exploded into space.
For the sake of argument, if you were placed outside the primordial BIG BANG you will see nothing until the big bang engulfs you. Actually there was no space outside the singularity as far as we are concerned. So the question itself was wrong-------- it is like what is the colour of number 9 ?
Time itself was created at the BIG BANG, so how can you tell what was there before it ?
I would like to conclude the article by writing a poem on creation written in the RIK VEDAS !
ORIGINAL CREATION : ( MANU, BY SACRIFICE )
Non being then existed not nor being !
There was no air nor heaven which is beyond it !
What motion was there ? Where ? By whom directed ?
Was water there and fathomless abysses ?
Death then existed not nor life immortal !
Of neither night nor day was any semblance !
The One breathed calm and windless by self impulse !
There was not any other being beyond it !
Darkness at first was covered up with darkness !
This universe was indistinct and fluid !
The empty space that by the void was hidden !
That one by the force of heat was engendered !
DESIRE then at the first arouse within it !
DESIRE which was the earliest seed of spirit !
The fond of being in non-being sages !
Discovered searching in their hearts with wisdom !
Whence was it born ? Who knows it truly ? Who can here declare it ?
Whence issued this creation ?
And did the Gods appear with the production ?
But then who knows from whence it has arisen ?
This world creation, whence it has arisen or whether it has been produced or has not ?
HE who surveys it in the highest heavens ------ HE only knows or even HE does not know it !!!
Acknowledgement : While writing this article I have consulted many books and references on astrophysics and cosmology amongst which the British popular science writer John Gribbin's and American astrophysicist and nobel laureate Steven Weinberg's names warrant special mention.
In the light of logic the big bang must have occurred I the primal interdimensional void between the spaces because nothing can only exist in the human brain when it's thinking of nothing worthwhile. A massive quantum energy density burst after trillions of years after a Big Rip may produce another big bang universe in the desolate space, the time taken is to satisfy the law of averages just as infinite multiverses may have to be created to produce only a handful of fruitful universes where intelligent life might evolve after billions of years.
This idea is also supported by Indian cosmologists and Hindu mythology too ! ---- Dr. Bibhash Chakravorty.