Thursday, January 27, 2011
A Brief History Of Time - Stephen Hawking
Before anything is said about this book, I think one must salute the man, Stephen Hawking, for his brilliance, his sheer interest in work, in spite of his medical condition. If miracles are possible, may the first one revive him!
The first time I attempted to read the book was when I was 19 or so. I found it fascinating but put the book down after the 2nd chapter or 3rd, for some reason.
The second time I attempted it was when I was over 21 I think. By then I had completed 3 years of studying physics as part of my B.Sc. syllabus. I enjoyed the book. I savoured it actually, as I understood (from my own intimacy with physics) exactly what the author was saying. I remember I reached the chapter about particles and antiparticles and I was turned off as there was less and less of ‘relativity’ there onwards and more of ‘quantum mechanics’, a subject I did not like much. You know, it deals with the very small, ‘3 into ten to the power of minus 23’ and all. Both – negative numbers and very small magnitudes – don’t capture your imagination.
Last year, I finally decided I would read this book whole and soul.
I picked up the book with a lot of anticipation; but alas, I had lost touch with physics by then; how memory betrays you!
This time, I had to make an effort to put the concepts into perspective; something that had been so effortless, a few years ago.
The first few chapters are most interesting. Understandable and awe inspiring. But the last few chapters were difficult.
The theory of relativity - All observes should measure the same speed of light no matter how fast they are moving. This simple idea has remarkable consequences…
You can only be more and more thrilled as the one theory leads to another and puts an end to the concept of absolute space and then absolute time!
I began to struggle with the chapter Black Holes Ain’t So Black. In this chapter, Hawking somewhat contradicts the concepts he introduced in the previous chapter. In the chapter on Black holes, he says black holes have infinite gravity and infinite density and therefore nothing, not even light can escape black holes and therefore they are completely black. This made perfect sense. But in the next chapter, he says, black holes actually or apparently emit radiation! And this radiation is emitted not from the black hole itself but from the empty space or region outside the event horizon of a black hole. There are particle-antiparticle pairs one of them falling into the black hole and the other falling away from it. Sounds very hypothetical – one of those adjustments we make to reality in order to justify our own preconception –sounded like that.
And then, in order to avoid singularity at the beginning of the universe, time is measured using imaginary numbers – the stuff I studied in complex mathematics in college –‘ i’ (lower case of the 9th English alphabet) denotes the imaginary number which is the square root of minus one.
The wave particle theory was palatable. Particles can be considered as waves and waves as particles. But in the last few chapters, a string theory is introduced. All matter particles in their elementary form are strings; strings with open ends or closed ends. This again sounded improbable and fictitious. At least difficult to come to terms with.
I love the Theory Of Relativity. Deals with the very large – interplanetary distances, huge astral bodies, 100 times the size of sun, millions of years and all. Very fascinating!
But I don’t like Quantum Mechanics that much. It’s not fascinating, the effects aren’t observable & it’s not easy 2 imagine. It doesn’t capture your imagination.
As I read about the anthropic principle, I realized it was a concept I had conceived years ago without being able to put in clear words.
The anthropic principle can be paraphrased as ‘we see the universe the way it is because we exist’. This addresses speculation about why there is life only on earth? And such others that suggest mystery or divine intervention.
The anthropic principle, in other words states that in a universe that is large or infinite in space and/or in time, the conditions necessary for the development of intelligent life will be met only in certain regions that are limited in space and time.
The intelligent beings in these regions should therefore not be surprised if they observe that their locality in the universe satisfies the conditions that are necessary for their existence.
It was common for people, to exclaim (especially when space exploration confirmed that there was no life on Mars, nor on Venus, nor Jupiter) that in this whole universe, life existed only on Earth! that oxygen was found only here! that our planet was at the perfect distance from Sun – any closer would have been too hot for us, and any farther, too cold! And then the right atmospheric pressure, the ozone layer to protect and so on… just how perfectly God had created everything for us!
And once or more, during one those of moments of epiphany, I had understood that “We are only the consequence of many complex incidental/accidental processes and not the purpose of all those”
In other words, we should not be surprised that all the million pieces should have fallen in place just right in our planet because for one instance where everything fell into place, there are a million instances in this universe where things did not fall in place. So our existence in this universe is no matter of bewilderment. It had to be this way by probability or chance.
So when I read about anthropic principle, I beamed with pride, that a concept discovered and expounded by famous scientists should be conceived by me in my childhood, without any guidance from anyone ! : - )
I made note of a few important points as I read.
Guth has remarked, “It is said that there is no such thing as a free lunch. But the universe is the ultimate free lunch”
The eventual goal of science is to provide a single theory that describes the whole universe.
We hope to find a complete consistent unified theory that would include all these partial theories as approximations, and that did not need to be adjusted to fit the facts by picking the values of certain arbitrary numbers in the theory. The quest for such a theory is known as ‘the unification of physics’. Einstein spent most of his later years unsuccessfully searching for a unified theory but the time was not ripe.
A completes consistent theory that unifies general relativity and quantum mechanics (with its ‘Heisenberg uncertainty’ principle) is what we seek.
The forces that have to be unified are Gravitational force, electromagnetic force, weak nuclear force and strong nuclear force.
The main difficulty in finding a theory that unifies gravity with the other forces is that general relativity is a classical theory; that is, it does not incorporate the principle of quantum mechanics.
Einstein objected to the element of unpredictability or randomness that quantum mechanics introduced into science despite the important role he had played in the development of these ideas. He was awarded the Nobel prize for his contribution to quantum theory. But he never accepted that the universe was governed by chance; his feelings were summed up in his famous statement “God does not play dice”.
Classical general relativity by predicting points of infinite density, predicts its own downfall just as classical (non quantum) mechanics predicted its downfall by suggesting that atoms should collapse to infinite density.
Scientists have been too occupied with the development of new theories that describe WHAT the universe is to ask the question WHY. On the other hand, the people whose business it is to ask WHY, the philosophers, have not been able to keep up with the advance of scientific theories.
It is amusing…As you read about scientists and their experiments and their constants and the adjustments they make to their observations to make them suitable for theories, how subsequent discoveries disprove the established… and the absolutely hypothetical theories they conjure up when faced with obstacles…
When you read in detail, you know not to trust science too much but to watch dispassionately.
This book, needless to say, is a must read – for all those who are comfortable with the basics of physics.
I will have to read this again, but before that I will have to go find my college lecturers, get their notes, and go through them all over again. May be study some equations and even solve a few problems!