Geometrical Physics in Minkowski Spacetime Book

An artist's sketch of a black hole's event horizon

Sometimes when we look at the evening sky, observe a shooting star far away or admire the beauty of moon, we are overpowered by this idea of our seemingly insignificant existence in the Universe. For if we compare our very own presence, that of our world or our country, even of our planet or our galaxy with the Universe, it is bewildering that we seem to occupy not even a speck of dust as compared to the vastness of the Universe. Many of us are then tempted to delve into the mysteries of this existence to make out some meaning, some significance. Whereas philosophy seems to correspond to our inner being in relation to world around, we need to turn to science in order to understand our relation with the Universe. The attempt thus taken, even though neither Science nor Philosophy seems to offer an absolute explanation, may bring about a more modest outlook towards our existence and empathy towards fellow beings.

But since most of the scientific theories and their explanation are available theoretically in a technical manner, not many of us make an attempt to understand them. In this work, Hawking not only suggests making scientific knowledge simpler enough for everyone so that more people can understand and benefit from it but also presents to us scientific theories in very simple way.

The work is a compilation of seven lectures delivered by Hawking in which he discusses various theories like Theory of relativity, Big Bang, Black Hole, Quantum theory, Quantum Gravity and String theory to finally propose a 'unified theory' which might one day be able to take every known theory into account and give us an explanation of the existence of Universe. Hawking is so lucid at explaining these theories and then presenting reasons as to why certain theories may not hold that even a naïve science reader like me can understand them. Moreover he is also quite witty at certain places, which makes the work an enjoyable read e.g.

"In other words, the singularities produced by gravitational collapse occur only in places like black holes, where they are decently hidden from outside view by an event horizon. Strictly, this is what is known as the weak cosmic censorship hypothesis: protect observers who remain outside the black hole from the consequences of the breakdown of predictability that occurs at the singularity. But it does nothing at all for the poor unfortunate astronaut who falls into the hole. Shouldn't God protect his modesty as well?"

"However, in the end most people, including John Taylor, have come to the conclusion that black holes must radiate like hot bodies if our other ideas about general relativity and quantum mechanics are correct. Thus even though we have not yet managed to find a primordial black hole, there is fairly general agreement that if we did, it would have to be emitting a lot of gamma and X rays. If we do find one, I will get the Nobel Prize."

Some concepts like Black hole radiation, arrows of time and quantum theory of gravity are very interesting. The idea of 'reverse arrow of time' made my head spin in a good way. Towards the end, when Hawking discusses the need of a unified theory and the question why such a theory may not be possible, he ends his lecture in the following manner:

However, if we do discover a complete theory, it should in time be understandable in broad principle by everyone, not just a few scientists. Then we shall all be able to take part in the discussion of why the universe exists. If we find the answer to that, it would be the ultimate triumph of human reason. For then we would know the mind of God.

I will recommend this book to all those who want a have an idea about the Universe in terms of theories developed so far.