AS you are reading this review, an exact copy of yours could be going to war in a galaxy far away, and yet another copy doing household chores in another universe, and yet another having dinner in a restaurant hundreds of light years away. This idea is not of science fiction but an inference from the equations of theoretical physics. Physics has come a long way from Aristotle, Galileo, Newton and others, so much so that if these great minds from the past were to visit us today, they would be totally confounded by the latest work that is being carried out by theorists like Stephen Hawking, Roger Penrose and others.
The Grand Design, by Stephen Hawking and Leonard Mlodinow, is a book that tries to explain the latest in physics to the non-specialist with the help of lively prose and excellent illustrations.
But what do theoretical physicists do? In the past, scientists conducted experiments in the lab or in nature and formulated theories to explain the laws of nature so that predictions could be made. Today, theories are so complex and elaborate that a lone scientist cannot conduct experiments to test a theory. Collaboration of several colleagues and huge financial and infrastructural resources are required. Some of the theories are so abstract that by the time experimental confirmation is made, most theoreticians will not be around. This is well reflected in a cartoon by Sydney Harris in the book. A woman is introducing a theoretical physicist to another theoretical physicist by saying: "You both have something in common. Dr. Davis has discovered a particle which nobody has seen, and Prof. Higbe has discovered a galaxy which nobody has seen."
In the past three of 400 years older theories have been constantly replaced with newer ones, and at this rate we might wonder if scientists might reach a stage when someone might formulate a theory that explains everything, in other words a theory which cannot be improved upon. The authors suggest that M-theory is the only one that a final theory ought to have. The book is about this theory. But why do we need such a theory?
About a century ago, Maxwell and Einstein united the theories of electricity, magnetism and light, and following that a standard model was created in the 1970s in the form of a single theory of the strong and weak nuclear forces, and the electromagnetic force. In order to include gravity, string theory and M-theory were formulated. M-Theory is not yet complete, but it has passed several tests.
But why do we need theories? After Newton gave his famous laws of motion and gravity, scientists have wondered how do laws originate, are there any exceptions to the laws, and if there is only one set of laws. Hawking and Mlodinow show us that laws are formulated by observing regularities in nature, and they are mathematically described. Secondly, there can be no exception to the laws, i.e., there is no room for miracles. This is called scientific determinism.
If the world is determined by the laws of science, you might ask if we have a free will. According to the authors, we are made of so many particles and processes and there are so many variables, that to make any prediction about human behaviour is impossible. As Richard Dawkins, the famous theorist and writer of The Selfish Gene has argued that the brain process is so complicated that it is better to assume we have a free will.
Furthermore, is there only one set of possible laws? In the chapter Alternative Histories, the authors show us how particles of matter fired at a screen with two slits in it could exhibit interference patterns just as water waves do. This happens because a particle does not have a unique history. In other words, as a particle moves from point ‘A’ to ‘B’, it does not take one definite path as our everyday experience would expect, but rather simultaneously takes every possible path connecting the two points. In such a scenario a particle could travel through both slits at the same time and interfere with itself. This was first showed by Richard Feynman who suggested that to calculate the probability of any particular endpoint, we need to consider all the possible histories that the particle might follow from its starting point to that endpoint. The authors say that we could also use Feynman’s methods to calculate the quantum probabilities for observations of the universe.
"In this view, the universe appeared spontaneously, starting off in every possible way. Most of these correspond to other universes. While some of these correspond to other universes. While some of those universes are similar to ours, most are very different. They aren’t just different in details, such as whether Elvis really did die young or whether turnips are desert food, but rather they differ even in their apparent laws of nature."
The usual assumption in cosmology is that the universe has a single definite history. Hawking and Mlodinow hold that we could use the laws of physics to calculate how this history develops with time. This is known as the "bottom-up" approach to cosmology. But since we must take into account the quantum nature of the universe, the probability amplitude that the universe is now in a particular state is arrived at by adding up the contributions from all the histories. Instead of the bottom-up approach, one should trace the histories from the top down, backwards from the present time.
As for the books title The Grand Design, it is argued that just as Darwin and Wallace explained how living forms could evolve through natural selection without the help of God, "the multiverse concept can explain the fine-tuning of physical law without the need for a benevolent creator who made the universe for our benefit".
Hawking and Mlodinow are great physicists, but they seem to have a very poor grasp of philosophy when they say that philosophy is dead as it has not kept up with modern developments in science, particularly physics. It is true that most philosophers have knowledge of physics that is over a century old, but that does not apply to all philosophers. When scientists say science ought to be done with a certain methodology, and when they talk about space, time, etc., they are giving us a framework of the scientific method, and they are formulating concepts. If this is not philosophy, then what is? It is a different matter that such a framework might be formulated by scientists themselves. But when they do so, they are doing philosophy, however, what they do with this framework and methodology is science. The antipathy towards philosophy is, perhaps, a hangover of the idea of elimination of metaphysics as suggested by some thinkers at the beginning of the 20th century. Philosophy is more than metaphysics; it includes ontology, epistemology, ethics, arts, religion, politics and logic. Without logic, science would be dead. When you say a thing "ought" to be done in a certain way, you are giving a philosophy; when you talk about space, time, matter, etc., you are formulating concepts, this is philosophy, and it is at the bottom of any discipline of knowledge.
Back to the question of
free will, we might recall that when Hawking was working on his PhD
thesis in the early 1960s, he was diagnosed with ALS, and he was told
that he would not survive for too long. Nearly 46 years have gone by,
Hawking is not only alive but is grappling with some of the most
stubborn problems of theoretical physics. One wonders if this is because
of his strong will, or it is the result of the position and spin of the
trillions and trillions of atoms that are tossing around in his body.