A Brief history of Time 10, 11, and conclusion

 

Chapter  11

The Unification of Physics

 Einstein refused to believe in the reality of quantum mechanics, despite the important role he had played in its development.

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 uncertainty principle of quantum mechanics.

 So this is the first step to be taken. 

This can produce some remarkable consequences, such as black holes not being black, and the universe not having any singularities but being completely self-contained and without boundary.

 The trouble is that the uncertainty principle means that even “empty” space is filled with pairs of virtual particles and antiparticles. These pairs would have infinite amount of energy and, therefore, by Einstein’s famous equation E= mc² they would have infinite amount of mass. Their gravitational attraction would thus curve up the universe to infinitely small size.

But can there really be a unified theory? Or are we perhaps chasing a mirage? There seem to be three possibilities:

1. There really is a complete unified theory and we will discover it one day.

2. There is no ultimate theory of the universe, just an infinite sequence of theories that describe the universe more and more accurately.

3. There is no theory of the universe: events cannot be predicted beyond certain extend but occur in a random and arbitrary manner.

The third choice leaves place for God.

·         With the advent of quantum mechanics, we have come to recognize that events cannot be predicted with complete accuracy but there is always a degree of uncertainty.

 

Chapter 12

Conclusion

In this book “I have given special prominence to the laws that govern gravity, because it is gravity that shapes the large-scale structure of the universe, even though it is the weakest of the four categories of forces.

According to the theory of relativity, there must have been a state of infinite density in the past, the big bang, which would have been an effective beginning of time.  Similarly if the whole universe recollapsed, there must be another state of infinite density in the future, the big crunch, which would be an end of time.

 Even if the whole universe did not recolapse, there would be singularities in any localized regions that collapsed to form black holes. These singularities would be the end of time for anyone who fell into the black hole. At the big bang and other singularities, all the laws would have broken down, so God would still have had complete freedom to choose what happened and how the universe began”.

When we combine quantum mechanics with general relativity, there seems to be a new possibility, that did not arise before: that space and time together might form a finite, four-dimensional space without singularities or boundaries, like the surface of the earth but with more dimensions. But this has profound implications for the role of God as Creator.

There may be one or a small number of complete unified theories such as the heterotic string theory, that are self-consistent and allow the existence of structures as complicated as human beings who can investigate the laws of the universe and ask about the nature of God.

·         Up to now, most scientists are too occupied with the development of new theories that describe what the universe is to ask the question why.

 

NEW DISCOVERIES AFTER THE LAST 1996 EDITION OF THE BOOK

1. In 1998 our picture of the universe was radically revised: the expansion of our universe is accelerating. This means the eventual recollapse of the universe no longer appears to be an option. Space it seems will expand forever.

2. We can now understand the origins of structure in our universe using measurements of cosmic microwave background radiation.

3. Eternal inflation and the no boundary proposal together predict that our universe is not unique. Instead, from the quantum fuzz at the big bang many different universes emerge, possibly with different local laws of physics and Chemistry.

4. Gravitational waves can be produced in the modern universe. Exactly a century after Einstein first predicted the existence of gravitational waves, a worldwide consortium of scientists known as the LIGO Scientific Collaboration announced in 2016 that these waves had been detected for the first time.

5. What falls into the black holes is not lost forever.