How does the universe behave?
What is the nature of reality?
Where did all this come from?
Did the universe need a creator?
This book aims to give the answers that are suggested by recent discoveries and theoretical advances.
According to the traditional conception of the universe, objects move on well-defined paths and have definite histories.
We can specify their precise position at each moment in time.
Although that account is successful enough for everyday purposes, it was found in the 1920s that this “classical” picture could not account for the seemingly bizarre behavior observed on the atomic and subatomic scales of existence.
Instead it was necessary to adopt a different framework, called quantum physics.
Quantum theories have been remarkably accurate at predicting events on those scales, while also reproducing the predictions of the old classical theories when applied to the macroscopic world of daily life. But quantum and classical physics are based on very different conceptions of physical reality.
Quantum theories can be formulated in many different ways, but what is probably the most intuitive description was given by Richard Feynman, a colorful character who worked at the California Institute of Technology and played the bongo drums at a strip joint down the road.
According to him, a system has not just one history but every possible history. As we seek our answers, we will explain Feynman’s approach in detail, and employ it to explore the idea that the universe itself has no single history, nor even an independent existence. That seems like a radical idea, even to many physicists.
Like many notions in today’s science, it appears to violate common sense. But common sense is based upon everyday experience, not upon the universe as it is revealed through the marvels of technologies such as those that allow us to gaze deep into the atom or back to the early universe.
Until the advent of modern physics it was generally thought that all knowledge of the world could be obtained through direct observation, that things are what they seem, as perceived through our senses. But the spectacular success of modern physics, which is based upon concepts such as Feynman’s that clash with everyday experience, has shown that that is not the case.
The naive view of reality therefore is not compatible with modern physics.
To deal with such paradoxes we shall adopt an approach that we call model-dependent realism. It is based on the idea that our brains interpret the input from our sensory organs by making a model of the world.
When such a model is successful at explaining events, we tend to attribute to it, and to the elements and concepts that constitute it, the quality of reality or absolute truth. But there may be different ways in which one could model the same physical situation, with each employing different fundamental elements and concepts.
If 2 such physical theories or models accurately predict the same events, one cannot be said to be more real than the other; rather, we are free to use whichever model is most convenient.