Summary | Excerpt | Reviews | Readalikes | Genres & Themes | Author Bio
CHAPTER 2
THE SHAPE OF TIME
EINSTEIN'S GENERAL RELATIVITY GIVES TIME A SHAPE.
HOW THIS CAN BE RECONCILED WITH QUANTUM THEORY.
What is time? Is it an ever-rolling stream that bears all our dreams away, as
the old hymn says? Or is it a railroad track? Maybe it has loops and branches,
so you can keep going forward and yet return to an earlier station on the line.
The nineteenth-century author Charles Lamb wrote: "Nothing puzzles me like
time and space. And yet nothing troubles me less than time and space, because I
never think of them." Most of us don't worry about time and space most of
the time, whatever that may be; but we all do wonder sometimes what time is, how
it began, and where it is leading us.
Any sound scientific theory, whether of time or of any other concept, should in
my opinion be based on the most workable philosophy of science: the positivist
approach put forward by Karl Popper and others. According to this way of
thinking, a scientific theory is a mathematical model that describes and
codifies the observations we make. A good theory will describe a large range of
phenomena on the basis of a few simple postulates and will make definite
predictions that can be tested. If the predictions agree with the observations,
the theory survives that test, though it can never be proved to be correct.
On the other hand, if the observations disagree with the predictions, one has to
discard or modify the theory. (At least, that is what is supposed to happen. In
practice, people often question the accuracy of the observations and the
reliability and moral character of those making the observations.) If one takes
the positivist position, as I do, one cannot say what time actually is. All one
can do is describe what has been found to be a very good mathematical model for
time and say what predictions it makes.
Isaac Newton gave us the first mathematical model for time and space in his
PRINCIPIA MATHEMATICA, published in 1687. Newton occupied the Lucasian chair at
Cambridge that I now hold, though it wasn't electrically operated in his time.
In Newton's model, time and space were a background in which events took place
but which weren't affected by them. Time was separate from space and was
considered to be a single line, or railroad track, that was infinite in both
directions. Time itself was considered eternal, in the sense that it had
existed, and would exist, forever.
By contrast, most people thought the physical universe had been created more or
less in its present state only a few thousand years ago. This worried
philosophers such as the German thinker Immanuel Kant. If the universe had
indeed been created, why had there been an infinite wait before the creation? On
the other hand, if the universe had existed forever, why hadn't everything
that was going to happen already happened, meaning that history was over? In
particular, why hadn't the universe reached thermal equilibrium, with
everything at the same temperature?
Kant called this problem an "antimony of pure reason," because it seemed to
be a logical contradiction; it didn't have a resolution. But it was a
contradiction only within the context of the Newtonian mathematical model, in
which time was an infinite line, independent of what was happening in the
universe. However, as we saw in Chapter 1, in 1915 a completely new mathematical
model was put forward by Einstein: the general theory of relativity. In the
years since Einstein's paper, we have added a few ribbons and bows, but our
model of time and space is still based on what Einstein proposed. This and the
following chapters will describe how our ideas have developed in the years since
Einstein's revolutionary paper. It has been a success story of the work of a
large number of people, and I'm proud to have made a small contribution.
Excerpted from The Universe in a Nutshell by Stephen Hawking Copyright 2001 by Stephen Hawking. Excerpted by permission of Bantam, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Heaven has no rage like love to hatred turned, Nor hell a fury like a woman scorned.
Click Here to find out who said this, as well as discovering other famous literary quotes!
Your guide toexceptional books
BookBrowse seeks out and recommends the best in contemporary fiction and nonfiction—books that not only engage and entertain but also deepen our understanding of ourselves and the world around us.