Light and Life in the Universe. Selected Lectures in Physics, Biology and the Origin of Life

326 Pages·1965·10.824 MB·English

by  S. T. Butler and H. Messel (Eds.)

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LIGHT AND LIFE
IN THE UNIVERSE
Selected Lectures in Physics, Biology
and the Origin of Life
EDITED BY
S. T. BUTLER
M.SC., PH.D., D.SC.
Professor of Theoretical Physics
AND
H. MESSEL
B.A., B.SC, PH.D.
Head of the School of Physics
UNIVERSITY OF SYDNEY
PERGAMON PRESS
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A course of lectures contributed to the Nuclear Research
Foundation Summer Science School for Fourth-year High
School students at the University of Sydney, January 6-17,
1964
For Copyright reasons
this Edition is not for sale
in Australasia
Copyright © 1965
Pergamon Press Ltd.
Library of Congress Catalog No. 65-18522
First published in
THE COMMONWEALTH AND INTERNATIONAL LIBRARY
1965
Printed in Great Britain by
Taylor Garnett Evans & Co. Lid
Watford, Herts
THE SPONSORS
The Nuclear Research Foundation within the University of Sydney
gratefully acknowledges the generous financial assistance given by the
following group of individual philanthropists and companies, without
whose help the 1964 Summer Science School for Fourth-year High
School students and the production of this book would not have been
possible.
Ampol Petroleum Limited
Australian Factors Group
Ducon Industries Limited
H. G. Palmer, Esq.
INTRODUCTION
The lectures of the 1964 Nuclear Research Foundation Sum-
mer Science School for High School Students, contained in the
chapters of this book, will be concerned primarily with various
aspects of life—life here on earth and life in the universe generally.
The main lectures of this Summer School, by Professors J. D.
Watson and M. Yeas, are concerned basically with the following
topics:
• The "units" of living matter.
• How life may have started on earth.
• The possibility of life on other planets.
It may seem to you that these topics can have very little to
do with ordinary physics and chemistry. Yet it is the purpose
of the first six chapters of this book to develop for you some of
the basic physics and chemistry which is necessary for appreciation
of the later biology lectures. You will find in these later lectures
how certain large molecules are characteristic of life forms—mole-
cules which themselves have amazing properties and which are
able to reproduce replicas of themselves. The question of how life
may have originated on earth is thus intimately connected with
how these large molecules may have been formed to start with.
Similarly, the question of life elsewhere in the universe is vitally
concerned with a number of other planets which may exist and
which may have properties that can support life.
But do you really know what a molecule is? Do you know
how electro-magnetic radiation can be responsible for the building
up of large molecules? Do you know what electro-magnetic radia-
tion is? Do you know the theories of what the earth was like
thousands of millions of years ago when life originated on it? Are
you aware of the scientific thoughts regarding the origin of our
solar system, and which are essential to any estimates of the possible
number of other planets with life?
These are all topics in physics and chemistry which go hand
in hand with our Summer School's main lectures on the subject
of life. In order that you be able to appreciate fully these later
lectures we devote much of the book's first six chapters to dis-
cussing the above-mentioned subjects.
Because all lectures have been specifically prepared, written
and edited for fourth-year High School students, we feel that they
will be of interest to the widest section of the public. We feel that
the material as presented will be appreciated not only by the increas-
ingly science-conscious layman in this scientific age but also, in
fields other than his own, by the specialised scientist.
The 1964 Nuclear Research Foundation Summer Science
School and, indeed, this book are intended to stimulate and develop
science-consciousness in Australia generally, and in particular in the
150 outstanding fourth-year High School students of 1963 who won
scholarships to attend the School. The Foundation wishes to
applaud and reward their ability and diligence.
Finally, we accept complete responsibility for the contents of
this book and apologise for any errors which may have crept into
the texts.
Sydney, January, 1964. S. T. BUTLER and H. MESSEL
CONTRIBUTORS OF LECTURES
R. N. BRACEWELL
Professor of Electrical Engineering,
Stanford University, Stanford, California,
S. T. BUTLER
Professor of Theoretical Physics,
University of Sydney.
H. MESSEL
Professor of Physics and Head of the School of Physics,
University of Sydney.
J. D. WATSON
Professor of Biology,
Harvard University, Cambridge, Massachusetts.
M. YCAS
Associate Professor of Microbiology,
State University of New York, New York.
CHAPTER 1
Atoms, Molecules and Nuclei
All matter, whether in life forms or in inanimate objects, is
made up of elementary particles called atoms. In many substances,
atoms are joined together into larger units called molecules. In
this chapter we describe, briefly, some of the properties of atoms
and how they join up to form molecules, for it is this very process
that has built up characteristic molecules of living beings. At the
same time we shall outline some of the properties of the central
core of each atom—the by now famous nucleus—because, as you
will see in Chapter 4, a certain amount of nuclear physics enters
into any discussion as to the origin of the sun and its solar system,
(a) Matter consisting of atoms or molecules.
As you know, most substances can exist in any one of three
states—the solid state, liquid state or gaseous state.
In the solid state the atoms or molecules are closely bound together
by forces between them, and are arranged in a regular geometrical
pattern called a "solid lattice." In this case the atoms or molecules
possess rather little freedom of motion ; their main motion is a
small to-and-fro movement around their proper positions in the
lattice. The distance between particles in such a lattice is about
the same as the size of the particles themselves.
In the liquid state the atoms or molecules are also fairly closely
bound together by forces between them, but they are no longer
arranged in a regular pattern, and it is possible for individual atoms
and molecules to wander all over the liquid. The atoms or molecules
slide over one another with great freedom, allowing the liquid to
assume any shape. But since the elementary particles are still quite
tightly packed and held together by strong forces, the liquid resists
any attempt to change its volume.
In the gaseous state the molecules are on the average widely separ-
ated from each other and exert but little attraction upon each other.
9
10 LIGHT AND LIFE IN THE UNIVERSE
The molecules of a gas move freely from place to place, the spaces
between them being much larger than their size.
It is on the basis of this picture of matter that we are able to
understand such properties as the pressure in gases and liquids,
heat content and temperature of bodies of matter, and sound pro-
pagation through a medium. Indeed all properties of matter are
determined by the charged and uncharged atoms and molecules of
which everything consists. As we shall see later the properties
of electricity and magnetism are a direct consequence of the
structure within an atom. To understand light, electricity and
magnetism we must make use of the fact that each atom consists
of a central positively charged core called the nucleus, around
which revolve negatively charged particles called electrons. It
will be our purpose in the present work to discuss in some detail
the relationship of all these phenomena based upon the above
picture of atoms.
For the remainder of this chapter we shall present the general
picture, as it is now known, of atoms and molecules.
(b) Fundamental Particles
Atoms and molecules themselves are made up from three funda-
mental building blocks—neutrons, protons and electrons. Their
properties are as follows:
Electron imaSS = 9*Π x 10"28 g (approx. 2 X 1030 lb>
(charge (negative) = 4-8 x 10~10 esu
Pr ton imaSS = 1#672 X 10~24 g
{charge (positive) = 4-8 x 10-10 esu
, (mass = 1-675 x 10"24 g
NXTeutron { . . , ,
(zero el ec4trical charge.
If we designate the mass of the electron by m, that of the proton
e
by m and of the neutron by m it has been accurately measured that
v n
m = 1836 m
v e
m = 1846 m.
n e
Thus protons and neutrons have very nearly equal masses and each
is very much more massive than an electron.
The proton has a positive charge, usually designated by +e,
which is exactly equal in magnitude to the negative charge of the
ATOMS, MOLECULES AND NUCLEI 11
electron — e. The neutron, however, has no charge whatsoever
and this made it much more difficult to discover. All three of these
fundamental particles are extremely small in size being 10'13 cm
or less in diameter.
Setting aside the question of the way in which these particles
were discovered and their properties determined, let us accept the
fact that they exist and see how they are built up into atoms and
molecules and thus into matter as we know it.
(c) Atoms
Matter which is made up purely of atoms of one kind is called
an element. There are 92 different types of atoms which occur
naturally, and there are thus 92 natural elements (although other
unstable elements can now be created artificially). Each atom con-
sists of a very dense and small central core known as the nucleus,
around which electrons move in satellite or planetary orbits. The
nucleus itself contains no electrons but consists of protons and neu-
trons. The number of protons in a nucleus is usually designated
by Z, the so-called atomic number, and the number of neutrons
in a nucleus is designated by N.
The total number of protons and neutrons in a nucleus is known
as the mass number A — N -\- Z. Atoms are electrically neutral,
and this means that there is a number Z of planetary electrons
moving around a nucleus. These electrons which move in planetary
orbits around nuclei do so because of their electrostatic attraction
to the protons in the nucleus. If an atom or molecule loses an
electron—we say it is ionized—it becomes a singly charged positive
ion. If it loses two electrons, it becomes a doubly charged posi-
tive ion, and so forth. On the other hand, if a neutral atom or
molecule gains an electron, it becomes a singly charged negative
ion.
If a nucleus has atomic number Z it contains Z protons each of
charge +e. An electron of charge — e is therefore attracted towards
such a nucleus; if the electron is a distance r away, the magnitude
of the Coulomb attraction is
Ze2
Attractive force on electron = —.
r2
It is to be noted that this is an inverse square force, exactly
analogous to the force of gravitation. (Indeed there is also a gravita-