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The
Grand Design by Stephen Hawking
and Leonard Mlodinow (Bantam Books, New
York, Trade Paperback, 2012) uses
religious questions to set out the
current state of thinking in physics
about the structure of matter and the
origins of the universe. It is
intriguing that the physicists see their
work in this context of religion and of
questions about the possibility of
god(s) and intervention. It was a shock
to me after 50 years away from physics
to find that the waters have moved on.
It was a delight to have a book which
tried to update me without the
patronizing which so often comes with
popular science. So what of the book? In sum, the steady
development of evidence confirming
quantum theory in the latter half of the
20th century has forced mind boggling
changes in what we must accept as the
way the world behaves when one is on a
small scale. Evidence of an expanding
universe implies a small beginning in
which these quantum effects would have
prevailed. Attempts
to produce an omnibus theory for all
kinds of forces have not yet succeeded,
but the M-theory seems to be a composite
which can make predictions in selected
situations. The book is rich in its
detail, but understanding what is going
on is work even at this readable level. The opening, “The
Mystery of Being,” sets up a religious
framework of questions: Where did all
this come from; Did it need a creator;
Why do we exist. Affirming “philosophy
is dead” and “scientists have become the
bearers of the torch of discovery …” the
opening chapter introduces concepts to
come. Feyman’s
new quantum theory will suggest that the
universe has no single history or single
existence. M-Theory may have the answers
to the big questions but it is a
collection of theories rather than one –
rather like maps can represent relevant
bits of a global world. The rule of law in
chapter 2 runs through the evolution of
scientific thought on our world. A point
of origin goes to Ionian thinking around
300 BCE. The formal idea of laws of
nature emerged with Kepler in the
seventeenth century. Galileo suggested
observation as the basis for science and
the quantitative relationships between
physical phenomena. Descartes formulated
the formal concept of laws of nature.
Descartes and Newton both believed god
set things going. The chapter explores
thinking about whether there can be
interventions into laws of nature by
prayer or miracles. When asked by
Napoleon how god fitted in, Laplace is
reported to have said that he had no
need for that hypothesis. The book
argues that free will is an “effective
theory” for predicting human behaviour
because the calculation of behaviour
from the many laws involved is
impracticable. Then why not an effective
theory of god or fate to cover what is
not yet predictable? Reality depends on
one’s point of view. Chapter 3 begins
with a goldfish in a bowl and a person
outside the bowl in a room. Using a
“model” does not need to claim its
reality. “Model based realism” allows
science to make predictions and make
observations. Planetary motion can be
predicted using Ptolemy’s earth based
model or using the later sun based
model. Electrons and Quarks are parts of
models which help explain phenomena at
atomic and subatomic levels. A good
modal: 1. Agrees with and explains all
existing observations; 2. Has few
adjustable factors; 3. Can predict
future observations with potential to
affirm or discredit the theory. Thus
the big-bang model of the universe,
which explains fossil and radioactive
records and the fact that we receive
light from galaxies millions of light
years away, is more useful than the “God
did it” model. Sometimes more than one
model or theory is required - for
example to describe the behaviours of
light. The model of light as particles
explains the bending of light by a lens
or the photoelectric emission of
electrons when a beam of light strikes
certain surfaces. The model of light as
waves explains phenomena called
interference such as Newton’s rings of
light and dark around a lens on a
reflective surface illuminated by a beam
of one colour of light from above. The fourth chapter
begins with an experiment with
Buckyballs. These are microscopic carbon
molecules shaped like a soccer ball.
(See my article from May 2009 on
nanotechnology.) Shooting these tiny
pieces of matter at twin slits produces
interference patterns, alternate rows of
matter and no matter, on
a screen at the other side. This is how
light would behave. How does one ball
know that another slit is there?
Feynman’s mathematical quantum theory
sums over all possible paths. The model
implies that a Buckyball which came
through a slit has a range of possible
histories – not a unique trajectory like
a full size soccer ball. If one uses
light to observe particles at one slit,
the interference pattern stops. If one
uses light to observe particles arriving
after the slit on the screen behind, the
interference pattern stops. Observing at
the slit affects the outcome but
observing after the slit also affects
the history. The chapter ends with a
hypothetical observing of a cosmic event
using a planetary equivalent of the two
slit type of system. If one were to
observe the interference pattern from
light from such a cosmic event, the
interference should stop although the
path choice was made by the light many
light-years ago. The history of the
universe would be changed by observing
of it. Bumper chapter 5
begins with the concept of a force
“field”- the pattern iron filings take
on a piece of paper on top of a magnet.
Electric currents produce this kind of
magnetic field and magnetic motion
produces an electric current. Maxwell’s
equations describe the electro-magnetic
relationship with a constant in the
equations which turns out to be the
measured speed of light. Einstein’s
special relativity theory assumes this
constant, the speed of light, is the
same when measured by any observer. Time
varies when observers moving relative to
each other measure an event. Time is not
separate from the dimensions of space –
the concept must be of space-time. Einstein
showed time and space are not fixed:
they are relative. Einstein’s general
relativity theory reduces to special
relativity when mass is absent. When
mass is present, it distorts space-time
so that space becomes curved and masses
move on geodesics. Newton’s observations
of falling objects are explained because
when space-time is not flat, the path of
an object appears to be bent giving the
impression a force is acting on it. GPS
positioning relies on General Relativity
theory . Without it, big errors would
accumulate. More than this, the theory
leads to a universe with gravitational
waves and black holes. However, like
Newton’s theory, General Relativity is
classical so that the universe has a
single history. At small atomic and
molecular levels the quantum theories
are needed to explain the observations.
The small compressed early universe
requires quantum theories to be
understood. There the sum over histories
approach is needed and a single history
is not part of the model. Of the four known
forces, gravity, electromagnetic, weak
nuclear (radioactivity) and strong
nuclear (holds atom nucleus together,
nuclear bombs) we only come into contact
with the first two. Quantum
electrodynamics, QED, developed by
Faynman and others is the model for all
quantum field theories. Forces are not
pictured as fields, but as particles
“bosons” such as the light photon flying
between matter particles “fermions” such
as electrons and quarks, transmitting
the forces. Feynman also developed
pictorial diagrams for representing
possible histories. The mathematics for
summing over all possible histories is
formidable and the necessary approach
which cancels positive and negative
infinite amounts, “renormalization,” is
described as “dubious.” But it seems to
work, that is, to predict behaviour like
the Lamb shift. Salem and Weinberg both
suggested a unified theory for
electromagnetism and weak forces which
could be renormalized and which
predicted new particles w+ w- and Z0.
Evidence for Z0 was subsequently found
in 1973. The strong force can
be renormalized in its own theory called
quantum chromo dynamics, QCD. This
theory models elementary nuclear matter
particles such as protons and neutrons
as made up of quarks with a property
called “colour” – red, green or blue. A
quark has an anti-particle with
anti-green, anti-red and anti-blue
colour. Combinations with no net colour
exist as free particles. A quark plus an
anti-quark forms an unstable meson
particle. All three colours or
anti-colours combine to form stable
Baryon particles like the protons and
neutrons which are the basis for all
matter in the universe. Quarks have
asymptotic freedom, that is, the force
between them increases with separation.
The QCD model is accepted because it
explains the behaviour of protons and
neutrons and the like. In the absence of
a convincing grand unified quantum
theory (GUT) for strong and weak forces,
the combination of QED and QCD, the
“standard” model, is used. This explains
observations, but does not bring
together the forces and does not include
gravity. Gravity quantum
theory poses problems because the
uncertainty principle applies to the
field. So a field and its speed of
change cannot both be known. A
consequence is that there cannot be
empty space – the field and its rate of
change cannot both be exactly zero.
There can be minimum energy – vacuum –
subject to quantum jitters. This is
viewed as virtual particles coming into
existence then annihilating each other. Virtual
particles cannot be directly detected
but their effects can be measured as
such things as small changes in electron
orbits. A major problem in that such
particles have energy, an infinite
number have infinite energy and that
should curve the universe to an
infinitely small size – which doesn’t
happen. The theories of supergravity and
supersymmetry may offer a way out.
Supersymmetry supposes that force and
matter are part of the same thing; that
each force particle like a photon has a
matter particle partner and each matter
particle has a counterpart force
particle. This has been hard to check.
Supergravity had its origins in earlier
string theory which views particles not
as points but patterns of vibration with
length but no height and no width.
String theory is consistent only if
space-time has 10 dimensions with extra
dimensions tucked away in a very small
space. The various string theories and
supergravity are seen as aspects of a
wider unifying theory referred to as
M-theory. Whether M-theory exists, or is
just the network of more specific
theories is still uncertain.
Nonetheless, some properties are known:
eleven dimensions; p-branes (points,
strings, membranes, 3-d blobs, up to
objects with 9-d); the math describes
the laws of nature we observe in our
universe; the math sets up more
fundamental laws. M-theory
laws allow for different universes with
different laws. The chapter ends
reflecting on the change from Newton’s
use of math to describe the world and
the current M-theory which postulates
multi-universes in astronomical numbers. Chapter 6 explores
the origins of our particular universe,
beginning with a typical creation
narrative. In the 1920s Hubble examined
the spectrum of light emitted by stars
and concluded that they are receding so
that the universe is not static as was
then assumed but is expanding. It is
expanding in the sense that the distance
between any two points is expanding like
dots on the skin of a growing balloon.
Hubble found that the further stars are
from us, the faster they move. That
supposes the universe grew from some
time when it was unimaginably dense and
compact – an event now referred to as
the “big bang.” Galaxies and stars do
not grow but space. The galaxies remain
governed by gravitational forces. Using
a simplified model for the universe, at
about the same time as Hubble, Friedman
showed that Einstein’s equations
predicted an expanding universe. Support
for a “big bang” type of beginning came
from observing cosmic microwave
background radiation (CMBR) around 1965.
Measurements of helium, hydrogen and
lithium are consistent with a hot tiny
early universe. Einstein’s theories do
not go back to the very beginning. They
break down at the point in space time at
which temperature, density and curvature
are infinite, but they can describe the
early universe. An early phase of the
expanding universe is postulated as
rapid “inflation” – as if a 1 cm coin
blew up to 10 million times the milky
way galaxy. Expansion of space itself
can move faster than the speed of light!
Quantum considerations lead to this
notion in 1980. Despite incomplete
quantum gravitation theory, the theory
predicts irregularities which would
cause tiny temperature fluctuations in
CMBR. These were eventually observed
then confirmed by successive satellite
observations. At the same time, the near
uniformity of the temperature of CMBR
observed across the universe also speaks
to a very rapid expansion. Traditional
inflation theory requires very special
and improbable starting conditions. Yet
near the beginning, when the universe
was very tiny, the molecular scale of
quantum theory is reached and quantum
theory must be more fully applied. In
quantum theory gravity warps space time. Using
the
analogy of a billiard table, the authors
show how a warp in the table can result
in distances followed by a rolling
billiard ball can be shorter than the
distance covered by traveling in the
straight line between starting and
finishing points. The diameter of a
circle can be more than the
circumference. In the universe
gravitational warping can stretch or
reduce the distances, changing the shape
in ways measurable from within.
Similarly, time can be warped. Time and
space mix with higher speeds and
gravity. In extreme cases such as in
inflation, quantum theory with general
relativity predicts time behaving like
another dimension of space. There is
then no time as we know it. One cannot
speak of a beginning of the universe.
One cannot speak, as did Aristotle, as
if the universe always existed. Nor can
one speak of a beginning which calls for
a “god” to begin things. The authors
speak of a beginning governed by the
laws of science. A quantum beginning
should follow the sum over histories
quantum approach of Feynman. Using the
buckyball model, a sub-microscopic
particle shot at a screen with two slits
exhibits inference patterns on
a screen on the other side – a particle
does not have a unique history. One adds
the histories which will produce that
pattern on the screen in the Feynman
version of quantum mechanics. Applying
this model to the universe, one adds up
all the histories which lead to the
universe of today - the histories going
from the top down, from the present
backwards. There are different histories
for different possible states of the
universe at the present time. The
histories in the Feynman sum depend on
what is being measured. Cause and effect
are changed in the world of quantum
theory. We cause the histories by
observing the universe. The laws of
nature depend on the history of the
universe and would be different for
different histories. For M-theory, there
are ten space dimensions and one time of
which it is supposed 7 dimensions are
curled up leaving us observing three
remaining large dimensions. Although
there are probabilities for other
histories, even a much greater
probability of something else is
irrelevant – we have the one we observe.
The shape of the remaining curled up
dimensions determines such things as the
charge on the electron and the forces of
nature. This theory of inflation is
testable by small irregularities in the
microwaves from many directions of
distant galaxies. The conclusion of the
chapter is that our universe is one of
many. One cannot predict our particular
laws of physics. These can take
different forms in different universes.
The seventh chapter
explores the lucky situation supporting
our life such as the distance from the
sun, the near circular orbit and the
sun’s mass provide a goldilocks
habitable situation. Newton felt this
was created by god. A variety of planets
exist and at least ours allowed life.
Inevitably, when we look at it we are
bound to find these conditions. This
situation can be considered in another
way. What does our existence allow us to
say about how old our universe is? This
is the weak anthropic principle. From
the need for carbon to form and condense
into planets an estimate is 10 billion
year – less than the guesstimated 13.7
million time zone of the big bang. A
stronger anthropic principle suggests
that our existence speaks to the form
and content of the laws of nature and of
our particular universe. The forces of
nature had to be able to produce heavier
elements including carbon from
primordial elements and remain stable
for at least billions of years. Heavier
elements were formed in furnaces called
stars.
Stars and galaxies had to form
from tiny inhomogeneities in the early
universe – uniform with 1 in 100,000
density variations. More, the dynamics
of
the stars had to allow some to
explode
in precisely the right manner to disperse
the heavier elements through space. And
more -
the laws had to allow these
elements to recondense
into stars and planets. And
certain events then had to occur on
earth to allow us to emerge. The
interplay of fundamental laws had to be
just right. The formation of carbon by
the triple alpha process and its
subsequent distribution by supernova
requires very particular conditions. Tiny
changes to the rules governing our
universe would preclude our emergence.
Take the circular orbits required for
temperate earth. These orbits are
possible in other dimensions – but there
they are unstable! In 1998, it was found
that the expansion of the universe was
accelerating. That required a force – a
cosmological constant which Einstein had
in his relativity equations. Quantum
calculations
predict a much larger value of this
constant which would have blown apart
the universe. Its
lower value is critical to the stable
continuing existence of our universe. Some
have argued that these coincidences
point to god. However, the fine tuning
of the physical laws in this one
universe among many serves as its own
explanation - just as Darwin could
explain human creation by evolution
within natural selection. The
book ends with the marvels of the laws
of nature as these are being
uncovered, enjoying the mystery for
its own sake. Along the way, the
authors noted that senior clerics have
suggested that these later more
remarkable laws of physics are
compatible with a god. The authors
clearly agree with Laplace’s words to
Napoleon – they have no need for that
hypothesis!
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