>>Stephen Hawking: It is a great pleasure
to be here at this Google Zeitgeist meeting.
Some time ago, I wrote a popular book, A Brief
History of Time. The book described my picture
of the universe, but it left a number of issues
unresolved.
I have, therefore, written a new book, The
Grand Design, with Leonard Mlodninov to try
to answer questions like: How can we understand
the world in which we find ourselves? What
is the nature of reality? How does the universe
behave and why does it exist? Does it need
a creator?
Most of us don't worry about these questions
most of the time. But almost all of us must
sometimes wonder: Why are we here? Where do
we come from?
Traditionally, these are questions for philosophy,
but philosophy is dead. Philosophers have
not kept up with modern developments in science.
Particularly physics.
Scientists have become the bearers of the
torch of discovery in our quest for knowledge.
The purpose of The Grand Design is to give
the answers that are suggested by recent discoveries.
They lead us to a new and very different picture
of the universe and our place in it.
In the book, we describe how regularities
in the motion of astronomical bodies like
the sun, moon, and the planets suggested that
they were governed by fixed laws rather than
being subject to the arbitrary whims and caprices
of gods and demons.
At first, the existence of such laws became
apparent only in astronomy or astrology which
was regarded as much the same.
The behavior of things on Earth is so complicated
and subject to so many influences that early
civilizations were unable to discern any clear
patterns or laws governing these phenomena.
Gradually, however, new laws were discovered
in areas other than astronomy.
This led to the idea of scientific determinism.
Given the state of the universe at a specific
time, there must be a set of laws that would
specify how the universe would develop from
that time forward.
These laws should hold everywhere and at all
times. Otherwise, they wouldn't be laws.
There could be no exceptions or miracles.
Gods or demons couldn't intervene in the running
of the universe. The laws of science describe
how the universe behaves, but to understand
the universe at the deepest level, we also
need to understand why. Why is there something
rather than nothing. Why do we exist. Why
this particular set of laws, and not some
other.
I believe the answer to all of these questions
is M theory. M theory is the only unified
theory which has all the properties that we
think the final theory ought to have. It is
not a theory in the usual sense, but it is
a whole family of different theories, each
of which is a good description of observations
only in some range of physical situations.
It is a bit like a map.
As is well known, one cannot show the whole
of the Earth's surface on a single map, the
usual Mercator projection used for maps of
the world makes areas appear larger and larger
in the far north and south, and doesn't cover
the North and South Poles. Instead, one has
to use a collection of maps, each of which
covers a limited region.
Like Google Earth, the maps overlap each other,
and where they do, they show the same landscape.
M theory is similar. The different theories
in the M theory family may look very different,
but they can all be regarded as limiting cases
of the same underlying theory when certain
quantities, such as the energy or some fields,
are small. Each theory has only a limited
range of validity, but where the ranges of
two theories overlap, they predict the same
observations. There is no single theory that
is a good representation of observations in
all situations.
M theory predicts that a great many universes
were created out of nothing. 
These multiple universes can arise naturally
from physical law. They are a prediction of
science. Each universe has many possible histories
and many possible states at later times. That
is, at times like the present, long after
their creation. Most of these states will
be quite unlike the universe we observe and
quite unsuitable for the existence of any
form of life. 
Only a very few would allow creatures like
us to exist. Thus our presence selects out
from this vast array only those universes
that are compatible with our existence. Although
we are puny and insignificant on the scale
of the Cosmos, this makes us, in a sense,
the lords of creation.
But I am sure some of you are asking: How
do we know M theory is true? How can you prove
it really describes our universe? It might
be mathematically elegant, but how can M theory
be tested experimentally?
Well, there is some hope that we might see
hints of M theory at the LHC particle accelerator
in Geneva. The LHC is the largest, most complex
machine in the world, possibly the universe.
From an M theory perspective, it only probes
low energies, but we might be lucky and see
a weaker signal of fundamental theory, such
as supersymmetry. The search goes on, and
already some possibilities have been eliminated.
However, to directly test M theory, we would
need a new LHC capable of achieving enormous
energies. It would have to be scaled up to
a collider ring about as large as our galaxy,
the Milky Way.
This technology is some way off, and I don't
think even Google could afford to build it.
[Laughter]
>>Stephen Hawking: Testing M theory is still
possible because there was a time when the
highest energies imaginable were actually
reached, at the beginning of the universe,
in the hot big bang. The very early universe
is the ultimate laboratory for testing our
ideas about the building blocks of space,
time, and matter. Different theories leave
behind different fingerprints in the current
structure of the universe, so astrophysical
data can give us clues about the unification
of all the forces of nature.
But the importance of cosmology as an experimental
science is a recent development.
When I first started out as a graduate student
in Cambridge in 1963, the situation was very
uncertain. it could be said then that a cosmologist
was cheaper to fund than a mathematician.
A mathematician needed a pencil and paper,
and a waste paper bin, but a cosmologist could
do without a bin. 
We could make up any idea we liked, such as
the steady state theory, knowing there was
no data to contradict it.
All that changed in 1965 with the discovery
of the cosmic microwave background radiation.
These microwaves are all around us, and they
are the same as those in your microwave oven,
but much less powerful. 
They would heat your pizza only to minus 271.3
degrees centigrade, not much good for defrosting
the pizza, let alone cooking it. The only
reasonable interpretation of the background
is that it is radiation left over from an
early, very hot and dense state. As the universe
expanded, the radiation would have cooled
until it is just a faint remnant we observe
today. 
Cosmology took another enormous leap forward
in 2003 when the first results from the NASA
WMAP satellite were published. WMAP was able
to produce a wonderful map of the temperature
of the cosmic microwave sky. This is a snapshot
or photograph of the universe as it was at
about one hundredth of one percent of its
present age. The irregularities you see mean
that some regions of the universe had a slightly
higher density than others. The gravitational
attraction of the extra density will slow
the expansion of the region and can eventually
cause the region to collapse to form galaxies
and stars. 
So look well at the map of the microwave sky.
It is a blueprint for all the structure in
the universe.
The WMAP data you see here has about a million
pixels, and it contained so much information,
it marked the dawn of a new era. Cosmology
became a precision science. For the first
time, cosmological parameters could be measured
to within a few percent, and we could start
in earnest testing our theories about the
origin of the universe.
The hot big bang model has become so well-attested
and quantitative that it is now called the
standard cosmology. It describes a seamless
history, from the first fractions of a second
after the big bang, through to the present
day, 13.7 billion years later, from the synthesis
of nuclei and the formation of atoms through
to the collapse of galaxies. And we are trying
to push this understanding further backwards
in time. At the LHC, we are testing physical
laws which describe the universe at one hundredth
of a nanosecond. But we are even more ambitious
than this in cosmology. Through WMAP and other
data, we are testing the theory of inflation
at about one trillion trillion trillionth
of a second.
The world record for inflation was in Germany,
after the first world war. Prices rose by
a factor of ten million in a period of 18
months. But that was nothing compared to inflation
in the early universe. 
Unlike inflation in prices, inflation in the
early universe was a very good thing. It produced
a very large and uniform universe, just as
we observe. 
However, it would not be completely uniform.
The marriage between quantum theory and general
relativity means that the universe became
slightly irregular. I was one of those who
proposed that these quantum fluctuations would
become frozen in spacetime and imprinted in
the cosmic microwave sky. 
We worked out all the details in Cambridge
in 1982 at a small meeting, known as the Nuffield
Very Early Universe Workshop. 
These irregularities are the key quantitative
prediction of inflation. The WMAP data has
been shown to have exactly the right kind
of variations predicted. So we know we are
on the right lines.
Inflation has successfully matched all the
key data to date, but it makes some other
truly remarkable predictions. Simple inflation
predicts that the primordial irregularities
have Gaussian or purely random statistics
to one part in a million, that is, their distribution
very accurately follows a so-called bell curve.
Many cosmologists today spend their time investigating
this random hypothesis, looking for strange
nonrandom features or correlations in the
data.
One frivolous example can be seen in this
WMAP snapshot. If you zoom in and search carefully,
you can just about make out the letters "SH."
[ Laughter ]
>>Stephen Hawking: This does not seem very
random, especially as these are my initials.
[ Laughter ]
>>Stephen Hawking: However, this is controversial
because Australian astronomers look at the
universe the other way up.
[ Laughter ]
>>Stephen Hawking: They could claim instead
to have found the initials of Homer Simpson.
[ Laughter ]
>>Stephen Hawking: Unfortunately, these features
are from an unreliable part of the map contaminated
by the Milky Way Galaxy. In fact, a careful
analysis of the WMAP data has established
that the fluctuations are purely random, to
one part in ten thousand.
The Planck satellite is the world's most ambitious
survey of the cosmic microwave sky. We are
using this new data to measure cosmological
parameters to subpercent accuracy, and we
are on the way to testing the random hypothesis
to nearly one part in one hundred thousand.
This is the most stringent test of inflation
to date. I will let you know when it passes,
because inflation is such a beautiful idea,
I am sure it is right.
But what if the universe is not purely random?
What if there are some unexpected correlations?
Well, this might not be such a bad thing.
It would mean the simplest model of inflation
is wrong, but there are alternative models
of inflation which are well-motivated by fundamental
theory. 
Each of these has a distinctive fingerprint
which could be observed in these nonrandom
correlations. 
Such fingerprints would be clues about the
origin of the universe and about the unification
of the forces of nature, maybe even about
M theory.
But Planck is just providing the best data
available for now. Ambitious future experiments
will supersede it, mapping billions of galaxies
so that we can better understand our place
in the universe. 
Perhaps one day we will be able to use gravitational
waves to look right back into the heart of
the big bang. 
Most recent advances in cosmology have been
enabled through space technology. 
From space, the view of our wonderful universe
is clear and uninterrupted, and we will depend
on it for future progress. 
I am a great supporter of space exploration,
and I am booked to participate in it myself
on one of the first commercial space flights.
I have already been through astronaut training
in zero gravity. 
In a time of shrinking government budgets,
we are going to need more private enterprise
and individuals taking up challenges like
this. 
I am pleased, for example, that Google has
set up the Lunar X Prize to encourage robotic
space exploration.
I have emphasized that cosmology has emerged
as a data-driven field. This deluge of new
data has challenged cosmologists to construct
increasingly sophisticated mathematical theories,
models of such complexity that it is no longer
feasible to solve them using pen and paper.
We need supercomputers to do the job, systems
like the Cosmos supercomputer at my Centre
for Theoretical Cosmology in Cambridge. 
We put our theoretical models on the computer
and create many big bangs to predict how the
universe might look and to compare with observation.
These technologies enable us to reach out
and touch the real universe, testing if our
ideas are right. Without them, we would be
mere philosophers. But we don't want to become
advanced programmers, either. We want to keep
our focus firmly on understanding the universe,
so we need I.T. companies to keep these vital
tools simple and accessible for us, even if
the scale of the problem grows like an inflationary
universe.
So let me finish by returning to M theory
and my original question, why are we here?
M theory is a unified theory Einstein was
hoping to find. The fact that we humans, who
are ourselves mere collections of fundamental
particles of nature, have been able to come
this close to an understanding of the laws
governing us and our universe is a great triumph.
But perhaps the true miracle is that abstract
considerations of logic lead to a unique theory
that predicts and describes a vast universe
full of the amazing variety that we see. If
the theory is confirmed by observation, it
will be the successful conclusion of a search
going back more than 3,000 years. We will
have found The Grand Design.
Thank you for listening to me.
[ Applause ]
(Standing ovation).
>>Eric Schmidt: On behalf of all of us, I
want to thank you, Professor Hawking and I
wanted to ask you to have the privilege of
one more question.
We recent -- as you know, Google, we recently
told the world about our new driverless car,
which I'm looking forward to driving around
when it's a little more debugged.
What is the single most exciting and the single
most frightening aspect of a future where
artificial intelligence begins to play a much
more central role in our lives?
>>Stephen Hawking: Artificial intelligence
will greatly change the future. We need control.
There is still a role for human intelligence.
[ Laughter ]
>>Eric Schmidt: Good.
Thank you very, very much.
Okay. Thank you.
[ Applause ]
