Questioning the universe Stephen Hawking
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there is nothing bigger older than the
universe the questions I would like to
talk about our one where did we come
from how did the universe come into
being are we alone in the universe is
there alien life out there what is the
future of the human race up until the
1920s everyone thought the universe was
essentially static and unchanging in
time then it was discovered that the
universe was expanding distant galaxies
were moving away from us this meant they
must have been closer together in the
past if we extrapolate back we find they
must have all been on top of each other
about 15 billion years ago this was the
Big Bang the beginning of the universe
but was there anything before the Big
Bang if not what created a universe why
did the universe emerge from the Big
Bang the way it did we used to think
that the theory of the universe could be
divided into two parts first there were
the laws like Maxwell’s equations and
general relativity that determine the
evolution of the universe
given its state over all space at one
time one second there was no question of
the initial state of the universe we
have made good progress on the first
part and now have a knowledge of the
laws of evolution in all but the most
extreme conditions but until recently we
have had little idea about the initial
conditions for the universe however this
division into laws of evolution an
initial
ditions depends on time and space being
separate and distinct under extreme
conditions general relativity and
quantum theory allow time to behave like
another dimension of space this removes
a distinction between time and space and
means the laws of evolution can also
determine the initial state the universe
can spontaneously created self out of
nothing moreover we can calculate the
probability that the universe is created
in different states these predictions
are in excellent agreement with
observations by the WMAP satellite of
the Cosmic Microwave Background which is
an imprint of the very early universe we
think we have solved the mystery of
creation
maybe we should patent the universe
encourage everyone royalties for their
existence I now turned on the second big
question are we alone or is there other
life in the universe we believe that
life arose spontaneously on the earth so
it must be possible for life to appear
another suitable planets of which there
seemed to be a large number in the
galaxy but we don’t know how life first
appeared we have two pieces of
observational evidence and the
probability of life appearing the first
is that we have fossils of algae from
3.5 billion years ago the earth was
formed 4.6 billion years ago and was
probably too hot for about the first
half billion years
so life appeared on earth within half a
billion years of it being possible which
is short compared to the ten billion
year lifetime of a planet of earth type
the suggests that the probability of
life appearing is recently high if it
was very low one would have expected it
to take most of the 10 billion years
available on the other hand we don’t
seem to have been visited by aliens
I am discounting reports of UFOs why
would they appear only to cranks and
weirdos if there is a government
conspiracy to suppress the reports and
keep for itself the scientific knowledge
the aliens bring it seems to have been a
singularly ineffective policy so far
furthermore despite an extensive search
by the SETI project we have heard any
alien television quiz shows this
probably indicates that there are no
alien civilizations at our stage of
development within a radius of a few
hundred light years issuing an insurance
policy against abduction by aliens seems
a pretty safe bet this brings me to the
last of the big questions the future of
the human race if we are the only
intelligent beings in the galaxy we
should make sure we survive and continue
but we are entering an increasingly
dangerous period of our history our
population in our use of the finite
resources of planet Earth are growing
exponentially along with our technical
ability to change the environment for
good or ill
but our genetic code still carries the
selfish and aggressive instincts that
were a survival advantage in the past it
will be difficult enough to avoid
disaster in the next hundred years let
alone the next thousand or million our
only chance of long-term survival is not
to remain in red lurking on planet earth
but to spread out into space the answers
to these big questions show that we have
made remarkable progress in the last
hundred years but if we want to continue
beyond the next hundred years our
futures in space that is why I’m in
favor of manned or should I say person’d
space flight all my life I have sought
to understand the universe and find
answers to these questions I have been
very lucky that my disability has not
been a serious handicap indeed it has
probably given me more time than most
people to pursue a quest for knowledge
the ultimate goal is a complete theory
of the universe and we are making good
progress thank you for listening
professor if you had to guess either way
do you now believe that it is more
likely than not but we are alone in the
Milky Way as a civilization of our level
of intelligence or higher
this this answer took seven minutes and
really gave me an insight into the
incredible act of generosity this whole
talk was for Ted
I think it quite likely that we are the
only civilization within several hundred
light years otherwise we would have
heard radio waves the alternative is
that civilizations don’t last very long
but destroyed themselves professor
Hawking thank you for that answer we
will take it as a salutary warning I
think for the rest of our conference
this week professor we really thank you
for the extraordinary effort you made to
share your questions with us today
thank you very much indeed
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you