Translator: Ariana Bleau Lugo Reviewer: Hugo Wagner
Hello, thank you for this introduction.
So a physicist is a man,
or a woman,
but if it's a woman, you'd rather say a lady physicist,
it is someone
who must solve two problems:
the first one is to determine
the existing link between
the physical theories he uses to describe reality,
nature, the physical world,
and that physical world.
Do these theories
say anything about nature?
Do they connect with it?
Do they even match locally?
Or are they just nonsense?
Do they express the lack of clarity?
To answer that question
physicists carry out experiments
on every possible level,
sometimes of a really large scope,
to try to see whether their theories
meet, partly or totally,
with physical reality.
But a second less talked about problem
is to determine the link we have to establish
between what we call physics
and the ordinary language.
How can we convey what we know?
Since Galileo, the natural language of physics
has been mathematics.
So physicists write equations.
Mathematics is a sort of Greek,
it's all Greek to many of us,
and as Lacan put it so well:
"Not everyone has the good fortune of speaking Chinese in their own language".
So if you want to translate for the general public
the knowledge we have acquired thanks to physics,
we must dig into language
to embed in it a kind of foreign language
that will provide us with the means to express,
in our own language, after working it,
what physics has taught us.
That's the question I am interested in today,
and I will deal with it by choosing the issue of the origin of the universe.
Are we really talking about the origin of the universe?
Does the way we address it acknowledge
what we know about the origin of the universe?
That is nearly a political issue,
since as you know,
stating what was the origin of the universe
always implies getting a certain power over people's minds.
Some people tell us about the origin of the universe as if
they had just flown back from there on a space shuttle.
So how do we talk about the origin of the universe?
Well, in the 20th century, as you know,
we found out that the universe had a history,
and this history is still being written.
When I say universe, I mean the Universe.
I don't mean a part of the universe.
I mean the universe as such,
that is as a physical body.
For a long time, people thought that the universe was the shell of all physical elements,
when actually it is itself a physical element,
it is a physical body with global properties
that are irreducible to local properties.
How did we find that out?
Through two consecutive major events.
First, when in 1915 Einstein developed -
actually from 1907 and 1915 -
he worked on a new theory of gravitation
called the Theory of General Relativity.
It is that theory we use to describe the universe
- since it's gravitation that dominates on a large scale -
and that allows us - I mean the theory -
to apply physical properties
to the universe as such.
For example a global curvature determined by
its matter and energy contents.
The second event is a discovery
arising from an observation made by an astronomer named Hubble,
who observed the movement of the galaxies,
and realized in the late 1920s
that galaxies move away from each other all the more quickly
as they are farther apart from one another.
And when you put these two events together,
and you extrapolate towards the past,
that is you consider time going backwards,
you go back further and further into the past,
you notice that the further back the universe is in the past,
the smallest it is,
the denser it is, and the hotter it is.
And when you extrapolate all the way,
you hit upon what is called an initial singularity.
That is a punctual universe,
where punctual doesn't mean it got there on time.
It means it is the size of a point.
It is the size of a point, its density is infinite,
and its temperature is infinite.
And this initial singularity is often associated with a time zero
called the Big Bang.
The phrase was coined in the 1950s,
and you are all familiar with it.
What comes next is interesting,
because that scientific discovery was made
within our culture,
which promotes the idea that the universe was created.
So there was this kind of conjunction
between what we inherited from our culture - the universe was created -
and a scientific discovery
which tells us that the universe went through an initial singularity
which made everything that exists appear:
space, time, matter, radiation, energy, and so on.
Obviously, once that overlap was made,
a metaphysical questioning came along:
What was there before time zero?
How could the universe come from nothing?
Did God or some transcendental being play a part in it?
Who acted as a cosmic match? And so on.
It is a fascinating issue that we must not hinder
because it pushes reflexion forward.
But it is a premature issue.
It is premature as this questioning is not imposed
by contemporary cosmology.
Please acknowledge that when I extrapolate in the past,
and I hit upon that initial singularity,
actually, before I get to it,
I hit upon extreme physical conditions - a very high energy,
particles containing more energy than a high-speed train,
a very high temperature -
so that the particles in that universe
are subjected to forces other than gravitation.
They are subjected to electromagnetic forces,
they are subjected to nuclear forces.
However, the theory of general relativity
that I have used to extrapolate
does not describe those forces,
since it only describes gravitation.
It is called the theory of general relativity,
but in fact it is specifically a theory of gravitation.
Indeed I reach a moment
when the equations of general relativity become distorted.
Not because they are mathematically wrong,
but because they no longer describe the physical world
corresponding to the physical conditions I have just mentioned.
And that moment from which I can't extrapolate anymore
is called Planck's wall.
It takes place at the very beginning.
So that I don't know, I can't tell
what happened before Planck's wall,
the very notion of space-time becomes a problem
and I can't talk about a time zero either.
Then, the story doesn't stop here,
because for a very long time, for twenty-odd years,
many theoretical physicists
have been trying to figure out a theoretical framework
to climb over that Planck's wall,
that is to say building some formalism, or new concepts in physics,
that would enable us to describe
gravitation, electromagnetic and nuclear forces as a whole.
If we get such a theory,
then we are intelectually equipped
to climb over Planck's wall
and tell what happened before it.
You may have heard about the Superstring theory,
which falls into this research category
attempting to climb over Planck's wall,
and that considers more than 4 dimensions in space-time -
contemplating a 10 dimensional space-time.
Other theories consider that, on a small scale,
space-time is not smooth and continuous as we usually picture it,
but it is granular.
It is discrete, as we say.
Eventually, several ideas are being tested
but they don't allow us to describe the primary universe very accurately,
because if for instance we take the case of the string theory,
particles are described by strings,
the strings are so entangled that calculations are impossible.
We simply manage some approximations,
we simplify the equations.
It enables us to build scenarios.
For example, if we look at the scenario associated with the superstring theory,
we can see that this theory predicts that,
at no point in its history,
and at no point in its space,
was the universe able to go beyond a certain maximum temperature,
which is very high, but not infinite.
This means that the initial singularity
associated with the first Big Bang model,
that only took into account gravitation along with Einstein's theory -
that singularity doesn't exist anymore in the string theory.
It vanishes, and we could say that within this framework,
time zero, to which we link the Big Bang,
is having a bad time.
So what's funny here is that
if you look at what happens with other theories,
other considerations,
we reach the same conclusion.
The singularity must go, and the Big Bang as we imagine it
is replaced by what we call a transition phase.
That is to say that there is a contracting universe,
it becomes denser and denser,
it reaches the maximum temperature allowed by the string theory,
and once it has reached it, it obviously can't go on shrinking
so it bounces on itself - there's no more singularity,
no more time zero, no more Big Bang in the usual sense.
So we can conclude
that we don't have scientific evidence
that the universe has an origin,
and I mean origin in a radical sense,
that is the absence of any thing becomes something.
We don't have any evidence that there was once nothingness.
A second conclusion is that, indeed,
it doesn't prove that the universe had no origin.
It merely proves that science didn't get it.
And we can ask ourselves: if the universe had an origin,
would we be able to tell it?
Would we be able to conceive it?
Would we be able to explain it?
My answer is we wouldn't.
Because to explain the origin
is to tell how nothingness, or a total absence of things,
can become something,
and to explain that,
we must grant nothingness
some properties allowing it to stop being nothingness.
We must set in it a sort of egg
that would be able to give birth to something else than itself.
But an egg placed into nothingness
is an egg.
So here we get caught in aporias
Greek philosophers had already alluded to,
and which blow up in our face today in 2011
because of the contemporary cosmology.
So here is my conclusion.
It's an anecdote.
You know that a few years ago, Pope John-Paul II
met astrophysicist Stephen Hawking in Vatican.
At the end of their exchange,
John-Paul II allegedly said to Stephen Hawking:
"Mister Hawking,
we agree that what came after the Big Bang
is yours,
what was before is ours." (Laughter)
And I think that, considering what I have just told you,
that anecdote, which is funny, indeed you laughed,
deserves -- the impact of that anecdote
deserves further questioning.
Thank you.
(Applause)