- So I'm Laura Mersini-Houghton,
I am a cosmologist and a professor of physics
at the University of North Carolina.
So I've been working on this theory of the origin
of our universe from a quantum multiverse.
What brought the idea about was the way of thinking
that our universe started only 13.8 billion years ago
and it's only 10 to the power 27 centimeters.
That's 10 with 27 zeros behind.
So although these are large numbers,
they are not extremely large.
They are not inconceivable and it's completely reasonable
to ask what was there before.
Say 14 billion years ago, or 15 billion years ago,
and what lies beyond the edge,
the horizon of our own universe.
These questions led me to propose that we introduce...
Since the universe was small in its infancy,
we introduce a wave function of the universe
before our universe went through
Big Bang inflation and grew.
And we addressed that question of how our universe
came into existence by using quantum theory,
by solving those equations.
And then that led to a larger and more intricate picture
of the cosmos where our universe is just one of many
similar universes that followed similar histories to ours,
and are still out there.
And we are just a humble member
in that vastness of the cosmos.
And in that sense, when you think about it,
not long ago, people thought that the earth
was the center of the universe.
And now, we are saying that the whole universe
is not the center of the cosmos,
but rather it occupies some corner
into that beautiful vastness that we call nature.
And that's an extension of the Copernican principle
to the whole universe.
So the common way of thinking in cosmology,
what we call the Standard Model of Cosmology,
is that our universe was a tiny smooth patch of spacetime
filled with a lot of energy
and then it was that energy that propelled the universe
into an accelerated growth,
and then made it grow very large, very quickly.
That type of energy, the same type of energy
seems to occupy, to dominate our universe at present,
and that goes under the name of dark energy.
Our universe is a plant.
At least the ingredients in our universe
are a plant of radiation, light, photons, matter,
including dark matter and energy.
Energy is the least familiar of all of us
because we see matter and radiation,
we see light around us every day.
So those are familiar concepts,
but the energy has got strange gravity properties
in the sense that it likes to blow things up.
It takes a small patch of space and it propels it
into a fast growth, into an accelerated growth.
We have come across that type of energy early on
and it seems to dominate the universe now.
What will happen in the future as our universe grows
is that all kinds of matter and light will dilute away
with the volume increase of the universe.
However, this type of energy, dark energy,
which is very similar to the inflationary energy
that produced the universe,
that type of energy seems to grow
with the volume of the universe
because it has a strange property that is density.
The amount you can stuff in one unit of volume,
that density has to remain a constant.
And therefore, the more volumes you produce of space
then the more of that energy you are producing.
In short, in not so far future,
that energy will be the main component left in the universe.
And therefore, it determines how our universe will end.
And there are many things we don't know, what dark energy is
in the same way that we don't know
what gave that energy of inflation.
There are many scenarios on what type of energy,
dark energies, and how the universe will end.
The three big classes are either a cosmic heat death
where dark energy is a pure constant,
it never varies with time.
And therefore, the universe grows infinitely large
but it's completely empty.
And if there are no fluctuations,
then it can't produce new structures including humans,
and stars, and planets.
And therefore, everything comes still.
That is the cosmic heat death in the universe,
that's the most dreadful of all the possible scenarios.
Another scenario is that dark energy,
although seems to be a constant at the moment,
in the far future, it might start behaving like matter.
In that case, we'll have too much matter in the universe
and the whole universe will go through a Big Crunch
like black hole where it will vanish in a place of fire
in one single point.
The next scenario,
which is more of a science fiction scenario,
is when dark energy makes the universe grow even faster
than the energy of inflation.
In that case, the very fabric of spacetime
will get ripped apart,
and that's called the Big Rip scenario.
Like almost any human now
or in the last few thousand years of evolution,
I approached the question of how our universe
came into being, and what was there before the Big Bang,
and what lies behind the horizon of our universe,
with that simple childlike curiosity,
without expecting any answer.
However, my decade long work along with collaborators
led me to a theory of the multiverse of our origins
from the multiverse,
which seems to have been successfully tested
by observation as well.
And I discuss all of that in my book
as well as the single-mindedness that is needed
and the hard work that goes
behind exploring those questions,
as parallels with my childhood in communist Albania.