>> The universe harbors
two kinds of matter,
regular atomic matter,
like the one you and I are made of,
and dark matter,
which outweighs regular
matter five-to-one,
yet we cannot see.
What we can see however,
are its gravitational
effects on regular matter.
Take for instance the
image of a bullet cluster
in the upper-left corner,
where we can see the regular matter
a sit amid an X-ray light.
But when we map where the
mass of this cluster is,
we get the blue clouds.
It seems that most of the matter there
is not amid light, it's dark.
What is this dark matter?
We tried to answer this question
same way we answer every
question in science.
Formulate hypotheses
and try to confirm them
or rule them out.
During my PhD, I have
worked on the hypothesis
that the dark matter
is made of black holes,
like the ones shown in
the upper-right corner.
Black holes do not emit
light; they are dark.
But are they the dark matter?
We need to find out.
For that I developed two tests.
First, it's a well-known consequence of
Einstein's Theory of General Relativity
that when two black holes orbit each other
they create ripples in
space time, as shown here.
These ripples travel outwards
in the form of gravitational waves,
and can be detected here on Earth.
The Light Observatory in
the U.S. has been trying
to detect them for years.
We predicted that if the dark matter
was made of black holes, we should detect
between one and 10 of
these events last year.
Light O. detected three,
exactly within this window.
To confirm that this is
not just a coincidence,
however, we need a different test.
And again, Einstein
provides us with an answer.
Light gets bent near black holes.
So much so, in fact,
that it can cause more than
one light wave per source
to reach us, the observers.
This effect is called
gravitational lancing.
As it focuses light waves towards us
the same way a regular lens would,
if the dark matter was
made of black holes,
this would be a rather common occurrence.
And in my PhD, I developed the tools
to search for this kind of signal
with telescopes that are
being built right now.
These telescopes will yield data
within the next three to five years.
This will finally help
us answer the question
of whether the dark matter
was made of black holes
or not.
Thank you.
(audience claps)
