Our universe is a vast expanse, and while we can stare up at the night sky and wonder at the mysteries our sky holds, there is so much more that we can’t see with just our eyes. Using today’s powerful telescopes, combined with our computational ability to interpret enormous amounts of data, we are now at a time when cosmologists can do more than just look upon our skies with wonder – they can now make measurements, and calculate theoretical models of the far reaches in our observational universe.
For postdoctoral fellow Alex Krolewski, who has been awarded the 2020 AMTD Postdoctoral Fellowship in Science, analyzing the universe quantitatively is an opportunity to test some of the standard models of physics on astronomical scales.
“I’m specifically interested in testing Einstein’s theory of General Relativity because we want to see if it works on all the scales in the universe. Also, looking at General Relativity may give us clues on what is going on with dark energy.”
Krolewski is just starting his 3 year postdoctoral fellowship in physics and astronomy at the University of Waterloo, where the AMTD fellowship will make it possible to work closely with collaborators around the world. The AMTD Fellowship is a new initiative to create a unique postdoctoral program bringing together world-class scholars from top universities across the globe.
“I’m super excited about the travel support that the AMTD fellowship offers,” says Krolewski. “Astronomy depends on collaborating with a variety of people from widely separated places, and once we are able, I look forward to being able to visit collaborators around the world.”
Krolewski
chose
to
come
to
Waterloo
because
of
the
countless
opportunities
for
collaboration
within
the
physics
community
in
the
region.
Between
the
University
of
Waterloo
and
its
newly
established Centre
for
Astrophysics,
and
the Perimeter
Institute,
Waterloo
Region
is
an
outstanding
hub
for
physics
collaboration.
During his time at Waterloo, he will be working with physics and astronomy professor Will Percival, who is currently involved with multiple large-scale surveys of the galaxies in our universe. In particular, Krolewski plans to use data from the Dark Energy Spectroscopic Instrument (DESI), which he has already been involved with during his PhD at University of California, Berkeley. DESI is a global collaboration that is observing about 40 million different galaxies, and measuring their position and the speed at which they are moving away from the Earth.
In order to put General Relativity and other recent cosmological measurements to the test, Krolewski will be looking at the background signal of the early universe – the Cosmic Microwave Background (CMB). This is the earliest source of light we can measure because it was the first radiation to escape from the early universe. As this microwave radiation travels across the expanses of space and time, the light’s path is deflected by the gravitational fields it passes. This is known as gravitational lensing. By measuring the gravitational lensing of light, cosmologists can calculate the position and density of mass that deflected the light.
Krolewski
will
use
DESI’s
measurements
of
galaxies,
alongside
a
variety
of
other
data
sets
to
measure
the
gravitational
lensing
that
the
CMB
radiation
experiences
passing
by
the
galaxies.
Through
this
research,
he
hopes
to
learn
about
and
answer
the
questions
“What
causes
the
universe’s
expansion
to
accelerate”
and
“What
is
the
mass
of
the
neutrino?”.
Neutrinos
are
small
subatomic
particles
that
do
not
have
a
charge,
and
usually
pass
through
normal
matter
undetected.
Since
they
are
usually
undetectable,
one
of
the
only
ways
to
learn
about
neutrinos
is
to
observe
their
impact
on
the
distribution
of
matter
and
galaxies
in
the
universe.
Measuring gravitational lensing will provide a large-scale system to test gravity and General Relativity, and also may resolve some inconsistencies between cosmological measurements in the distant universe and the local universe. Additionally, gravitational lensing measurements from DESI may also provide some clues to the universe’s biggest unknown component – dark energy, a force that is currently theorized to make up 70% of all the energy in the universe and causes the accelerated expansion of our universe, but is completely unknown.