Fast Radio Bursts the mystery that weighs the Universe
[Music]
we all love a mystery
every good detective story has a mystery
and clues suspects
and red herrings
scientists are the same
solving mysteries is our job
it’s my job
and right now i’m deep into a case that
began with a mysterious signal
let me take you back to 2007.
a team of astronomers was looking at
data taken with the park’s radio
telescope in new south wales
they were looking for anything strange
anything different anything unexplained
they’re looking for a mystery to solve
and they found
nothing
and
nothing
and nothing
and nothing and then boom
a giant burst of radio waves
lasting one thousandth of a second
and then nothing
what caused this fast radio burst
where did it come from
might there be more out there these are
the kinds of questions that get
scientists excited
but before they could investigate
further
they had to ask themselves one very
important question
did that burst
even really come from space
you see
electronic equipment can also generate
bursts of radio waves
how did they know that this fast radio
burst
wasn’t produced by somebody using their
phone too close to the telescope
they didn’t know
see the problem was this burst came and
went in a thousandth of a second
it was gone
and what’s more
it was long gone the data the scientists
have been looking at had been taken back
in 2001
six years before they discovered it
any clues as to its origin had long
since vanished
so there was only one more thing they
could do detect more of these fast radio
bursts
and this time they made sure that they’d
identify these signals the instant they
arrived
they found 16 more fast radio bursts
what new clues as to the origins did
these contain
well to understand that you need to
understand a little bit about the park’s
radio telescope itself
it’s like the megapixel digital cameras
you probably all have in your phones
except it detects radio waves
and it only at the time had 13 pixels
now why does this matter
well things in the universe might be big
but they’re also really really far away
a star a million kilometers across
might appear as a tiny speck of light in
the night sky
if these fast radio bursts had been
coming from space
they would appear in only one of these
radio pixels in the parks radio
telescope
these new 16 bursts appeared in all 13
pixels
they can’t have been coming from space
so that was a
disappointment but the mystery wasn’t
solved
so the suspects now became the
electronic equipment near the park’s
radio telescope
and in searching for the culprit
the astronomers were aided by one very
important clue these signals
all seem to come around lunchtime
it was the microwave that the
astronomers used to heat up their lunch
when the microwave door was opened
before the power was turned off a burst
of radio waves would escape and voila a
fast radio burst
mystery solved case closed
except
scientists also detected four additional
bursts
and these bursts occurred in only one
radio pixel
when the microwave wasn’t on
the microwave turned out just to be a
red herring
there really were fast radio bursts
coming from somewhere in the universe
but where we could now go back and ask
these questions what was producing fast
radio bursts how many more might there
be
but where was the next clue going to
come from
it turned out that clue came from the
radio signal itself
you see just like radio stations have
different frequencies
the radio waves from space also have
different frequencies
and as these radio waves are traveling
through the universe
the very small amounts of gas in the
universe
cause the low radio frequencies to
travel a little bit slower than the high
radio frequencies
by measuring the time delay between the
high and the low radio frequencies
scientists could tell how much gas these
bursts had passed through
so
how much gas had they passed through
more gas than is in our solar system
more gas even than is in our own galaxy
these bursts must have been coming from
somewhere in the distant universe
okay so we had our answer
not our galaxy
it’s not much of an answer there’s a lot
of universe out there
to do better we had to build a new radio
telescope
ascap
this is located right here in western
australia
maybe 600 kilometers away in the desert
it’s actually 36 telescopes all working
together to act like just one big
telescope
now not only could ascap detect fast
radio bursts
but it could determine the direction
that they were arriving from to within
100
000 of a degree
that’s about the size of a coin
seen at a distance of 100 kilometers
when scientists
used as cap to detect a fast radio burst
we then got the world’s most powerful
optical telescopes in chile hawaii and
the hubble space telescope in orbit
and we pointed them back in the
direction that this fast radio burst
came from
and this is what we saw
this is the galaxy
it’s a very distant galaxy
this is what a galaxy looks like
not when you have them nice up close to
create beautiful images perhaps for
other tech talks
but rather
when this galaxy is so far away
that you have to push the world’s most
powerful telescopes to the absolute
limit just to detect that it’s there
the fast radio burst that arrived from
this galaxy
took 3.5
billion years to reach us
now
how could it possibly be seen over such
a huge distance
imagine how energetic it must have been
the energy from this fast radio burst
was the same as is produced by our
entire son
in a whole year
packed
into one thousandth of a second
and that’s not even the most remarkable
thing about them
in order to produce a birth that lasts
such a short time
whatever is producing them must be
really small
now
i’m an astronomer
what does small mean to me
we’ll take the earth 12
742 kilometers in diameter
the earth astronomically speaking is
tiny it’s minuscule it barely even
exists
how could something as small as this
earth
produce something that’s seen after 3.5
billion years
whatever was producing this fast radio
burst
in order for that to last only a
thousandth of a second
had to be no more than 10 kilometers in
diameter
that’s smaller than the city of perth
so what could possibly be doing this
we don’t know
but we have suspects
one suspect is something called a
neutron star
a neutron star is like a giant atomic
nucleus
only a few kilometers in diameter
but so dense it has the mass of our
entire sun
we’re testing this theory by looking at
neutron stars in our own galaxy the
milky way and seeing if we can find fast
radio bursts coming from them
another theory is when two neutron stars
collide if that a collision occurs they
should produce gravitational waves which
are ripples
in the fabric of space-time and we’re
searching for these that may or may not
occur at the same time as these fast
radio bursts
but for now we don’t know
and that’s okay because science isn’t
about knowing
it’s about finding out
however
the mystery of fast radio bursts
is not the only mystery i’ve been
working on
back in 2007 there was another mystery
puzzling astronomers
we have this theory the big bang which
describes the birth and evolution of our
universe
it’s a beautiful theory it explains so
much
and this theory predicts how much gas
there should be in the universe
but when astronomers went out and looked
for this gas and they added up all the
gas in stars and galaxies
they couldn’t find it all
the mystery of the missing gas
my late mentor jean-pierre mccar had an
idea
do you remember how i said earlier that
when fast radio bursts are moving
through the universe
the low frequencies
go slower than the high frequencies
because of the gas they pass through
he realized that if we could measure the
time delay between the high and low
radio frequencies from these fast radio
bursts coming from distant galaxies
we could measure all the gas in the
universe
so that’s exactly what we did
a team of astronomers here at the
international center of radio astronomy
research in perth together with other
collaborators in australia and overseas
used as cap to detect fast radio bursts
we measure the time delay between the
high and low frequencies
and we determine the distant galaxies
that we’re coming from
and we measured all the gas in the
universe
how much was there did we have to
overturn decades of scientific thinking
and come up with a completely new model
for everything for the entire history of
the universe
or was the big bang theory correct
did we find the missing gas
we did
thankfully
we found exactly the amount predicted by
the theory of the big bang
but where was this missing gas well it
turns out
this gas is almost invisible
it’s not dark matter that’s something
else entirely but it’s not bright either
it doesn’t glow like the gas in stars
and it’s not dark it doesn’t absorb
light
like the gas we see in our own milky way
it just sits in the giant voids in
between galaxies
and does nothing
nothing
except slow down the low frequency radio
waves
scientists love mysteries and we just
solved one of them
but do we have all the answers
not by a long shot there’s still loads
of unsolved mysteries out there
what
is producing fast radio bursts
how can something so small
produce something so powerful
and might there be one lurking in our
own galaxy the milky way
just waiting to be discovered
science isn’t about staying safe
it’s about venturing into the unknown
and so
our investigation continues
we have new evidence to uncover
new forensic data analysis to perform
and we’ve got loads of suspects
we’ll solve this mystery too
thank you
[Music]
you