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