How the Universe Works (2010–…): Season 3, Episode 9 - The Search for a Second Earth - full transcript

the earth is not alone in the last few

years scientists have found that our

planet is just one of billions out there

in the Milky Way galaxy

there's a really decent chance that

there are more planets in the galaxy

than there actually are stars

we're now scouring these planets for

evidence of atmospheres liquid water and

life itself

we are going to know where in the night



sky

you can point and find another earth we

have a scientific method to actually

determine whether there is life on

another planet another earth alien life

the truth is out there but are we ready

for it

the earth gives us the blueprint for

life as we know it the Sun warms our

oceans creating the perfect environment

for all scales of life from the very

smallest to the Giants that eat them

Mountains Plains and forests teen with

plant and animal species and it's all



cocooned in a thick atmosphere that

nurtures and protects for us it's

paradise twenty years ago

a group of scientists decided to find

out if there were other paradises out

there so-called exoplanets orbiting the

stars that light up our night sky just

in the last decade we've had this

explosion and the discovery of these

exoplanets which has revolutionized the

whole field of astronomy

the early days of exoplanet hunting

turned up enormous jupiter-sized planets

by the boatload

these hot gas each iins proved easy to

find but hostile to life as we know it

now though new telescopes and

technologies have allowed astronomers to

target smaller planets earth-sized ones

and the stunning results have

transformed the way we see our place in

the universe

we now know something precious that our

planet Earth is not unique it's not even

rare there are tons hoards flocks if you

will of other earth-like planets out

there fluttering around the other stars

some stars probably have multiple earths

orbiting them that's how common

earth-like planets are

we owe this exoplanet explosion to a

Space Telescope called Kepler the Kepler

space telescope is an observatory in

space that is staring at one spot in the

sky it's looking at roughly 150,000

stars and it's looking for the tell-tale

sign of planets orbiting those stars

then every time the planet passes in

front of the star it'll block a little

bit of that star light and if you plot

the amount of light you get from the

star it drops and then goes back up as

the planet passes in just four years

scientists have detected over a thousand

exoplanets just from their shadows

but Kepler has a problem it can't tell

if the shadow is made by a giant gassy

planet hostile to life or a potentially

habitable earth-like planet

what we're measuring when a when a

planet passes in front of its host star

is what is the area of the planet

relative to the area of the star that

it's passing in front of it's a it's a

ratio basically but Jupiter sized

planets crossing giant stars full Kepler

because they block the same fraction of

light as earth sized planets crossing

smaller stars to prove a planet is earth

sized you first need to measure the size

of its star using the world's biggest

telescopes but that's time-consuming

expensive and it creates a huge

exoplanet backlog but astronomer Kavon

Stassen has come up with an ingenious

shortcut by turning the raw Kepler data

into sound what the Kepler telescope

directly measures and the data that we

use is small changes in brightness that

a star produces due to the flickering

arising from the boiling and roiling

motions of gas at its surface what we

can do then is take that light

flickering data and transform it in a

sound studio for example into audio

frequencies and so then we can represent

with sound what we're actually detecting

with light

the bigger the star the more its surface

boils with activity making big stars

flicker more powerfully converted to

sound this boiling becomes a deafening

hiss well let's listen to some stars

okay can we hear the red giant star

please I'm gonna bring up the volume

here

this is a very large star very low

density and so that large amount of hiss

is the result of vigorous boiling and

churning at the surface of this large

red giant star can we get the dwarf star

please on smaller stars sunspots

dominate the sound profile creating a

low-frequency drone

actually sounds like a series of clicks

come but below the clicks lies the faint

hiss Kavon needs to size the star

underneath it at a very low level is a

little bit of hiss

that little bit of is actually the light

flickering that we're interested in by

accurately measuring the level of this

background hiss Kavon can work out the

size of the star in this case it's

around the same size as our star the Sun

cave-ins work could be the breakthrough

exoplanet hunters have been hoping for

it's cheap the results are practically

instantaneous and once you know the size

of the star figuring out the size of the

planets casting shadows over it is

child's play

it feels like a very privileged time to

be a scientist to be an astronomer

working in this area and contributing to

the hunt for the next earth here we are

actually discovering these worlds by the

hundreds and now on the cusp of being

able to identify the next earth

astronomers suspect there could be tens

of billions of rocky earth-like planets

in the Milky Way places where perhaps

life has gotten a foothold

but life as we know it requires water

how can scientists possibly find this

miracle substance on planets light-years

away water divides our living world

those with it prosper

those about suffer remarkably the water

we drink today contains the same atoms

as the water dinosaurs drank 100 million

years ago it's the same water that

formed clouds of the earlier four

billion years ago and every organism

that has ever existed on earth has used

this single ration of water as the

biochemical powerhouse that keeps it

alive

on earth all life requires liquid water

to grow and reproduce it's the common

ecological requirement for life liquid

water is just so good for getting

evolution going molecules can dissolve

in the water actually interact with each

other for more complex chains it does it

with charge there's positive charges and

negative charges separated between the

hydrogen and the oxygen in h2o those

charges break apart the hydrocarbons the

carbon-based molecules that persist

everywhere in nature

now that's very rare hardly any other

liquids do that so liquid water is a

natural starting place when you look out

into the universe and say what planets

could possibly have life

to understand how much liquid water is

out there astronomers must first

calculate how common water is in all its

forms

amazingly they find it everywhere they

look water is incredibly common in its

gaseous form we see water vapor filling

the space between the stars we see it in

clouds of material that are actually

forming new stars and planets right now

since water is a fundamental building

block of stars and planets exoplanet

worlds must surely have it in abundance

but if you're looking for life you need

to find liquid water and plenty up to

find it

astronomers take their cue from a fairy

tale

everybody knows the famous story of

Goldilocks and the three bears and the

the cup of para girar one was too hot

one was too cold I was just right when

it comes to cooking up life like a

porridge you need to have an environment

that's not too hot not too cold just

right and traditionally we look for that

at a certain distance around a star at

first astronomers based this magical

distance known as the Goldilocks zone on

the Earth's orbit around the Sun but as

they found more and more exoplanets

they've had to re-evaluate the

boundaries for liquid water there isn't

a single distance it depends on the

brightness of your parent star a dim

star you need to be closer a hot star

very bright need to be farther away

scientists have calculated just how many

rocky planets may lie within the

Goldilocks zone of their stars

it comes out to over 30 billion

potentially watering worries even more

remarkably recent discoveries have shown

us it's not just planets that can bask

in the warmth of the Goldilocks zone

there may be moons paint blue with

oceans - most of the planets were

finding our big jupiter-sized planet

however a lot of them were are orbiting

roughly where the earth is orbiting the

Sun so even if the planet that we're

finding can't support life it could have

a moon a moon with an atmosphere that

could support life

and the biggest of these rocky moons may

resemble our home there could be

billions upon billions of XA means out

there and even perhaps countless

paradises teeming with life

David kipping searches for exomoons by

looking for double dips in the

brightness of distant stars we look for

XA means in a very similar way to the

way that we look for planets by looking

for them transit the host star

now if that planet had a moon then we

should expect to have one big dip due to

the planet and then one smaller depth

either to the left or to the right due

to the new

habitable exomoons may play host to one

of the most spectacular sights in the

universe

imagine a warm rocky world just like our

own with oceans mountains but in the sky

a massive ringed planet with a fiery

sister moon shooting hot magma into

space

exoplanets and now the vast potential of

exomoons int a galaxy filled with the

possibilities for life but a rocky

surface and liquid oceans may not be

enough

biology needs the breath of life air

backlit by the Sun a halo appears around

the earth a pale blue ring of light our

atmosphere and we owe it everything the

Earth's atmosphere provides the gases

that fuel the biochemistry of advanced

life but it also protects the oceans

from the full fury of the sun's rays

preventing the water from boiling away

into space without an atmosphere there

would be no wind no rain no fresh water

and probably no life atmospheres are

absolutely essential for life take a

look at the planet Earth and you realize

that just like the skin of the Apple the

skin of the apple preserves the Apple

well the atmosphere of our planet

preserves the oceans and makes possible

the presence of life as we know it

scientists in search of living

exoplanets hope to detect the thin gassy

envelope that should surround these

alien worlds to do it they're turning to

the power of rainbows in the same way

that water splits sunlight into a

rainbow astronomers use instruments to

split starlight into a band of colors

called a spectrum

it's one of the oldest tricks and

science

and one of the most revealing several

hundred years ago scientists first began

to take something like a prism and put

it in front of their telescope so he

started taking the light from stars like

the Sun and actually spreading it out

into a spectrum and what they saw was

kind of surprising so instead of seeing

a rain continuous rainbow of light they

saw that rainbow but they saw these dark

lines superimposed on top

each chemical elements of the star's

atmosphere absorbs different parts of

the spectrum creating signature dark

bands for instance up the top there's a

pair of lines in the yellow part of the

spectrum which are due to sodium like a

DNA profile for stars spectral analysis

has taught us almost everything we know

about stars today but these same lines

may hide a marvelous secret the faint

signal of alien atmospheres and perhaps

also alien life so the challenge is that

these planets are very small and very

faint so we can't actually go and

directly measure the light emitted from

the planet the same way that you go and

measure this lovely spectrum for the Sun

instead we have to rely on more indirect

methods so one indirect way of doing

that is to wait until the planet passes

in front of the star when the light of a

star passes through an EXO atmosphere

the gases that surround the planet

should stamp their own faint lines on

the star's spectrum so as we watch the

light from the stars transmitted through

that atmosphere its

atmosphere is going to act like a little

filter so a part of the star light is

going to pass through that atmosphere

and we're gonna see that in printing

extra lines on it which are due to the

planet's atmosphere so that change in

the spectrum tells us something about

the properties of the planet's

atmosphere

the one chemical astronomers most want

to find is oxygen because only life can

produce enough oxygen to be easily

detected it's a so-called bio signature

the race is now on to find bio

signatures in the atmospheres of rocky

exoplanets and while some groups look

for rainbows indirectly others are

tackling the challenge head-on 29 all

right we're off

then Oppenheimer is part of a team

trying to take direct photographs of

exoplanets using massive ground-based

telescopes

we're within minutes of taking our first

long exposure and I hope it's good the

greatest challenge to imaging exoplanets

is the blinding light of the parent star

which shines tens of millions of times

brighter than the planet itself

the trick is to stop the light of the

star from entering the telescope sensors

by blocking it using a series of masks

and lenses called a coronagraph right

now we're standing right underneath the

telescope's primary mirror and the light

comes through a hole in the middle of

the mirror and goes into this crazy box

here which is full of optics motors

sensors and electronics that all allow

us to precisely control the star light

that's coming through the system using

state-of-the-art software they

manipulate the coronagraph to black out

the unwanted light under good conditions

we can actually carve dark holes into

this image of the star so that we can

see really faint things in those regions

coronagraphs present an intriguing

problem though errors within the optics

produce tiny flares of starlight called

speckles that look just like exoplanets

but man has come up with an ingenious

way to tell speckles from planets so

we've developed a technique where we

exploit an aspect of speckles which is

that they change position in the image

depending on what color you take your

image at so Ben takes the same image of

the star through different color filters

and runs them like a movie the speckles

appear to move across the screen but the

planets stay stuck still allowing Ben to

easily pick them out and so I'd like to

point out that there is a little thing

right here that if you watch for you're

careful you'll notice that it doesn't

move and the speckles are washing over

it

this stationary blob is a candidate

exoplanet and below it and to the left

is a second they both appear to orbit a

star around 200 light-years from the

earth just a decade ago capturing an

image like this through a telescope was

unthinkable but today thanks to the

ingenuity of astronomers like Ben we

have hundreds

and by analyzing the light for these

distant worlds scientists can work out

their chemical composition

and potentially the fingerprints of life

at this point we're studying much larger

planets gaseous things like Jupiter that

most likely don't have any kind of life

like we know it but that's a first step

and we're going to fainter and smaller

and smaller planets as time goes on as

we develop this technology in the

not-too-distant future scientists may be

able to simply scan a star for

earth-like planets and find the

signature of life there we can look

right at the light from a little planet

around its distant star and that opens

up a whole range of possibilities for us

to not just detect the planet but to

starting the planet I mean this all

sounds like science fiction but there is

a reality to this we have a scientific

method to actually determine whether

there is life on another planet life is

one thing intelligent life another all

together that requires billions of years

and a powerful force field like the one

we owe our lives to every day

if an alien astronomer were to file a

report on our home solar system they

might make a surprising observation

because of all the eight planets that

orbit the Sun they could easily conclude

the two not one were suitable for life

it's an easy mistake to make because the

Sun has two planets within its

Goldilocks zone

the Earth and Mars

both planets have surfaces warm enough

for liquid water to pool on but while

the earth is blessed with warm liquid

oceans Mars is dry and dead

the one crucial difference between these

two planets could be the key to finding

truly habitable exoplanets a magnetic

shield our Sun is constantly hurling

deadly radiation out towards us only our

magnetic shield the magnetosphere saves

us without it the solar wind would blow

our atmosphere away and without an

atmosphere liquid water could not exist

on the surface in order to have liquid

water not only do you need the right

temperature but you need the right

pressure you know if there were no

atmosphere here right now even at the

same temperature we are today all of the

water would boil off into vapor

immediately so where does the Earth's

magnetosphere come from and why does it

Mars have one actually in the past both

Earth and Mars had magnetospheres but

Mars lost its around 4 billion years ago

and with it the potential for life

both the earth and Mars were born into a

realm of violence asteroids smashed into

their surfaces turning rock and metal

into a molten mass

as they started to cool a solid crust

formed on surface but the molten metal

below churned as the planets turn

inducing a magnetic field which rose

high up above the surface of both

planets at the same time active

volcanoes pumped gas into the space

around each planet protected by the

newly formed magnetic field these gases

built up into thick atmospheres creating

the air pressure for liquid water to run

on the surface for over a hundred

million years both Mars and Earth for

warm wet paradises primed for life to

take off then quite suddenly

Mars's magnetic protection disappeared

the solar wind blew its atmosphere into

space and its oceans boiled away leaving

the dry sterile red rock we see today

Mars is fundamental problem is is that

it's smaller than Earth and because it's

smaller the internal core of Mars cooled

down and solidified and once it becomes

a solid metal there's no more magnetic

field magnetic field shuts off

essentially and the atmosphere therefore

is vulnerable to both energy and

radiation from the Sun and the rest of

the galaxy and probably just blew off

whatever life was on there at least on

the surface is now completely exposed

all rocky planets will one day lose

their magnetospheres as their cores cool

and turn solid so to know if an

exoplanet is alive you need to work out

if its magnetosphere is still active but

magnetospheres are tough to measure

because they are unbelievably weak the

earth has a magnetic field of

approximately half a Gauss which when

you think about it is actually really

weak our fridge magnets are about a

hundred Gauss they're much stronger

Excel planets are too far away for us to

measure such weak magnetic fields

directly but there is an indirect method

when electrons in the solar wind

interacts with a planet's magnetosphere

they emit radio waves that beam out into

space turning the planet into a giant

radio beacon

astronomers like of geniu hoped to use

these signals to spot habitable

exoplanets not only that the frequency

of the signal should also tell her how

big the planet is if we're looking for

the magnetic signature in the radio

waves of a giant planet say a hot

Jupiter we expected to have a strong

magnetic field and therefore would have

a high frequency and around 100

megahertz kind of where the limit of

this radio is however a weaker field

like Earth's requires us to go down to

lower and lower frequencies so instead

of a hundred megahertz we go down to ten

megahertz but hunting for exoplanets at

ten megahertz presents a unique

challenge

because the Earth's own magnetic sphere

creates a deafening radio roar at that

frequency so define alien Earth's using

radio requires a dish in space when we

want to look for magneto spheres of

extrasolar planets we really need to get

outside of the earth-moon system in

order to get away from all the radio

frequencies that are bouncing around the

earth

with a slew of new technologies and

upcoming technologies scientists are

edging ever closer to the ultimate prize

finding a second earth

I wouldn't be surprised if we have that

data about an earth and about life on it

around another star in 10 or 15 years

I'm hoping to see that soon

using shadows rainbows and now radio we

finally have the tools to detect a

planet just like our own

but in the rush to find the Earth's

identical twin are we missing something

big

what if earth is an outlier a freakishly

lucky place on the very fringes of

habitability could there be another kind

of planet out there even better for life

for years astronomers have scanned the

heavens for planets that could sustain

life they faced their search on the

earth seeking the exact same conditions

an exact same size I think right now

there is a huge focus to finding

earth-like planets now whether or not

there actually is life there that is

another question altogether but after 20

years of searching for an earth clone

the exoplanet hunters may be about to

switch targets recent observations have

revealed a brand new class of planet

it's one that may eclipse our own home

we've learned something in the last few

years that really shocked us with the

Kepler space porn telescope we have

found hordes of planets that are a

little bigger than the earth we never

imagined that there would be such

planets in fact in our own solar system

there are no planets between the size of

the earth and the next largest planet

that of Uranus and Neptune astronomers

call these mysterious planets super

Earths

super earths are about three to five

times the mass of the earth and there's

nothing like that here we don't know

what they're like it's an entirely alien

sort of planet in just the last few

years astronomers have begun to imagine

the conditions on this new class of

planet and they've come to a startling

conclusion super earths could be super

habitable

there are probably planets out there

that are even more hospitable for life

planets that have even more chemicals

necessary to create the organic

materials that create life conditions

that make it more likely to get life off

the ground

imagine a rocky planet twice the size of

the earth

dramatic volcanism on the surface

betrays a vast heart of fire that beats

within its core

we expect that a heavier earth will be

more geologically active that the

increased amount of geothermal heat

within the super earth will lead to

stronger motions of the magma underneath

the crust

belching volcanoes dot the surface of

this super earth

their gases feed a super thick

atmosphere and help to regulate a super

stable climate many times life on Earth

was nearly extinguished for example once

upon a time the earth was snowball earth

completely covered in ice maybe in these

other planets there are earth in which

snowball earth never happened that the

taught climate was always stable and

temperate the grip of gravity is three

times stronger here than we're used to

it pulls mountain ranges down to a third

the height they'd be on earth

gravity also flattens the ocean bed

making shallower CDs filled with

volcanic island chains and the

nutrient-rich waters that surround these

archipelagos provide the perfect

conditions for life

in these other planets perhaps they have

conditions which would make DNA get off

the ground much earlier and flourish

much more quickly

finally our super earth may be protected

by a super magnetosphere the magnetic

field strength is a condition both of

the mass of the planet as well as its

rotation speed and so it is quite likely

that a planet that is a couple of times

bigger than the earths would be able to

develop a stronger magnetic field may

shield the planet even better than our

magnetic field shields us having a

stronger magnetosphere would be a

distinct advantage for life on a super

earth surrounding the Milky Way's most

plentiful kind of star the M dwarf or

red dwarf star red dwarf habitable zones

are much closer in than the earth is to

the Sun because their host star is so

dim as if you took the terrestrial

planets in our own solar system and

zapped it with a shrink ray gun and

shrunk them down to orbital periods that

are less than about 30 days meaning that

they're very close to their stars some

astronomers believe these planets are at

risk from solar activity such as deadly

flares

but a super-earth with a super

protective magnetosphere may well resist

these deadly rays allowing life to

flourish under a psychedelic sky full of

swirling Aurora's if one was standing on

a super earth we would see the aurora

come down to lower latitudes might get

different colors

if I had the opportunity to travel to

one of these exoplanets I would snap

that up pretty quickly most intriguing

of all if life does exist on a red dwarf

super earth it could be home to the

longest-lived civilizations in the

entire universe the advantage of the M

Dwarfs is that they last for much longer

and if you had a super earth then

keeping a strong magnetic field going

for billions and billions of years

especially now around a red dwarf that

is going to exist for billions and

billions of years you might be in that

perfect system where life can exist and

evolve into even more complex beings

than us

we're getting so close

our local neighborhood of stars teens

with red dwarfs bursting with the

potential for advanced life

but they're also cosmic killers out

there lurking in our galaxy prime to

wipe out life on a regular basis

is anywhere safe the exoplanet

revolution is in full swing the Kepler

space telescope has scanned our local

neighborhood of stars for planets and

it's found them by the thousands

for a long time we didn't know if the

other stars in our galaxy had planets

and for thousands of years there was no

way to answer that question finally now

with modern technology we can do that

and to our surprise we found they are

extremely common from Kepler's small

sample astronomers believe there could

be tens of billions of rocky earth-like

planets throughout the Milky Way where

life may already be thriving but how

many of these countless worlds is held

onto this life long enough for

intelligence to evolve

the answer surprisingly may depend on a

planet's galactic zip code

the universe is not a happy safe place

the universe wants to kill us

it's incredibly violent out there

they're solar flares and supernovae and

black holes and colliding galaxies and

all these really amazingly dangerous and

violent events it's actually kind of

amazing that we're here at all

in order to develop advanced intelligent

life an exoplanet

may have to avoid these cosmic killers

for over three billion years if we look

at the history of the earth the first

thing that happens that's important is

the origin of life right away very

quickly but then nothing for a long time

you have nothing but microbes stomping

on the earth

for the first two and a half billion

years the earth was ruled by

single-celled Goom multicellular life

has only been around for a billion years

fish for 500 million mammals for 200

million

and modern humans have only walked the

earth for the last 200,000 years

the lesson is clear it takes a long time

to cook up intelligent life

but most planets in the Milky Way don't

have that kind of time

astronomers believe that a planet's

position within a galaxy may determine

if it gets hit by global extinction

events there's an idea of a habitable

zone for a galaxy and it's an analogy to

the habitable zone around stars stars

too close to the galactic center are in

the firing line from their violent

neighbors which frequently blast them

with deadly high-energy radiation

in the middle of a galaxy we have a lot

of bright stars and young stars and

maybe even supernova going off and so

there's a very harsh radiation field

that's not good for life fired up by the

supermassive black hole that sits at the

center of the Milky Way

this cosmic Killzone stretches out

around 8,000 light years from the

galactic center and extends out along

the densely packed spiral arms any

planets that exist within this zone are

likely to have their surfaces regularly

scrubbed clean of life fortunately for

us our home star the Sun sits in a

relatively empty quiet zone between two

of the galaxy's spiral arms so there's

this idea that there's a band in the

middle of the galaxy that's the Galactic

habitable zone where you don't have too

many stars going off you don't have too

many supernovae so it's quiet in that

way those might be great places for

complex life

these green zones are like the suburbs

the Milky Way galaxy they're sheltered

from the worst of the galaxy's radiation

it's here that earth-like worlds will

have the luxury of long uninterrupted

periods for life to take hold and

develop into more complex forms and

eventually perhaps intelligent life like

us

the Galactic habitable zone is no more

than a fledgling theory but if it's true

it reduces the number of places where

advanced life could flourish in the

Milky Way

the good news is those places should be

near us and aliens more likely to be on

our doorstep and with our technology

getting better every day it surely won't

be long before we find them

I think in 20 years time I'm gonna be

able to look up into the night sky and

say there really is another place I

could stand like this and feel at home

suddenly we humans will realize for the

first time that there are other cultures

other civilizations probably other

religions out there among the stars and

we are just one member of a grand

galactic tribe to have cousins that we

one day may communicate with seems to me

to be potentially one of the greatest

developments that humanity will ever

ever experience and if that isn't worth

doing I don't know what is