Kind: captions
Language: en
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over the past few weeks we've talked to
scientists who've shown us how stars
release energy
how galaxies form
how life might exist on exoplanets
and how black holes work
but there is a question that's gone
unanswered and it's a biggie
why are we here
it's a question someday
when my baby daughter learns to speak
and explore the world on her own two
feet that she'll probably ask me
she'll expect an answer that's
straightforward
but i won't be able to give her that
i don't know if anyone will
because even though scientists across
the world are systematically deciphering
the universe chipping away at all that
we don't know
the question stands
why are we here
why is the earth here
why is the sun the milky way the
universe why is any of it here
why do we exist
so i'll give my daughter what we do know
that 13.8 billion years ago in a
billionth of a trillionth of a
trillionth of a second
the universe expanded into being
that expansion slowed eventually and let
loose all this matter radiation energy
essentially all we know today
even the little kiss i give my daughter
on her forehead tonight is the result of
all of this
and then
after the inevitable questions
i'll tell my daughter to keep exploring
today on nova now universe revealed the
big bang the beginning and our
inevitable end
i'm alok patel
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studying the origin of our universe is
no small task
for millennia entire civilizations and
religions have attempted to explain our
cosmic origins
but in the scientific community there's
a generally accepted model used to
explain how the universe began
it's a household name the big bang
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this model hypothesizes that the
universe once had a period of rapid
expansion
which set the conditions for the
creation of all the matter we see today
but this expansion was not actually an
explosion as the name implies
so i talked to not one but two experts
to help me wrap my head around this
thing called the big bang when maybe it
should be called something different
i mean the universe is big it's old it's
been around for a long long time and yet
there's just so much more that really
genuinely is a deep mystery david kaiser
is a physicist and historian of science
at mit i respect people's personal
beliefs about their own origin stories
but i want to find out an answer that
makes sense in the language of science
from which we can actually make
predictions for things we haven't seen
yet haranya pearis is based at
university college london and stockholm
university and works as a cosmologist
that's somebody who studies the universe
its origins how it's evolving and what's
going to happen to it in the future so
let's rewind to the beginning of time
itself
so we know that the universe is
expanding
and that it was hotter and denser in the
past and if you extrapolate all of that
back into
the time when it was basically a dot
that is time equals zero
by rewinding the expansion of the
universe we can imagine all the matter
contracting back upon itself into one
point
and the idea of all the matter of the
universe condensed into a single dot is
known as a singularity you can't
actually really extrapolate everything
back into the dot we don't have a theory
of physics that holds in that regime so
maybe the universe didn't actually start
as a single dot per se so it can be
thought of as a phase transition you see
them every day when you boil a kettle of
water right what happens to the water it
causes bubbles to form
in the water bubbles containing gas and
eventually you know the steam rises you
know you can see the phase transition
where there's water and then there's a
bubble just like that
you can form a bubble universe
and we could be inside one of those
bubble universes and in that scenario
the time equals zero is the moment the
bubble popped into b
what we see as a singularity in the big
bang theory is just the moment the
bubble was born so there's no actual
singularity happening
the idea is an alternative to the notion
that the universe began as a single
point
when water boils bubbles form as the
water molecules spread apart from each
other and transition from liquid to gas
they're expanding they didn't begin as a
single dot even the smallest bubble is
bigger than a singularity
since we can't rewind all the way back
to when time equals zero we can try to
get as close as we can to the moment we
now call the big bang
but just as there was water in the
kettle before the heat boiled it into
gas
there was something there had to be
something some set of conditions that
allowed the big bang to occur this is
where an idea called inflation comes in
which is the idea that the universe
expanded very fast in a tiny tiny tiny
fraction of a second right at the start
and that takes us back not to time
equals zero but to about time equals 10
to the minus 32 seconds or so
so we can rewind very close to time
equals zero so inflation was a kind of
precursor and in fact this very early
blip of cosmic inflation helped to set
the conditions that we now call the big
bang the universe might have inflated
rapidly but it didn't explode like a
bomb or fireworks like i always imagined
the big bang describes a phase through
which the universe has evolved as
opposed to the start of everything it's
a set of conditions that are very
different than what we're used to today
so what do we mean by the big bad what
are those conditions really comes down
to three related kind of criteria
one was that the matter filling the
universe was in thermal equilibrium
that was really important there weren't
some regions of space that were much
hotter than others or colder than others
if there were there would have been some
heat exchange until they've reached that
equilibrium balance moreover it was at
equilibrium at a very high temperature
much hotter than what we would expect
even at the in the centers of stars
today
and the third again related part is that
the stuff that filled the universe the
kinds of matter the particles zigging
and zagging around
had such high energies because of that
high temperature
that they ran around and behaved much
more like radiation
you all got that
steady super hot temperatures and matter
behaving like radiation
it's not exactly an environment that
anyone would find familiar if anyone had
been there at the time they'd probably
have superpowers by now
that special set of conditions is what
we now call the big bang
but now we've come to understand there
were processes almost certainly before
that that set up those conditions the
big bang was the outcome of some prior
physics and stuff happening
so if there was something before the big
bang what did the universe look like
then
even before what we now refer to as the
big bang when the universe was filled or
dominated at least with a very very
simple form of matter
electrons are actually more complicated
to describe mathematically than this
other form of goop that seems very
likely to infilling the universe or
dominating when i say it was simple i
mean it had zero electric charge
it almost certainly had zero intrinsic
angular momentum or spin
and that means it could actually store
up potential energy even better than the
more familiar forms of matter around us
can do today
this goop wasn't goop as we know it
think of it more like an energy field
with tiny quantum fluctuations in it
according to quantum physics empty space
isn't empty at all
but instead it's filled with particles
that pop in and out of existence
and when energy particles pop in and out
of existence like this they're known as
quantum fluctuations
so a completely flat
space if you visualize it as a rubber
sheet perhaps acquires tiny little
ripples in it rubber sheet is two
dimensional this is really happening in
three dimensions but it's basically like
a little ripple in the curvature of
space
and that then gets stretched to the size
of the universe
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if you think about how matters
distributed in our universe
you'll notice there are areas like
galaxies where huge amounts of matter
are clumped together
at the same time there are also huge
voids between galaxies where matters
less abundant
if the universe had expanded from
completely uniform homogeneous goop
matter itself would be distributed
evenly everywhere creating a consistent
unvarying universe
since we can observe that the
distribution of matter in our universe
is uneven
the original source of all that material
must have had some variations in it as
well
according to the theory of inflation
these quantum ripples were those
variations that were then amplified by
the rapid expansion in the universe that
happened in a tiny fraction of a second
the variations ultimately determined
where large or small clumps of matter
would end up in the universe
but inflation doesn't expand the
universe forever
when we talk about early universe
inflation or primordial inflation that
definitely ended
and in fact in our current understanding
that's what set up the conditions for
that big bang phase after inflation
ended the structure that was imprinted
on the universe by the quantum ripples
eventually gave way to the formation of
basic particles
particles you all know and love protons
neutrons and electrons
and these particles formed a kind of
primordial soup so actually what most
people mean by the big bang when you're
an astronomer is the hot big bang it is
the very early primordial soup that
cooked up all of the elements that we
see in the universe today but just
hydrogen helium bit of lithium very
light elements so that hot dense soup
can be called the hot big bang
in the primordial soup
these light elements weren't evenly
dispersed which ultimately led to them
being distributed unevenly across the
universe
there were also clumps of dark matter
there which led ordinary matter to
condense to form stars and galaxies
and as we learned in our episode about
fusion it's stars that go on to cook up
the heavier elements in our universe
but there's still that tantalizing
question of what happened in that teeny
amount of time between inflation and the
primordial soup
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i must say this era which is between the
end of inflation
and
about the first three minutes where all
the elements get cooked that era is a
kind of pb dragon's era it's kind of
dark in terms of our current
understanding
despite inflation having ended our
universe continues to expand but it's
doing so at a much slower rate than
during inflation and check this out we
can actually measure the precise rate at
which our universe is currently
expanding
so to do that you need to measure a
distance and a velocity
so there's a thing called redshift
which is basically that when the
universe is expanding
light gets stretched out
so the wavelength of light gets
stretched out with the expansion of the
universe
waves of red light have longer
wavelengths than waves of blue light
this effect is called red shift because
as wavelengths of light in the universe
get stretched out
they get redder
if you installed a bright white light on
the back of a spaceship and watch it fly
away super fast at millions of miles an
hour
the light will look red to your eyes
that effect of red shift allowed people
to work out that things that were far
away were getting further away that
there's a general velocity away from us
and because we are not at a unique
location in the universe it's not that
everything's getting further away from
us everything's getting further away
from everything else
you know if i'm trying to make an
analogy here if i'm trying to think
about this and i say hey we're in a ice
skating rink in the ice skating rink is
the universe
and i have skaters in the ice skating
rink
are the skaters moving around from one
another or is the rink just expanding
and making it seem like the skaters are
moving apart when in reality we aren't
and i guess maybe the skaters could be
galaxies
that's a great way to think about it so
both are happening but the dominant
effect when astronomers get their
biggest telescopes the dominant effect
is the rink getting bigger so of course
galaxies move there are what we would
call local motions that would be like
the skater doing some fancy maneuver
so there's real motion galaxies move
they change
but the dominant effect when we look at
on the largest distances that we can
measure with our most powerful
telescopes is that space itself is
stretching between those skaters between
those galaxies
so by measuring the redshift of the
light from far away galaxies we can
determine that the universe is expanding
in all directions at once so that
allowed us to start to use light
like a time machine
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so the further you look out into the
universe
it's like a form of time travel you see
things as they were earlier
in the history of the universe
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since light travels at exactly 186 000
miles per second
a light year is the distance light
travels in one year
when we observe a galaxy that's 5
billion light years away from us we're
seeing light that's traveled across
space for five billion years before
reaching our telescope or eyeball
so by looking at this light it's as if
we've traveled back
five billion years in time so now if we
think about the oldest light in the
universe
the first light ever emitted
you'd think it would be from the very
beginning 13.8 billion years ago
but we can't measure what light there
was at the very beginning it wasn't
until a few hundred thousand years after
the big bang before light could actually
travel freely
we think of light being able to travel
so easily i can see across the street
our telescopes can look deep into the
nice sky but in the earliest phases of
our universe's history the universe was
opaque light simply couldn't travel
it was filled with a plasma of charged
particles
that's like a thousand soccer players
trying to play soccer on one crowded
soccer field
all these charged particles are like
those soccer players and the light is
like a soccer ball every charged
particle is either scattering or
absorbing light so light just can't
travel very far before it gets kicked or
scattered or absorbed
our universe was like that for its
earliest moments during and after this
big bang phase there was no free light
to travel
the first time it begins to travel
conditions are changed just enough
that those free electrically charged
particles sort of team up into
electrically neutral atoms and that
happened at a particular moment in our
universe's history about 380 000 years
after this big bang set of conditions
so only after nearly 400 000 years was
light able to travel any substantial
distance and that remnant glow from that
first moment light could begin to travel
that fills the universe and it's been
cooling and stretching ever since for
the next 13.8 billion years
that is the leftover heat of the big
bang so at the time that this light was
released it was very very high energy
light like gamma rays and over time
the wavelength of that light got
stretched out so much
that it is now observed in the microwave
frequencies
the oldest and farthest away light in
the universe is known as the cosmic
microwave background it was detected by
accident they had built a radio
telescope at bell labs and it was built
to do something far more mundane
basically they wanted to measure the
radiation from gas between the stars or
something like that and when they turned
it on they found that there was a hiss
or noise in the instrument
and it was coming from all over the sky
and they were very confused and they
thought there was something wrong with
their
experiment and they actually thought it
was pigeon droppings
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that's right the researchers thought
pigeon poop was causing distortions in
their readings so what did they do they
climbed into the telescope and they
cleaned the droppings out
that didn't change it and the noise
continued to go on and then they
happened to communicate with their
colleagues at princeton university which
was looking for this after club of the
big bag they had been actively looking
and these guys found
a hiss that actually was you know
what was expected so that's how it was
discovered
and so that microwave light if you can
observe it
then you see a picture of the universe
when it was about 380 000 years old it's
now about 13.8 billion years old so it's
the baby picture of the universe
it wasn't until
1992 that we learned that this hiss that
radio history is coming from all over
the sky which seemed very very uniform
in its signal
had tiny variations in it because those
tiny variations are the signals the
fingerprints of the origin of structure
entirely new instruments were developed
that were sensitive enough to measure
such miniscule differences
nasa's kobe satellite short for cosmic
background explorer was the first to
take readings of both the temperature of
the cosmic microwave background and its
tiny variations
since then we have been mapping that
better and better
to date the highest resolution data we
have on the cosmic microwave background
comes from the european space agency's
planck satellite which released its
first set of data in 2013.
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this image
which is
the closest one to date to the big bang
and you can see the seeds
from which the universe is coming
galaxies stars planets and humans
it could measure
tiny tiny variations of about a
millionth in the temperature of the
cosmic microwave background and it had
high resolution and by measuring in many
frequencies you can make a very pristine
clean map of just the background
and that map was both extremely high
resolution compared to the previous
satellite missions and also very
sensitive to tiny variations at small
scales so it was a precision mission it
took the cosmological model and refined
it
and is there a point where we won't be
able to see
the radiation anymore like are we lucky
like hey we caught it in this moment in
time
that's an extremely good question so i
think you know it just gets colder and
colder and colder as time goes on right
so that means you need more and more and
more sensitive instruments to measure it
it's hard enough as it is
one of the reasons we measured it was it
was still possible to see it by accident
in a radio telescope
and that's why we knew there was
something to look for right but if you
don't know that there's something to
look for why would we go after it so i
do think that you're right that at some
point whatever intelligent creatures
arise in the future might not be able to
measure it
by looking up at the night sky
we've been able to figure out how the
entire
cosmos came to be
back to a billionth of a trillionth of a
trillionth of a second
by uncovering our origins maybe we can
start to understand how and why we're
even here at all it's not a completely
fleshed out theory
i think that it's fair to say that what
we have currently is a toy model
of working understanding of the very
early universe
if the models of the early universe can
make predictions about what we should
see in the present
can we also use those models to predict
where our universe is headed
after the break the future
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so what does this all tell us about the
future
of our universe is there a point in
which all of a sudden we won't have the
matter to contain the universe and it's
going to collapse back on us like what
does this tell us about the next billion
years
so actually this is something we figured
out by studying among other things the
cosmic microwave background here again
is cosmologist hiranya pearis and just
in the last couple of decades we figured
out actually that it is going to expand
forever at an accelerated rate
as the distance between galaxies expands
and stars gradually die out
the universe will become colder and
darker
but physicist david kaiser says this
won't quite be the end so then we get to
more exotic possibilities in this very
distant dark cold lonely future
we know that there are gajillions of
very massive black holes in the centers
of most if not all large galaxies for
example these are called supermassive
black holes because they're millions or
even billion times more massive than our
own sun so there are enormous enormous
monstrous collections of mass
and so those can attract each other from
gravity they can merge one can absorb
the other so we might have a phase where
black holes kind of duke it out for a
while and those become the dominant kind
of players in the story but even black
holes have a limited lifetime so if you
want to ask what's going to happen
really really really forever from now
even those monstrous colliding black
holes will have become
a memory will become a thing of the past
so it looks like we're heading towards a
big fat
empty nothing it's not the most
inspiring view
it's a very bleak
cold
horrible future sadly
sorry it's going to take trillions of
years so don't worry let's worry about
climate change instead
i listen i'm with you on that
if the idea of a cold dark empty future
seems full of despair
maybe there's still hope in the idea of
a multiverse a possibility mentioned in
movies like spider-man far from home
i'm sorry you're saying there's a
multiverse because i thought that was
just theoretical i mean that completely
changes how we understand the initial
singularity we're talking about an
internal inflation system and how does
that even work with all the quantum
c
so is it possible that we are just in
one
universe and somewhere else that there's
another bubble universe and we're we
haven't seen the connection between the
universes yet absolutely that's exactly
what the theory i told about earlier
actually implies that there are bubble
universes elsewhere if there's one
there'll be others and there will
outside our current observable horizon
i think of a bathtub with soap bubbles
and here the bathtub itself is growing
and you have more and more bubbles in
between so it will be extremely unlikely
as far as our best estimates would
suggest extremely unlikely for two
bubbles ever to collide so we would be
causally disjoint meaning we're no way
to influence or be influenced by
these other bubbles most likely and yet
they could very well be popping up all
the time and in fact there could be not
just one or two there might be an
infinite number of them
i can't even wrap my head around that i
can't wrap my head around the fact of
how big the milky way is let alone the
fact that there's 100 billion other
galaxies and now you're saying there
might be another universe also yeah but
our conception of ourselves in relation
to the size of the universe has changed
dramatically in the last 100 years or so
in the early part of the 20th century we
didn't even know that there are other
galaxies
right so first we thought the earth was
the center of the universe then we found
out there was sun at the center of our
solar system then we found we were
living in a
galaxy and then we found out that there
were other galaxies now we think there
are billions of galaxies in the
observable universe and
you know to me it doesn't sound that
surprising that there are other
universes
i want to caution that these ideas
spring from well-motivated well-tested
theories but they're beyond what we can
sort of directly measure or test they're
at that really at the kind of cutting
edge of some of our theorizing and i
think it's not just that there would be
separate bubbles in this scenario
the laws of physics themselves might be
different in each bubble so it's not
just that there's many copies in which
there might be many milky way galaxies
are kind of the same
i mean there could be different nuclear
forces there could be different
particles they could have different
properties
the laws of nature might actually in
that sense be local
just a local accident as opposed to
forced by the laws of nature and i find
that just amazing
i love this stuff it's so rad total
sci-fi
but is it actually worth spending our
resources on studying these cosmic
origin theories
first of all it's worth it because this
is to my mind on unparalleled human
adventure i mean to be able to not just
sort of daydream about what's the
universe like but to be able to try to
pose increasingly well posed questions
get increasingly precise measurements
from the world well beyond are familiar
this is extraordinary and then of course
along the way we learn a lot we train a
lot of really smart people who can do
lots of things with those critical
thinking skills we think about the
impact from say quantum theory on the
world we live in
you know quantum theory has been
responsible indirectly at least for the
consumer electronics revolution for
lasers for all the things we rely on in
getting around the world every day
and so how do you put a price tag on the
fundamental curiosity for how atoms
behave
if you really try to bundle up what has
come from our effort to learn in a very
you know curiosity driven way about the
structure of atoms or the structure of
our cosmos
it has led to
directly important ways that have
improved and changed our lives but we
can't deny the fact that it's expensive
and we really have to be able to make
that case in a proactive way
it's a search for our own origins isn't
it
and all the work that i do is working
out smaller
pieces of that very big question
and eventually maybe we will learn maybe
not during my lifetime but you know we
will learn why there is something rather
than nothing
haranya pearis and david kaiser aren't
alone in their philosophical musings
everyone i've spoken with for this
podcast has reflected on what inspires
them in their pursuit to understand our
universe
looking up at the stars i think is a
universal age-old phenomenon that leaves
you full of wonder and so i think
curiosity does drive
a lot of our exploration in this area
but it's also this sort of innate
human sense for connection right of
belonging of knowing is there anyone
else out there
there's this trade-off between
exceptionality and loneliness
until we find
life out there
we're exceptional
but there's only us and if we can make
that trade there's a whole universe out
there of life and
i just can't wait to be
mediocre on a universal scale
it's the young people they inspire me
because of their dedication to what not
just how cool the science of fusion is
it's just like can we bring this to bear
on the most important problem of our
generation
just look at what we've done in you know
the short time we've had the scientific
method
you know i can't imagine the next two
three hundred years
the last hundred word doozy
so we are made of stardust and this
stardust has undergone billions of years
of chemical evolution and cosmic
recycling
i think it reminds us
when we're at our
smallest and most tribal
that we're all connected we're all
progeny of this earth
we were born together in the same
observable
universe that was anjali trapathi clara
souza silva dennis white hakeem oluseyi
rana ezzadine and janna levin
for me thinking about the vastness of
our universe continues to feel both
humbling and inspiring
someday when my daughter asks me how the
universe came to be and why we exist
i won't have all the answers
but at least i'll have a few
and until that day i'll keep encouraging
her to explore nothing less than the
entire universe while making sure she
always feels grateful for this small
quick moment she has that we all have on
our tiny blue planet
nova now universe reveal is a production
of gbh and prx it's produced by terence
bernardo jenny cattaldo ari daniel
caitlin folds and jocelyn gonzalez
julia court and chris schmidt are the
co-executive producers of nova
suki bennett is senior digital editor
christina manan is associate researcher
robin kasmer is science editor robert
boyd is digital associate producer and
devon maverick robbins is managing
producer podcast at gbh
i'm alek patel thanks for joining me on
this cosmic baffling fascinating
adventure
if you love stories about our universe
visit pbs.org nova now podcast
and check out nova universe revealed a
five-part film series about the same
topics we've been discussing right here
streaming now in the pbs video app visit
pbs.org
nova
this podcast has been made possible by
the gordon and betty moore foundation
that's all for now earthlings
catch y'all soon in the multiverse
gbh
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