What is Space Time and How it Works

what is our universe made of
it’s the biggest unanswered question
space itself is something there’s a
hidden structure and a force that exists
within space idli fundamental it’s
really part of the fundamental
architecture a force that connects
everything in our universe it’s an
active player and the game of life
it underpins our reality tying together
all of space and time since the very
beginning we call it space-time
it’s everything space-time is what the
universe really is space-time is how our
universe works but what exactly is it
and how does it control our past present
and future
we can’t see it we can’t touch it but
without spacetime we wouldn’t be here
space-time is a fabric of our reality it
shapes and governs our lives if we want
to understand the story of the universe
it’s absolutely crucial we understand
how space-time behaves space-time has
been active since the beginning of
everything and is the key to the
evolution of everything we have to
understand space-time in order to
understand the history of the universe
to understand how the universe began how
it evolved and what’s gonna happen in
the future the story of space-time is
the story of our universe to know how
the story plays out how it will end we
need to go back to the very beginning
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to a time when there was nothing no
stars no space a time before there was
time then all of a sudden our entire
universe was born in the Big Bang it
started in a instantaneous moment where
from nothing our universe was created
the very definition of the moment of the
Big Bang is that space and time were
created at that instant it is as far as
we currently know that coming into
existence of space and time itself
the infant universe a tiny speck of
energy and space-time materializes from
nowhere then the universe suddenly
expands the idea of inflation is that a
very tiny region in an incredibly short
amount of time far shorter than a second
grew by many many many orders of
magnitude so imagine myself suddenly
becoming the size of a galaxy in a
fraction of a second the universe grew
from smaller than the size of an atom to
the size of a baseball
in cosmic terms that’s like a grain of
sand growing almost to the size of the
observable universe
the universe at the instant of inflation
actually expanded faster than the speed
of light it seems to be a violation of
everything you’ve heard in physics you
may be thinking hey hey hey mister
astronomy guy nothing can move faster
than the speed of light it turns out
that’s kind of true but the rule is
nothing can move through the universe
faster than the speed of light in
inflation its space itself that is
expanding so there is no violation there
is no paradox
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inflating fast the universe went through
a phenomenal growth spurt at the moment
of the Big Bang space-time was this
entity that was flying out in all
directions it was space itself that was
expanding but the universe didn’t expand
evenly one spot in the universe was ever
so slightly more dense than a spot right
next to it and we’re talking about a
tiny tiny fraction of a percent one part
in a hundred thousand but that was
enough fluctuations in expanding
space-time created areas with higher
density
conflation made these high-density
regions larger
and this allowed our universe to take
shape when parts of the universe didn’t
inflate quite the same way as others all
of a sudden things could start to come
together as the universe cooled energy
turned into matter
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and in the denser regions that matter
started to clump together
crucially these regions had more mass
than others
masse bends space-time so anything that
is made of matter bends space-time and
the more matter you have in one place
the more you bend it in fact I’ve been
in space-time right now when I flex I’ve
been it even more because of my
incredibly high bustle density I don’t
bend at the maximum I don’t want to
destroy the earth in the solar system
but you know it’s an effect it’s a real
thing
space isn’t constant it’s not something
that is always the same everywhere it
actually bends curves it warps depending
on the matter inside of it we’d see a
curving grid of space-time moving and
reacting to objects within it and we’d
feel the curving of space-time as the
force we call gravity
gravity is different from all the other
forces it is intimately connected with
the curvature of space-time something
that can bend space and time has gravity
that’s what gravity is the bending of
space and time itself it’s hard to
visualize this but a good analogy is a
trapeze artist and their safety net you
can imagine a trapeze artist falling
into a net on purpose that net is flat
and looks like a nice orderly evenly
spaced grid but when they fall into it
they distort that grid well that’s a lot
like space if you have matter in space
it warps the framework when the trapeze
artist is resting in the net they’re
bending that space-time grid a little
bit if you had two trapeze artists in
there double the mass in roughly the
same volume you would get a bigger dip
you have a bigger Distortion and that’s
how space-time works more mass equals a
bigger curve in space-time equals more
gravity but understanding the nature of
gravity and space-time there’s no easy
thing it’s an idea developed by one of
the greatest minds ever Einstein had the
idea that space itself is something
something that can be bent something
that can be stretched that we are all
bound together by space-time Einstein
says it’s space and time have a geometry
they have a life of their own they have
dynamics
those dynamics are what we call gravity
the more dense the region of matter the
greater the gravity the deeper the curve
this connection is the foundation of our
physical reality it’s the interaction
between matter and energy and space-time
that created the universe that we see
around us today but that doesn’t mean we
fully understand it there is much more
that we don’t know and that’s
frustrating with the laws of physics I
can talk about how space-time behaves
but it does appear to be something that
stretches that contracts and that
gravity is the embodiment of space-time
born in the Big Bang space-time and
energy combined to create our infant
universe
these basic materials were the
foundations but how did we get to the
incredible complex structures we see
today
how did space-time build our majestic
cosmos
our entire universe was created in the
Big Bang 13.8 billion years ago
everything came from nothing
but our modern universe is a complex
mosaic of matter
I mean Marvel through our telescopes
that the fantastic structure of our
universe
and it’s galaxies if you want to ask
where that come from matter in the
universe arranges itself on a vast
cosmic web galaxies and galaxies
clusters are strung out on sheets and
filaments it seems this intricate web is
organized by a cosmic architect
space-time it shaped everything from
planets to galaxies atoms to cities the
universe is made of space-time whatever
the substance is time and space bound
together that’s expanding and creating
the universe we see around us it’s
everything space-time is what the
universe really is it’s a hard concept
to grasp and even harder to visualize
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scientists observe the universe in
different wavelengths of light this is
the Sun in visible light x-ray and
ultraviolet now imagine if we could see
it in the space-time spectrum we would
see space-time distorting as objects
move through it
spacetime can warp and push things
around it can expand and pull things
apart but it’s the shape of space-time
that dictates how we experience it
imagine you’re in your car you go up
hills and you go down hills so the shape
of Earth’s surface determines how you
travel across Earth’s surface in the
same way the geometry of space-time
determines how light and matter move
through space-time
the rules are simple matter in fact any
object tells space-time how to curve the
curvature of space-time tells matter how
to move
because the shape of space-time tells
matter how to move what we call gravity
this means that gravity and the shape of
space-time tells matter how to clump
together and form larger and larger
structures but at the beginning the
space-time landscape was very different
from today’s
and the very first matter started to
change the shape of space-time so this
space right here has a tiny bit more
matter in it than this over here
wherever there was a little bit of extra
mass that would Bend space a little bit
more well if you’re bending space a
little bit more then more mass would
collect there in the early universe the
denser regions of matter created deeper
curves in space-time and as the mass
gets bigger as stuff falls into that
well it gets deeper and deeper and
deeper and attracts more stuff it’s just
a runaway process gravity increased
pulling in more and more matter more
dams got more dad’s got more downs and
then before you know it you’ve got a
star and you’ve got a bunch of stars and
you start to make a galaxy and these
stars evolved and began forming large
structures they sort of burn through all
their nuclear fuel and exploded and they
made all the heavier elements and with
time we got down to having things like
planets atmospheres people all the
things that we care about today all of
this started out as energy fluctuations
in expanding space-time these at first
very tiny fluctuations became these
gigantic structures that we actually see
today and over billions of years that
material began to coalesce into
individual galaxies stars planets and
you
fluctuations in the expansion of
space-time laid out the pattern of the
universe
the curvature of space-time controlled
the evolution of everything we see today
if space-time didn’t have that property
and bringing mass together then all we
would be is a thin haze of hydrogen gas
not a very interesting Universal if
space-time didn’t curve because of
matter inside of it the universe would
be a really weird place I mean there’d
be no gravity there’d be nothing to make
things stick together no force of
gravity means no stars no planets and no
people we owe our existence to
space-time but even scientists struggle
to understand it I wish I knew what
space-time is we know things about
space-time but at the same time we feel
like we know almost nothing about
space-time then in 2015 we caught a
break
and for the first time we heard ripples
in space-time
generated by one of the most violent
events in the history of the universe
the universe is filled with space-time
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we think it’s been around from the
beginning of everything quietly pulling
the strings of the cosmos
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and sometimes we get a glimpse of this
elusive puppet master in action 2016
astronomers witness a strange optical
phenomenon a weird circle of light like
a cosmic halo this is actually what you
would see in the sky if your eyes were
as sensitive as a telescope
they’re real this is not some artifact
of how we adjust the images something is
actually bending space and time itself
into a lens that something is a red
galaxy which is over 7 billion light
years away from Earth it’s bending the
light from a blue galaxy which should be
hidden behind it
it’s called gravitational lensing
gravitational lenses are caused by
objects with huge masses say clusters of
galaxies that distort space and time so
much that when light comes from farther
objects has to pass around the galaxy
clusters the light bends it really is a
true warp in space-time
mass from the foreground galaxy creates
curves in space-time which we know is
gravity
light follows those curves and is warped
so it bends around the galaxy massive
objects like clusters of galaxies can
bend the path of light through
space-time a lot like a piece of glass
can bend the path of light so when we
look at a distant galaxy as the light
passes through a galaxy cluster we see
multiple images of the same galaxy we
see arcs in circles as if that galaxy
cluster were made of glass we are seeing
the warping of space-time literally
played out in front of our very eyes
gravitational lensing gives us a way of
seeing the effects of space-time on
light
but it’s only an indirect observation of
space-time could there be another way of
experiencing space-time right here on
earth not everything that happens in
space can be seen sometimes you have to
listen for it as well
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believe it or not space is a material
much like this iron sheet and like this
iron space can distort if I put a very
heavy weight on this sheet of metal its
shape is gonna change and it’s gonna
distort amazingly space can carry waves
and so can this iron sheet but to get
this sheet wavy you need something
really powerful something like me and my
hammer to see those ways to travel
through that iron sheet
well waves pass through space in exactly
the same way we call these gravitational
waves gravitational waves are vibrations
from cosmic events– transmitted through
the material of space-time to set off
waves in space you need the biggest
baddest most powerful events in the
universe something like the collision of
two black holes when two black holes
collide the energy released sends
shockwaves through space-time across the
universe
by the time they reach Earth they’re so
small they’re immeasurable almost in
2015
scientists at the LIGO Observatory made
a groundbreaking observation they
detected ripples in space-time
gravitational waves rumors began flying
but became clear after a while that this
was indeed the first direct detection of
gravitational waves seen by man-made
instruments on the earth when we
discovered gravitational waves it had
been so long that we’ve been waiting for
signals not only did most of us not
believe it I went so far as to be so
skeptical as to look into all kinds of
conspiracy theories for ways it can be
faked when I saw this data
I still think back on it now and the
emotional impact it has on me the only
thing capable is when I saw my
daughter’s face for the first time after
she had been born it was that kind of an
emotional impact just having all of this
things that we had worked for coming to
fruition in one moment it’s mind-blowing
we can actually hear these gravitational
waves on earth part of what makes this
so amazing it’s a bit of a coincidence
but it’s a really cool coincidence is
that the signals that LIGO actually
measures are in the same frequency band
as the sounds that the human ear is
sensitive to we can hear the waves
change frequency as the two black holes
get closer and collide it’s a swoop up
in frequency that sounds like what we
were hearing in that where two black
holes that are orbiting around one
another and then coming together that
was it
listening to ripples in space-time has
given us a powerful new tool to
investigate the universe we are now
hearing things in gravity for the first
time it’s a sense that we have never
been able to apply to the universe and
we’re beginning to learn what is out
there the observation of gravitational
waves from black holes is one of the
most significant findings in astronomy
by anyone in the recent hundred years
it’s hard to overstate the importance of
gravitational wave astronomy much like
when Galileo first pointed his telescope
at the stars to see something new we now
have an entirely new window into the
universe
gravitational lensing and gravitational
waves offer us an insight into the
complex relationship between gravity and
space
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but what about the other half of the
equation time but it turns out you know
it’s space time gravity not only
distorts space it actually distorts time
too we think of time is something that
can’t be changed it simply flows ahead
at a constant rate but that’s not the
universe we find ourselves in and some
crazy circumstances my time might even
according to you stop
it might even be possible to travel
through time and go back to the future
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for sci-fi fans space is the final
frontier for scientists exploring time
is a much bigger challenge originally we
thought of time is the same thing as the
Sun rising and setting but now we’ve
come to realize the time is a more
fundamental concept than that time isn’t
just something that passes time is an
essential part of our universe it’s part
of the fabric of space-time
the Big Bang was the beginning of space
and time since then space has been
expanding and time has been ticking
forward it’s been doing this for 13.8
billion years creating the universe we
see today there’s sort of two sides of
the same coin
you can’t have time without space or
space without time so when matter
influences space-time it’s not just
creating deformations in space it’s also
affecting the flow of time this is where
space-time becomes really cool just as
gravity bends space it also distorts the
flow of time this isn’t how we perceive
time this is actually the rate at which
time flows very massive objects can warp
and twist space-time itself so not only
a space distorted but time itself can
slow down or even stop the stronger the
gravity the greater the distortion what
has the most gravity a black hole
found in space near a strong
gravitational tug from a black hole
clocks can do funny things and this is
where things start getting really
interesting around the black hole space
time warps and twists slowing time down
scientists dream of sending a probe
there to test their hypothesis
there’s a famous way of thinking about
this called the twin paradox where two
twins are born on exactly the same time
right so they’re the same age but one of
them zips very very close to a black
hole hangs out awhile and then comes
back if I had an identical twin who
stayed back on earth while I flew near a
black hole when we had our daily video
phone calls he would see me and I would
see funny we would literally notice the
time is running in a different pace for
all the other one the closer to the
black hole the slower time passes
if instead of coming back home I
accidentally fell backwards into the
black hole my twin back on earth would
see me slow down even more ago
and completely dry into halt and seemed
frozen on the event horizon time appears
to stand still why we just have a
sinking feeling that I would be able to
come home again but if the twin could
escape from the black hole he would be
returning to the future maybe it’s only
been a few days or weeks experienced by
the one that traveled to the black hole
while the other is you know gray-haired
and as grandkids by now as it lived
decades here on earth
the black hole warped space-time so much
that the ultimate science-fiction
fantasy becomes reality
time travel is a staple of science
fiction and we know that time travel
into the past
appears to be ruled out in our universe
but time travel into the future is
totally acceptable time travel isn’t
possible just yet but space-time has a
very real effect on our daily lives it
controls how we age
the key to different rates of flows of
time is gravity
if you experience different
gravitational environment you will have
a different flow of time as I climb up
these stairs and I put myself further
away from the mass of the earth my own
clock runs a little bit faster if you go
down closer to the surface the more your
clock slows down we have sensitive
enough clocks that we can measure this
different flow of time
exaggerate this effect and we would see
the flow of time change in front of us
those closer to the earth would look
slowed down those higher up the opposite
which means the wealthy in their pent
houses actually would age faster than
people on the ground this is a
mind-blowing concept but it’s reality
Earth’s gravity even controls time high
above the planet twelve and a half
thousand miles up there’s an array of
global positioning satellites crucial to
the navigation systems and our cars and
cell phones we here on earth use the
global positioning system as a way of
getting around okay most people these
days would be lost if they have to go
more than about a kilometer from their
house unless they have their GPS app on
their phone to tell them where to go the
GPS receiver in your cell phone bounces
signals over four satellites to figure
out exactly where you are it’s an
exercise in precision timing onboard
each satellite is an atomic clock the
weaker gravity in orbit means the
satellite clocks tick fractionally
faster than those on the ground
if we didn’t know to correct for the
fact that the clocks and our satellites
move at different rates the GPS system
here on earth would not work it would
actually lose accuracy at such a rate
that the entire global positioning
system will become useless in less than
an hour we correct for that every moment
of every day space-time has controlled
every phase of the universe’s evolution
since its birth
now we’re discovering space-time will
also dictate how the universe will die
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our universe started with a bang 13.8
billion years ago it’s been expanding
ever since
will this expansion last forever or will
our universe come to a violent end for
almost a hundred years we’ve now known
that the universe is expanding
everything in the universe is expanding
away from everything else we can test
this by measuring light from exploding
stars type 1a supernovas all explode
with the same brightness so scientists
can accurately work out their distance
from Earth for decades astronomers have
measured this light being stretched by
expanding space-time the universe is
expanding and there’s matter in it that
matter has gravity and that is
distorting the curvature of space-time
so it made sense to us that as the
universe expanded all of the matter in
the universe would hold on to each other
gravitationally if there’s enough matter
in the universe it can actually pull on
itself enough that the expansion gets
slower but in 1998 astronomers took new
measurements and made a sensational
discovery people had expected it to be
slowing down to decelerate but instead
they found the opposite the expansion is
accelerating
if expansion was slowing then these
distant lights should seem brighter
instead they were dimmer
they were getting farther away much
faster than expected it could only mean
one thing that expansion is getting
faster it’s accelerating every day
this discovery turned our understanding
of the universe upside down for the
first seven billion years of the
universe the rate at which the universe
was expanding was going slower and
slower but then something crazy happened
It was as if gravity had become the
opposite instead of attracting the
galaxies it was almost as if it was
pushing them apart that’s a very
surprising result we’re still struggling
to understand it was gravity losing its
power
where was there something else pushing
space apart there is another ingredient
in our universe an ingredient that
behaves very oddly the mysterious
quantity called dark energy
like space-time dark energy is all
around us we can’t see it but it makes
up 70% of the stuff in our universe but
what is it exactly
dark simply means that we have no idea
what it is we don’t know what form it is
in something is pouring energy into the
universe causing it to accelerate we
don’t know what it is no clue whatsoever
we don’t understand it that’s the
greatest mystery out there today
dark energy behaves in mysterious ways
ordinary matter is attractive dark
energy is repulsive that’s why it’s
causing an acceleration ordinary matter
feels gravity it comes together but this
stuff doesn’t his dark energy a new
force in the universe or like gravity
could it come from space-time itself
dark energy may very well be a property
of space-time it may be that space
itself has an energy and it’s this
energy that’s driving it to accelerate
in its expansion dark energy is a thing
we don’t really know exactly what it is
but it will have a huge effect on the
future changes in the universe so what
will happen if dark energy keeps
accelerating the expansion of our
space-time universe
because of the presence of dark energy
it’ll expand faster and faster and
faster which means the universe is going
to become a lonelier and lonelier place
to be all the galaxies are accelerating
away from each other the universe gets
dimmer and dimmer and colder and colder
everything gets darker and more desolate
and right now that is the leading
candidate for what’s going to happen in
our future eventually our space-time
universe freezes the big freeze is the
ultimate endgame of the universe as we
know it it is an ugly fate it’s a
depressing fate but luckily for us it’s
not until an unimaginably long time from
now
trillions of years from now the universe
could end in a big freeze
but a 2017 study hints had an even more
frightening possibility dark energy
might be getting stronger one horrible
scenario for the ultimate fate of the
universe is if dark energy eventually
grows so strong enough that it can
overwhelm the gravitational attraction
of a galaxy itself it’s even able to rip
black holes apart the very fabric that
holds everything together could be
ripped apart this idea is called the big
rip first clusters then galaxies like
our own Milky Way will be torn apart
then our solar system will break up and
in the final half-hour of the universe
the earth will explode in the final
second atoms will vaporize everything in
the universe would individually be torn
apart by the expansion of space we don’t
understand dark energy is it constant is
it getting stronger is it getting weaker
at this stage we simply don’t know the
future of our space-time universe hangs
in the balance
will it end in a big rip a big freeze or
is the end really just the beginning
spacetime controlled the birth of our
universe it will also dictate its death
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now we’re discovering these two events
may be linked a link that reveals a flaw
in our understanding of the Big Bang
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all the galaxies all the planets and
stars all of this matter was compressed
into a tiny volume shrunk down to
infinitely small size we call this tiny
infinitely dense point a singularity
singularities are predicted by the
general theory of relativity but the
universe is also governed by another set
of rules quantum mechanics quantum
mechanics is our description of the sub
atomic realm of fundamental particles
and fields and forces in how they
interact
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quantum mechanics says that nothing can
be infinitely small or dense
so singularities cats exist singularity
is a bit where everything kind of goes
to hell because the densities become
infinite gravitational forces become
infinite things just sort of break down
there in the equation sort of stopped
making sense no singularity would be no
big bang as we understand it
so then how did the universe spark into
existence
scientists now think they have an answer
a solution that works with both general
relativity and quantum mechanics quantum
space-time
a successful theory of quantum
space-time should answer the question of
what really happened in the earliest
moments of our universe
hopefully the correct quantum theory of
gravity won’t have any singularities it
will replace the Big Bang with something
else if we only knew what that something
else was we might have a clue as to how
and why the universe began
in a quantum space-time Big Bang there
was no singularity bursting from nothing
the universe formed from the remnants of
another dying universe it’s possible
that before the Big Bang there was still
universe there was still space and time
but rather than expanding the universe
was contracting perhaps universes don’t
end in rips or freezes perhaps they
collapse an ancient universe expands but
then begins to collapse under its own
gravity
crunching space-time down to a spec but
instead of forming a singularity
space-time once again explodes as matter
gets more dense than as the matter
crunches down this force will push
everything back out the near verse would
bounce and reignite in a new round of
expansion a new Big Bang what we
perceive as the Big Bang is the
aftermath of that bounce
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this suggests that the space-time that
dictates our lives today comes from the
collapse of an old universe and we live
in an infinite space-time cycle of birth
death and rebirth
a bouncing space-time universe if we
live in a bouncing universe it’s very
plausible universes infinitely old that
it’s gone through an infinite series of
bounces and there is no absolute
beginning it could be that we are just
one iteration of an infinite number of
cycles in the lifetime of some meta
universe we barely understand space-time
perhaps we will never understand it
completely
but one thing is clear without
space-time we would not be here
space-time is something absolutely real
it’s really part of the fundamental
architecture the furniture of reality to
really understand the ultimate fate of
our cosmos it’s not enough just look
more with our telescopes you also have
to understand the basic nature of
space-time
I think the biggest thing to take out of
all of this is that the universe is
weird you hear about these very weird
things that we talk about when we study
the universe and cosmology and
relativity it sounds like it could be
all made up
but trust it’s not
you really are right now living in a far
more complex and beautiful universe than
the human mind can comprehend
you

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