we take it for granted that our universe
contains planets stars and galaxies
because those are the things we see but
the only reason these big structures
exist is because of the nature of
nothingness empty space but to
understand why we have to go back to the
beginning the very beginning the Big
Bang you know I always thought that in
the Big Bang the observable universe
started as a point and then just
expanded steadily more or less to the
point that we're at today but that's not
actually how it happened there were four
different phases in the universe's
expansion to start it was expanding
steadily but then after just a tiny
fraction of a second the expansion just
blew up and the whole universe increased
in size by like 10 to the 26 times in a
very short period of time and that
period is known as inflation and then
just as abruptly as it began
inflation stopped and after that the
universe continued expanding but at a
decreasing rate so the expansion of the
universe was actually slowing down which
is exactly what you expect if the
universe is full of massive objects that
gravitationally attract each other but
then about five or six billion years ago
the expansion of the universe started
speeding up again and this is thought to
be caused by dark energy an energy tied
to space so before that time there was
enough matter the matter density was
high enough that it was pulling
everything back together slowing down
the expansion but once the universe
reached a critical size well then there
was enough dark energy to start pushing
things apart and that is the phase that
we're still in the expansion of the
universe is accelerating now this story
doesn't really explain the formation of
galaxies until you tie in the nature of
nothingness now ordinarily we think of
everything around us as made of
particles of atoms and electrons but our
best theories of physics are actually
field theories that say all of these
particles should be seen as just
excitation in fields the word field
always gets me because it makes me think
of well fields but a field
just something that has a value
everywhere in space so every subatomic
particle has its own field an electron
field an up quark field a down quark
field a neutrino field and so on and
anywhere there's an excitation in this
field that is some energy in the field
well that is where we will observe
particles so out in completely empty
space or the values for all of these
fields are basically zero but here's the
thing it's impossible to make a field
perfectly flat and zero you cannot take
a quantum field and make it completely
quiet you know it's the Heisenberg
uncertainty principle it says you can't
take a particle and pinpoint it to
exactly zero energy
likewise you can't take a quantum field
and make it exactly flat everywhere now
this is important because ordinarily
these fluctuations are really really
tiny and they only affect subatomic
processes but during that period of
inflation the universe expanded in size
so rapidly and so incredibly that those
tiny fluctuations got blown up to the
scale of the observable universe
now without them we think the matter
distribution in the universe would have
been completely homogeneous completely
uniform and that means the gravitational
force on any object in the universe
would have been the same in all
directions which means nothing would
ever have collapsed into the big
structures that we see today but thanks
to these fluctuations there were
slightly denser and less dense regions
and of course the denser regions had
stronger gravitational fields so they
pulled in the matter from around them
and that clumped together the matter
into huge gas clouds that would go on to
be the galaxies that contain the Stars
and the planets and the things we know
today you can actually see the imprint
of these quantum fluctuations in the
leftover radiation from the Big Bang
cosmic microwave background radiation
the quantum fluctuations in the fields
were amplified two big classical
fluctuations in the density of matter
from place to place and those
fluctuations in the density matter show
up in the universe today as temperature
differences in the cosmic background
radiation and ultimately and things like
stars and planets and galaxies I think
it is incredible that without these
fluctuations in the vacuum these tiny
insignificant things that we take for
granted our universe might really
contain nothing nothing of interest
anyway speaking of the vacuum this
episode was supported in part by Dyson
who sent me their 360 I vacuum in robot
it's got this little camera on the top
that can see 360 degrees around it now
it uses that vision plus some complex
math and trigonometry to work out its
location precisely and to figure out
where it's cleaned already and where it
still needs to clean it actually makes a
map that you can see on your phone using
the Dyson app and you can use that app
also to control the vacuum or to
schedule it even when you're not at home
so I for one welcome robots taking over
the house work if you want to find out
more you can click the link in the
description so I want to thank Dyson for
supporting me and I want to thank my
patreon supporters and of course you for
watching