Kind: captions
Language: en
[Applause]
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 5 or 6 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
excitations in fields the word field
always gets me because it makes me think
of well Fields but a field is just
something that has a value everywhere in
space so every subatomic particle has
its own field an electron field an up
Quirk field a down Quirk field a
neutrino field and so on and anywhere
there's an exitation in this field that
is some energy in the field well that is
where we will observe particles so out
in completely empty space well 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 that 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 ly 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 the cosmic
microwave background radiation the
quantum fluctuations in the fields were
Amplified to Big classical fluctuations
in the density of matter from place to
place and those fluctuations in the
density of matter show up in the
universe today as temperature
differences in the cosmic background
radiation and ultimately in 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 uh this
episode was supported in part by Dyson
who sent me their 360i vacuuming robot
it's got this little camera on the top
that can see 360° around it now it uses
that 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 housework 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