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if the earth was one giant atom its
nucleus could fit inside of a baseball
stadium
everything outside the stadium the rest
of the planet
that's where the electrons live in a
sort of wavy quantum-y cloud
the stuff that makes up stuff doesn't
contain
much actual stuff huh but if an atom is
just a minuscule nucleus surrounded by a
wavy quantum-y cloud of mostly nothing
kind of makes you wonder why doesn't
light just whoosh right through atoms
and bricks or steel
or chocolate ice cream why aren't you
and i transparent
[Music]
hey smart people joe here so why
aren't we all transparent well we are
if you're an x-ray our bodies just
aren't transparent to visible light
of course visible light and x-rays are
both just different forms of
electromagnetic radiation with different
wavelengths and energies so what's the
difference
well have a seat because glass is in
session
glass is transparent to visible light if
we zoom
down to the atomic level we see glass is
made up of a bunch of
silicon and oxygen atoms same as this
stuff
sand when that sand was melted down into
a liquid
those molecules left the nice perfectly
repeating crystal shape that they were
living in
and they went wild until we cooled them
down really fast and they froze in place
in a sort of
organized jumble all those atoms are
surrounded by wavy quantum electron
clouds
but the electrons around a nucleus can't
be just anywhere
they live on specific energy levels you
can think of them as
different distances from that tiny
nucleus when a photon comes by with
exactly the right amount of energy
it gets absorbed bumping an electron to
a higher energy level
but if that photon doesn't have just the
right amount of energy
it passes right by whoosh
imagine i'm an electron i'm hanging out
here at a low
energy level but i want to move up there
to a higher energy level
to make it happen i have to have just
the right amount of oomph
in my jump too little i don't make it
too much and well oops
just right for the particular atoms that
make up glass the energy levels are so
far apart
that visible light doesn't have enough
energy to boost those electrons up to
the next level
that's why visible light just passes
right through
but photons of uv light do have the
right amount of energy to power up those
electrons and they get absorbed which is
why glass is opaque
to most uv and why it's pretty hard to
get a sunburn through a window
how transparent something is depends on
this relationship between
light energy and an atom's electrons
different elements have different energy
requirements for their electrons to
absorb light
like how invisible light hits my atoms
it's absorbed some light might get
through a few top layers of skin cells
but within a few millimeters
all those photons get gobbled up that's
why i'm not transparent
but hit me with higher energy waves like
x-rays and
i am transparent glad we cleared all
that up
[Music]
but thinking about how atoms are these
wavy quantum-y
mostly empty clouds makes me wonder
something else
why am i even here why aren't the mostly
empty atoms in my feet passing right
through the mostly empty atoms in the
ground
sucking me into earth's superheated iron
core
why can i sit on a chair or kick a ball
or smash those like and subscribe
buttons
why can i touch anything let's say i'd
like to
boop this snoot my finger or booper
and the snoot are both made of about a
gajillion atoms
give or take a squadrillion and all of
those atoms are surrounded by negatively
charged electrons
as the two objects get close enough
together the negatively charged electron
clouds at both surfaces
repel each other thanks to what's called
electrostatic repulsion
the actual boop itself the sensation of
touch
is caused by an actual force from this
repulsion acting on the pressure
sensitive nerves in my skin
kind of like how we're never really
aware of the atmosphere until there's
wind pushing against us touching
something doesn't
really mean decreasing the distance
between me and something else to zero
it's just getting my atoms and that
other object's atoms as close as the
electrons
and physics will allow of course there
is one more way that electrons can
interact
it is actually possible for two
negatively charged electrons to occupy
the same
quantum cloud energy level as long as
they have opposite directions or signs
for a property called spin and sometimes
electrons in two
different atoms can be squished close
enough together
that their waviness even overlaps that's
the reason covalent chemical bonds exist
which is pretty convenient like the ones
in your body
all those molecules that keep you alive
full of atoms
absorbing visible light photons and
just like the bonds between oxygen and
silicon
in this camera lens in the fiber optic
cables of the internet
even in the glass of the screen that's
between us right now
that are letting photons of visible
light pass right through
and which i hope is making this touching
bit of science
just a little bit clearer stay curious
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you can't see me you can't see me well
you can see me in the next video
bye