►
From YouTube: Sights of the Cosmos - Introduction to Astronomy
Description
This event provides a different introduction to astronomy than our "Intro to the Night Sky" talks. During this hour, you'll gain an appreciation for the size and scale of the cosmos and our place within it. You'll see many examples of the beautiful objects visible in the night sky, learn something about how we see them through our telescopes and what we can deduce about them through the light they send us. And then you can make your own prediction of whether we're alone in the universe.
A
Hello
good
evening,
everyone
you've
tuned
into
the
san
jose
astronomical
association.
My
name
is
wolf,
and
this
is
science
of
the
cosmos,
an
introduction
to
astronomy.
This
is
our
august
edition
of
this
talk
and
it's
intended
for
folks.
Who've
recently
become
interested
in
astronomy
and
want
to
find
out
what
it's
all
about
or
folks
who
have
recently
come
across
sja
and
want
to
see
what
we
do,
but
if
you've
already
been
in
astronomy
for
a
while
or
you're
already
an
sga
member.
That's
also
great,
so
welcome.
A
A
A
Now,
as
we
go
through,
the
next
hour
feel
free
to
ask
questions
over
youtube
chat.
We
do
appreciate
your
participation.
You
know
please
chime
in
with
any
questions
you
have,
or
just
some
interesting
comments,
go
ahead
and
throw
them
out
there.
I
do
have
swabi
with
me
tonight.
He
is
another
member
of
sj
hi,
swamy
hi
will
hi
everybody
thanks
mommy,
so
tommy's
going
to
be
monitoring
the
youtube
chat,
and
you
know
when
you
ask
questions
some
questions.
A
A
Okay
and
also
before
you
leave
tonight.
Please
give
us
your
feedback.
We
do
appreciate
any
thoughts
you
have
on
how
this
went
ideas
for
doing
it
better
or
anything
that
you
liked.
We
do
try
to
use
that
feedback
to
make
these
events.
You
know
better
as
we
learn
how
to
do
this
more
and
more,
and
you
know
as
we
prepare
for
future
events,
a
quick
tip
for
you
do
consider
youtube's
dark
theme.
A
We're
going
to
be
talking
about
outer
space
outer
space
is
dark,
and
so,
when
I
show
you
pictures
of
outer
space,
they
may
look
better.
If
you
go
to
youtube's
dark
theme-
and
you
can
do
this
by
finding
your
own
little
avatar
icon
in
the
top
left
of
your
youtube
window.
If
you
click
on
that
this
menu
should
pop
open
and
then
somewhere
in
the
middle
you'll,
see
this
dark
theme
thing.
If
you
click
on
that,
you'll
get
another
window
with
this
little
dark
theme.
A
B
A
That
a
try,
if
you
like,
entirely
optional,
but
it
may
make
some
of
this
content,
look
a
little
bit
better
tonight,
give
it
a
shot.
Also
before
we
go
into
the
rest
of
the
material.
I
do
want
to
quickly
just
just
mention
something
about
sj
in
general,
so
we
are
an
educational
organization.
We
are
also
a
non-profit
and
we
run
a
whole
bunch
of
public
events.
We
do
public
star
parties
usually
out
at
dark
sites.
At
the
moment.
A
We
do
these
events
virtually
but
yeah
we
do
star
parties,
we
typically
also
do
school
star
parties
or
we
specifically
go
out
to
middle
schools,
high
schools
whatever-
and
you
know-
do
some
astronomy
and
space
science
with
the
young
ones.
We
have
public
talks.
You
know
like
this
introductory
talk,
but
also
once
a
month
we
have
other
focused
science
talks,
either
with
presenters
from
universities
or
sometimes
even
presenters
from
high
schools.
We
had
a
really
cool
presentation
not
long
ago
about
some
high
school
kids
who
built
a
radio
telescope.
A
So
all
kinds
of
cool
stuff
happens
during
these
public
talks.
We
have
equipment,
help
where
we
can
help.
You
figure
out.
What
to
do
with
an
old
telescope
that
you
might
have
found
somewhere
in
the
back
of
your
closet
or
maybe
something
that
you've
newly
acquired
and
we
also
have
swap
meets
where
you
can
pick
up
some
equipment
nicely?
Sometimes
now,
if
you
choose
to
become
a
formal
sja
member
which,
by
the
way,
is
only
20
bucks
a
year,
I
think
of
that
as
kind
of
the
price
of
a
pizza.
Not
so
bad,
you
know.
A
So
if
you
choose
to
invest
in
the
equivalent
of
one
pizza
and
sja,
you
can
take
advantage
of
our
imaging
workshops
where
you
can
learn
how
to
take
nice
fancy
pictures
of
the
deep
night
sky.
We
have
beginner
training
where
we
can
help
you
find
things
in
the
night
sky
and
how
to
use
your
equipment.
We
also
have
an
equipment
loaner
program
where
you
can
check
out
equipment
and
try
things
out
before
you
might
go
out
and
buy
something
for
yourself.
A
We
have
a
nice
library
of
books
and
we
have
private
observing
events
now,
of
course,
this
whole,
you
know
coronavirus
and
covert.
19
situation
has
impacted
what
we
do
so
a
lot
of
our
public
events
have
had
to
be
cancelled,
unfortunately,
but
instead
we're
trying
to
bring
new
content
virtually
like.
We
are
tonight
and
at
some
point
in
the
future.
I
hope
we
can
get
back
to
our
regular
program,
of
course
as
well.
A
If
you
want
to
find
out
more,
you
can
go
to
sj.net
or
check
us
out
on
meetup
here,
where
we
are
showing
all
of
our
public
events,
and
that
may
actually
be
how
you
found
us
tonight.
I
suppose,
normally
our
location
is
in
san
jose
in
a
place
called
hoagie
park.
We
have
a
lot
of
our
events
there
or
other
dark
sky
dark
night
sky
sites
and
yeah.
You
know.
Maybe
we
can
meet
there
sometime
in
the
future
when
life
returns
kind
of
to
normal,
okay,
let's
see
and
before
we
move
on.
A
I
also
want
to
plug
our
other
introduction
to
astronomy
right
so
I'll,
be
talking
to
you
about
astronomy
tonight,
giving
you
a
nice
introduction,
but
we
have
another
session
and
the
next
one
of
this
particular
type
will
be
in
about
two
weeks.
Please
check
meet
up
for
the
details,
and
this
intro
to
the
night
sky
in
two
weeks
will
be
nicely
complementary
to
what
we
do
here
today.
You
know
astronomy
has
many
facets.
There
are
many
ways
to
approach
it
and
enter
to
the
night
sky.
A
Will
give
you
some
introduction
on
how
to
read
the
night
sky,
how
to
find
constellations
things
like
that.
So
that's
a
nice
complementary
talk
to
what
we're
going
to
do
here
tonight.
So
keep
that
in
mind
if
you'd
like
to
check
that
out,
here's
an
outline
of
what
we're
going
to
do
tonight,
but
you
know
this
is
too
many
words.
I
always
say
this
looks
too
much
like
a
business
presentation,
so
instead
I
just
think
of
it.
This
way
right,
it's
a
sampler
of
astronomy,
stuff,
right
astronomy
has
a
lot
to
offer.
A
A
So
let's
get
started
with
this
okay.
So
when
you
look
out
into
space
what
kind
of
stuff
do
we
see
there?
Well,
if
we
believe
the
movies
right,
we
see
this
kind
of
stuff
right
and
here's
kind
of
a
test
of
your
nerd
cred.
So
if
you'd
like
to
play
along,
you
can
type
into
the
youtube
chat.
You
know
what
these
different
things
are
I'll
help
you
out
with
a
couple
of
them
right,
of
course,
here
on
the
top,
everybody
should
really
get
this
one.
A
This,
of
course,
is
the
death
star
from
star
wars,
and
then
we
have
down
here.
You
know
the
millennium
falcon,
also
from
star
wars.
Some
of
the
other
ones
are
going
to
be
a
little
harder
right.
I
don't
know
what
about
this
guy
over
here
on
the
middle
left
right.
Anybody
know
what
this
one
is.
I
know
I'm
probably
dating
myself
by
including
this
but
hey
I
used
to
like
this
show
and
you're
not
going
to
tell
me
any
different,
so
yeah.
A
A
These
are
the
kind
of
things
that
we
see
when
the
movies
show
us
outer
space,
and
I
like
spaceships
and
I
like
sci-fi,
but
when
we
really
look
into
outer
space,
what
we
see
is
actually
this
stuff
instead,
so,
unfortunately,
there
are
no
spaceships
here,
but
I
do
think
that
these
objects
that
we're
seeing
here
now
are
actually
also
really
cool
in
their
own
way
right
and
there's
a
lot
to
learn
from
them.
There's
a
lot
of
beauty
to
enjoy
so
we'll
talk
about
these.
A
So
there's
a
lot
of
stuff
ahead
in
this
presentation,
because
there's
a
lot
of
different
stuff
in
space.
Please
do
ask
questions
like
we
mentioned
earlier
and
if
you're
lucky,
I
might
even
know
the
answer
now.
Don't
remember.
Don't
worry
about
remembering
all
this
stuff
that
I'm
going
to
tell
you
just
enjoy
the
show,
but
I
do
have
an
assignment
for
you
maybe
pick
something
from
this
talk
and
then
ask
someone
about
it
later
and
it
turns
out.
A
You
might
have
a
great
opportunity
to
ask
a
question
tomorrow,
because
tomorrow
we
have
our
armchair
star
party.
This
is
one
of
our
online
virtual
star
parties
that
we're
doing
now.
You
know
due
to
the
coronavirus
restrictions,
so
this
will
be
tomorrow.
You
can
check
out
the
details
on
meetup
it'll,
be
at
8
45,
because
we
have
to
go
by
the
sunset
somewhat
so
yeah
so
here
check
it
out.
This
will
be
on
tomorrow.
A
Okay,
also,
please
visit
meetup.com
to
sign
up
for
this
okay.
So
now
you
are
here,
of
course,
we're
all
usually
we'd
be
doing
this
in
a
hall
where
I'd
be
speaking
to
you,
live
and
we'd
all
be
sitting
in
the
hall
in
hokie
park.
Instead,
you
know
we're
all
sprinkled
about
sitting
at
our
computers
or
tablets
or
phones,
but
regardless
you
know
we
are
all
here
on
earth
right.
This
is
our
home.
This
is
where
we
were
born.
This
is
where
we
live.
A
This
is
where
we
will
be,
and
I
imagine
that
many
of
you
from
all
over
the
place
right.
So
you
know,
of
course
you
know
I'm
right
now
somewhere
over
here.
You
know
we're
over
here
on
the
west
coast
of
the
us,
but
I
was
born
in
germany
and
I
imagine
that
you
know
some
of
you
are
from
various
places
here
right
all
over
the
globe.
So
yeah.
This
is
our
home.
We
are
here
now
we
can
zoom
out
a
little
bit
and
we
can
include
the
moon
in
this.
A
You
are
here
neighborhood
right,
so
the
moon,
of
course,
is
something
that's
very
familiar
to
us
and
it's
definitely
part
of
our
neighborhood
and
and
here's
a
picture
of
the
earth
moon
system,
but
from
a
very
different
perspective
right.
This
is
a
historic
picture.
This
was
the
first
time
we
saw
the
earth
from
the
perspective
of
another
world.
This
was
taken
when
apollo
8
orbited,
the
moon,
and
this
picture
is
called
earthrise
right
yeah.
So
this
is
the
first
time
we
saw
the
earth
like
this.
A
You
know
with
the
horizon
of
the
moon
in
the
foreground,
so
it's
a
pretty
amazing
historic
picture,
but
neither
of
these
pictures
this
one
or
the
prior
one
really
gives
you
a
good
feel
for
how
far
away
the
moon
is
from
the
earth.
It
used
to
be
that
you
know
in
historical
times
people
thought
hey.
Maybe
the
moon
is
pretty
close.
A
Maybe
if
I
climb
a
really
tall
mountain,
I
could
actually
reach
it,
but
it
turns
out
that
doesn't
work
and,
of
course
we
know
that
now,
but
still
we
don't
really
have
a
good
feel
for
how
far
away
the
moon
is,
and
it
turns
out.
This
picture
is
a
much
better
representation
of
that
distance.
So
this
is
a
real
photograph.
A
You
can
see
the
earth
over
here
and,
of
course,
over
here,
this
smaller
dot
is
the
moon,
and
this
picture
was
taken
by
a
spacecraft
that
we
launched,
and
that
was
receding
from
the
earth
moon
system
and
took
that
picture
as
it
was
moving
away.
So
here
you
have
a
much
better
feel
now
for
how
far
the
moon
really
is
from
the
earth,
and
this
is
kind
of
a
theme
of
tonight's
talk.
A
I'm
hoping
that
I
can
give
you
a
good
perspective
of
you
know
how
things
are
arranged
in
space
right
so
that
we
get
a
better
feel
for
what
we're
really
looking
at
when
we're
looking
out
into
the
night
sky.
So,
okay,
if
we
take
another
step
back,
we
can
say
hey.
You
know
we're
not
just
part
of
the
earth
moon
system.
We
are
in
fact
part
of
our
solar
system
right
and
so
here
is
a
nice
representation
of
our
solar
system.
This
looks
pretty,
but
it's
an
artist's
representation.
A
This
is
not
at
all
scientifically
accurate.
I
mean
the
planets
are
in
the
right
order.
That's
nice!
You
know
mercury
is
over
here
and
then
we
have
venus
earth
mars
and
so
on.
That's
all
good,
but
the
sizes
and
spacings
are
all
wrong,
and
so
this
next
picture
gives
you
a
much
better
feel
for
how
things
are
really
spaced
out
and
one
key
takeaway
from
this
is
hey.
Take
a
look
so
here
over
on
the
left.
You
see
these
little
four
bunched
up
dots
right
so
again.
This
is
mercury.
A
A
So
it
turns
out
that
jupiter,
you
know,
is
a
pretty
big
step
out
and
then
saturn
and
uranus
and
neptune
and
pluto
are
way
out
there.
You
see
these
units
down
here.
It
says
10,
aau
or
20
au.
We'll
see
this
again
later,
but
I'll
give
you
a
preview.
An
au
is
an
astronomical
unit.
That
is
a
unit
we
use
just
to
to
describe
the
distance
between
the
earth
and
the
sun,
and
so
the
earth,
by
definition,
is
one
a
you
away
from
the
sun.
A
So
you
can
see
that
saturn
is
about
10
of
those
distances
away
from
the
sun,
and
you
can
see
that
pluto
is
almost
out
here
at
40,
a.u,
so
yeah.
So
this
you
know,
is
a
much
better
representation
of
how
things
are
spaced
out.
In
the
solar
system
again,
a
key
takeaway
is
that
the
first
four
planets
actually
quite
bunched
up
and
then
the
rest
is
much
more
stretched
out.
A
Okay,
but
we
can
take
another
step
back
and
we
can
say
hey.
We
are
here
as
residents
of
the
milky
way
galaxy
and
usually
when
I
do
this
talk
in
front
of
a
live
audience
I'll
ask
here.
You
know
who
has
seen
the
milky
way
galaxy
and
usually
a
few
hands
will
go
up,
but
not
everybody
will
have
seen
this
and
I
really
encourage
you
to
go.
A
I
did
not
really
see
the
milky
way
in
a
dark
sky
until
I
was
in
my
30s
and
man
that
was
way
too
late,
so
go
out
there
and
see
it,
it's
really
beautiful.
It's
really
awe
inspiring
and
yeah.
You
can
see
something
like
what's
shown
here
in
this
picture.
Perhaps
right
depends
on
the
time
of
the
year
and
how
dark
the
site
is,
but
it
is,
it
is
a
very
beautiful
sight,
so
yeah,
so
the
milky
way
galaxy
is
part
of
our
home,
and
you
know
it
looks
something
like
this
from
the
outside
right.
A
So
when
we're
in
it-
and
we
look-
you
know
into
the
sky-
we
see
you
know
these
light
and
dark
bands.
If
we
were
to
look
from
the
outside,
we
would
see
something
like
this
flattish
spirally
disc.
Now
we
do
run
into
a
problem
here
right,
and
you
see
my
note
on
the
side.
It
says
not
our
actual
galaxy,
but
a
lot
like
home
and
it's
not
our
actual
galaxy
because
yeah,
it's
too
big,
we
cannot
go
outside
it
to
take
a
picture
of
it
right.
A
So
it's
imagine
like
imagine
like
you're
stuck
in
your
house.
Actually
that's
almost
too
close
to
home
right
now,
given
the
coronavirus
situation
right,
we've
all
been
stuck
in
our
houses.
Imagine
you're
stuck
in
your
house
and
you
just
cannot
go
outside
you've,
never
seen
your
own
house
from
the
outside.
How
could
you
learn
about
your
own
house
from
the
outside?
If
you
cannot
go
outside
to
really
look
at
it?
That
way?
Well
turns
out.
You
can
still
learn
quite
a
bit
right.
A
You
could
walk
around
your
own
house
and
you
could
explore
the
inside
your
floor
plan
right
and
you
could
look
out
your
window
and
you
could
look
at
other
people's
houses
right
and
combining
the
information
you
learned
by
walking
around
your
own
house
and
then
looking
at
other
people's
houses
through
your
window.
You
can
kind
of
get
an
idea
of
what
your
house
must
look
like
from
the
outside
and
that's
kind
of
how
we
learn
about
owen
galaxy
right.
A
We
cannot
see
our
own
galaxy
from
outside,
but
we
can
sort
of
explore
from
the
inside
a
little
bit.
We
can
look
around
and
we
see
other
ones
out
there
and
we
can
use
that
information.
You
know
and
combine
it
all
and
get
an
idea
of
what
things
really
look
like,
but
I
know
I
may
be
actually
jumping
ahead
a
little
bit
right.
I
understand
often
that
at
some
point
some
of
you
at
this
point
might
be
asking
wait
a
minute.
What's
a
galaxy
exactly
well,
it
turns
out
a
galaxy.
A
A
A
So
when
we're
looking
at
the
sun
from
the
earth,
we
see
against
the
blue
sky,
because
the
atmosphere
scatters
the
light,
and
you
know
everything
that
looks
nice
and
blue,
but
when
we
see
it
from
the
outside
earth's
atmosphere,
we
see
from
outer
space
yeah.
We
just
see
this
bright
ball
hanging
out
there
in
space
for
comparison.
Let's
take
a
look
at
this
down
here.
So
here's
a
night
sky
picture
that
an
sja
member
took
at
a
place
called
pinnacles
national
park
where
we
sometimes
have
events
and
let's
focus
on
this
dot
right
here.
A
This
star
is
a
star
called
sirius,
and
if
we
look
at
that
one
more
closely,
it
looks
like
this
picture
here
on
the
bottom
right
and
you
might
go
this
picture
on
the
bottom
right
and
the
picture
of
our
own
sun.
They
actually
look
pretty
similar
and
it
turns
out
they
are
right.
So
the
key
thing
here
is
that
our
sun
and
other
stars
are
essentially
the
same
kind
of
thing,
and
this
is
not
something
we've
known
forever
right.
It
turns
out.
This
is
actually
a
relatively
recent
discovery.
A
I
think
only
about
200
years
or
so
ago.
Did
we
realize
that
hey
those
little
dots
in
the
night
sky
in
our
sun
are
the
same
kind
of
thing
right?
That
was
actually
quite
a
profound
realization
and
then
here's
a
picture
of
some
star
clusters
that
are
inside
our
galaxy
in
here.
If
you
were
to
start
and
count,
you
could
count.
A
You
know
a
few
thousand
stars,
so
that's
already
quite
a
lot,
but
if
we,
you
know
take
an
even
bigger
chunk
of
stars,
then
we
talk
about
a
galaxy,
so
galaxies
tend
to
look
like
this.
There
are
a
few
other
variants
as
well,
but
very
commonly
they
are.
You
know
these
flatter
structures
with
the
bright
core
and
kind
of
these.
The
spiral
arrangement.
You
know
around
that
core
and
now
this
galaxy
has
our
galaxy
has
about
two
to
four
hundred
billion
stars.
That's
a
lot
right.
A
Our
sun
is
one
of
them,
but
there's
a
whole
bunch
of
other
ones.
But,
like
I
said
earlier,
this
is
not
our
actual
galaxy
right.
So,
let's
see
so
a
better
view
of
home
of
our
home
galaxy
is
this
now
like
I
said
we
cannot
really
see
it
from
the
outside,
so
this
is
not
a
photograph,
but
this
is
a
drawing
that
we've
created
based
on
scientific
data.
A
So
this
is
our
best
understanding
of
the
structure
of
the
milky
way
galaxy
as
it
would
look
from
the
outside,
and
you
can
see
that
there's
a
little
dot
marked
sun
here,
so
we
live
here.
And
finally,
I
guess
right
so
here
are
these
really
nice
big
fancy
spiral,
arms
right
like
the
sagittarius
arm
here
and
notice,
we
don't
live
in
the
fancy
spiral,
arms
we
kind
of
live
in
the
cheap
part
of
town
right,
which
is
right
here.
You
know,
that's
where
the
sun
is
sitting,
but
hey
our
home,
still
pretty
nice.
A
So,
let's
not
knock
it
so
yeah.
This
is
a
slightly
bigger
view
of
the
same
thing.
Right
and
again,
the
the
sun
is
is
right
here.
So
this
is.
This
is
our
home
about
halfway
between
the
core
and
the
outer
extents
of
the
galaxy
okay
and
within
the
milky
way
galaxy
within
our
home.
We
see
stuff
like
this.
We
see
stars
planets,
nebulae
and
other
cool
things
right,
and
if
we
look
far
enough
out,
we
actually
see
other
galaxy.
A
That's
like
looking
out
like
you're
looking
out
your
window
and
seeing
other
houses
right
so
so
these
are
all
things
that
we
can
observe
when
we
look
into
the
night
sky
and
we'll
talk
about
each
of
these
a
little
bit
more,
but
before
we
do
that,
I
want
to
take
a
moment
and
talk
about
large
numbers.
So,
let's
see,
let's
do
a
thought
exercise
here.
You're
all
familiar
with
pennies
right.
You
may
have
some
rolling
around
your
car.
A
You
know
if
you
went
for
a
drive
today,
maybe
there's
some
loose
pennies
somewhere
there,
or
maybe
some
pennies
got
lost
somewhere
in
your
sofa
cushions.
So
imagine
a
penny
right
and
now
here
is
a
bottle
of
pennies.
So
let's
do
a
quick
estimate
here,
so
you
guys
can
help
me
out.
Look
at
this.
This
kind
of
milk
bottle
full
of
pennies
and
help
me
estimate
how
many
pennies
are
in
this
bottle.
A
I
don't
know
so.
Usually
you
know
when
we
do
this
with
the
live
audience.
I
kind
of
pull
the
audience
and
I
get
different
kinds
of
estimates.
Usually
estimates
I
get.
Maybe
oh
a
couple
hundred
or
500
or
2000,
or
something
like
that
right,
so
the
estimates
will
vary
quite
a
bit
and
the
answer
is
well
turns
out.
I
don't
know
the
answers
that
may
be
disappointing,
but
I've
done
a
little
bit
of
math
and
I
think
it's
about
1500
pennies
in
this
case
right.
A
So
by
doing
a
little
bit
of
math,
I've
estimated
this
to
be
1500
and
the
key
takeaway
here
is
that
yeah,
the
estimates
that
we
come
up
with
just
by
quickly
looking
at
it
right
and
and
just
going
with
gut,
feel
we'll
we'll
be
all
over
the
place
like
I
said,
200
400,
2,
000
right.
So
the
the
message
here
is
that
estimating
or
visualizing
counts
of
things
can
be
very
difficult,
especially
if
we're
talking
about
really
large
numbers
right.
A
So,
let's
calibrate
ourselves
a
little
bit,
because
when
we
talk
about
astronomy
numbers
will
get
big.
Here's
a
thousand
pennies.
This
is
pretty
easy
to
understand
right.
You
can
imagine,
having
this
pile
of
pennies
just
right
in
front
of
you
on
your
desk,
no
big
deal
100
000
pennies,
still,
not
so
bad
right.
This
could
be
like
two
cubic
feet
of
pennies
sitting
in
front
of
you
on
your
desk
again,
not
too
bad.
A
Okay,
now
here's
one
million
pennies,
but
now
for
the
next
step.
I
want
you
to
do
a
quick
thought
exercise
right.
So
imagine
a
friend
calls
you
up
right
and
you
answer
the
phone
and
your
friend
says:
oh,
I
have
to
go
on
a
vacation,
but
I
don't
want
to
leave
my
penny
collection
unattended.
Can
you
please
help
me
out
and
take
care
of
my
penny
collection?
A
While
I'm
gone
and
you
ask
well
how
many
pennies
do
you
have
and
your
friend
says:
oh
I've
got
a
billion
pennies
I'll,
be
over
in
an
hour,
get
ready
and
your
friend
hangs
up
and
gets
ready
to
go
right,
and
so
now
your
friends
coming
over
the
billion
pennies.
Where
would
you
put
those
in
your
house
how
much
space
would
they
take
the
million
pennies
we
see
right
here
they
might
fit
into
your
bathtub.
I
think
right,
roughly
about
a
billion
pennies.
A
Where
would
you
put
those
it
turns
out
a
billion
pennies
is
well
I'm
sorry.
Here
we
have
10
million
pennies.
This
is
a
pretty
big
cube
next
to
this
little
person
here
right
and
then
a
billion
pennies
is
like
five
school
buses
worth,
so
that's
probably
more
pennies
than
I
could
fit
in
my
house
right
so
yeah.
You
know
these
things
get
really
big,
really
fast.
Here's
a
hundred
billion
pennies.
A
So
here
we
have
that
big
cube
of
100
billion
pennies
sitting
on
a
football
field
for
a
comparison
and
the
little
person
that
we
had
for
comparison
earlier
is
now
down
here.
You
know
like
a
couple
pixels
tall
and
to
tie
this
back
to
the
discussion
of
the
milky
way
galaxy.
We
had
earlier
right,
so
we
said
we
have
at
least
200
billion
stars
in
the
milky
way,
so
that
would
be
equivalent
to
at
least
two
huge
cubes
of
pennies
like
this.
A
If
we
bump
it
up
to
one
trillion
pennies
here
we
are,
you
know
having
this
giant
cube
sitting.
You
know
next
to
a
few
structures
like
sears
tower
and
the
empire
state
building,
and
also
the
washington
monument
and
the
football
field
is
down
here
and
a
quadrillion
pennies
looks
like
this
and
here's
one
quintillion
pennies.
That's
a
billion
billion
pennies
or
one
with
18
zeros
right
so
now
you
know:
we've
completely
lost
the
football
field,
and
you
know
even
those
big
buildings
are
pretty
tiny
looking
down
here.
A
So
as
we
continue
through
this
material,
keep
these
numbers
in
mind
right
we're
going
to
need
to
remember
how
big
all
these
numbers
really
are,
and
it
turns
out.
Even
these
big
numbers
will
not
be
enough
when
we
talk
about
astronomy,
astronomical
terms
so
armed
with
this
information
about
numbers,
let's
talk
about
distances
in
space
for
a
moment,
okay,
so
how
far
is
far
well
earth
to
the
moon
is
238
856
miles
on
average.
Okay,
we
could
deal
with
that.
Earth
of
the
sun
is
about
93
million
miles
and
earth.
A
The
nearest
star
other
than
the
sun
is
well
that
really
big
number,
I'm
not
even
going
to
try
to
say
it
right
now
and
then
earth
the
center
of
the
milky
way.
Galaxy
is
an
even
bigger
number
of
miles,
which
I'm
also
not
going
to
try
to
say
so
we're
already
running
into
a
problem
where
these
numbers
are
getting
too
big
and
just
hard
to
manage
right.
So
it
turns
out
in
astronomical
terms,
we
often
deal
with
distances
in
a
different
way,
and
so,
let's,
let's
see
if
we
can
get
there.
A
So
let's
talk
about
how
we
see
things
right,
so
we
see
objects
in
space
through
light
that
they
emit
or
reflect,
and
that
light
then
reaches
us
right.
For
example,
you
see
me
because
it's
a
lamp
turned
on
next
to
me,
light
comes
from
the
lamp
bounces
off
me
hits
the
camera
and
then,
ultimately,
that
makes
your
monitor
light
up
right
and
that
light
hits
your
eyes
and
that's
how
you
see
stuff
right.
So
we
see
things
through
light
and
it
turns
out
that
light
travels
at
a
very
specific
speed.
A
We
call
that
speed
c,
and
that
is
exactly
299
million
792
458
meters
per
second
in
a
vacuum.
Now
that
also
is
hard
to
say
right,
so
we
often
just
approximate
that
at
as
300
000
kilometers
per
second
or
186
000
miles
per
second
okay.
So
how
long
does
it
take
before
we
see
stuff?
So
in
a
moment,
we're
going
to
imagine
a
mirror
on
the
moon
and
we're
going
to
bounce
a
laser
off
that
mirror,
but
to
get
a
little
better
feel
from
what
we're
talking
about.
Actually,
I
have
a.
A
I
have
kind
of
a
laser
in
my
hand
here.
This
is
like
the
presentation
laser
and
let's
pretend
for
a
moment
that
my
hand
is
the
moon,
and
I
can
you
know
I
can
bounce
this
laser
right
off.
My
palm
and
the
question
is:
how
long
does
it
take
from
the
moment?
I
push
the
button
until
we
see
the
laser
beam
bouncing
off
my
hand,
and
you
know
for
this
little
experiment
with
my
hand,
the
answer
is
well,
it
seems
to
be
immediate
right.
A
I
push
the
button
and
I
see
the
light
essentially
right
away,
but
it
actually
does
take
some
time
for
the
light
to
travel.
It's
just
that
the
distances
are
so
short
that
we
don't
perceive
that
time
at
all.
It
seems
like
it's
instantaneous,
but
it
really
isn't
and
if
we
now
get
back
to
the
imaginary
mirror
on
the
moon,
we
can
do
it.
You
know
just
experiment
with
much
larger
distances
and
see
what
happens
then,
and
it
actually
turns
out.
A
We
don't
even
need
to
imagine
the
mirror,
because
there
really
is
a
mirror
on
the
moon.
We
put
it
there.
The
apollo
missions
left
what
we
call
lunar
arranging:
retro
reflectors,
that's
nasa's
term,
for
a
mirror
up
on
the
moon.
So
this
is
the
lunar
surface
right.
You
can
see
footprints
here
left
by
our
astronauts.
I
always
see
this
ziploc
bag
over
here
and
hope
that
we
didn't
leave
it
there,
because
that
you
know
I
wouldn't
have
wanted
to
leave
trash
up
there
on
the
moon.
A
But
the
key
thing
here
is:
is
the
mirror
right
and
so
imagine
that,
instead
of
bouncing
light
off
my
hand,
I
can
shoot
my
laser
at
this
mirror
and
then
have
the
light.
Beam
come
back
down
to
earth.
So
how
long
would
it
take
to
bounce
a
laser
off
this
mirror?
Well,
it
turns
out
it
takes
about
two
and
a
half
seconds
right.
So
that's
the
round
trip
time.
So
that
means
the
moon
is
about
one
and
a
quarter
light
seconds
away
right.
A
It
takes
light
one
and
a
quarter
seconds
to
get
there
and
then
another
one
and
a
quarter
seconds
to
get
back
down
to
us
all
right
so
yeah.
So
now
we
can
express
distances
in
terms
of
light
right.
So
how
far
does
light
travel
in
different
amounts
of
time?
Well
in
one
second,
it's
about
186
000
miles
right
then
we
call
that
one
light.
A
So
now
we
can
revisit
this.
How
far
is
far
to
slide
right
and
we
can
express
our
distances
in
terms
of
light,
so
the
earth
to
moon
distance
is
about
one
and
a
quarter.
Light
seconds,
like
we
discussed
a
moment
ago,
earth
of
the
sun
is
about
eight
and
a
third
light
minutes,
and
we
also
call
that
one
astronomical
unit,
like
I
mentioned
earlier,
the
nearest
star
is
about
four
and
a
quarter,
light
years
away,
okay
and
then
earth.
A
The
center
of
the
milky
way
is
about
25
000
light
years
and
yeah,
and
I
think
these
numbers
are
much
more
manageable,
they're,
easy
to
remember
and
they're
certainly
easier
to
see
and
yeah.
So
here's
our
nearest
galactic
neighbor
right
if
we
look
at
other
galaxies
around
us
and
dramatic,
is
the
nearest
one,
and
this
thing
is
about
two
and
a
half
million
light
years
away.
A
A
Okay,
so
let's
do
a
really
quick
rerun
of
this.
You
are
here
kind
of
with
a
new
perspective
right,
so
again
here's
earth.
We
talked
about
that
before
right,
we're
all
sitting
here
living
our
lives,
and
if
you
wanted
to
walk
all
the
way
around
earth,
it
would
be
8
000
miles.
I'm
sorry.
The
diameter
is
about
8
000
miles
and
if
you
wanted
to
walk
all
the
way
around,
you'd
have
to
be
walking
about
25
000
miles
to
make
it
all
the
way
around
the
sphere.
A
Our
solar
system
is
here
it's
about
14,
light
hours
across
again
notice
that
you
know
all
the
rocky
planets
are
bunched
up
really
close
to
the
sun,
and
then
things
get
much
more
spread
out
and
if
I
were
to
take
a
laser
beam
and
shoot
it
off
over
here
and
have
it
go
all
the
way
across
right
that
would
take
14
hours.
The
laser
beam
would
need
14
hours
to
go
all
the
way
across,
so
this
is
14
light
hours
of
distance
across
the
next
slide
is
our
solar,
interstellar
neighborhood.
A
So
this
is
roughly
the
bright
stars
that
you
see
with
the
naked
eye
under
under
good
sky
conditions.
You
know,
and
so
this
solar
interstellar
neighborhood
is
about
60
light
years
in
each
direction
or
120
light
years
across,
so
so
the
earth,
sorry,
the
sun
and
the
earth
are,
you
know,
kind
of
here
in
the
center
and
then
yeah,
it's
60
light
years
in
each
direction.
If
we
take
a
step
back,
here's
our
milky
way
galaxy
right
again.
A
This
is
not
our
actual
galaxy,
but
it
shows
that
we
are
about
halfway
from
the
center
and
the
whole
galaxy
has
about
a
hundred
thousand
light
years
across
and
we're
about
25
000
light
years
from
from
the
core.
If
we
take
another
step
back,
we
call
this
the
local
galactic
group.
This
is
our
immediate
galactic,
neighborhood
right,
and
so
we
are
here
and
then
here
is
the
andromeda
galaxy
that
I
mentioned
earlier
right.
So
this
is
two
and
a
half
million
light
years
away.
This
is
our
nearest
big
neighbor
notice.
A
There
are
actually
a
couple
of
fuzzies
down
here
right.
These
are
the
large
and
small
magellanic
clouds.
We
call
those
dwarf
galaxies
and
those
things
are
visible
from
the
southern
hemisphere.
So
if
you
ever
go
to
australia
or
new
zealand,
if
you're
there
at
the
right
time
of
year
check
this
out,
this
should
be
cool
to
see.
I
was
in
australia
last
year
and
it
was
the
wrong
time.
I
didn't
get
to
see
it
so
now.
I
have
to
go
back
just
to
see
the
magellanic
clouds
so
yeah,
but
this
is
our
local
galactic
neighborhood.
A
If
we
take
another
step
back,
we
find
ourselves
in
something
called
the
virgo
super
cluster.
So
our
galaxy
is
part
of
a
larger
group
of
clusters.
Excuse
me
a
larger
cluster
of
galaxies
that
we
call
the
virgo
supercluster
right
and
here
this
is
about
50
million
light
years
in
each
direction
or
about
100
million
light
years
across
next
step.
Back
is
kind
of
the
group
of
local
superclusters
right,
and
this
is
about
1
billion
light
years
in
each
direction.
A
A
giga
light
year,
1
billion
light
years,
each
direction
or
about
2
billion
light
years
across,
and
then
here
is
the
observable
universe.
So
here
we
are
in
the
center
and
it's
about
46
billion
light
years
in
each
direction
or
about
you
know,
92
light
years
across
now
we
appear
to
be
in
the
center.
It's
like
wow,
who
knew
that
we're
the
center
of
the
universe.
Well,
it
turns
out
that
actually,
no
matter
who
you
are,
you
could
be
an
alien
living
on.
A
You
know
a
planet
around
a
star
somewhere
over
here
and
from
your
perspective
as
that
alien,
you
would
also
appear
to
be
in
the
center
of
the
universe.
So
don't
get
a
big
head,
no
matter
where
you
are
in
the
galaxy,
you
know
it
always
looks
like
you
know
we're
in
the
center
of
it.
So
there
you
go
right.
Don't
let's
not
think
that
we're
all
that
important,
because
we
appear
to
be
in
the
center
all
right,
so
this
was
kind
of
a
visit
of
where
we
are
in
space
right.
B
A
About
13.8
billion
years
old,
the
milky
way
galaxy
has
been
around
for
most
of
that
time,
actually
right
about
13.5
billion
years,
our
solar
system,
you
know
sun
and
the
earth
have
been
around
for
about
4.5
billion
years
and
humanity
has
been
around
for
about
300
000
years
right
and
that
little
line
I
drew
over
here
right.
So
this
this
little
line
is
actually
not
even
thin
enough
right.
If
I
drew
it
truly
to
scale,
we
probably
couldn't
see
it.
A
So
this
puts
us
into
perspective,
you
know
so,
most
of
the
time
the
universe
has
gotten
by
just
fine
without
us.
You
know
we
have
been
a
relatively
recent
addition
to
this,
so
I
find
this
fun
to
think
about
right.
So
you
know,
universe
is
just
really
really
big
and
also
you
know,
time
has
been
around
for
a
long
time
right,
but
we've
actually
only
taking
up
a
small
percentage
of
both
time
and
space.
You
know
yet
we
are
here
and
we're
able
to
think
about
all
this
stuff
and
investigate
and
understand
it.
B
A
A
Is
it
a
sphere
or
I'm
sorry?
Why
is
it
a
cylinder
right
in
this
diagram?
Yeah,
that's
a
good
question
and
I
think
I
got
a
similar
question
actually
the
last
time
I
gave
this
talk,
so
whoever
the
other
person
was
asking
you
guys
have
the
same
brain
waves.
So
it's
a
good
question
and
I
have
to
say
I
borrowed
the
slides
from
somewhere
else.
I
can't
remember
I
have
it
in
the
credit
somewhere
and
I
think
it's
just
a
way
to
represent
data
on
the
slide,
so
I
think
you're
right.
A
You
know,
as
a
sphere
projected
on
a
flat
screen
on
a
flat
slide,
as
opposed
to
the
cylinder
projected
on
a
flat
slide.
So
I
hope
that's
a
satisfying
answer.
So
actually
I
mean
I
like
your
suggestion
that
you
know
really.
We
should
think
of
it
as
as
a
as
it
was
for
you
yeah
good
question.
Thank
you,
and
maybe
the
other
person
who
asked
last
time
is
your
long-lost
sibling,
so
go
go,
find
that
okay.
A
All
right,
so,
let's
boogie
on
so
now,
let's
go
ahead
and
look
into
space
and
yeah.
I
would
say
we
can
just
start
by
looking
up.
I
mean
even
right
now:
don't
do
it
right
now,
because
we're
not
done
with
this
presentation,
but
when
we're
done
with
this
presentation,
you
can
go
outside
and
just
look
at
the
night
sky
and
you'll
see
bright,
dots
and
there's
cool
stuff
up
there.
A
For
example,
jupiter
is
up
in
the
night
sky
right
now
the
brightest
dot
you'll
see
tonight
is
jupiter
and
if
you
come
to
the
armchair
star
party
tomorrow,
we'll
show
you
what
that
really
looks
like
up
close
but
yeah
there's
a
lot
of
stuff.
You
can
see
just
by
looking
up
right.
So
when
you
look
into
the
night
sky,
you
can
get
a
lot
done
just
with
your
eyeballs
right.
A
You
don't
even
need
equipment
and
there's
still
a
lot
you
can
appreciate,
or
if
you
have
binoculars
right,
you
can
use
those
to
look
at
the
night
sky
and
that
reveals
even
more
details
than
you
can
see
with
your
naked
eyes
unaided
eyes.
But
I
realize
that
most
of
you
guys,
you
know,
probably
come
to
astronomy
and
want
to
listen
to
a
talk
like
this,
because
your
cure
is
also
about
telescopes.
So
we'll
talk
about
that
for
a
moment.
A
So
why
are
we
using
telescopes
at
all?
What
do
they
really
do
for
us?
And
again,
usually
I
pose
this
question
to
the
audience
and
I
collect
some
answers.
But
since
I
can't
easily
do
that
right
now,
I'll
just
say
that
often
the
one
of
the
first
answers
I
get
is
to
magnify
right.
People
will
say
yeah
telescopes,
magnify
things
and
that's
true.
They
absolutely
do,
but
it
turns
out.
That's
actually
not
necessarily
the
most
important
function
of
our
telescopes.
A
The
telescopes
really
are
there
to
collect
light
right
to
make
faint
objects
appear
brighter
and
let's,
let's
talk
about
what's
happening
there
and
how
that
works.
So
when
we
see
things
with
our
own
eyes
right
light
enters
our
eyes.
We
collect
light
through
our
pupils
right,
which
is
the
little
little
hole
here
in
the
middle
right,
and
the
pupil
varies
in
size.
You've
all
seen
this
in
your
own
eyes
or
in
the
eyes
of
others
around
you
in
bright
light
right.
A
A
Harder
to
open
up
that
pupil,
so
that's
one
reason
why
it's
still
harder
to
see
things
as
we
age
but
yeah
to
be
able
to
put
more
light
into
our
eyeballs.
We
need
a
light
funnel
right
and
here's
kind
of
how
I
think
about
this.
Imagine
now
you're
really
thirsty,
but
you
don't
have
any
water
nearby,
no
water,
fountains,
no
water
bottles,
nothing
hey,
but
it's
raining
outside.
A
So
if
you
go
outside
and
just
stand
there
with
your
mouth
open
right
and
try
to
collect
raindrops
and
you
will
catch
raindrops
in
your
mouth-
and
you
know
if
you
wait
long
enough-
that
will
quench
your
thirst
but
you're
going
to
have
to
stand
there
a
long
time
to
collect
enough
rain
drops
because
your
mouth
is
not
that
big
right.
But
now
imagine
you
had
a
big
funnel
you
could
put
over
your
mouth
right.
A
Then
you
could
be
collecting
a
lot
more
raindrops
in
a
given
amount
of
time
and
you
could
probably
quench
your
thirst
much
faster.
So
it
turns
out
light
kind
of
works.
The
same
way
right.
We
want
to
be
able
to
funnel
light
into
our
eyes.
Just
like
we
would
funnel
the
raindrops
into
our
mouth.
If
you
try
to
quench
your
thirst
in
the
rain
and
so
yeah,
so
it
turns
out,
then
things
like
binoculars.
They
are
essentially
light
funnels
right
and
so
binoculars
have
what
we
call
apertures
or
openings
of
50
to
100
millimeter.
A
Typically,
and
there
are
other
sizes
there
lots
of
kinds,
but
this
is
just
an
example,
and
so
what
we're
saying
here
is
that
this
opening
right
here
this
is
the
aperture.
This
is
where
light
enters.
You
know
one
side
of
the
binoculars
here
and
this
might
be
50
millimeters
across
and
then
the
binocular
mechanism
squeezes
that
light,
and
it
shoots
out
the
back
and
shoots
into
your
pupil
right
so
effectively.
We've
now
made
your
pupil
larger
right
so
from
its
natural
size
effectively.
A
You
now
have
a
pupil,
that's
this
big,
which
is
a
much
bigger
opening
for
your
funnel
right.
So
therefore,
we
can
collect
more
light
and
see
fainter
things
same
idea
holds
for
telescopes
right.
So
here
is
a
telescope
and
this
right
here,
that's
where
the
objective
lenses
and
here's
the
aperture,
which
might
be
70
millimeters,
100,
millimeters,
250,
lots
of
sizes.
You
know
and
yeah.
You
know
they're
all
light
funnels.
Essentially
so
here's
a
collection
of
telescopes.
A
When
you
come
to
a
star
party
that
we
do
out
in
the
field,
you
would
see
astronomers
out
there
with
all
kinds
of
telescopes.
You
know
like
the
ones
you
see
here
and
other
kinds
as
well,
but
for
all
of
these
you
know
aperture
diameter.
You
know
how
big
the
opening
is
here
right
like
here
or
here
that
measures
how
much
light
the
telescope
can
collect
and
magnification
it
matters,
but
it's
actually
not
so
important,
no
matter
how
big
this
aperture
is
right.
A
So
if
you
have
to
go,
buy
a
telescope
which
one
would
you
choose
the
one
on
the
left
or
the
one
on
the
right?
You
know
notice
that
on
the
right
here
there
is
like
a
person
or
model
of
a
person
down
here
for
size,
comparison
right,
so
yeah.
If
you
want
aperture,
you
probably
want
to
choose
this
telescope
on
the
right.
I
actually
bought
the
one
on
the
left
because
I
couldn't
fit
the
other
one
in
my
car
and
it
turns
out
that
you
know
amateur
telescopes
in
general.
A
You
know
are
around
those
sizes
right,
so
we
make
amateur
telescopes
in
two
ways
we
use
refractors
that
use
lenses.
So
just
like
your
eye
eye
glasses,
perhaps
right
so
lenses
like
your
eyeglasses
are
used
in
refractor,
telescopes
and
reflector
telescopes.
Excuse
me
our
telescopes
that
use
mirrors
and
I'm
sorry
one
second.
A
A
Some
amateur
astronomer
telescopes
go
up
to
like
30
inches
of
aperture.
You
know
these
will
all
be
reflectors
done
with
mirrors,
but
all
of
these
telescopes
have
a
problem
in
common.
They
all
have
to
look
through
the
atmosphere
right.
The
telescope
would
sit
here
on
the
ground
and
we
look
into
space
and
we
have
to
look
through
the
air
we
breathe.
Now
we
like
the
air,
it's
really
important
right.
We
want
to
be
able
to
breathe,
but
for
astronomy,
it's
actually
not
that
good,
because
it
turns
out
that
the
atmosphere
distorts
the
image.
A
Imagine
we
can
think
back
to
the
pennies
we
had
earlier
right.
So
if
you
have
a
penny
and
you
throw
it
in
the
water,
let's
say
into
a
wishing
well
right
that
will
cause
the
surface
of
the
water
to
ripple
right.
Then
you
see
the
image
of
the
penny
right
through
the
rippling
water
surface,
and
that
distorts
the
image
of
the
penny
and
it
turns
out
the
same
kind
of
thing
happens
here
right.
A
So
as
we
look
at
objects,
you
know
through
the
night
sky
into
the
night
sky
through
our
atmosphere,
we
have
the
atmosphere,
distorting
the
image,
just
like
the
rippling
water
would.
Okay,
now
the
hubble
space
telescope,
which
was
the
other
thing
you
know
on
the
prior
slide
that
I
couldn't
fit
in
my
car,
that
is
a
reflector
it's
built
with
mirrors.
The
mirror
is
about
2.4
meters,
which
is
maybe
just
a
little
bit.
A
You
know
taller
than
I
am,
and
its
key
advantage,
though,
is
that
it
has
a
clear
view
through
space
right,
it's
outside
the
atmosphere.
It
does
not
have
to
deal
with
the
ripples
right,
so
it
sees
much
crisper,
clearer,
stable
images
than
we
could
ever
see
here
from
the
ground.
So
that's
one
of
the
key
advantages
of
having
telescopes
out
in
space
now.
Nevertheless,
we
have
some
really
big
telescopes
here
on
the
ground.
A
Now
on
the
prior
slides,
we
just
talked
about
how
we
collect
more
light
through
larger
light,
funnels
right,
bigger
apertures,
but
it
turns
out.
We
can
also
collect
light
by
looking
longer
now.
This
sounds
funny
and
it
doesn't
quite
work
with
our
eyes,
because
you
know
you
can
stare
at
something,
but
that
doesn't
make
it
brighter,
because
your
eye
just
keeps
sampling
the
light
at
the
same
rate,
no
matter
what
you
do,
but
it
turns
out
cameras.
A
You
have
control
over
right,
so
our
eyes
pretty
much
see
continuously,
but
especially,
if
you're
a
photographer
out
there.
You
know
what
you
do
right
when
you're
adjusting
the
exposure
right,
you
can
expose
more
light
by
opening
the
shutter
longer
right.
You
can
open
your
camera
shutter
for
a
fraction
of
a
second
or
several
seconds
or
minutes
or
hours,
even
right
and
the
longer
you
leave
your
camera
shutter
open,
though
more
light
is
hitting
the
film
or
the
sensor
right
collecting
over
time.
A
Right
and-
and
that's
that's
just
like
standing
in
the
rain
with
your
mouth
open,
you
know
a
minute
or
ten
minutes
right.
You
will
collect
more
raindrops.
As
you
stand
there
longer
so
yeah
with
cameras.
We
can
collect
more
light
just
by
exposing
longer
right,
and
that
then
also
applies
to
really
all
professional
space
and
ground
telescopes.
You
know
we're
past
the
age
where
astronomers
professional
astronomers
look
through
telescopes
with
their
eyes
most
of
the
time
right
now,
most
of
the
time.
Instead,
this
is
all
done
with
instruments.
A
A
So
here,
for
example,
are
images
of
our
sun
and
the
moons,
of
course
the
moon
you're
quite
familiar
with,
but
you
probably
haven't
seen
the
sun
look
like
this
before
and
if
you'd
like
to
see
more
about
the
sun.
Like
this,
you
can
join
one
of
our
solar
sunday,
events
which
we
also
do
online
these
days.
I
think
the
next
solar
sunday
will
be
in
about
three
weeks
from
now,
so
you
can
check
it
out
and
we'll
talk
more
about.
A
You
know
the
sun
that
looks
like
this
and
what's
happening
in
pictures
like
these,
our
planets
right.
So
hey
these
are
cool
pictures.
So,
let's
see
on
the
bottom,
of
course
we
have
jupiter.
This
is
usually
easy
to
identify
here.
Saturn
then
there's
mars
on
the
bottom
right
and
this
little
guy
in
the
top
left-
hey,
that's
pluto!
So
not
long
ago.
A
Pluto
has
some
really
amazing
features,
including
what
looks
like
the
heart
like
this
feature
here
and
I
think
people
kind
of
dub,
the
heart
of
pluto
so
yeah,
so
the
planets
look
really
cool
right
and
tomorrow,
during
the
armchair
star
party,
we
will
be
looking.
You
know
like
these
two
guys
in
more
detail.
For
example,
you
know
jupiter
and
saturn,
okay,
but
beyond
our
planets.
We
also
have
lots
of
stars
in
space.
We
said
earlier
right:
the
galaxy
is
full
of
stars
and
let's
not
worry
so
much
about
the
details
here.
A
Quite
yet,
we
will
get
back
to
that.
But
for
the
moment
we
can
look
at
these
and
just
one
appreciate
that
they're
pretty
and
two
look
for
some
high
level
patterns,
because
you
can
probably
see
that
this
thing
in
the
top
left
and
this
thing
on
the
bottom
right.
They
look
very
similar.
They
appear
to
be
the
same
kind
of
thing
and
they
are
right.
A
So
we'll
talk
about
little
later,
what
those
things
are,
and
it
turns
out
that
also
the
opposite
corners
here,
this
guy
on
the
bottom
left
and
the
top
right,
they're,
actually,
the
same
type
of
thing
and
in
the
middle
we
just
have
a
beautiful
double
star.
Two
nice
colors
we'll
talk
about
that
one
tomorrow
on
the
armchair
star
party
too,
then,
if
you
look
at
other
spots
in
the
night
sky,
we
can
see
these
things.
A
We
call
nebulae
and
nebula
is
basically
a
fuzzy
thing
in
space
and
long
time
ago,
when
astronomers
had
no
clue
yet
what
all
these
things
were.
Yeah
we
just
called
any
fuzzy
thing
and
nebula,
but
since
then
we've
learned
a
lot
about
what
these
things
really
are
and
again
for
the
moment
we
can
just
look
at
patterns.
You
know
look
at
these
two
things
on
the
top
left.
They
seem
to
be
kind
of
similar
right
they're.
These
bubbly
shaped
things
right,
so
yeah
it
turns
out
these
are.
A
These,
are
you
know
two
examples
of
a
particular
class
of
nebula
and
then
this
guy
on
the
bottom
left
and
top
right.
There
also
the
same
kind
of
nebula
and
then
there's
also
another
different
one
here
on
the
bottom
right.
We'll
talk
about
all
these
a
little
bit
more.
For
the
moment
we
can
just
say:
hey
these
all:
look
pretty
cool
right
and
and
yeah,
so
here's
some
galaxies
that
we
can
see
right.
A
If
we
look
beyond
our
own
house,
our
own
galaxy
top
is
the
andromeda
galaxy
which
we
visited
before
and
then
here's
a
couple
other
examples
that
are
super
pretty.
I
think
now.
All
of
these
things
are
just
amazing
to
look
at
in
these
colors
right,
so
wow
they're,
all
these
pretty
colors
in
space,
and
we
need
to
talk
about
that
color
a
little
bit
more
to
really
understand
what's
going
on
here.
So
let's
talk
about
color
in
space.
A
So
I'm
going
to
disappoint
you
here
for
a
moment
right,
because,
if
you're
going
to
get
used
to
these
pictures
like
this
over
here
on
the
left
like
this
andromeda
picture,
we've
seen
more
than
once
now,
you
know-
and
you
expect
that
when
you
look
through
a
telescope
yourself,
you're
not
going
to
see
it
I'll,
tell
you
right
now
right,
you're,
going
to
see
something
that
looks
more
like
this
over
here.
In
fact,
let
me
go
to
the
next
slide
and
yeah
again.
Here's
that
really
fancy
picture
well
on
a
really
good
night.
A
Maybe
you
would
see
this.
You
know
through
your
telescope
with
your
eyes
right
or
maybe
it
would
look
more
like
this
on
a
really
poor
night,
when
you
don't
have
good
conditions,
maybe
you
just
barely
see
like
this
bright
splotch
in
the
middle,
so
yeah,
so
it
turns
out
that
you
know
on
an
average
night.
Maybe
you
see
this.
A
You
still
see
structure
here
right,
so
there's
still
structure
to
be
seen,
but
it
certainly
doesn't
look
as
splendid
as
the
hubble
picture
right
and
on
one
hand
it's
kind
of
a
bummer
right,
but,
on
the
other
hand,
yeah
looking
at
it
from
the
ground
with
our
own
eyes.
We
cannot
expect
to
see
the
same
level
of
detail
that
the
hubble
can
see
from
outer
space
right
and
I
still
really
enjoy
looking
through
my
telescopes
right
and
seeing
these
objects
directly
because
of
something
very
direct
and
visceral
about
it.
A
Right
on
one
hand,
I
keep
in
my
mind
these
pictures
that
I
see
you
know
on
the
web
from
hubble,
and
you
know
keep
that
on
one
side
of
my
brain
right.
On
the
other
side,
I
keep
the
stuff.
I
see
myself,
and
I
kind
of
you
know
put
these
together
in
my
mind,
and
that
really
makes
this
a
great
experience
so
yeah.
So
looking
through
a
telescope
yourself
will
look
a
little
bit
more
like
this
compared
to
what
you
see
in
hubble.
A
So
then,
so
what
is
up
with
this
color
right
that
you
see
in
all
these
pictures?
If
we
don't
see
this
ourselves
directly
with
our
eyes
right,
well,
there's
a
couple
different
things
going
on,
so
some
color
is
real,
but
it's
effectively
invisible
to
our
eyes.
Our
eyes
are
optimized
kind
of
for
daytime
vision,
right,
color
vision.
They
don't
work
that
well
in
dim
light,
and
so
a
lot
of
things
in
space
actually
glow
red
because
of
hydrogen
gas-
and
here
is
the
famous
horse
head
nebula
and
yeah.
A
It's
a
really
fancy
and
well-known
image,
but
it
turns
out.
This
is
really
hard
to
see
even
with
telescopes,
even
if
you
have
a
telescope
in
front
of
you
and
looking
through
that
right,
this,
this
object
is
very
difficult
to
pick
up,
because
this
red
light
is
our
eyes
are
not
very
sensitive
to
this
red
light
right.
So
we
just
don't
see
it
well
with
a
camera.
You
can
make
this
pop
out,
but
with
your
eyes,
just
not
so
much
because
our
eyes
just
are
not
sensitive
enough
to
this
red
light.
A
There's
also
another
aspect
to
this
color.
What
we
call
false,
color
right,
so
some
light
like
on
the
previous
slide.
We
just
cannot
easily
see,
and
then
we
also
have
this
stuff
called
false.
Color.
That's
often
present
in
hubble
pictures
or
or
pictures
like
it,
but
false
color
doesn't
mean
fake
right.
So
this
false
color
serves
a
couple
different
purposes.
One
example
is
illustrated
by
these
pictures.
I
have
on
the
bottom
in
the
center.
Again
is
our
old
friend
the
andromeda
galaxy
invisible
light.
A
So
this
is
what
we
you
know
can
see
just
in
visible
light,
but
then
we
know
there's
other
types
of
light
right.
For
example,
there
is
infrared
light,
that's
the
kind
of
light
that
you
feel
is
heat.
During
the
day
on
your
hand,
let's
say
right,
or
there
is
ultraviolet
light-
that's
the
kind
of
light
that
burns
your
skin.
It
gives
you
sunburn
right,
you
know
the
x-rays.
A
A
Here's
another
example.
This
is
another
famous
picture
of
the
eagle
nebula
and
what
we
call
the
pillars
of
creation.
This
is
a
famous
hubble
picture,
invisible
light.
It
looks
like
this
thing
on
the
left
and
there's
lots
of
cool
stuff
to
see,
but
hey
check
out
this
picture
on
the
right.
So
this
is
the
exact
same
structure,
but
this
is
seen
with
infrared
light,
so
it
turns
out
infrared
light.
Detectors
can
see
a
lot
of
new
and
different
things
right
and
that's
key
right.
A
A
So
yeah
color
is
key.
Different
wavelengths,
invisible
colors
allow
us
to
learn
more
about.
What's
out
there
and
color
reveals
what
I
call
the
building
blocks
and
the
structure
of
the
universe.
So
let's
take
a
moment
for
questions
and
then
we'll
talk
about
those
building
blocks,
maybe
a
little
bit
more.
So
let
me
check
in
with
swami
and
see
how
things
are
going
in
the
chat.
B
B
A
Know
if
I
have
a
single
answer
actually,
I
think
it
depends
on
a
lot
of
factors.
I
can
tell
you
that
I
mean
we
we
can.
I
mean
it
depends
a
lot
on
sky
conditions
right
how
dark
the
sky
is,
and
we
are
actually
not
really
used
to
dark
skies
around
here
right.
You
know
the
city
lights,
even
when
we
go
to
dark
sky
sites
around
here,
there's
often
glow
around
the
horizon
from
cities.
A
So
how
much
you
can
see
depends
a
lot
on
your
environment
first
of
all
right,
but
I
can
tell
you
that
even
around
here
you
know
we
can,
we
can
see,
you
know,
objects
galaxies
that
could
be
20,
30
40
million
light
years
away
right.
So
so
I
don't
think,
there's
a
single
answer
for
this
right,
but
but
yeah
we
can
see
things
that
are
pretty
far
away.
This
will
all
be
different.
A
Galaxies
and
I'll
show
you
a
picture
much
later,
actually,
where
we
have
seen
much
more
deeply
into
space,
certainly
with
professional
scientific
equipment
right.
You
know
we
have
the
observable
universe
and
we
can
well
observe
that
right.
So
it's
actually
pretty
amazing
one.
One
key
message
here
is
that
telescopes
are
time
machines
in
a
way
right.
So
when
I
look
at
an
object,
that's
20
million
light
years
away
the
light
I'm
seeing
left
there
20
million
years
ago
right
so
so
we
can
use
telescopes
to
look
very
deeply
into
space.
A
You
know,
especially
if
the
conditions
the
night
sky
is
dark
right,
and
I
don't
even
necessarily
need
that
big
of
a
telescope
for
it
right.
But
the
key
thing,
then,
is
yeah,
we're
actually
seeing
light.
That's
been
traveling
for
ages
right
and
they
really
allow
us
to
look
into
into
the
deep
deep
past,
so
that's
kind
of
a
cool
takeaway.
So
I
don't
know
if
that
answered
the
question.
I
don't
think
there's
a
single
answer.
Was
there
a
better
answer
in
the
chat.
A
B
B
A
Enough
site-
and
it
doesn't
even
have
to
be
that
dark-
we
could
do
it
at
one
of
our
common
locations
called
rcdo
where
we
normally
have
outside
events
and
yeah.
If
things
are
pretty
good,
I
can
show
you
how
to
find
the
andromeda
galaxy
with
the
naked
eye.
So
hey
look
at
that
right.
You
can
see
something.
That's
two
and
a
half
million
light
years
away
and
you
can
do
that
with
the
naked
eye.
A
Okay,
so
we'll
enter
a
part
of
the
talk
that
I
call
nature's
lego
blocks,
so
so
here's
lego
blocks
right.
We
all
know
these
things
if
you
have
kids
you
may
have
stepped
on
one
recently,
and
the
key
thing
here
is
that
yeah
so
lego
blocks
are
something
we
can
use
to
build
almost
anything
right
out
of
a
small
number
of
unique
types
of
building
blocks
right.
A
You
could
just
have
these
little
square
dudes
here
right
and
you
can
still
build
all
kinds
of
different
things
right
just
by
putting
them
together
in
different
ways
and
yeah.
You
can
build
an
almost
countless
number
of
objects
from
very
few
different
types
of
blocks,
and
that
relates
very
much
to
this
thing
right.
So
do
you
remember
this
this
table?
You
know
maybe
from
high
school
chemistry.
A
Some
of
you
may
actually
be
chemists
out
there
and
probably
know
more
about
this
than
I
do,
but
all
of
you
have
probably
seen
this
at
some
point
right
and,
depending
on
you
know
your
memories
of
it.
You
know.
Maybe
you
reacted
with.
Oh,
my
god.
This
is
boring
or
holy
crap.
This
looks
scary.
I
was
more
in
homer's
camp.
You
know
when
I
first
saw
the
product
table
when
I
was
a
kid
in
high
school,
but
it's
actually
a
really
interesting
thing
right
and
let's,
let's
quickly
relate
that
to
our
daily
lives.
A
It
turns
out
a
lot
of
these
things.
You're
familiar
with
here's
gold.
It's
on
the
periodic
table.
You
probably
have
some
in
your
teeth.
I
do
here's
carbon
right.
If
you
use
the
pencil
today
right,
there's
carbon
in
in
the
pencil
lead,
we
don't
make
pencils
out
of
lead
anymore.
It's
actually
carbon
there.
That
you're
riding
with
here
is
oxygen
right.
I
can't
easily
show
it
to
you,
but
take
a
deep
breath
and
you'll
have
inhaled
some
oxygen.
That's
keeping
you
alive!
A
Here's
helium
that
you
might
find
in
your
party
balloons
right:
here's,
calcium,
it's
a
metal
but
actually
you'll,
probably
think
of
it
more
something.
That's
in
your
bones
and
yes,
you
actually
have
metal
in
your
bones,
even
though
we're
not
like
wolverine
right,
we
all
actually
have
some
metal
in
our
bones
and
then,
if
we
take
some
of
these
objects
or
these
elements
on
the
product
table-
and
we
put
them
together
like
the
the
sodium
over
here
and
the
chlorine
hey,
we
make
salt
and
you
almost
certainly
ate
some
salt
today
and
yeah.
A
So,
let's
focus
on
like
three
of
these
building
blocks
very
precisely
right.
So
here
is
carbon
oxygen,
hydrogen.
They
were
things
on
the
periodic
table
and
it
turns
out.
Carbon
is
kind
of
like
this
lego
block
that
can
connect
to
four
things.
You
see
like
little.
Four,
you
know
buttons
on
the
lego
block
here:
oxygen
connect
to
two
things,
and
hydrogen
is
like
this
guy,
which
can
connect
to
one
thing,
and
so
here
they
are
on
the
periodic
table
right,
and
so
let's
say
we
have
those
three
lego
blocks
at
our
disposal.
A
A
If
I
took
any
one
of
you
or
myself,
and
I
took
you
apart
and
I
made
piles
of
atoms
right
piles
of
building
blocks
that
are
inside
of
you
right,
I
mean
one
pile
of
hydrogen
one
pile
of
oxygen,
one
pile
of
carbon
that
would
be
almost
all
of
you
right
so
in
terms
of
counts
of
lego,
blocks,
counts
of
atoms.
That
would
be
99
of.
U
would
be
just
these
three
building
blocks,
that's
by
count
of
atom.
A
Now,
if
I
go
by
weight,
it
turns
out
those
three
things
account
for
only
about
93
of
your
weight,
because
there
are
some
other
things
in
you
right
that
are
that
are
heavier
than
let's
say:
hydrogen,
for
example,
which
is
actually
a
really
light
small
building
block
so
yeah.
So
let's
say
we
wanted
to
build
ourselves
a
human
and
we're
not
going
to
do
it
the
old-fashioned
way.
Let's
say:
instead,
you
just
want
to
go
out
to
the
store,
buy
all
the
ingredients
and
mix
it
together
in
your
garage
and
boom.
A
You
know
make
yourself
a
human
being
what
what
you
have
to
put
on
your
shopping
list
and
it's
these
things
right.
So
there's,
certainly
the
hydrogen
carbon
and
oxygen
we
just
had
and
then,
in
addition,
you
also
need
these
other
things
like
sulfur,
for
example
it's
phosphorus
and
potassium
and
calcium.
So
so
that,
then
you
know
accounts
for
pretty
much
everything
that
is
in
you
and
me.
So
I
find
this
amazing
right
so
so
on
one
hand,
our
bodies
are
actually
really
simple.
A
If
you
take
them
apart
and
do
what
some
of
their
smallest
bits
right,
it's
actually
pretty
simple
stuff.
On
the
flip
side,
we're
clearly
very
complex
and
complex
enough
that
we
can
sit
here
and
have
this
conversation
over
the
internet
and
look
out
into
space
and
marvel
at
the
universe,
so
yeah.
I
find
this
pretty
amazing
and
mind-blowing
right.
A
So
all
of
nature's
lego
blocks
are
here
98
natural
elements
and
some
other
ones
that
we've
learned
to
make
in
labs,
and
the
key
message
here
is
that
everything
and
everyone
you've
ever
seen
anything
you've
ever
touched.
Everything
you
know
is
made
from
these
building
blocks
right
and-
and
the
really
quick
story
is
that
13.8
billion
years
ago
right,
the
young
universe
had
only
hydrogen
and
maybe
a
little
bit
of
helium
in
it
right,
but
it
was
mostly
hydrogen
out
there,
then,
that
hydrogen
formed
into
stars.
A
It
turns
out
that
stars
are
mostly
hydrogen
right
and
they
shine
by
burning
hydrogen
in
a
certain
way
right,
that's
how
they
make
energy
and
over
time
those
stars
actually
make
all
the
elements
on
the
periodic
table.
I
realize
I'm
skipping
a
lot
of
steps
here
right
now,
but
this
is
what
happens
right
stars
are
the
engines
or
the
factories
that
make
all
these
building
blocks
over
time.
A
So
that's
a
key
cool
message
and
it
turns
out
when
we
take
any
one
of
these
elements
on
the
product
table
and
we
energize
it,
meaning
like
we
heat
it
up,
for
example,
then
it
will
glow
with
a
very
unique
set
of
colors
and
I
think
of
it
as
like
a
barcode.
If
you
go
to
the
store
and
you
go
shopping
right,
you
know
now
there
lots
of
even
self
checkout
lines.
We
just
go
boop
right
and
you
scan
the
barcodes
and
the
computer
knows
what
you
bought.
Well.
A
It
turns
out
that
we
can
do
something
very
similar
here
right
when
I
heat
up,
for
example,
hydrogen
right.
Here's,
what
happens
at
the
top
is
essentially
the
rainbow.
You
know
all
the
colors
that
we
can
see
with
our
eyes
and
if
I
heat
up
hydrogen
gas,
if
I
energize
it
turns
out,
it
will
glow
with
this
very
specific
pattern.
A
It
glows
with
these
very
precise
four
colors
in
the
visible
range
and
this
picture
that's
down
here-
shows
all
the
stuff
that
hydrogen
does
in
colors
that
our
eyes
cannot
see,
but
our
instruments
can
see
it
so
yeah.
So
these
visible
things
are
kind
of
bunched
together
down
here
right
and
then
there's
all
kinds
of
invisible
stuff
to
invisible
to
our
eyes
right
that
hydrogen
does
too
so
yeah.
This
looks
very
much
like
a
bar
code
at
the
supermarket
right
and
so
every
element
every
lego
block
on
the
product
table.
A
Does
this
in
a
unique
way?
Here's
some
other
examples
of
it
right.
So
you
can
see
helium,
for
example,
lithium
oxygen
carbon.
You
can
see
they're
all
unique,
so
the
cool
thing
here
is
that
stuff
can
be
immensely
far
away
right,
we'll
never
get
there.
It's
like
one
of
those.
You
know
millions
of
light
years
things
we
talked
about
earlier,
but
we
can
look
at
the
light
and
we
can
look
at
these
barcodes
and
we
can
still
tell
what
it's
made
of
imagine
that
right.
A
So
it
can
be
immensely
far
away
and
we
still
know
what
it
is.
So
now,
let's
take
a
closer
look
at
the
objects
we
see
in
space,
so
our
solar
system
has,
you
know,
eight
planets.
It
used
to
be
nine.
Then
pluto
got
reclassified
as
a
dwarf
planet,
but
don't
worry,
pluto
is
still
really
cool.
It
hasn't
lost
any
of
its
coolness
right,
but
yeah.
We
don't
call
the
planet
anymore,
so
we
have
four
rocky
planets.
A
A
But
since
then,
we've
learned
a
lot
right
so
30
years
ago
we
had
no
clue
now
we
found
4
000
plus
exoplanets,
and
you
know
when
I
first
made
this
presentation,
which
wasn't
even
that
long
ago
the
number
was
only
two
thousand
and
you
can
see
here.
I
had
to
revise
it
right,
so
we're
finding
stuff
more
and
more
all
the
time
and
actually
here's
a
picture
of
another
planetary
system.
So
there's
a
star
in
the
middle,
but
here
we
blocked
it
out.
A
A
Now
moons
right
planets
have
moons,
not
all
planets,
but
some
we
have
one
moon
and
some
other
planets
have
a
lot
more
moons
right
and
moons
are
distinct,
individual
worlds,
so
jupiter,
for
example,
shows
us
four
moons,
but
we
know
of
now
79
wounds.
Even
here
I
had
to
make
a
correction
because
science
always
discovers
new
stuff
right
and
we
keep
refining
our
view
of
the
universe
so
yeah.
A
So
if
you
were
to
look
through
a
telescope,
you
might
see
jupiter
here
with
the
moons
lined
up
kind
of
like
this,
and
then
there
is
this
composite
picture
here
on
the
left,
where
you
will
see
the
moons
really
close
to
jupiter
kind
of
for
size
and
texture
and
color
comparison.
They
will
never
be
arranged
like
this.
In
reality,
this
is
just
a
composite,
but
you
can
see
that
each
one
is
very
different
right.
So,
for
example,
your
rope
right
here
has
a
very
icy
surface
right.
A
A
Now
we
wouldn't
see
planets
and
moons
if
it
weren't
for
stars
stars
light
up
the
universe
right,
that's
what
allows
us
to
see
stuff.
So
our
sun
is
a
star
like
we
said
earlier
right.
Some
stars
are
really
big.
You
know,
and
some
existing
stars
are
almost
as
old
as
the
universe,
so
they've
been
around
almost
since
the
beginning
of
time,
and
it
turns
out
it's
actually
the
tiny
stars
which
is
often
very
counter-intuitive.
A
Now
a
star's
color
indicates
its
temperature,
so
we
have
a
picture
here
on
the
right
side,
where
you
can
definitely
tell
that
different
stars
have
different
colors.
You
know
there's
some
reddish
ones
here.
A
lot
of
them
are
more
white
or
bluish
and
yeah.
The
red
ones
are
actually
a
little
bit
cooler
and
the
blue
ones
are
a
little
bit
hotter,
relatively
speaking,
so
yeah,
so
even
with
a
naked
eye
or
well,
maybe
looking
through
a
telescope
but
otherwise
unaided
eye
right.
A
You
can
do
some
basic
science
and
tell
something
about
a
star's
temperature
just
by
noticing
its
color.
Now,
who
is
this
guy
right?
So
usually
I
throw
this
question
out
to
the
audience
and
pretty
much
everybody
knows
the
answer.
So,
of
course,
this
is
albert
einstein
right,
one
of
the
most
famous
scientists
ever
I
think
right
and
here
he
is
with
one
of
his
most
famous
equations
right,
equals
mc
squared.
A
I
think
everybody's
heard
this
equation
just
about,
but
we
probably
don't
think
about
it
all
that
much,
but
actually
is
an
equation
that
that
we
rely
on
every
day
right.
So
I
want
to
just
talk
about
that
for
just
a
moment,
so
this
equation
talks
about
how
mass
and
energy
are
equivalent
in
some
way
and
can
be
converted
from
one
to
the
other
right.
So
in
this
equation,
e
stands
for
energy
m
is
mass
and
c
is
the
speed
of
light
that
we
met
earlier
a
few
slides
ago,
and
so
within
our
stars.
A
So
imagine
that
we
have
these
these
two
hydrogen
atoms
that
we
start
with
and
we
weigh
them
right.
We
measure
their
mass
and
now
I
do
the
fusion
thing
right
and
it
turns
out
the
helium
I
get
out.
If
I
now
measure
its
mass,
it
turns
out,
some
mass
got
lost,
so
the
helium
I
have
at
the
end
has
a
little
less
mass
than
the
hydrogen.
I
started
with
it's
like
wait:
where
did
that
go
and
it
turns
out?
A
That's
the
mass
that
got
converted
to
energy
and
that's
what
we
see
as
light
and
feel
this
heat
during
the
day
when
the
sun
shines
right
and
so
yeah,
our
sun
actually
converts.
5
million
tons
of
mass
into
energy
every
second
right,
that's
a
lot
of
mass!
Now
it
turns
out,
the
sun
is
really
big,
so
it
doesn't
really
feel
it,
but
it's
still
quite
a
bit
and
the
energy
is
like
3.8
times
10
to
26
joules
of
energy,
which
probably
means
nothing
to
almost
anybody
on
the
call.
A
So
I've
converted
this
to
twix
bars
for
you
right.
So
it's
about
that
many
twix
bars
per
second.
If
you
could
eat
that
much
twix
in
a
second
or
you
could
substitute
your
favorite
candy
bar
that's
cool
right,
but
if
you
ate
that
much
every
second
you'd
be
consuming
as
much
energy
and
food
as
the
sun
produces
every
second,
so
that's
a
lot
and
our
sun
is
pretty
big
right.
So
here's
a
picture
of
our
sun
compared
to
jupiter
and
the
earth
is
this
little
dot
down
here.
A
A
Okay.
Here
we
shrunk
down
earth
here
and
now
we
compare
this
to
our
gassy
planets
right
with
jupiter
being
the
biggest
object
in
our
solar
system
other
than
the
sun,
and
now
we
shrink
down
jupiter.
Look
it's
this
little
doodad
down
here
now:
here's
a
star
called
wolf
359,
which
is
smaller
than
our
own
sun,
but
then
here's
our
sun
and
then
here
is
a
star
called
sirius.
B
A
We
can
shrink
aldebaran
down,
look
to
this
little
guy
down
here
right
and
we
move
to
a
star
called
beetlejuice.
This
is
a
star,
that's
visible,
actually
in
the
winter
sky
as
part
of
the
constellation
of
orion.
So
beetlejuice
is
a
red
supergiant.
If
we
were
to
put
beetlejuice
where
the
sun
is
yeah,
we
would
be
inside
it.
A
I
think
even
jupiter
would
be
inside
it
right,
so
this
thing
is
way
way
bigger
than
our
sun,
but
even
that
guy
we
can
shrink
down,
and
you
know
then
draw
here
the
one
of
the
largest
known
stars
so
yeah.
The
key
message
here
is
man:
our
sun
is
big,
but
some
other
stars
out.
There
are
monsters
compared
even
to
our
own
sun.
A
And
so
stars
like
to
hang
out
with
friends,
there
are
things
called
open
clusters.
Open
clusters
are
basically
siblings
of
stars
that
were
born
from
the
same
hydrogen
gas
cloud
so
like
we
said
hydrogen
gets
together,
form
stars,
then
the
stars
shine.
So
an
open
cluster
is
a
bunch
of
siblings
that
were
worn
together.
A
That's
usually
hundreds
to
thousands
of
stars
and
some
kind
of
a
loose
arrangement
and
many
open
clusters
exist
within
our
galaxy
and
we
can
see
them
with
binoculars
or
telescopes
and
sometimes
even
a
little
bit
with
the
with
the
naked
eye,
and
then
there's
also
a
thing
called
a
globular
cluster.
So
a
globular
cluster
is
a
somewhat
different
structure.
A
That's
a
bunch
of
stars
that
are
packed
into
a
tight
spherical
shape,
globe-like,
that's
where
globular
comes
from
right
and
that
tends
to
be
hundreds
to
thousands
of
stars,
they're,
often
very
old,
and
we
know
of
about
150
globular
clusters
that
orbit
the
galaxy.
So
our
galaxy
remember
is
like
a
flatter
spirally
thing.
So,
if
my
hand
is
the
galaxy,
these
globular
clusters
are
companions
that
kind
of
orbit
around
and
through
you
know,
our
our
galaxy
and
then
yeah.
So
here
these
are
open
clusters.
A
All
right,
so
at
the
bottom
left
is
something
we
call
the
double
double
of
actually
two
open
clusters
very
near
each
other.
This
is
one
of
my
favorite
open
cluster
object
and
the
top
right
is
the
pleiades.
This
is
an
open
cluster,
where
you
can
see
a
bunch
of
stars
with
a
naked
eye
more
in
the
winter
sky,
and
these
are
two
globular
clusters.
I
also
think
these
are
very
beautiful.
Some
of
my
favorite
objects
to
look
at
through
telescopes
nebulae.
I
said
earlier.
A
nebula
is
a
fuzzy
thing
in
space
and
turns
out.
A
We
can
have
bright
nebula,
so
a
bright
nebula
could
be
an
emission
nebula.
That
is
a
gas
cloud.
That's
somehow
energized
and
it's
glowing
right.
So
it's
emitting
light
because
it
somehow
got
energized
or
we
could
have
a
reflection
nebula.
That
could
be
something
that's
like
back
here.
Maybe
it's
a
cloud
of
gas
or
dust
and
there's
a
star
over
here
and
that
star
light
bounces
off
the
nebula
and
then
gets
to
our
eyes.
A
So
nebula
is
basically
a
reflector
and
the
gas
out
there
that
that
makes
up
these
nebulae
is
is
often
less
dense
than
the
best
vacuum
on
earth.
This
takes
us
back
to
our
sci-fi
movies
from
the
very
beginning
a
little
bit
right,
because
if
you
see
the
enterprise,
for
example,
or
some
other
spaceship
trying
to
get
through
a
nebula,
that's
often
depicted
as
the
spaceship
going
through
this
dense
fog,
maybe
with
lots
of
rocks
floating
around
there
as
well,
but
in
actuality.
A
Nebula,
are
often
very
sparsely
populated
with
gas
right,
they're,
very
they're,
not
very
dense
at
all.
You
might
not
even
see
that
you're
inside
one,
if
you're
there,
then
we
also
have
a
dark
nebula
that
our
absorption
nebula.
So
this
could
mean
that
there
is
a
star
here
and
then
there's
maybe
a
cloud
of
dust
here
and
that
cloud
of
dust
is
blocking
light
from
reaching
our
eyes.
A
So
this
this
then
looks
like
a
dark
splotch
right,
because
it's
blocking
a
light
emitter,
that's
behind
it
and
yeah
these
things
can
be
huge
up
to
thousands
of
light
years
across.
You
know,
and
these
these
nebula
basically
represent
a
lot
of
these
nebula
represent
what
I
call
stars
of
tomorrow
and
yesterday
right.
So
some
of
these
nebula
are
star-forming
regions.
A
We
call
them
stellar
nurseries,
you
know
stars
are
newly
forming
and
the
baby
stars,
they're
energizing
the
hydrogen
gas
around
them,
and
these
things
will
ultimately
turn
into
open
clusters,
and
then
we
also
see
stars
at
the
other
end
of
their
life
cycle.
So
we
see
things
called
planetary
nebula.
That
name
is
really
confusing,
don't
get
stuck
on
it
now,
but
a
planetary
nebula
is
one
type
of
dead
star
that
we
see
out
in
space
and
also
things
called
supernova
remnants.
A
These
are
also
remnants
of
stars
that
are
much
much
bigger
than
our
own
son
of
at
least
eight
times,
bigger
and
yeah.
These
dead
stars
leave
behind
the
material
for
future
planets
in
life
because,
like
we
said
earlier,
stars
manufacture
all
the
other
building
blocks
that
are
on
the
periodic
table
and
so
yeah.
So
these
two
pictures
are
star-forming
nebulae.
So
these
are
stellar
nurseries,
you
can
see
young
stars
inside
them
and
the
young
stars
are
causing
the
hydrogen
gas
cloud.
That's
the
parent
of
these
stars
to
be
energized
and
glow.
A
So
these
are
emission
nebula
that
are
forming
baby
stars
and
then
here
on
the
top
left,
we
have
planetary
nebula,
so
these
are
dead
stars.
What
happened
here
is
that
a
star
similar
to
our
own
sun
reached
the
end
of
his
life.
It
proved
its
outer
layer
off
into
space
at
the
very
core
of
this
is
what
we
call
the
white
dwarf
star.
A
That
is
essentially
inert
now,
but
still
hot
and
cooling
for
a
long
time
and
that's
causing
the
bubble
of
gas.
It
blew
off
at
some
point
to
glow
and
then
on
the
bottom
right.
We
have
in
this
case
the
crab
nebula,
which
is
a
supernova
remnant.
Here,
a
big
star
actually
blew
up
it
exploded.
These
things
are
some
of
the
most
energetic
events
we
see
out
there
in
the
universe,
supernova
explosions,
and
so
this
nebula
here
is
full
of
material.
That,
at
some
point
you
know,
could
form
a
planetary
system
and
maybe
life.
A
Who
knows
something
like
this
happened
in
our
history
here
we
are
here
because
something
like
the
crab
nebula
occurred
in
our
distant
cosmic
history.
Here's
a
couple
more
pictures
of
just
supernova
remnants.
These
things
are
huge
and
I
just
think
they're
very
beautiful,
and
then
finally,
we
get
the
galaxies
right.
So
we
just
talked
about
objects.
A
We
see
inside
our
own
galaxy
and
then,
if
we
look
beyond
it
yeah
again,
here
is
the
andromeda
galaxy
we've
seen
before
2.5
million
light
years
away
about
a
trillion
stars
and
by
the
way
it's
coming
towards
us
or
we're
coming
towards
it.
We
will
actually
merge
with
the
andromeda
galaxy
in
about
four
and
a
half
billion
years,
so
our
view
of
the
andromeda
galaxy
will
keep
getting
larger
and
larger
over
time
and
it's
actually
already
pretty
large.
So
here
is
again
a
composite
picture.
A
You
would
never
see
the
moon
and
andromeda
in
these
locations
in
the
sky
because
they're,
you
know
they're
actually
more
opposite
in
the
sky
typically,
but
this
is
a
composite
just
to
show
the
relative
sizes,
so
here's
the
size
of
the
moon
for
comparison
with
andromeda
and
yeah
the
whole
andromeda
galaxy
is
about
six
full
moons
across
now.
I
told
you
earlier
that,
if
at
the
right
condition,
I
can
show
you
how
to
find
this
thing
with
the
naked
eye
right
and
when
you
find
the
andromeda
galaxy
with
a
naked
eye.
A
What
you
end
up
seeing
is
the
very
bright
core
like
right
here
and
even
with
telescopes,
we
tend
to
see
the
the
bright
glowy
part
right
and,
and
these
fainter
outskirts
are
much
harder
to
see.
But
when
you
do
see
the
andromeda
galaxy,
with
the
naked
eye
or
through
telescope
yeah,
keep
in
mind
how
big
that
thing
really
is
right.
I
will.
I
would
love
to
see
this
hole
extend
with
my
naked
eye,
and
that
would
just
just
be
mind-blowing.
I
think
so.
This
thing
is
huge
hanging
out
there.
A
Here's
some
more
galaxies.
I
don't
know
they're
just
cool
pictures
right
now,
galaxies
we
might
see
from
different
perspectives
right.
I
said
there
are
flatter
structures
and
sometimes
you
might
just
see
them
edge
on
right.
That's
like
the
one
on
the
bottom
right
that
happens
to
be
a
galaxy.
That's
positioned
like
this
from
our
perspective,
and
sometimes
we
see
galaxies
like
face
on
right
and
that
would
be
more
like
the
ones
on
on
the
top
or
actually
the
other.
A
Three
all
kind
of
you
know
face
on
view
and
just
beautiful,
beautiful,
different
types
of
spirals.
Here's
a
couple
more
m81
and
m82.
So
this
is
a
really
nice
picture,
and
one
thing
that's
worth
noting
here
is
that
yeah
it
says
down
here.
This
was
taken
with
almost
35
hours
of
photography
time.
This
goes
back
to
when
I
said
earlier.
We
can.
We
can
collect
more
light
by
looking
longer
right
by
exposing
our
cameras
for
a
long
time.
This
was
done
with
35
hours,
almost
of
total
exposure
time,
not
all
at
once.
A
Things
were
collected
together
here,
but
still,
but
you
know
you
don't
actually
need
necessarily.
You
know,
35
hours
of
exposure
time
to
see
something
cool
here
on
the
left
is
a
picture
I
stole
from
the
prior
slide.
So
this
is
from
that
photograph,
but
on
the
right
side
is
a
photograph.
I
took
very
quickly
actually
it's
kind
of
a
snapshot
of
sorts
at
at
pinnacles
national
park
and
it
turns
out
under
good
sky
conditions.
A
You
can
see
this
kind
of
structure
with
with
your
eyes
through
a
telescope,
so
I
think
that's
very
cool
right
notice.
You
can
see
a
lot
of
the
detail.
That's
also
in
this
bright
picture.
You
can
see
the
structure
inside.
You
know
this
this
edge
on
galaxy
yeah,
so
galaxies
right,
the
universe
is
full
of
them.
It's
just
amazing
here
here
is
something
that's
called
the
hubble
deep
field,
so
here
hubble
stared
at
a
very
small
patch
of
sky.
A
You
know
2.4
arc
minutes
across
we
measure
you
know,
area
of
the
sky
and
in
like
parts
of
degrees
and
it's
basically
ten
percent
of
the
moon
diameter
for
comparison.
So
here's
the
moon
for
comparison
and
hubble
stared
at
like
a
little
rectangle
space
like
this
and
staring
at
that
long
enough.
You
know
keeping
the
camera
shutter
open
a
long
time
revealed
all
this
stuff
right,
so
yeah.
So
all
most
of
these,
these
splotches
are
galaxies
and
which
one
is
the
brightest.
Well,
I
think
it's
this
one
down
here.
A
Look
at
this
right,
so
this
is
7.7
billion
light
years
away.
But
again
it's
a
beautiful
spiral
structure
now
again
we're
looking
into
the
past
right.
This
is
a
time
machine
in
a
way
we're
seeing
this
galaxy
the
way
it
looked
7.7
billion
light
years
ago-
and
this
is
another
version
of
the
hubble
deep
field-
you
know
lots
and
lots
of
galaxies.
A
It's
just
amazing
what
we
see
in
this
tiny
patch
of
sky
and
so
yeah.
If
we
kind
of
extrapolate
from
this,
it
looks
like
there
are
about
10
to
the
29th
or
100
octillion
stars
in
the
universe.
That's
a
lot!
That's
a
like!
100
trillion,
giant
penny
cubes!
You
know
again,
it's
just
a
number
too
big
for
us
to
really
comprehend.
A
Okay,
thanks
for
making
it
with
me.
This
far,
let
me
kind
of
wrap
this
up
so
enjoy
your
views
of
the
night
sky
and
the
cosmos.
You
can
just
look
up
with
your
naked
eye
and
you
can
still
see
a
lot
or
you
can.
You
know
unpack
a
binocular
somewhere
right
and
give
that
a
shot
or
do
some
telescope
viewing.
When
you
do
look
at
the
night
sky,
I
think
beyond
what
you
see.
You
know
that
light
has
been
traveling
for
a
long
time.
A
You
know
space
and
objects
in
it
are
really
big
and
think
about
how
the
stuff
you
see
fits
into
cosmic
history
right.
You
know,
we
see
stars
being
born
and
we
see
stars
that
have
died.
You
know,
and
of
course
we
here
are
somewhere
in
the
middle
of
that
with
our
sun.
So
what
does
it
say
about
our
history
and
future
and
also
what
does
it
say
about
the
chances
of
other
life
in
the
universe
we
haven't
met
any
but
I'll?
A
Let
you
decide
for
yourself
whether
you
think
there's
something
out
there
and
and
kind
of
as
part
of
that
story,
I'll
just
quickly
review
right.
We
start
out
with
hydrogen
hydrogen
form
stars,
you
know
put
enough
stars
together,
you
have
a
galaxy
in
that
galaxy
stars
will
live
and
die
and
form
things
like
the
crab
nebula,
which
is
a
big
blob
of
material
where
stars
have
made
the
other
elements
of
the
periodic
table
and
there's
our
periodic
table-
and
you
know
stuff
like
that-
builds
the
earth
in
us
again
I'll.
A
A
A
Okay,
if
you
like
this
stuff,
you
know
what's
next
so
sja.
Normally
we
have
star
parties
in
in
hokey
park
and
other
observing
events
I'll
kind
of
skip
over
these
a
little
more
quickly
because
of
coronavirus,
we're
all
stuck
canceling
these
for
the
moment
and
deferring
them.
But
again,
instead
we
have
the
online
armchair
star
party
tomorrow,
but
you
can
look
forward
to
these
at
these
events.
A
We
also
do
astronomy,
science,
outreach
for
schools,
like
I
said
again
right
now,
that's
a
little
tougher,
but
you
know
please
do
approach
us
if
you
have
a
school
but
you'd
like
something
like
that
to
happen.
We
have
telescope
fix-it
sessions
like
I
said
where
you
can
bring
out
your
equipment,
we
can
help
you
get
it
going.
We
have
speakers
with
in-depth
topics,
usually
once
a
month
on
the
full
moon
weekend,
we
have
the
astra
imaging
special
interest
group.
A
Now
excuse
me
now,
if
you're
interested
in
getting
involved
with
sja,
we
could
really
use
your
help.
You
know
we
are
all
volunteer
run.
You
know
non-profits,
so
there's
lots
of
stuff
we'd
like
to
do
and
we
can
always
use
more
help
to
do
it.
So,
if
you're
interested
in
helping
out-
and
you
know,
learning
more
science
and
then
promoting
astronomy
and
science
in
general,
we
can
use
your
help
in
technical
and
non-technical
areas.
A
If
you
would
like
to
contribute,
let
us
know,
even
if
you
feel
you're,
not
ready,
don't
worry
about
it,
we'll
help
you
get
ready.
Okay,
now
what
else?
There's
a
bunch
of
suggestions
here
of
things
you
can
follow
up
on
and
one
of
the
things
we
need
to
do
actually
is
I
really
want
to
make
sure
the
stuff
is
on
the
website,
so
it's
easy
for
you
to
access,
because
you're-
probably
not
going
to
remember
this
right
now,
but
there's
something
called
the
astronomy
picture
of
the
day
crash
course:
astronomy
on
youtube.
A
A
A
You
can
get
these
kind
of
sky
maps
on
the
web
here
and
you
know
we
can
help
you
figure
out
how
to
use
these
if
you
like,
and
then
there
are
also
places
like
the
chabot
space
and
science
center
in
oakland
and
again,
they're
also
dealing
with
coronavirus.
But
this
is
a
great
place
to
visit.
You
know
when
you
can
and
some
other
resources
are
the
astrology
society
of
the
pacific,
and
there
are
citizen
science
places
where
you
can
help
do
science
right.
A
So,
if
you
visit
these
sites,
you
can
help
participate,
for
example,
classify
galaxies
and
there
have
been
cases
where
citizen
science
participants
have
made
discoveries
and
have
ended
up
on
scientific
papers.
So
that's
kind
of
cool
and
regardless
just
go
ahead
and
look
at
the
sky
and
just
kind
of
in
closing.
You
know
science
is
our
tool
for
unlocking
the
universe,
there's
a
lot
of
stuff
and
a
lot
of
stuff.
We
don't
know
yet
right,
but
we
keep
working
on.
A
You
know
pushing
things
over
right
and
more
and
more,
you
know
things
we
don't
know
yet
become
things.
We
know,
and
this
is
kind
of
a
message
also
to
young
people
out
there
right.
You
can
help
us
figure
out
stuff,
we
don't
know
yet
a
lot
being
remains
to
be
discovered
and
you
can
help
us
so
yeah.
Thank
you
very
much
for
listening.
My
name
is
wolf.
If
you
want
to
send
me
a
note,
I'm
here
at
director
ford
sjaa
stuff
in
space.
A
I
hope
you
enjoyed
this
this
little
tour
and
if,
against
all
expectations,
you
send
up
seeing
this
stuff
in
space.
You
know
when
you
look
through
your
telescopes.
Please
call
me
immediately
because
I
really
want
to
see
this
too
so
yeah,
that's
basically
the
show
for
today
thank
you
and
we
can
take
a
final
break
for
some
questions.
So
let's
do
that.
B
A
Okay,
so
that's
a
good
question.
It's
a
really
good
question
I'll
I'll
have
to
give
a
short
answer,
because
otherwise
we'll
be
here
probably
too
long.
So
I
think
the
first
part
of
that
answer
is
there's
more
than
one
way
it
kind
of
depends
on
how
far
away
an
object
is
I'll.
Give
you
a
couple
examples.
One
thing
we
use.
A
I
look
at
my
thumb
with
my
left
eye
and
now
the
thumb
appears
to
shift
right,
so
the
thumb
appears
to
shift
in
space
because
the
perspective
changes
right,
you're
looking
you
know
with
this
eye
and
then
with
that
eye,
and
that
basically
sets
up
some
geometry
right.
You
know
something
about
the
distance
between
your
eyes
and
that
allows
you
to
you
know.
You
can
then
measure
the
shift
and
you
can
do
it
on
geometry
and
figure
out
how
far
away
your
thumb
is.
A
Essentially,
I'm
skipping
over
a
couple
details,
but
that's
one
approach
we
use
now.
You
might
wonder:
okay,
I
mean,
does
the
thumb
work
and
we
look
at
the
night
sky
and
the
answer
is
well.
No,
we
need
to
do
something
a
little
different.
The
substitute
for
shifting
your
eyes
with
astronomy
is
to
wait
for
the
earth
to
make
half
a
revolution
around
the
sun.
So
we
would
so.
Let's
say
this:
is
the
sun
right
here,
right
and
and
right
now
the
earth
is
here.
So
we
would
look
at
the
object
in
space
from
here.
A
So
another
method
we
use
is
something
called
using
standard
candles,
and
so
imagine
this
right.
Imagine
you
have
a
100
watt
light
bulb
right.
So
here
you
have
a
light
bulb.
You
know
how
bright
it
is
because
you
bought
it
as
a
100
watt,
light
bulb,
and
now
you
take
that
light
bulb
and
you
carry
it
out
into
a
field
or
you
have
someone
a
friend
carried
away
from
you
right
and
as
that
friend
carries
that
light
bulb
away.
It
will
appear
dimmer
and
dimmer,
but
you
still
know
it's
a
100
watt
light
bulb.
A
So
again
we
could
do
some
math
and
we
can
say:
okay,
I
know
how
bright
it's
supposed
to
be
right,
because
I
know
what
it
is.
I
know
it's
100
white
light
bulb
and
then
I
can
take
the
brightness
that
I
appear
to
see
and
based
on
that,
I
can
drive
the
distance
now
again.
We
cannot
really
take
100
wide
light
bulbs
out
into
space,
but
it
turns
out
there
are
certain
types
of
events
in
space
that
also
represent
standard
candles.
A
There's
something
called
a
type
1a
supernova,
it's
a
type
of
star
explosion
that
turns
out
it
blows
up
with
a
very
well
controlled
brightness,
there's
also
something
called
a
cepheid
variable
star.
It's
a
similar
idea,
so
these
are
objects
that
serve
as
standard
candles,
kind
of
as
hundred
watt
light
bulbs,
and
we
can
look
at
their
apparent
brightness
and
we
know
what
the
actual
brightness
must
be
and
based
on
that,
we
can
derive
distance
and-
and
I
could
go
on
for
a
little
longer,
but
I
want
to
make
sure
we
have
some
other
questions.
A
A
A
Okay,
I
I
guess
I'm
not
quite
sure
what
interference
you
might
be.
Thinking
of.
Maybe
that's
something
you
can
quickly
clarify
in
the
chat
to
make
sure
I'm
really
understanding
your
question
I
mean,
but
we
certainly
do
deal
with
like
light
pollution
and
things
like
that.
So
that's
probably
not
what
you
mean.
I
think
I
mean
when
we
look
at
stars,
for
example.
Maybe
this
is
more
of
what
you
mean.
A
So,
in
other
words,
we
could
have
been
confused
because
we
didn't
know
that
there
were
actually
two
stars
very
near
each
other
and
their
light
was
kind
of
adding
up
before
we
got
to
look
at
it
closely
enough.
I
don't
know,
if
that's
the
kind
of
thing
you
mean
so
so
we
do
have
yeah.
So
we
do
try
to
look
at
things
very
deeply
in
a
way
right
and
try
to
detect
whether
you
know
there
are
maybe
multiple
objects.
You
know
somehow
participating
in
something
that
initially
appears
like
it's
a
single
thing.
Is
it.
B
Yeah,
I'm
not
quite
sure
if
that's
what
he
meant,
but
I
think
there's
no
further
response
on
the
chat.
So,
okay,
yeah,
your
guess,
is
as
good
as
mine.
Okay,
I
think
I
think
the
the
related
question
was
that
how
can
one
conclusively
determine
that
the
light
is
from
the
source
that
you're,
observing
and
and
I'm
thinking?
B
B
A
So
yeah,
usually
it's
not
you
know,
conclusions
about
what
things
are
is
typically
not
based
on
a
single
observation.
Right,
usually
you
have
to
observe
things
over
time
and
you
know
record
data
over
time
and
you
also
have
usually
multiple
people
or
scientists.
You
know
doing
that
and
comparing
their
data,
but
I
think
really
key
is
the
comparison
over
time.
So
we
tend
to
look
at
light
curves.
So
you
know
how
is
the
light
changing
over
time
and
that
helps
us
figure
out.
You
know
what's
really
going
on.
For
example,
I
mentioned
beetlejuice
earlier
right.
A
It's
a
really
big
star
by
the
red
super
giant
that
we
see
in
the
winter
sky
and
last
wasn't.
I
think
this
started
last
year,
maybe
the
year
before,
it's
like,
oh,
my
god
that
star
is
dimming,
it
seems
to
be
getting
fainter.
What's
going
on
right
and
so
yeah
there
were
thoughts,
oh
maybe
that
stars
undergoing
change
and
it's
going
to
go
supernova
pretty
soon,
which
would
be
amazing
to
watch
but
yeah.
We
didn't
quite
know
what
was
going
on
right.
A
So
at
first
we
thought
the
star
itself
is
doing
this,
but
but
longer
term
observation
and
study
of
the
light
curve.
How
light
changes
over
time
has
kind
of
updated
our
understanding
of
this
and
right
now
we're
things
like?
Oh
probably,
that
was
just
some.
You
know
dust
and
gas
right
that
was
kind
of
interfering
with
the
light
that
we're
seeing
that
was
causing
this
change
in
brightness,
so
yeah,
so
observation
over
time
is
really
important
right
and
then
that
that
temporal
story
has
to
make
sense.
I
don't
know
if
that
helps.
B
A
A
Well,
cool,
thank
you
all
you
know,
so
I
have
a
couple
questions
for
you.
I
mean
if,
if
you're
still
there,
if
you're,
still
listening
before
you
log
off
I'd,
be
curious
to
find
out
what
you
found
most
interesting
over
the
last
hour,
and
maybe
if
there
was
anything
that
was
really
surprising
to
you.
What
was
that
right?
I'd
love
to
hear
those
kind
of
things
because
it
helps
me
understand.
You
know
how
this
presentation
works
for
you
and
maybe
can
help
me
improve
it
for
the
future.
A
So
yeah,
if
you
wouldn't
mind
taking
a
moment,
you
can
tell
me
what
you
found
most
interesting
or
most
surprising
over
the
last
hour.
You
know,
but
again
really.
Thank
you
very
much
for
listening.
I
hope
you
enjoyed
the
last
hour.
Hope
you
got
something
out
of
it
and
remember
that
tomorrow
is
the
armchair
star
party,
we'd
love
to
see
you
there
as
well.
It
should
be
a
good
show
and
maybe
at
some
point
in
the
future
we
can
all
meet
in
person.
You
know
at
a
nice
dark
sky
event
under
the
stars,
so.
B
A
A
So
there
have
been
times
in
history
where
people
here
on
earth,
even
before
there
were
lots
of
astronomers
crawling
around
right
where
people
have
observed
supernova
events,
I
I'm
terrible
with
dates,
so
my
brain
always
forgets
the
historical
dates
was
it
in
the
1700s.
I
think
I
can't
remember
right,
but
but
there
have
been
records
of
people
observing
supernova,
just
with
the
naked
eye.
A
nearby
star,
turning
supernova
would
be
visible
during
the
day.
It
would
be,
you
know
quite
bright,
but
space
is
really
big.
A
So
most
supernova
are
not
right
here
in
the
neighborhood,
but
we
do
observe
them.
You
know
in
distant
places
in
our
own
galaxy
and
in
other
galaxies
right.
So
we
do
look
at
other
galaxies.
I
showed
you
some
pictures
earlier
and
yeah
every
now,
and
then
we
notice
a
supernova
right
and
that's
usually
an
exciting
event
right.
So
somebody
off
notice
them
by
accident
because
especially
the
far
away
ones,
we
can't
predict
right.
Then
everybody
goes.
Oh,
my
god.
A
B
B
A
A
So,
if
you're
out
there
wondering
how
you
might
help
sga,
this
is
one
way
right,
because
so
again
I'll
kind
of
hand
wave
this
right
so
remember
you
earlier
saw
like
the
crab
nebula
right,
where
a
star
blew
up
and
a
whole
bunch
of
stuff
got
spewed
out
into
space.
It's
like
a
bubble
right,
so
yeah
you'll
have
like
bubbles
of
stuff
out
in
space
and
yeah.
Somehow
we
get
from
a
bubble
of
stuff
to
a
flat
structure.
You
know
galaxies
are
flat
right.
A
Solar
systems
tend
to
be
flat
right,
so
we
have
the
sun
in
the
center
of
our
solar
system
and
all
the
planets
are
more
or
less
orbiting
in
a
plane,
there's
a
little
bit
of
variation,
but
for
the
most
part,
yeah,
the
solar
system
is
a
flatter
structure
as
well.
It's
like
well
that's
interesting.
How
does
that
happen,
and
it
turns
out
that
yeah,
you
start
out
with
a
blob
of
stuff,
and
this
blob
of
stuff
will
tend
to
have
some
rotation
it'll
be
spinning
in
some
orientation
right.
A
A
Gravity
will
tend
to
want
to
compress
this
blob
of
stuff
into
a
flatter,
smaller
structure,
but
because
you
have
it
spinning
to
start
with,
you
have
to
preserve
that
angular
momentum,
and
so
you
know
you
cannot
stop
the
spin
there's
nothing
that
will
stop
the
spin,
so
the
spin
will
continue
and
gravity
will
end
up
pulling.
It
then
into
a
plane,
and
it
will
keep
spinning
in
whatever
the
you
know.
Plane
of
net
rotation
was
in
the
first
place.
There
are
some
nice
animations
of
this
kind
of
stuff
on
youtube.
B
A
B
A
It's
good
to
have
a
section
on
that
sometime.
I
agree,
and
actually
I
I
have
a
presentation
on
you
know
like
telescope
equipment
which
I've
given
once
and
yeah.
I
could
certainly
dust
that
off
and
have
a
session
on
that
again
we're
all
volunteers.
We
all
do
this
in
addition
to
our
day
job.
So
that's
the
limitation,
but
thank
you
for
expressing
your
interest
because
that
certainly
motivates
me
to
you
know,
get
off
my
button
and
do
that.
So
thanks
thanks
for
asking.
A
Okay,
well,
great
again,
thank
you
very
much
for
attending.
I
hope
you
enjoyed
the
last
hour
or
actually
it
was
more
like
90
minutes.
I
guess
I
talked
too
much
today.
Well,
thank
you
for
your
participation
answering
and
asking
questions
it's
great
to
have
that
participation
from
the
group
and
I
hope
to
see
you
at
tomorrow's
armchair
star
party
and,
like
I
said,
maybe
at
a
future
in-person
event.