RONALD SMITH: I'm Professor 
Ron Smith from the
Department of Geology
and Geophysics.
And if you're in the right
place, you know that this is
the course called the
Atmosphere, the Ocean, and
Environmental Change.
There's a lot to talk
about today.
If some of you are shopping, I
want to be sure you get enough
information about the course
to make your decision about
whether to take it or not.
And for those that are
definitely in, I want to get
you started toward some of the
course material that we have
in this course as well.
So as I will usually do in the
mornings, I'll have some notes
in the upper left there.
And I want to run through
some of those.
This is just informational
stuff, logistical information
about the course.
There's some confusion
about this.
The lab is required.
So everybody that takes this
course takes the lab.
And everybody that takes the
lab takes this course.
You get graded separately for
the two, but the subject
material is merged and
coordinated in a certain way.
So you have to take
both of those.
That means when you're signing
up for the course, be sure to
sign up for the lab as well.
It has a different
course number.
For example, EVST 201 is this
course, 202 is the lab.
Or if you signed up under
Geology, it's 140,
and 141 is the lab.
Also, the Classes server,
they're separate sites.
So be sure to register on both
of those because I'll be
posting information about the
lab on the lab course number.
Now the labs aren't
going to start
actually until week three.
So we're not going to do lab
section sign ups yet.
But I will tell you that
the labs are on
Monday and Tuesday afternoon.
There's four sections
altogether.
And you've got to be
able to fit into at
least one of those.
And we hope more than one
because we're going to have to
even you out.
But those labs are at 1:30
and then at 3:30 on
both of those days.
So we'll be doing those lab sign
ups next week when you
have a better idea of what
your schedule is like.
But try to keep those Monday and
Tuesday afternoons open,
so you can fit into
one of the labs.
Because if you can't
take the lab, you
can't take the course.
Let's see, there's already a
problem set posted on the
Classes server.
And it is due next Friday,
a week from Friday.
And you may ask, how could I
have already posted a problem
set when I haven't
given a single
lecture about the course?
Well, that's because this
particular problem set is kind
of a warm up.
It's got questions on there
that you could do with an
elementary knowledge of
high school physics.
And I'd like to get you
started on that.
Both because we need you to be
fresh and familiar with those
subjects, but also those of
you that don't have a good
background might want to use
that as a guide as to whether
this is the right
course for you.
So take a look at that problem
set as soon as you can.
And if you have any problems
with it, talk to me,
talk to your TAs.
Speaking of TAs, let me see if
I can introduce them to you.
Ravi is there.
Jennifer is there.
Is Meng here?
Meng is right there
beside them.
And Srikanth.
No Srikanth today.
OK.
And by the way, Melanie here on
the left, on my right, is
going to be helping with
the taping transcript.
So we're going to have
this course taped.
And I'm afraid these tapes--
they're not going to be
available to you during
the semester.
There's too much of a lag
time, I think, to
get those to you.
But I don't think it'll
be a problem in class.
One thing I want to mention
though, this course--
well, it seems like we got
a pretty big class here.
But still, even with this class,
it's a very convenient
room and a very convenient
class to have a lot of
discussion, questions,
answers.
So be prepared for that.
Don't be shy about
asking questions.
And I think that will really add
a lot to the course if you
get in the habit.
If you've gone for a period
or two and haven't asked a
question in class, you should
ask yourself why?
Because it's probably not the
clarity of my lectures.
It's probably that you're just
reluctant to put your hand up.
So try to gauge this
a little bit.
And if you're asking too many
questions, which hasn't
happened yet, but if
it happens, I'll
tell you about that.
And we can scale it back.
The textbook--
I went down the bookstore
yesterday, and I saw it there.
It didn't look like they
had that many copies.
But I should mention that if
you get a copy that's an
edition or two old,
that would be OK.
And you might be able to really
save some money by
doing that.
But get that book right away
because you're going to need
that starting immediately.
And if you have to order it
online, and it's going to take
a couple weeks, that's
probably not good.
So get that coming to you.
But anyway, the book is this
one, Essentials of
Meteorology.
And a word or two about it.
It's a descriptive
book primarily.
It describes things
that go on in the
atmosphere in the ocean.
And that'll be really great.
That'll supplement what
I do in lectures.
The course, however, is more
quantitative than this.
And the quantitative material
will come from my lectures.
And you'll be working on the
quantitative side of the
course every week with
these problem sets.
So try to understand that,
you're going to be reading
this to get the descriptive
material.
And you're going to be working
off my notes and the problem
sets to do the quantitative
material.
I wanted to mention that final
exam date because these exam
dates cycle through.
Yale tries to be fair in how
they assign exam dates to
different courses.
And last year, our final
exam was on the
first day of exam period.
Well, we cycled off.
And now we're on the last day
of exam period, December 17.
So if you're booking flights
home, please
keep that in mind.
You have to be here on--
I forget what day of
the week that is.
But that's the last day of exam
period for this course.
Any questions so far?
So what's this course
all about?
I would say a lot of the course
simply has to do with
how the atmosphere and
the ocean work.
How does the air and the water
move and mix in the
atmosphere?
That's the winds.
Also, storms. How do
storms--We're going to be
talking about in some organized
way, I hope, the
different kinds of storms:
thunderstorms, frontal
cyclones, tropical cyclones,
and so on.
So we're very interested in the
basic physics of how the
atmosphere in the ocean move.
For example, in the atmosphere,
we're going to be
studying clouds.
How do clouds form?
What is a cloud made of?
And why do very few clouds
precipitate, but some do?
And we want to ask that question
because it has to do
with climate, which brings
me to a big part of
the course is climate.
Climate is defined usually as
kind of average weather.
I don't like that definition.
I'll give you a better one when
we come to that section
of the course.
But we certainly want to
understand how climate varies
around the globe.
Why does Central Africa have
a different climate than
Connecticut, which is different
from Southern
California, which is different
from, well, any place?
There's a distribution of
climates around the planet
that controls how people live,
how they do their agriculture,
how they live their
daily lives.
We really want to
understand that.
That's a key part of this course
is understanding the
distribution of climates and
the impact on human beings
around the globe.
And of course, once we
understand that, we can then
go on to the subject of
change in climates.
How have climates changed over
the history of the earth, and
how might they change
in the future?
And of course, the human impact
as well, not only how
climate impacts humans, but how
do humans impact climate
as a subject of increasing
importance?
So questions yet?
All right.
Now I've already mentioned this
but the way you're going
to be studying this course,
there are about five to six
different things you need to be
looking at for sources of
information: the book, my
lectures, which are more
quantitative, the problem sets,
which are quantitative.
We're going to have three exams
during the semester.
Now why am I listing that as
something you learn from?
Well, of course, you'll be
tested on these exams. But I
think you could also learn a lot
from taking these exams.
Through the lab, you'll be
having lab exercises,
including a field trip for
getting up on the roof
launching balloons, measuring
things in the atmosphere.
You'll learn a lot
from doing that.
But the one thing that I can't
control, it's entirely in your
hands, is to develop a new
habit of observing the
environment as you
walk around.
So for example, when you walk
to class every morning, and
for some of you, it's a good
walk, instead of just turning
on your iPod or zoning out,
start to look up and around,
and try to figure out what's
going on that day.
What clouds are up there?
What direction are
they moving?
What direction is the
wind blowing in?
Are there clouds at different
altitudes moving in different
directions?
That's a really important
thing to know.
So that's a new habit.
Now I want to tell you something
about this because
you're all online several
times a day probably.
And let me see if I can just
give you some good sources.
I put this little document--
oh, I lost my control here.
Wait a minute.
I put this document up on the
Classes server last night, so
you have it there.
But when something interesting
is happening in New Haven,
like happened last weekend with
Hurricane Irene, I love
to go on to these data sources
and follow along and see
what's happening
with the storm.
And of course, you don't
have to do it that way.
You can tune in to
the television.
The television weather guy is
more than happy to give you
his or her interpretations
of what's
happening with the weather.
But you don't have to be
satisfied with that.
You can go to the data itself.
And that's more fun than
just listen to
someone talk about it.
So a few sites that I find
really useful, one is this
Tides Online site.
Most of these are .gov. They're
government sources for this.
Now you can go to coastal cities
all around the coast of
our country.
But what I've done here is
go to the New Haven one.
And let me darken this
a little bit so you
can see that better.
There's time on this axis and
feet above mean low water.
So this is a record of tides
for New Haven Harbor.
It's at the coast guard station
right on the east side
of the harbor there.
And the blue curve is what was
predicted for the tides based
on the moon and the sun.
Right?
The moon and the sun produce--
their gravitational pull
produces a tide in the ocean.
Here in New Haven and most
places around the world, it's
a semidiurnal tide, that is to
say it's a twice a day tide,
two high tides and
two low tides.
And that's what you see
in the blue curve.
The red curve is what's
actually measured.
They've got a water
level gauge there.
And as it goes up,
they record that.
And now this date goes back to
the twenty-eighth and the
twenty-seventh, which
was last weekend.
And what you see here is that
the sea water level rose quite
a bit above what was predicted
from the normal tides.
And of course, that's what's
called the storm surge.
Right?
So as Hurricane Irene came up
the coast and with the winds
blowing counterclockwise around
it, as it approach, the
winds were from the east. In
fact, that's on this curve.
I'll show it to you
in just a minute.
Well, that wind from the east
pushed water into Long Island.
And the water level rose.
And they subtracted one curve
from the other to get the
green curve.
So that's the difference between
the observed water
level and the predicted
tide level.
And you see that it rose about
four feet above normal, and
then dropped a couple of
feet below, and then
came back to normal.
So that's a typical example of
what happens with sea level as
the hurricane comes up.
Now, here's the wind data.
It's too small for you read
through the back, so I'll try
to walk through it.
The same time scale
is on the bottom.
You're spanning about
three or four days.
This is in knots, which
is a traditional
unit of wind speed.
Unfortunately, it's not the
one we'll use primarily.
We'll use meters per second.
But knots is a traditional
speed.
A knot is a nautical
mile per hour.
So it's kind of like
a mile per hour but
a little bit greater.
So the wind speed increased
as the Hurricane Irene
approached.
And from the little vectors that
you can see, the wind was
from the east. It reached a peak
of about 30, 32 knots.
And then as the storm
moved away,
the wind speed decreased.
But then the wind was from
the west. Remember?
So just to sketch this out
if I can for a second.
So here we are in New Haven.
And the cyclone is like
this, winds going
around in that direction.
As it approaches us, the winds
are going to be from the east.
And then as it passes by a day
later, the top here, the winds
have the same direction
around it.
Suddenly, the winds are from
the west. So you're seeing
that pattern there.
And then, of course, that's
what's reflected
in the storm surge.
First, it pushes water into
Long Island Sound.
Then it pushes the water back
out of Long Island.
So it's not too complicated.
And the data is right there
for you to see.
So here's another one.
If you go on to water data USGS,
that's the United States
Geological Survey, and hit on
the Quinnipiac River, which is
the main river that comes down
through New Haven, there's
three rivers, we're going to
do a field trip along the
Quinnipiac as part of
lab two or three.
So you'll learn a lot about
the Quinnipiac.
But I went on just after the
hurricane to get this data.
This is the river discharge.
Again, it's not in a metric
unit, I'm afraid.
It's in cubic feet per second.
That's how much water is
coming down the river.
And these are dates along,
August 23, 24, 25, 26, so on.
So that, of course,
is the big--
By the way, this is a
logarithmic scale.
So that's a really big increase
in the amount of
water coming down the rivers.
And of course, that's because
of the heavy rain that fell
from the hurricane.
So check that one out as well.
Let me see what else
I have that I
think is really important.
Well, the radar--
I love to watch the radar.
You can get there a lot of
different ways, for example,
radar.weather.gov. But usually,
I go right to the--
the closest weather radar
to us is on Long Island.
It's about here at a station
called Upton, U-P-T-O-N. So if
you just Google Upton radar or
Upton NOAA radar, you'll go
right to that site.
And you get a nice visual
representation of the
precipitation in the region.
One thing to remember about
radar, I think you
know what it is.
It's a microwave signal
that gets sent out
from the radar antenna.
It scatters off raindrops
and then
comes back to the receiver.
And from the time it takes for
the signal to go out and back,
you get the distance.
And of course, from how the
antenna was aimed, you know
the azimuth angle, so
you could figure
out where that is.
And it's put together in
a nice map like this.
This was taken just as the front
part of the cyclone was
coming into Southern
New England.
And you see this nice heavy
rain shield out here.
The eye of the storm is
probably about here.
It wasn't a very well
developed eye.
But the center of it was
probably about here.
And the backside was fairly
dry, surprisingly dry.
We'll talk about
that later on.
Some people think that it was
transitioning away from a
tropical cyclone to a different
type of a storm at
this point.
But that's getting ahead
of the story.
But you can check--I check it
frequently when I'm about to
walk out to go someplace
on campus.
And sometimes I'll go on to the
Upton radar and just check
the radar to see if
it's raining.
I got a window, but what I
really want to know is not
whether it's raining now, but
is it going to rain in 5, 10
or 20 minutes.
Well, if I see a big squall line
coming towards New Haven,
then I can decide whether--
maybe I can sprint to where
I'm going before
it gets there.
Or maybe I better just wait
until it runs through, and
then I'll walk off to my car
or walk off to my meeting.
So that is a very nice--
in meteorology, we got a
funny word for that.
We call it nowcasting.
It's like forecasting except
it's forecasting for just the
next few minutes.
And the best way to do that is
with the Upton radar because
that will tell you--
New Haven's right there.
And it'll tell you if there's
a little thunderstorm or
something just about to
move over New Haven.
So it's very, very convenient
for that purpose.
Another great one, of course,
is the satellites.
And there's a picture
of Irene.
Now there's lots of ways to
get at the satellite data.
www.goes.noaa.gov is
one way to do it.
And GOES stands for
Geostationary
Environmental Satellite.
That means it's a satellite
that is--
it's over the equator.
And it takes twenty-four hours
to go around its orbit, just
like the Earth takes
twenty-four hours
to spin on its axis.
So it stays over the same
point on the equator.
So we say it's geostationary.
It's like it's parked
right up there.
And it's the best satellite for
watching cloud patterns
develop and move.
Because you're not just getting
an occasional snapshot
when the satellite comes
back around.
No, that satellite is there.
And it's taking a picture
about every 10 minutes.
So you get a really good way
to follow the structure of
these cloud patterns as they're
swirling around.
So there's a good example.
Now, also notice these clouds
are quite different than the
ones up here.
The radar show that
these were not
precipitating, but these were.
So the deeper clouds with the
big anvils on them were
precipitating, but these
low level clouds
were not at that moment.
Any questions on this?
Well, do I have anything else?
Oh, yes.
So this gets a little more
techie maybe, but I love it.
And that's getting the
balloons sounding.
So the National Weather
Service launches
balloons--weather balloons
--twice a day from a couple of
hundred places around the United
States and 400 or 500
around the globe.
And they're all accessible.
The balloons are launched
at 00:00 and
12:00 universal time.
You're going to have to become
familiar with what we call
universal time.
Sometimes we call it Greenwich
Mean Time.
In the military, it's
called Zulu Time.
We'll most of the time call
it just universal time.
And so 00:00 and 12:00 universal
time, when we're on
Eastern Daylight Time, like
we're on right now, it would
be 8 o'clock in the morning and
8 o'clock in the evening.
So those balloons are launched
at 8 o'clock in the morning, 8
o'clock in the evening.
They'll launch them a few
minutes before that time
because they take a couple
hours to rise.
But if you go on to--
what I usually do is go on to
the University of Wyoming
website because they got a
really great website where you
can get all the soundings all
the way back in time.
Back 50 years, you can get
soundings from all these
different sites.
So that's a really handy
one to go into.
So what I did here was
pull off the--
I forgot to say, the closest
radius on site to us is also
Upton, New York, same place
where that radar is.
They launch balloons
from there as well.
So what I did here was to
go on to the Upton--
Wyoming site, pull down the
sounding as the storm was
approaching, and then
as it was leaving.
So this is a balloon carrying
a small instrument package.
You'll be working with
this kind of data
later in the course.
So this is a little
bit of a preview.
But what's plotted here is,
well, I'll say altitude.
But really it's pressure because
that's how we know how
high the balloon is from the
pressure that it is recording.
Pressure decreases as you
go up in the atmosphere.
So it's a convenient way to keep
track of your altitude.
And then on this scale
is temperature.
And two lines are plotted, one
is the air temperature, one is
the due point.
So when they're close together,
that means the air
is saturated with water.
So that's not a surprise, that
as this hurricane was coming
over us, the air was saturated
at least three or four miles
up in the atmosphere.
Maybe that's not saturated,
but it probably is too.
Probably that's just an
instrument air or something to
do with ice versus water.
It's probably saturated
all the way up.
And then the winds are given
over here in a traditional,
meteorological wind barb.
It's a little feather
that you draw--
a little arrow with
feathers on it.
And the number of feathers
tell you how
fast the wind is blowing.
And the direction
tells you what
direction the wind is blowing.
So for example, here, the wind
was, I think, 30 knots from
the east. Well, that
makes sense.
That's when the storm
was approaching.
So here in Southern Connecticut
or Long Island,
the wind is from the east.
And then as the storm was moving
away, we had 40 knots
from the west. That was taken
twelve hours later, 00Z on the
28th and 00Z on the
twenty-ninth.
That kind of brackets the
hurricane passage.
And then you can see this
begins to dry out
a little bit aloft.
You saw those low clouds
in the satellite image.
That's this saturated air.
But then it was drier aloft.
So you can understand that
vertical cloud structure we
saw in the satellite
image by looking
at the balloon sounding.
So this is great because this
stuff is online all the time.
And so whenever something's
happening not only here, but
anywhere, go on to the website,
take a look at it.
And I'd like you to work with
this raw data rather than just
listen to what the weather
forecaster has to say.
Question?
Yeah.
STUDENT: Does it make
a difference if
those lines were connected?
Some of them kind of
look like a flag--
PROFESSOR: Oh, here you mean?
Yeah.
So there's a little
thick barb there.
That's the 50 knot.
It's kind of like Roman
numerals in a way.
So that's 40.
That's 55, a thick
and a short.
Short is 5.
A long is 10.
And the thick one is 50.
So it's kind of like a Roman
numeral way of keeping track
of wind speed.
Yeah?
STUDENT: You told us two lines
measure, one was air
temperature, one's due point.
Is there a reason why the second
one-- like the first
one goes all the way up and
the second one --like the
first one goes all the way up
and the second one like one of
them kind of stops short?
PROFESSOR: Yeah.
Probably it got so dry that
the sensor could not
accurately measure.
So they probably just stop
the data because
they're getting too dry.
We were getting--as that cyclone
moved away, we were
getting cold air coming
in behind it
descending down from Canada.
And that was very dry air.
And you're getting a hint of
it, but then I think the
sensor probably couldn't
keep track of the real
dry air behind it.
It's not a perfect instrument.
Be aware of that.
Whenever you're looking
at real data, it's not
necessarily always going
to be perfect.
Other questions on this?
OK.
Well, let's see what else
we have to do today.
So I've gone through all the
things that I wanted you to be
aware of as sources
of information.
And I think there's just a
couple of other things I want
to do today.
Oh, before I forget, I want to
say a couple words about
myself because some of you may
be curious to know what I do,
although it may become obvious
as the semester unfolds.
So I started out in--
when I started college, I had
no idea I was going to move
into geoscience, or geophysics,
or atmospheric science.
I was interested in airplanes.
I want to fly airplanes.
And so I got an undergraduate
degree in aeronautical
engineering and a master's
degree in aeronautical
engineering.
I thought I was going to
be a military pilot.
And then things developed in the
way that made me realize
maybe that's not my career
goal after all.
So I switched--I went in the
navy for three years, spent
some time on ships.
And during that three years,
I realize I was really more
interested in the atmosphere in
which the airplanes fly and
the oceans than I was in the
airplanes themselves.
So as many of you will find, the
careers you have in mind
right now may not be the
ones you end up with.
Because as you have new
experiences, you realize there
are other interesting things
to do out there.
And so just be flexible and
keep your options open.
So when I got out of the
military, I went back to
school then in geoscience, the
study of the earth, and its
atmosphere, and its oceans, and
developed a career there.
So my interests today are
primarily in what I call
regional climates.
How does a climate one part
of the world differ from a
climate somewhere else?
Does that have to do with just
where it stands on the earth,
its latitude, its longitude?
No, it also has to do with local
features in the land:
coastlines, mountains, land
surface structure.
So these are the things that
I'm interested today.
I've done projects in many
places around the world trying
to understand how the
local climates in
those regions work.
So you'll find as I go through
the course that I'll be
occasionally referring to some
of the work that has been done
in that area.
Are there questions?
OK.
Well, you're not going to get
away today without a little
bit of lecture.
So I wanted to run through
one argument--
I think we have time
for that today--
that I think is important for
forming a foundation for
everything else we
do in class.
And so I'm going to address this
one question, what is an
atmosphere?
My answer is going to be that
it's a layer of gas held to a
planet by its gravitational
field.
So that's my definition
of an atmosphere.
And I want to illustrate this
by doing what's called a
Gedanken experiment.
A Gedanken experiment is a
thought experiment, comes from
the German word for thought.
So we're not actually
do this experiment.
We're going to think
our way through it.
And so here is my little
Gedanken experiment.
I got a planet here.
It has some mass, M,
has no atmosphere.
But I got an alien.
I've hired this alien to
bring in an atmosphere.
And he's over here, and
he's got a box of air.
And the molecules are there.
And he's far away from Earth.
So he doesn't feel the
gravitational field of the
planet yet.
And so these molecules are
going to be uniformly
distributed through the box.
They don't feel the tug yet from
the planet that's going
to maybe want to squeeze
them towards this
corner of the box.
They're too far away for that.
So they're just sitting there
freely bouncing around in the
box having a good time.
Then we bring that box
down to Earth.
We set it there for a minute.
Well, now it feels the gravity
field of that planet.
Now the molecules are
still moving around.
They're bouncing.
There's pressure in that gas.
But the gravity field is going
to play a role too.
So more of those molecules are
going to sink to the bottom.
There's going to be a few
up here at the top.
But most of them are going to
be down at the bottom simply
because of that gravitational
field.
And then the final step of this
experiment is I'm just
going to open a door.
When I open the door, that
gas is just going
to flow right out.
The box is going to become
empty, and I'm going to have
an atmosphere.
Obviously, it's held to
the planet by that
gravitational field.
Just like it was in the box
here, there's going to be few
more molecules down below
and fewer up at the top.
So you're going to have that
gradient because of the
gravity field.
But basically, it's going
to be held there
by the gravity field.
So that's what I mean by layer
of gas held to the planet by
the gravity field.
Now, a couple of things that
I've already misled you about.
First of all, of course, that
isn't how planets get their
atmospheres.
They're not brought
in by aliens.
There are two leading theories
for how a planet really get
its atmosphere.
One is that it is a so-called
primordial atmosphere.
That is to say it was formed
with the condensing planet.
When the planet was first
formed, it was formed from
material out in space that
was collected together
gravitationally, kind of
a gravitational inflow.
And at the same time, there
would have been lighter
molecules out there that
didn't want to become
incorporated in the solid
planet's surface.
But they would have been
attracted too.
And so you would have formed the
solid atmosphere from the
heavier compounds or ones that
like to bond together.
And the lighter molecules or
the ones that don't like to
bond together would have
formed this envelope
of gas around it.
So that's one possibility.
The other is that--
well, maybe there was an
atmosphere formed in this way.
But maybe it was lost. After
all, the earth is almost 6
billion years old.
So whatever atmosphere it had
at the beginning isn't
necessarily the same atmosphere
we have today.
We'll talk about
that next time.
But even if the atmosphere was
never there or was lost, the
planet could still over
geologic time give off
additional gases from
its interior.
I'll just call that
outgassing.
For example, if you go to a
volcano today, you could
measure gases coming out
of the planet into the
atmosphere.
So this is an active dynamic
ongoing process where gases
come from the interior of
the planet out into
the atmosphere itself.
So either one or some
combination of the two is
where the Earth and the other
planets actually got their
atmosphere from.
Now, I misled you in another
way too, the
way I've drawn that.
I've drawn the atmosphere
relatively thick that distance.
If I called the radius of the
planet capital R and the
thickness of the atmosphere,
let me call that little d,
I've drawn them with the ratio
about five or six to one.
Actually, the ratio is much
smaller than that.
If I take the ratio of d to R
for the Earth, the radius is
about 6,370 kilometers.
Whereas the depth of the
atmosphere-- it's a little bit
hard to define the depth of the
atmosphere because it has
a gradual top.
There isn't suddenly a
level where suddenly
the atmosphere stops.
But I'll make a rough estimate
and say 100 kilometers.
So that's a lot smaller ratio
than I've drawn there.
In fact, probably more like the
thickness of my pen line
would be a more accurate
representation of how thick
the atmosphere is relative
to the planet itself.
Questions on that?
Yes?
STUDENT: Is like the ratio
of the thickness of the
atmosphere to the planet stable,
or are we constantly
losing gas?
PROFESSOR: We are.
I'm going to talk about
that next time.
I'm going to talk about
the loss mechanism.
And we're going to compare the
different planets, some of
which have lost all their gases,
some of which have
retained some, like the Earth,
and some of which have
retained almost everything,
like Jupiter.
So we're going to put that
into a context next time.
Anything else?
OK.
Well, I want to address
this question then.
We've done that one.
The Earth's atmosphere is made
primarily of nitrogen, oxygen,
and a little bit of argon.
And all three of those molecules
are constructed in
such a way that they do not
absorb light in the wavelength
range to which our
eye is sensitive.
In other words, air is
invisible to us.
That's interesting.
So then how do we even
know there is air if
we can't see it?
How do we know there is air?
Someone want to suggest a way
that we know there's air?
Yeah?
STUDENT: From breathing.
PROFESSOR: Breathing.
That's a really good one.
Yes.
STUDENT: Friction.
PROFESSOR: Friction
STUDENT: Like, friction
with regard to how--
PROFESSOR: Yeah.
For example, let's say I've
got this piece of
paper and I drop it.
It falls very slowly.
If there were no atmosphere,
of course, it would fall
faster than my pen
with a clunk.
Well, no, there wouldn't be
a clunk, would there?
STUDENT: No sound.
PROFESSOR: Right.
There's no sound.
The sound is transmitted
through the air.
So if there were no air, you
wouldn't hear me speaking.
That'd be good.
Or you wouldn't be able to
hear any noises that I'm
making up here.
What other ways do we know that
there's an atmosphere?
Yeah?
STUDENT: Pressure.
PROFESSOR: Pressure.
How do you know there's
pressure?
STUDENT: Well when
you're up like I
guess trying to breathe--
PROFESSOR: It is to breathing.
STUDENT: When you're on a
mountain it's harder--
PROFESSOR: Right.
Is there something you're
going to do today--
think about this
pressure thing.
How do we sense atmospheric
pressure?
Can have an instrument
that does it, but
how do we sense it?
Yeah?
STUDENT: How difficult
it is to breathe?
PROFESSOR: Well, not
so much because remember the
pressure is here.
But it's also here.
So it's kind equalizing
in a way.
All we have to do with our lungs
is to produce a little
bit of difference between what's
here and what's here,
and we can breathe in and out.
You could change the absolute
pressure by a factor of two.
And that wouldn't change.
You would still be doing pretty
much the same thing.
But there maybe some other
ways in which you
would notice pressure.
STUDENT: Like your ears
like sinuses ?
PROFESSOR: Ears.
Yes.
So if you got a sudden
change in pressure--
for example, when the aircraft
is beginning to descend, then
you might feel it in
your ears as well.
I remember when I was in the
navy years ago, first part of
flight training school, they
wanted to show us what it was
like to have a sudden
decompression.
So you're flying on an aircraft,
window pops out or
whatever happens suddenly,
you have much
less air in the cabin.
So they took us into a
room about the size
of this area here.
And there was another chamber
next to it with a big pipe
connecting the two.
So what they did, they closed
the valve in the pipe.
They pump down the
other chamber.
And then all of a sudden,
they opened the valve.
So half of our air
went over there.
So what do you think happened?
Just imagine.
Let's do a Gedanken
experiment.
What do you think we noticed?
Or what happened to us
when we did that?
Any guesses?
STUDENT: Bloody nose?
PROFESSOR: Sorry?
STUDENT: Bloody nose?
PROFESSOR: No.
My nose didn't bleed.
Other guesses?
STUDENT: Your ears popped?
PROFESSOR: Ears popped.
Yeah.
STUDENT: You got a little
light-headed?
PROFESSOR: Yeah,
that came later.
So the first thing
that happened is
the air turned white.
You couldn't see anything.
Why was that?
Well, when the air-- we're going
to talk about this in
length in the course-- but
when the air expands like
that, it cools.
And a cloud formed in our
chamber just like that.
And that happens, by the way,
extremely fast, like in a
fraction of a second.
You got a very thick
cloud in there.
So that was the first
thing I noticed.
Then, this gets a little bit
indelicate, but the next thing
that happened is we
all began to--
let's use the word outgas for
lack of a better term.
So we kind of leaned over a
little bit in our chairs, and
we outgassed for a while.
And then we began
to feel faint.
So what they had us doing is
writing out our name over and
over again.
So later on, we could look and
see what we had written.
Of course, you write it the
first few times, it looks OK.
And then it begins to scrawl.
And then you lose
consciousness.
And they bring the
air back up.
So that's some sense.
So I guess the follow-on
question would be--
related to the first--
if we suddenly lost all the air
in this room, what would
kill us first?
It may be closest to your
answer actually.
But it won't be exactly that.
What would kill us first?
STUDENT: The lung.
PROFESSOR: The lung?
Yeah.
So any scuba divers
in the course?
What do you worry about when
you've been diving deep and
you come up suddenly?
STUDENT: The expansion of gas.
PROFESSOR: Bends.
It's called the Bends, right?
So what happens when you're
scuba diving, you're down at a
high pressure for a while,
nitrogen dissolves in your
blood at a higher fraction
than it is normally.
Then when you suddenly come up,
that gas bubbles out of
solution, like taking a can of
Coke and shaking it basically.
The gases come out of solution
forms bubbles.
And of course, then you got
bubbles in your bloodstream.
So that's the Bends.
And you can die from that.
And it's kind of like
having a stroke.
That would probably be the
thing that would--
basically, your blood boils.
That's probably the best
way to think of it.
You drop the pressure so
suddenly that then the gases
that are already in your
bloodstream just suddenly
begin-- it would happen
in an instant.
And you would be in
excruciating pain.
And then you would be dead.
So that's probably first.
What would happen next?
Yeah?
STUDENT: Is that what happens
when like an astronaut
depressurizes in space?
PROFESSOR: Right.
So an astronaut is in
a pressure suit
for just this reason.
And if you were to develop a
leak in that, and he would to
lose his pressurization, he
would die just like I've
described, instantly and in
great pain because of the
blood boiling, basically.
All the dissolved gases coming
out of solution.
So the pressure-- you mentioned
the pressure--
the pressure does that for us.
It keep those gases
in solution.
And if you suddenly release
it, out they come.
The breathing was mentioned.
So we couldn't breathe.
And that would knock
us out after what?
You could hold your breath
for a minute or so.
But then you might become
unconscious after that.
Some other things would
take a lot longer.
So they're not really
relevant.
You're dead.
But some other things that
would be probably good to
write down would be the
atmosphere has a great
moderating influence on our
climate as I'll show later on.
Were it not for our atmosphere,
the temperature of
the surface of our earth would
be much, much colder than it
is, colder than we than
we could survive.
That's a long- term effect,
but the atmosphere is very
important for that.
And the atmosphere protects us
also from X-rays, ultraviolet
radiation, small micro particles
coming into the
atmosphere.
They burn up in the
atmosphere.
So the atmosphere has a great
protective role to play in
allowing us to exist
on this planet.
So we're exactly out of time.
And I'll see you next time.
See you on Friday.
