Greetings and welcome to the
introduction to astronomy! In this
lecture video, we will talk a little bit
about astronomy and science. So some of
the things that we look at in an
astronomy course - some of the different
objects that astronomers study. And then -
why do we want to study astronomy at all?
And why - what do astronomers use - the
scientific method we want to discuss how
that works in astronomy and in general.
Those are a few of the things that we're
going to go over in this lecture. So
let's start off with - first of all - what
is astronomy? Well most simply put
astronomy is the study of the universe
and everything in it. So anything that we
see in the universe is part of the study
and of astronomy. I've given a number of
things here that are included but
anything within the universe - it is not a
comprehensive list. There's a lot more
that could be studied. So let's start off
looking at one example and that is an
example of a planet. Within our solar
system we have planets and moons that we
study in astronomy. And here we have an
example and this is the planet Mars. Mars
has some interesting features we see
some great volcanoes over here on the
side that are present - not currently
active but have been active in
the past. We see a great rift valley here
that we call Valles Marineris - so a great
rift in the crust of Mars that would
stretch across our entire country across the
entire United States if it were
here on the Earth. So an incredibly large
Valley there. Mars also will have polar
caps and does have a thin atmosphere as
well. There are of course lots of other
planets and moons that would be studied
as well but here is Mars as one example
of objects that are studied by
astronomers. Now also we study not only
within our solar system do we have
planets and moons but we also have
comets and asteroids so here's an
example of a comet. We see on the
comet a number of different features - we
see the head or coma of a comet
and that's here at the front - which is
this outer layer - outer region here that
is the head of the comet and then we see
the tail or tails in most cases a comet
will have two tails stretching back away
from the Sun. Comets are essentially
an ice ball that maybe is the size
of the city - a few miles across and when
they get close to the Sun the material
gets vaporized and forms the head and
the tail. Comets like planets are one of
those objects that have been known to
people since ancient times. But of course
with modern technology and being able to
actually go visit these objects we have
a much better understanding of them
today than we did hundreds of years ago.
Now not everything we study in astronomy
is within our own solar system. We also
look at other objects and that would
include things like stars. Stars - a
picture of an individual star doesn't
look like much because stars are so far
away that even to the largest telescopes
they just look like points of light. So
this is an example of a star cluster
that we see. So a cluster of stars or a
grouping of stars here taken by the
Hubble Space Telescope. Stars can be
grouped together in clusters they can be
alone by themselves pretty much like our
own Sun and they can be grouped together
in larger groupings. But star clusters
would be a part of an example of what
we'd see within a galaxy. So that leads
us to our next slide that shows us a
galaxy here and this is an example of a
spiral galaxy. Galaxies come in
different types and spirals are one
example - our own galaxy is a spiral
galaxy and you can see coming from the
central portion here that there are
spiral arms that stretch out and around
the galaxy as it sits
here. So we see those spiral arms that's
where a lot of the stars are forming
within the galaxies we would also see
star clusters forming within the galaxy
as well as other objects that we would
look at. There are also different types
of galaxies - a spiral is one type of
galaxy but there are also other types of
galaxies that we see including things
like ellipticals and irregular galaxies
that astronomers would also study. As we
look at others one of the other
things that we can see is nebulae. So
within the galaxy there are also nebulae.
Nebulae come in different types this is
one example and this is an example of a
supernova remnant. So what we have here
is the remnant of a supernova that
occurred a long time ago. This is the
remnant of it - not seeing the supernova
of itself - but we are seeing
the remnant what the material left
behind. What happened - visible here on
earth in 1054 was a really bright star -
what we called a supernova. A nova is a
new star and a supernova was an
extremely bright new star and became one
of the brightest objects in the sky.
A supernova can actually be visible
during the daytime. In the nearly
1,000 years since the supernova was seen
to occur the material has been expanding
outward and you see the filaments and
structures within that nebula as it
expands outward as it is been doing so
for nearly a thousand years now. At
the center of this this nebula in this
case would be a neutron star the
collapsed core of the star left behind -
The mass of the Sun or
even a little bit larger and the size
would be the size of a city maybe about
six or so miles across. So compacted down
to extremely dense levels - not quite a
black hole which is our next topic but
very very close to it and something that
we call a neutron star. As I said
black holes were the next thing to look
at so let's look at the black hole here.
How do we get an image of a black hole?
Well we don't this is actually an
artist's conception
or drawing of what we believe a black
hole would look like. The black hole
itself is invisible because it is matter
that is condensed down so much that even
light cannot escape from it so nothing
escapes from a black hole because
nothing can travel faster than light.
However outside what we call the event
horizon of a black hole which is the
point from which light can no longer
escape - again we call that the event
horizon. Then when we're further out than
that then material can escape and here
we're seeing as the artist conceives and
some black holes seem to be doing - that
material is being pulled from a
companion star and then spirals in and
around in towards the black hole. That
gives the black hole a source of energy
and then allows us to see the material
around the black hole as it is heated up
to incredibly high temperatures. So as
this material spirals in it's heated up
to very very high temperatures and that
allows it to give off radiation that can
then be detected. Once it crosses this
event horizon we can no longer get any
more information about that black hole.
These are just some of the objects
that astronomers study and not a
complete list by any sense. There are a
lot more objects that we will study in
that one would study of taking a class
in astronomy. So why? The next question
would be why do we want to study
astronomy other than learning about all
of these interesting objects
that we've looked at - why would we want
to study this? Studying astronomy or
any other science really teaches a way
of thinking and that's an important
thing - is that it's a different way of
thinking and a way to critically analyze
information and then even apply that to
everyday situations. So what we'll look
at coming up here in the scientific
method is a way of thinking about things
and how things work not only in the
universe but even in everyday life. It
also gives us a broader understanding of
the universe.
So even though I know that most students
who take my astronomy classes are not
going to become professional astronomers.
However it hopefully teaches them a way
of thinking and gives them an
understanding of appreciation of the
universe. So let's look a little bit at
the scientific method here and what we
mean by scientific thinking.
Scientific thinking uses a couple of
definitions here - just a couple of things
we want to look at first. That would
include some of the terminology like the
idea of what we mean by a theory -
sometimes you think of a theory is
- Oh, it's just a guess but it really isn't.
Theories are based on observations and
studies - so things that have
have survived many many tests. So an
example of a theory or a hypothesis that
would be a good one would be something
that is testable that is the most
important thing in a theory is that it
has to be some way to test it. If we come
up with a theory that Einstein was the
greatest scientist in the history of
mankind -  then that would not be something
that we have any way to test. It's not
something that is testable. Or the Mona
Lisa is the greatest painting ever done.
That is not something we can test - it is
a matter of opinion. An example of
something that we could test as a
scientific hypothesis would be that the
moon is made of green cheese. We may know
that as a ridiculous statement now but
it makes perfect sense in terms of being
testable. We could take a trip to the
moon - send a robotic probe to the moon -
get a sample of the material there and
find out what it's made of. Now of course
we've already done that so it's less of
a scientific theory now than it was for
example in the past. But it is an example
of something that could be tested. We
also use models in astronomy. Models are
ways of simplifying how things work. So
for example we looked at a galaxy - in
order to understand the galaxy and its
motions we have to understand how the
matter is distributed in it. We cannot
possibly model exactly how the matter is
distributed so we have to make
assumptions and approximations as to how
things work. We use this in a number of
cases - ways of simplifying how things are -
to be able to make us better able to
model them simply because it is not
possible to calculate
the exact position of every atom within
a galaxy to be able to figure out how
it's going to work. We have to make
specific assumptions and that's what we
mean by a model and we have to take that
into account when we think of how things
are determined from models that we did
make a number of simplifications going
into them and that may have an impact on
our final results coming out of the
model. Now coming back to hypothesis
we've kind of looked at that when we
talked about theory the difference
between a theory and a hypothesis is
that our hypothesis is more the moon is
made of green cheese up here that we've
just given some general idea as to you
know maybe this is what this is what the
moon is made up of. Whereas a theory is
something that has been tested over and
over something like the theory of
relativity - something that has been
significantly tested and tried over a
good period of time. A hypothesis
again is a proposal that ww would give to
explain some observation that we see.
An example here is we see the
observation - something that we don't
debate is that the Sun rises in the east
every day. What is open to interpretation
is why that occurs. So this is the
observation that we see and this is the
possible explanation - why does it occur?
The Sun orbiting the Earth - or we may
want to say that the Earth spins. A
completely - another example of how we can
explain that the Sun rises in the east
and sets in the west every day could be
that the earth is spinning. Each of
these would make other predictions and
you would then use that to test your
hypothesis and find out which one best
supports it. This all leads us to
this idea of the scientific method -
so we'll look at the scientific method
here. It is again a way of thinking.
So it starts - it has a starting point - it
starts with some observation that is
made but it has no ending. So you can
start it -  you observe something happens
but in key it never ends we are always
continually modifying our theories,
modifying our hypotheses to have them
better fit the observations - to get
better models that better explain what
is going on in the universe. So you start
with that observation - you come up with a
hypothesis that explains that
observation and as I mentioned before
the key is that it must make some kind
of testable prediction - something that
you can test. Once you do that you test
your predictions and make more
observations and then one of two things
could happen: one is that your
predictions could be found to be correct -
great!  that's good
but you're not done. So you're not done
even if this is the case you don't stop
once my predictions are correct - my
predictions are correct my model was
correct -  it's now perfect and that is
that is exactly how things work. You
continue on - you make more predictions
you refine your model - try to find out
where it works and possibly where it
does not work. Or you may find out that
your predictions were incorrect - oops! I
made a prediction that this was going to
happen and something completely
different happened. That leaves you with
a couple of options - you can either
modify the hypothesis and make
adjustments to it to have it fit your to
fit your observations. Or you may if
things are bad enough - you might have to
reject your hypothesis all together and
go back and start up over here. Let's
come up with a new hypothesis that then
explains not only what our original
observation, but our new observations as
well. So let's look at this in a little
bit more of a picture form. Here's a
diagram that kind of shows the
scientific method and the process that
is used. It starts off with exactly
what I've shown you on the previous
slide - you start off up here with
making observations - you formulate your
hypotheses what kind of hypothesis will
explain the observations that you saw.
Then as I said - the key is to develop
testable predictions and then make more
observations to test those predictions.
Then here's where things go over and
over again - you may have to make
refinements and alter your predictions
you might have to reject your hypothesis
all together in which case you actually
come back here and come up with a new
hypothesis. Then you develop new
testable predictions. So this cycle right
here is continually ongoing. Once this
has gone for a while and you've got very
good thoughts and very good ideas then
you may end up with a general theory
that explains a lot of the things that
you were looking at. Although even at
that point again it's still an ongoing
process and you continue to test what is
happening here and that you make further
observations and you may find more
hypotheses - maybe you will confirm your
theory - maybe you'll find some regions
where your theory does not work and you
need to modify your theory and or modify
your hypotheses to come up with a new
better theory and a better model. So
let's finish up here with a little bit
of a summary. What we have is just a
little bit about what we've looked at in
this in this lecture. We've looked at
astronomy - What is astronomy? Well it's
the study of everything it is the study
of the universe and everything in it so
everything from the earth out to the
edges of the universe is a part of
studying astronomy. Why do we study
astronomy - other than maybe to get our
science credit that we need to get, is to
learn a scientific way of thinking that
can be applied in everyday situations.
Then finally we looked at the
scientific method which kind of is that
way of thinking that we want to
emphasize and it is a never-ending
process. So it never ends you start with
some observation but you continually
make more and more observations to allow
scientists and us to continually modify
and improve the theories and the models
that we have made so we can better
improve those to be able
make better predictions and help us to
better understand the universe. So that
concludes this lecture on astronomy and
science and I hope you've been able to
get some good information out of it and
get a little bit of a beginning
understanding of astronomy. So until next
time have a great day everyone and I
will see you in class.
