2.1
2.1
This graphic, from USA Today a couple of weeks ago, shows
changes in the numbers of jobs as a result of the recent
economic downturn sorted by job type.
Astronomers are doing pretty well.
So if you learn your lessons well, you will always have at least a
start on a back-up career that, according to USA Today, is
growing.
You might be still better positioned if you were to learn math or
statistics, but a 16% job growth is not shabby.
If you are pre-med, well then you have it made, according to
USA Today.
2.1
The graph shows 3 possible future scenarios for CO2 emissions:
1) We are incredibly virtuous for the next couple of decades,
and then we begin drastically cutting our emissions.
2) We are just incredibly virtuous from now on.
3) We are who we are, and so are those guys in China and India.
Which do you think best describes the future?
These scenarios have been produced at NCAR, your
government’ss atmospheric research facility, using the best
government
means presently available in the scientific community.
This issue of global warming is something that you might wish
to keep in mind as we discuss, starting with the next lecture,
the Copernican Revolution.
2.1
At the end of each chapter in your textbook there are lists of problems.
None of these are assigned to you to write out. However, they are
useful for you to review your reading and to be sure that you
understand the chapter. Below are listed the problems from each
chapter that concern the topics we will be discussing, however briefly,
in class. Use them to review the material, if you wish.
The following “problems” are for those of you who are reading Edition 3 of
the textbook. If you are reading Edition 4, look on the next slide for the
“review questions” that apply.
Chapter
p 1,, 3rd Edition,, “Problems”:
11, 13, 14, 15; rest covered by your lab on astronomical distances.
Chapter 2, 3rd Edition, “Problems”:
11-14, 16-19, and 20-22 are optional.
Chapter 3, 3rd Edition, “Problems”:
12-16
Chapter S1, 3rd Edition, “Problems”: 19, 20, 22a-d, 24
Chapter 5, 3rd Edition, “Problems”: 10, 12-15, 17-20; the rest are fun but
you don’t need to be able to do them.
2.1
2.1
1
The following “review questions” are for those of you who are
reading Edition 4 of the textbook. If you are reading
Edition 3, look on the previous slide for the “problems”
that apply.
The following “review questions” are for those of you who are
reading Edition 4 of the textbook. If you are reading
Edition 3, look on the previous slide for the “problems”
that apply.
Chapter 1, 4th Edition, “Problems”:
Chapter 1, 5th Essential Edition, “Review Questions”:
5th
1, 6.
11, 15, 16, 17, 18, 22; rest covered by your lab on astronomical
distances.
Chapter 2,
Essential Edition, “Review Questions”:
10, 12, 14-16.
1, 3-5, 8-
Chapter 2,
2 4th Edition,
Edition “Review
Review Questions
Questions”::
3-10,
3 10 12
12-16.
16
Chapter 3,
3 5th Essential Edition,
Edition “Review
Review Questions
Questions”::
5-10.
5 10
Chapter 3, 4th Edition, “Review Questions”:
7-14.
Chapter 4, 5th Essential Edition, “Review Questions”: 5-11, 1315.
Chapter S1, 4th Edition, “Review Questions”: 7, 9, 10.
Chapter 5, 4th Edition, “Review Questions”:
2, 7, 8, 12, 14-18.
2.1
Chapter 1, the Vastness of the Universe:
Chapter 5, 5th Essential Edition, “Review Questions”:
12, 15, 16.
1-4, 8-11,
2.1
The
Andromeda
Galaxy
(M31)
1. light-years as distance.
2. Light connects distance and time.
Examples are computers, Internet, control of Mars rover.
Looking back to dawn of universe with Hubble deep field.
Our galaxy’s
nearest big
neighbor.
neighbor
3. Best guess is universe is 14 billion years old.
4. Vastness of the universe means we observe, but essentially
cannot converse.
a) Andromeda galaxy 100,000 light-years across
and 2.5 million light-years away.
b) Newly discovered solar systems are much closer (50 to 200
light years or so), but I will be dead by the time they
answer my question (like E-mail as compared to the
telephone, but on a much longer time scale).
2.1
Chapter 1, Implications of the Vastness of the Universe:
5. Everything is so far away that the sky looks like a (2-D) dome.
6. Measure distances over the sky in angles, not in light-years.
7. Patterns of stars on the sky seem constant.
a. Rearrangements of star patterns take millennia.
b. Takes really high tech to measure any changes.
c. Example of EJW’s star.
d. One talks about “astronomical distances,” but “geologic
times.” But times tend to be just as big in astronomy too.
8. The “fixed” stars provide a frame of reference, “the celestial
sphere.”
2.3
2
Chapter 2, Implications of the Earth’s and Moon’s Motions:
1. Getting a feel for angles on the dome of the sky:
a. The disk of the moon or sun is about 1/2º
b. The separation of the stars in the big dipper that point to
Polaris is about 5º
c. Your fist held at arm’s length subtends about 10º
2 Using
2.
U i your fist
fi t in
i the
th moon observing
b
i project.
j t
a. Noting the local time (standard time or daylight time).
b. Finding the meridian by facing south.
c. Measuring distance in degrees from meridian (hour angle).
2.5
Chapter 2 , Implications of the Earth’s and Moon’s Motions :
Figure 1.9
Winter
Triangle
3. Orion easy to recognize (in winter).
a. Constellation as a group of bright stars.
b. Also a region of the sky, defined by the IAU in 1928.
4. Constellation names from Mediterranean area ~5000 yrs ago.
5. Southern constellations from European explorers in 17th century.
6. Don’t memorize constellations, names or locations. If Alan
Sandage and Martin Schmidt didn’t know them, why should you?
7. The earth rotates, not the stars.
8. From equator, you can see everything.
9. We see less.
10. Telescopes in Hawaii and in Chile do it all.
2.8
3
Figure 1.8
The pattern
of stars in
the
constellation
Orion
Size of the Star
Size of the Earth’s Orbit
Size of Jupiter’s Orbit
The first direct image of the surface of another star.
The Faint Object Camera of the Hubble Space Telescope observed Betelgeuse, a bright red star in
the constellation Orion. It is a red giant star, with a diameter comparable to the diameter of the
orbit of Jupiter about the sun. Its great size allowed its surface to be resolved.
Figure 1.14
The apparent
rotation of the
celestial sphere
S
t
a
r
T
r
a
c
k
s
A
t
A
r
c
h
e
s
2.21
4
2.22
Chapter 2, Implications of the Earth’s and Moon’s Motions:
Figure 1.17
11. The earth is like an enormous gyroscope.
a. Rotation axis nearly constant → our frame of reference.
b. Defines north and south celestial poles.
c. These define celestial equator.
d. Meridian is great circle through poles (north-south line).
e. Longitudes on celestial sphere are hard, because the earth is
rotating.
(We can’t use the location of Greenwich, or any other city.)
f. Ecliptic is path of sun on celestial sphere.
Depictions of
latitude and
longitude on
the Earth.
Celestial
latitudes are
the same, but
longitudes are
different.
g. Two equinoxes are points where ecliptic crosses equator.
h. This allows us to construct a coordinate system.
(You don’t need to know any more about it.)
2.24
Vernal
equinox
defines zero
of celestial
longitude not
longitude,
any spot on the
Earth, like Greenwich.
5
2.28
2.28
Chapter 2, Implications of the Earth’s and Moon’s Motions:
12. Earth revolves about sun ══►
sun appears to move against the background of fixed stars.
a. Sun’s apparent path is called the ecliptic.
b. Constellations along the ecliptic are “signs of zodiac.”
c. These constellations invisible when sun is near them.
d. Hence some are summer or winter constellations.
e. Wise men (or women) have always been expected to know
1) why these heavenly motions occur,
2) how to predict them, and
3) how to divine their significance.
2.28
2.29
2.31
6
2.31
2.31
In summer, sunlight is more intense, depositing more heat energy
per unit area on the ground.
In addition, there are more hours of sunlight per day in summer.
This picture was meant to illustrate something else, but it shows how the earth is illuminated
by the sun at a solstice. A person at a northern latitude (left-most yellow circle) is carried by
the earth’s rotation in sunlight for most of the day. A person at a southern latitude (rightmost yellow circle) is carried by the earth’s rotation in darkness most of the day.
7
Chapter 2, Implications of the Earth’s and Moon’s Motions:
13. Moon revolves about Earth ══► phases.
a. If you didn’t have an explanation, you were not wise.
14. Further tests of wisdom:
a. Eclipses (think of Cortez)
(reason why the sun’s path in the sky is the “ecliptic”).
b. Meteors and comets.
c. The motions of the planets.
d. Auroras.
15. Modern astronomy provides very satisfying explanations, . . .,
for these and far more arcane phenomena.
2.42
2.43
2.44
8
9
2.56
2.60
10
2.61
11