FYS 71b, Spring 2017 “Exploring Dark Matter and Dark Energy in the New Universe”

Course description: Ninety six percent of the mass-energy content of the universe is utterly mysterious, and we don’t know what it is. This is the dark matter and dark energy, and together they represent one of the biggest challenges facing physics (some have said even all of science) today. Exploring what we know and don’t know about the dark universe and the experiments with which we are trying to find out more, is an intellectual adventure tailor made for a First Year Seminar.

Purpose of the Course and Learning Objectives:
1) To give first years a fresh and exciting experience that may attract them into the sciences.
2) To challenge them to work on subject matter that is far beyond their introductory courses.
3) To give them the experience of a small, interactive, argumentative and creative seminar, in contrast to the large lecture courses that dominate the freshman year.
4) To give them an experience of science today, in contrast to the 19th and 20th century content of their other introductory science classes.
5) To show them science at its most naked, at the boundary of what we understand, where there is no road-map and we are groping in the dark (literally) for ideas and ways forward.

Target audience:
This seminar is for first year students only, but it is not restricted to those intending to major in science. In order to cover the course material at an appropriate level, I will use geometrical arguments, some trigonometry and algebra, and also exponentials and logarithms. Together these might be called pre-calculus and many (most?) high school students have taken these even though they enter Brandeis to pursue their main passion in English or Music or the Classics. This course would be greatly enriched by such students and I hope they will enroll in order to satisfy their quantitative reasoning (qr) or science (sn) requirement, or even better out of unbridled curiosity. This will be in keeping with a true liberal arts education, in which astronomy, of course, is part of the original quadrivium.

Syllabus: I will cover the following topics

Part I: The Evidence for Dark energy

1. What does the Universe actually look like? -- The Hubble deep fields, and what we can learn by looking; Homogeneity and isotropy; Source counts; the Cosmic Microwave Background Radiation; the Copernican Principle .

2. How do the galaxies move? -- Vesto Slipher, Hubble’s first plot; The expanding universe and the Hubble law;
The apparent age of universe.

3. How do you measure distances across the Universe? Parallax; Angular size; Apparent brightness.

4. The dynamics of an expanding universe -- General Relativity and the Friedman models.
Critical density; the cosmological constant; Type 1a supernovae and the accelerating universe; Dark energy.

Part II: The Evidence for Dark matter

5. How to weigh things: Orbits and Kepler’s laws; Newton’s law of gravity; Weighing Black Holes; Vera Rubin and galaxy rotation curves; How much do galaxies weigh?

6. Weighing clusters of galaxies.
Fritz Zwicky and the virial theorem; X-ray observations of cluster gas; How much do clusters of galaxies weigh?

7. Gravitational lenses.
Strong and weak lensing; the Bullet cluster.

Interlude: How old is the Earth?
Bishop Ussher, the geologists, Lord Kelvin, Charles Darwin and Ernest Rutherford.

Part III: What do we know, what do we not know?

8. Nuclear reactions at the Big Bang -- Limiting the Baryon density; Dark Matter is not made of baryons!

9: The nature of dark matter.
Hot and cold dark matter; galaxy formation and large-scale structure in the Universe

10. Trying to learn more.
Current searches for dark matter; Baryon acoustic oscillations; the Large Synoptic Survey Telescope.

Text Book: Robert Kirschner: The Extravagant Universe: Exploding Stars, Dark Energy, and the Accelerating Cosmos. This book is written by the leader of one of the teams that discovered that the expansion of the universe is accelerating, which is the direct evidence for Dark Energy. You can buy it from the campus bookstore for about $22. You can get a used copy from Amazon.com for about $7. The edition doesn’t matter.

And also, my monograph: The Dark Universe. This is currently being written and is designed for a class like this.

It will be augmented by readings from
Alan Lightman: Ancient Light
Brian Green: The Elegant Universe
Steven Hawking: A Brief History of Time

plus articles in Scientific American, Nature, Science, and original sources such as

E. Hubble (1929) Publications of the National Academy of Sciences, v.15, p.168 “A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae”

F. Zwicky (1937) Astrophysical Journal, v.86, p.217 ”On the Masses of Nebulae and of Clusters of Nebulae.”

V. Rubin, K. Ford, N. Thonnard (1980) Astrophysical Journal, v. 238, p. 471 “Rotational properties of 21 SC galaxies with a large range of luminosities and radii.”

A. Riess et al. (1998) Astronomical Journal, v. 116, p.1009 “Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant”

Class structure and activity:
This is a seminar class of not more than 25 students, that will meet for 80 minutes twice a week. I will lecture as little as possible, except to bring students up to speed so that they can understand the more technical readings. Classroom time will be divided between discussion of the readings and activities based on real observational data. Two examples: the students (working in small groups) will construct the rotation curves of galaxies and calculate their masses; they will construct radio source counts from the FIRST survey (Faint Images of the Radio Sky at Twenty-Centimeters) and explore the homogeneity and isotropy of the universe.

In general, the assigned readings will require written responses submitted through Google forms prior to class. This is sometimes called “just in time” teaching. It serves several purposes: it ensures that each student does the reading and is able to contribute to the in-class discussion; it encourages students to read more deeply and thoughtfully. Also, it tells me what material or ideas are difficult or confusing to the students, and this informs the structure and discussion in the next class.

The quizzes and midterm serves mainly to focus learning. There will not be a final exam. The major grade component for each student is an independent project which will be shared with the class in a short (15 minute) presentation, and also submitted as a (10 page) paper.

Grading rubric
20% participation in class (this includes attendance, which is mandatory. Permission is required to miss a class)
15% midterm and quizzes
15% written responses to readings – using Google forms.
50% group or independent project, presentation to class, and final paper.

I do not grade on a curve. It is therefore possible for everyone to earn an A.

Success in this 4 credit hour course is based on the expectation that students will spend a minimum of 9 hours of study time per week in preparation for class (readings, papers, discussion sections, preparation for exams, etc.).

Logistical information:
Instructor: Professor John F. C. Wardle
Office: Abelson 329
Telephone: x 6-2889
e-mail:
Class Hours: T 2:00-3:20 p.m., Th 2:00-3:20 p.m. (Block N)
Location: Abelson 126
My Office Hours: T, Th 1:00-2:00 p.m. and Th 3:30-5:00 p.m. (i.e. before and after class), or by appointment, or just drop by. I am here nearly all the time.

Every effort has been made so that the information on this sheet is correct. However, the following disclaimer is necessary:

All information on this sheet is subject to change. Any changes will be announced in class. It is the responsibility of each student to be aware of changes, deadlines, and all information about the course.

Also, any student with special needs or who needs accommodations should see me as soon as possible.