Introduction to Astronomy

Physics 090, Spring 2019

A grand tour of painstaking observations, remarkable inspiration, and an occasional wrong turn, beginning with the light refracting in a drop of water and finishing with the red-shifted photons that have been traveling to us for 13 billion years since the Big Bang.
Last Updated: May 7th, 2019
Instructional Team

Astronomy is a wonderful subject just for the pleasure of perusal, and the variety of exotic phenomena in the sky makes it a life-long interest for many people.

However, the goal of the discipline of astronomy is to understand the great variety of observations in terms of the rather few principles of physics.

Understanding astronomical observations from physics turns out to be a two-way street. Some of the principles of physics — for example, Newton's Law of Universal Gravitation — or that neutrinos change type as they travel — were deduced from astronomical observations in combination with laboratory physics experiments. The relationship is so close that the field is now often called "astrophysics" and it can be considered a specialty of physics, like condensed matter physics or particle physics.

The associated laboratory course (Physics 91) will have roughly about five Wednesday indoor labs where physics experiments (light, optics, spectroscopy, the Doppler shifts and gravitation) are performed, and about five Wednesday outdoor labs where you will learn to operate and make observations with the College's telescopes. Evening labs begin a little after dark. Whether we are having an indoor or outdoor lab depends unavoidably on the weather. Furthermore, the time gets later (because sunset gets later) as spring progresses. By the time of Monday's 8am class, we will have made a decision whether the weather is good enough to have an outdoor lab on Wednesday evening. You need to keep Wednesday evenings clear for lab whether it is indoors or outdoors. One lab can be missed with no impact on your lab grade. One makeup lab will be provided.

Necessarily, the class will include mathematics. This is integral to the scientific method. Every physics theory that we are confident of, we are confident of precisely because it has been tested quantitatively as well as qualitatively. Theories that are motivated principally by esthetic considerations, or only give qualitative answers, have generally turned out to embarrassingly far off in the weeds. We will review high school math and science subjects such as scientific notation, algebra and trig functions, the periodic table, and others, as we need to use them.

The interplay between astronomical observations, physical principles and quantitative predictions is an excellent example of what the Core Curriculum refers to as "Mathematical and Scientific Understanding" — one of the Core’s four pathways to knowledge. This course is designed for you to acquire a new-found or deepened understanding of that pathway while simultaneously having the pleasure of studying the most spectacular phenomena that nature has to offer.


The College's summary of what constitutes Mathematical and Scientific Understanding states as its overall learning goal that students "will develop quantitative, observational, and problem-solving abilities." In addition, it states that "students will examine mathematics and science as a creative endeavor," and "they will also consider the social and ethical issues of scientific inquiry and application."

The course is designed to address those overall learning goals and five more specific outcomes enumerated in the mathematical and scientific pathway to knowledge:


For the Spring Semester we are allotted 14 weeks, not counting the additional week reserved for the Final Exam Schedule. Subtracting one week for Easter break, there remain 13 weeks available to cover the five units:

Five units in 13 weeks means that our pace will be faster than 3 weeks per unit. There will be an exam after each of the first four units, and a final exam that is cumulative and cover the fifth unit. The exam dates are:

Exams and Grading

35% for assignments, 10% on each unit exam (totaling 40%), 25% final.

Many quiz and exam problems will be multiple choice. To ease my and the teaching assistant's loads, many of the in-class and take-home assignments will simply be graded for effort and completeness. Carefully compare your work with the detailed solutions whenever solutions are discussed in class or handed out, even if you got full credit. You may have gotten full credit just for effort.

Late in-class and take-home assignments are generally accepted with a valid excuse, but only until the corresponding unit exam! In other words, Unit 1 assignments will not be accepted after the Unit 1 exam is given. Athletes who have given me their schedule of away games have a totally valid excuse that I will do my best to accommodate. Expect that there will be a lot to make up. Rely on your classmates, their notes, and/or the optional textbook. I simply can’t re-deliver lectures to all the people who will inevitably miss one or more of them.

STEM Center Tutoring

Saint Mary’s has a center for students taking STEM classes in Assumption Hall, Room 200. The STEM Center provides several services, including free tutoring in math, chemistry, physics, and biology. Please be very respectful of the Assumption Hall residents. Physics tutors may be able to help with astronomy problems. For best results, use Ariana Hofelmann's STEM Center hours as listed above.

Academic Honor Code

The Saint Mary's Academic Honor Code (AHC) is applicable to this (and all) Saint Mary's courses. You are responsible for familiarizing yourself with it: AHC Website.

Student Disability Services

Accommodations that take into account the context of the course and its essential elements for individuals with qualifying disabilities are extended through the office of Student Disability Services (SDS). Information regarding the services available may be found on the SDS Office Website.

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