AST121 - The Origin and Evolution of the Universe

Instructor: Prof. R. G. Abraham
Lectures: Wednesday and Friday, 12 noon, MP202
Office: AB206 (2nd floor of the Astronomy & Astrophysics Building, 50 St. George Street)
Office hours: Thursday 3:00-4:00 and by appointment

Please refer to the Weblog for announcements, updates, and copies of lecture notes.

Aim of the course

This introductory course is aimed at science students, but no prior knowledge of astronomy is assumed. The course is self-contained in the sense that it is not required for any other course. The course is not part of the Astronomy Specialist program, although students intending to enter the Astronomy Specialist program are quite welcome to take this course.

The aims of the course are two-fold: First, it is intended to show students the fundamental and exciting nature of modern astronomy. Astronomers are seeking to answer very basic questions about the origin of the Universe and of all the things that we see in it, such as stars, galaxies, planets and even ourselves. These are questions which only a few decades ago seemed far beyond the reaches of scientific inquiry.

Secondly, and of more relevance to the majority of students, the course is intended to give students who are studying other scientific disciplines an astronomical perspective on these other areas of science. For instance, chemists will learn where and when the elements of the Periodic Table are created and biologists will acquire an understanding of how the prerequisites for complex life on Earth came about. Scientists of all persuasions should be interested in questions such as to why there is anything at all in the Universe.

The course will not try to teach you a great deal of basic physics or indeed even of astronomy. Rather, the aim is to use a few simple ideas to move towards an understanding of the Universe as a whole. More than anything, the intention is to provide you with an overall cosmic perspective on things.

Important Dates

Assignment 1 due: Jan. 27
Midterm: Feb.12
Assignment 2 due: TBD (sometime late Feb – early March)
Assignment 3 due: TBD (sometime mid March – late March)

Course prerequisites and exclusions


OAC Physics/SPH4U and OAC Calculus/MCB4U

Please note that there are several other introductory courses offered by the Department of Astronomy, e.g. AST 101, AST 201, AST 210, AST 251, which are much better suited to non-science students and to students who are not particularly happy with using mathematics as a tool to understanding. It is important to appreciate that AST 121 is not any easier than the 200-level courses mentioned above - in fact for students who are not reasonably strong mathematically it is considerably harder. Non-science students are therefore strongly advised to take one of the other courses listed above.


AST101, AST201, AST210. Also excluded are AST221, AST222 if taken previously or concurrently.


The course divides naturally into three parts. The first is entitled Finding our Place in Space and Time. As an introduction to the course, we will first discuss the general nature of Cosmology as a science, before moving on to consider the nature of light. An overview of the forces and particles in the Universe will be given, including a review of Newtonian gravitation. We will then embark on a Grand Tour of objects in the Universe, and consider what the Universe is made of, including the question of the mysterious "dark matter". We will explore how we can estimate how old the Universe is and how large it is, or rather how large the bit of it that we can observe, is.

The second part is entitled The Big Bang: the Origin of the Universe. We will start by reviewing some basic observations about the Universe, and then look at the expansion of the Universe both in the past and in the future, and see how this implies that the Universe "began" in a state of very high temperature and density and rapid expansion some 15 billion years ago. We will review the great successes of this idea in explaining some of the most basic observed features of the Universe that lead us to conclude that the theory provides an accurate description of the Universe from the time that it was about a millisecond old up to the present. We will then turn to some areas where the simple Big Bang theory does not provide a complete explanation and sketch out some of the more speculative ideas about processes in the Universe that may have occurred when it was only 1.0E-35 second old which potentially fill in these gaps.

The Universe that was formed in the Big Bang was a remarkably simple place compared with the rich complexity that is observed in the Universe on every scale at the present time. In this final part of the course, entitled The Origin and Future of Complexity in the Universe. We will first look at how structures such as galaxies and stars form out of an initially homogeneous Universe. We will then look in some detail at how the complexity at the atomic level comes about by looking at the processes whereby the different chemical elements are produced. This will lead us back to a discussion of how stars evolve and what happens when they die. Finally, we will look at how planets form and evolve as a background for the emergence of the greatest degree of complexity that we know about in the Universe, namely the carbon-based terrestrial Life of which we are a part. Finally, we will speculate on the future prospects for life in the Universe.


There is no perfect book for this course, but an excellent book which we will be using is Quarks, Leptons and the Big Bang by Jonathan Allday. As we go through the course I will indicate on this web page the sections of this book that you could read with profit before each class.

I will make fairly heavy use of web pages from various locations in the internet, particularly for topical material, and sometimes will assign these as readings (e.g. certain Wikipedia articles).

From time to time I will be providing you with web-based “handouts” that deal with some of the more difficult material, especially the more mathematical parts of the course. You should note that some parts of the textbook will not be covered at all in the course and, conversely, that significant course material is not covered at the same level, or at all, in the book. The recommended readings are thus simply those parts of the book where a given subject is mentioned and in no sense are a substitute for the lectures. You will be examined on the material that we discuss in the lectures and the web-based handouts that I provide etc.

There are also several more comprehensive textbooks in astronomy that are available in the bookstore and elsewhere, often at great cost. Particularly if you are thinking of studying astronomy later you may wish to invest in one of these.

Teaching Assistants

In teaching this course I will be assisted by a number of TA's from the Department of Astronomy & Astrophysics. Their duties will be conduct the help sessions, to assist in marking the exams and assignments. In exceptional circumstances, an occasional lecture may be given by them.


There will be three forms of assessed work in this course: a class test/midterm (worth 25%), three assignments (worth 30%), and a final exam (worth 45%). Here are the details:

Class Test/Midterm

The Class Test will be on February 12 in the usual lecture hall at the usual lecture time.  This will contribute 25% to your final grade. If you are unable to take the test owing to illness then you must (a) notify me within one week of when the test was written, and (b) produce a U of T Student Medical Certificate or provide a note from your registrar before I will allow you to take a make-up test.


There will be three assignments through the semester. These will constitute 30% of your final grade. Due dates for these assignments will be announced beforehand. The aim of these worksheets is to enable you to explore the subject in a more quantitative way than in the lectures by working through some problems. These are intended to educate as well as to test, and you should not hesitate to seek assistance with them if necessary, and to discuss approaches to solutions with your fellow students. However, blatant plagiarism of another student's work will not be tolerated, and will be dealt with severely. If you are caught cheating on one assignment we reserve the right to give you a zero on all assignments (in addition to all other penalties).

Regular help sessions (see below) will be scheduled that are specifically intended to help you with these assignments.

Assignments that are handed in late will be accepted, although a penalty of 15% per day will be deducted from that assignment's grade.

Especially given the extensive help that will be available, most students do relatively well, in an absolute sense, on the Assignments (scores of well over 90% are not uncommon on the assignments). Therefore, in order to assess how well you are doing in the course as a whole, it is wise to pay attention to how you are doing relative to the other students.

Final Exam

Finally, there will be a 2-hour Final Exam at the end of the semester. This will primarily be on the remainder of the course not examined in the Class Test, but will also refer to introductory topics from the first part. The time and place for this Final is published later in the semester. This will contribute 45% to your final grade.

Office Hours and the Help Sessions

Regular help sessions (whose times and locations will be announced in the second week of the course) will occur throughout the term. Attendance at these help sessions is purely voluntary. These will be led by one of the TA's and, from time to time, by me. Help sessions will take the form of an informal clinic devoted to answering your questions about the course material and, in particular, about the worksheet assignments. There will be plenty of space if you want to sit and work through the worksheet assignments during these periods. Sometimes discussions develop in which we talk about material not covered in the lectures.

These help sessions are the best way to interact with me and the TA's. If for some reason you wish to talk to any of us individually outside of the help sessions, please arrange an appointment. I work full time on the St George Campus and am happy to see you in my office on Thursday from 3:00-4:00 or by appointment. To make an appointment with me, please see me in class, at one of the help sessions or contact me by e-mail at Don't expect detailed answers to course-related questions by e-mail. If you just turn up or phone in with a question, without an appointment, then I'm afraid it is unlikely that I will be able to give you my attention at that time.