Module 1: Foundations
Weeks 1–3 | The tools we’ll use all semester
Why this module matters
Before we can understand stars, galaxies, or the universe itself, we need a shared language. This module builds that language: how to handle astronomical scales, how gravity shapes orbits, and how light carries information across cosmic distances.
Everything in this course—every calculation, every inference—rests on the tools you’ll master here. The equations may seem abstract now, but by Week 4, you’ll use them to measure the distances to stars.
Learning objectives
By the end of this module, you will be able to:
- Perform dimensional analysis to check equations
- Apply Kepler’s laws and derive Newton’s law of gravitation
- Explain how blackbody radiation encodes temperature information
- Calculate energy and angular momentum for orbiting bodies
Lectures
Lecture 4 is split across two slide decks: Day 1 and Day 2.
Spoiler Alert: The Universe Is Weird
January 20, 2026A trailer for the semester: how astronomers turn photons into physical claims.
Lecture 2: Tools of the Trade
January 22, 2026Four problem-solving tools that transform points of light into physical understanding.
Lecture 3:
Gravity and Orbits
January 27, 2026
Kepler told us what planets do; Newton told us why. The transition from empirical patterns to physical explanations marks the birth of predictive physics.
Lecture 4 (Day 1):
Light as Information
February 3, 2026
Light is our messenger. Today we connect wavelength, frequency, and photon energy to what telescopes measure — and learn how color encodes temperature.
Lecture 4 (Day 2):
Light as Information
February 5, 2026
We finish the radiation foundation: why the Planck curve has limiting cases, how spectral lines encode composition, and how telescopes turn photons into inference.
Lecture Readings
Lecture 1: Spoiler Alerts — The Universe Is Weird
January 20, 2026A trailer for the semester: how astronomers turn photons into physical claims (and how we stay honest about assumptions).
Lecture 2: Tools of the Trade
January 22, 2026Four problem-solving tools—dimensional analysis, ratios, unit conversions, and order-of-magnitude estimation—transform points of light into physical understanding.
Lecture 3: Gravity and Orbits
January 27, 2026Kepler’s empirical laws become Newton’s gravity: circular motion, orbital and escape speed, and how energy, angular momentum, and the virial theorem predict orbital behavior.
Lecture 4: Light as Information
February 3, 2026Everything we know about the cosmos comes from light. By understanding how light is emitted, absorbed, scattered, and collected by telescopes, we can infer temperature, composition, and more without ever touching a star.
Solutions
Solutions are posted for practice problems after homework deadlines. Use them to study and to check your reasoning.
Required Textbook Reading
- Chapter 1 (pp. 3–7): Introduction
- Chapter 7 (pp. 43–46): Gravity and Orbits
- Chapter 4.1–4.3 (pp. 25–27): Light and Spectra
- What is dark energy? It makes up ~68% of the universe and drives accelerating expansion, but we don’t know what it actually is.
- Why does gravity exist? We can describe it (Newton, Einstein), but we don’t know why mass curves spacetime.
- Is the speed of light truly constant? Some theories suggest it may have varied in the early universe.