An Introduction to Solar System Astronomy
Prof. Richard Pogge, MTWThF 2:30
Lecture 1: An Introduction to Astronomy
"The most incomprehensible thing about the Universe is that
it is comprehensible."
"It will seem difficult at first, but everything is
difficult at first."
Miyamoto Musashi, The Book of Five Rings (Gorin no sho)
What is Astronomy?
Astronomy is derived from the Greek astronomos:
- astron = star
- nomos = a system of laws
Today "Astronomy" is synonymous with "Astrophysics", the
study of the physics of celestial objects; the solar system and its
consituents, the properties, birth, life and death of stars,
interstellar gas and dust, galaxies and clusters of galaxies, and
finally the study of the Universe as a whole ("Cosmology").
In this course we will be studying the historical development of modern
astronomy, starting with our discovery of the nature of our Solar
What is Science?
Astronomy is one of the oldest of the sciences. There are many ways to
define science in general, but a way I have found useful is as follows:
Science is not so much about what we know, but about how we
have learned to confront what we do not know.
We will be seeing illustrations of all of these aspects of science
in our study of astronomy.
- Science provides us with a framework in which to ask questions
about the world around us.
- Science relies on observations of the natural world. These
observations take the form of verifiable data
ranging from detailed descriptions to quantitative
- Science is a practice of critical examination of the validity of the
interpretations drawn from our data.
Three Questions of Astronomy:
Astronomy as practiced often comes down to addressing three broad
questions about a phenomenon, in this order:
1) What is it?
- Describe it: how bright is it, how far away, what is it made of, ...
2) How does it work?
- Underlying physics (testable theories).
3) How does it evolve?
- How did it form, how will it develop over time?
The main topics covered in Astronomy 161
We will be covering 4 related topics in this course:
The Historical Origins of Astronomy
- Apparent Motions of the Sun, Moon, & Stars
- The Seasons
- Timekeeping & Calendars
- The Phases of the Moon
- Eclipses of the Sun and Moon
- Motions of the Planets
The Physics of Astronomy: Gravitation, Matter & Light
- Ancient Astronomy & the Ptolemaic System
- The Copernican Revolution:
- Nicholaus Copernicus
- Tycho Brahe
- Johannes Kepler
- Galileo Galilei
- The Newtonian Synthesis
The Solar System
- Newtonian Gravity
- Law of Gravitation
- Nature of Matter
- Nature of Light
- The Electromagnetic Spectrum
- Interaction of Light and Matter
- The Tools of the Astronomer
- The Earth & The Moon
- The Sun
- Comparative Planetology
- The Terrestrial Planets
- The Jovian Planets
- Dwarf Planets, Comets, Asteroids, and Meteorites
- The Origin of the Solar System
- Worlds beyond the Solar System
Main Themes of this Course
There are three main themes that tie together all of the material we
will cover in Astronomy 161:
- The Scientific Revolution: How have we come by our present
understanding of the world around us, and how we use scientific methods
of observation and theoretical interpretation to learn about the
- Universal Physical Laws: A key discovery of the scientific
revolution is that the fundamental physical laws we have discovered here
on Earth also apply to the rest of the Universe. Not only can the study
of these laws (physics) teach us about the Universe, but observations of
the Universe (astronomy) can teach us about physics.
- The Solar System: What do we currently know about the
constituents of the Solar System, the characteristics of the planets,
moons, comets, and asteroids, the possible origins of our Solar System,
lessons for Earth from the study of other planets, and finally solar
systems around other stars.
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Updated: 2007 September 16
Copyright © Richard W. Pogge, All