ASTR 1210 (O'Connell) Study Guide


The European Southern Observatory Very Large Telescope, Chile.

This introductory lecture places astronomy in the broader context of science. It discusses the nature of science, how science is distinguished from other modes of thought, the difference between science and technology, and some of the main results of science.

Astronomy has had a strong influence on other sciences and defines the limits of the scientific universe. We will illustrate some of the mind-boggling cosmic spatial and temporal scales revealed by astronomical research.

A. What is Science?

My definition: science is the systematic understanding of empirical natural phenomena.

Characteristics: Key feature:

The scientific method in practice:

Science and "Truth"

Science and "Common Sense"

Science and Mathematics

B. Alternative Modes of Thought

It is worthwhile distinguishing science from some other important modes of thinking.

Revelation (religion)




C. Skepticism

"Cultivated skepticism" is a cornerstone of science.

All good scientists are skeptics. This means that they maintain an attitude of doubt or of suspended judgement about scientific ideas.

Skepticism based on facts is not an established element in many other modes of human thinking. In fact, most people are uncomfortable with skepticism and instead see virtue in conviction, certainty, and strong beliefs.

Errors occur in science, as in any human endeavor. Historically, there have been many more wrong ideas in science than right ones. Understanding the natural world is hard. Every scientist has a long list (usually private) of mistakes he or she has made. But because of skepticism and a reliance on real evidence, there is a strong self-correcting mechanism operating in science: the errors are identified and discarded.

"He believed in the primacy of doubt, not as a blemish upon our ability to know
but as the essence of knowing."

---- J. Gleick, writing about physicist Richard Feynman.

Golden Gate Bridge

The Golden Gate Bridge, a premier example
of 20th century technology

D. Science vs. Technology

Science and technology are symbiotic but distinct

All technology has a societal motivation, whether for good or ill, but the main motivation for "basic" science is simply curiosity and the desire to understand.

Job descriptions:

E. Results of Science

The basic result of science

Some other key results


How well determined are scientific results?

Influence on society

Dusk @ Mt. Shasta

The Moon and Venus at dusk

F. Astronomy as a Science

Astronomy is the study of the physical universe beyond the Earth's atmosphere.

It is the oldest science, nearly universally practiced in literate & pre-literate societies, and it has been a major stimulus to other scientific fields from Greek times to modern physics

Relevance to society

  1. Astronomy investigates ultimate origins (an adjunct or alternative to religion)
  2. Astronomy provides our basic global perspective of time & space, i.e. a cosmic context
  3. Astronomy was fundamental to the historical development of scientific thinking and the formulation of the first generalized physical laws (Newton).
  4. Study of the other planets and our cosmic environment is essential to assessing the viability of Earth's biosphere and prospects for long-term human survival.

History of societal influence

MW Starfield

Starfield in center of Milky Way. How many stars can you count here?
Click for a full-resolution enlargement. (Image from the Hubble Space Telescope.)


Astronomical time- and distance-scales are tremendously larger than the "common sense" scales we encounter in everyday life. Unfortunately, this means that astronomical scales (not to mention atomic or molecular scales) are utterly non-intuitive for us.

It is important for astronomers to develop a good cosmic perspective that transcends the perceptual biases of everyday experience. But it is difficult for anyone to visualize the scales involved. Because the cosmic range is so enormous, scientists make regular use of scientific mathematical notation ("powers of ten"). For a review of this notation, see
Supplement I (PDF file).

Example astronomical scale models

  1. As an example of the contrast between human perceptions and physical reality consider the Earth's atmosphere. It seems enormous and all-encompassing, right? Atmospheric disturbances (rainstorms, tornados, hurricanes, droughts) easily destroy human structures and livelihoods.

  2. A sample cosmic time scale:

  3. Finally, a healthy, fruit-based cosmic distance scale model:

Reading for this lecture:

Reading for next lecture:

Web Links:

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Last modified September 2017 by rwo

Text copyright © 1998-2017 Robert W. O'Connell. All rights reserved. Twilight image of Moon and Venus over Mt. Shasta by Jane English. These notes are intended for the private, noncommercial use of students enrolled in Astronomy 1210 at the University of Virginia.