Challenges of Teaching Astronomy and Cosmic Scale

Introduction: The Complexity of Teaching Space Science

There are various complexities that affect the way astronomy is taught, not the least of which is the enormity of scale that space science involves.

One of the basic requirements for understanding astronomy is coming to terms with the vastness of the universe. For example, a basic unit of astronomical measurement is the light-year. Merriam-Webster defines the light-year as "a unit of length in astronomy equal to the distance that light travels in one year in a vacuum or about 5.88 trillion miles or 9.46 trillion kilometers" (2011). While this definition conveys factual data, it does little to make the concept real — that is, accessible to the average student.

Grasping the Scale of the Universe

Trying to convey the reality of light traveling at the unimaginably fast speed of 299,792 kilometers per second (186,282 miles per second) is indeed mind-boggling. Even at such amazing speeds, light takes years to travel to us from the stars, and thousands or even millions of years to travel the depths of space between galaxies. When dealing with those kinds of distances, it is easy to understand why they seem beyond the grasp of the average individual. To make these quantities more manageable requires putting them into the context of a well-understood frame of reference; doing so helps them to have more meaning (Discovery Education, 2011).

Historical Misconceptions and the Limits of Earth-Based Observation

Another challenge for students is being able to relate to how the body of knowledge that makes up modern astronomy has been accumulated. This scientific process has been impacted by many constraints, not the least of which is that scientists must study the universe while remaining grounded here on Earth. This limitation affects our ability to understand where we fit into the universe.

Visual biases resulting from this limitation led to misconceptions that persisted in the field of astronomy for centuries. The Earth-centered model of the universe dominated Western thinking for nearly 2,000 years, influencing not just astronomy, but philosophy, theology, and other disciplines as well. Such misconceptions lingered until the 16th century, when Copernicus proposed a heliocentric system. Even then, the Copernican system did not gain widespread acceptance immediately, in part because it contradicted what astronomers believed they had observed (University, n.d.).

Likewise, the physics of light affects our knowledge of the universe. The light we see from distant objects travels immense distances across the vastness of space, but how we perceive it is also affected by the object's brightness.

What Scientists Know and Don't Know

Astronomy and astrophysics professor Angela Olinto points out another challenge in teaching space science: clearly defining the boundary between what cosmologists know and do not know about the universe. Scientists have learned quite a lot about what happened from ten billionths of a second after the Big Bang to today, 13.7 billion years later. However, scientists still do not know what 95% of the universe is made of, nor do they know what happened before ten billionths of a second after the Big Bang (Koppes, 2011).

Pedagogical Strategies for Teaching Astronomical Scale

Bennett (1999) offers solutions to the challenge of presenting ideas of scale in a way that gives students some perspective. He argues that merely telling students about astronomy in terms of numerical relationships is ineffective for students with weak mathematical skills. Bennett suggests instead an approach that compares astronomical scales to familiar scales. For example, the number of stars in the observable universe is on the order of 10²². One way to give meaning to this number — and at the same time help students develop a contextual framework for the enormity of the universe — is to have students imagine counting grains of sand on a beach. Even with the vast sum that would result from this exercise, that number is still smaller than the quantity of stars in the observable universe. For temporal comparisons, Bennett prefers using Carl Sagan's cosmic calendar, in which one imagines the entire history of the universe from the Big Bang to the present compressed into a single year (Bennett, 2011).

Conclusion: The Ongoing Challenge of Scale in Astronomy Education

Given the scope of such numbers, building any scale model of the solar system is challenging because the distance between proportionally-sized objects representing celestial bodies would render them all but invisible to the human eye without assistance. These examples summarize many of the challenges associated with teaching astronomy.

Works Cited

Bennett, J. (2011). Teaching resources — strategies for teaching astronomy. Retrieved August 12, 2011, from http://www.jeffreybennett.com/astronomy.html

Discovery Education. (2011). Astronomical scales. Retrieved August 12, 2011, from http://www.discoveryeducation.com/teachers/free-lesson-plans/astronomical-scales.cfm

Koppes, S. (2011). Award-winning teachers find the unexpected. University website. Retrieved August 12, 2011, from

Merriam-Webster. (2011). Light-year. Retrieved August 12, 2011, from http://www.merriam-webster.com/dictionary/light-year

University. (n.d.). The Copernican model: A sun-centered solar system. Retrieved August 12, 2011, from http://csep10.phys.utk.edu/astr161/lect/retrograde/copernican.html