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A Brief Introduction to Astronomy

J. Timothy Unruh

”In the beginning...” Genesis 1:1 is where astronomy, cosmology, and astrophysics all begin. Astronomy is perhaps the most sublime and, undoubtedly, the oldest of the sciences. The term astronomy is derived from the Greek words astron, a star, and nomos, a law. The word science itself means knowledge. Astronomy in the broadest sense is the knowledge of the spatial, material, and temporal characteristics of the universe. It is the study of the universe above the Earth's atmosphere and includes the Sun, Moon, stars, planets, comets, meteoroids and realms unseen. Since there is little opportunity for direct experimentation or analysis of the stellar realm most of what we know or believe is through Earthbound observation. This science of observation from afar parallels the history of humanity. When the first man, Adam, opened his eyes toward the starry heaven his awe, wonder, and curiosity for that half of creation perpetually overhead inaugurated an inquiry that continues to our day. No other science is so mysterious, no other science so stimulates us to ask questions and seek answers about the created order in which we live, and no other science confronts us personally with the questions of who we are and of our purpose and destiny as does observational astronomy. Our fascination with the heavens is as old as man's ability to think; and as ancient as his ability to wonder and dream. In company with other special enchantments of human life, the unique appeal of astronomy is its intellectual challenge in the exploration and discovery of incredible things, the aesthetic pleasure of celestial sight seeing from one object of beauty to the next, and most of all the incommunicable personal experience unique to each individual as he or she experiences the incomprehensible vastness and grandeur of God's creation.

As collectors of rare and precious things champions of other disciplines must usually be content with second and third rate specimens. Few mineralogists could even yearn to own such a specimen as the Hope diamond, and very unlikely would an amateur fossil collector be able to display a complete dinosaur skeleton in his cabinet. In contrast, the backyard astronomer equipped with the magnifying eye of a modest astronomical telescope has access at all times to the original objects of his study - the masterworks of the heavens - which belong to him just as much as to any of the great museums or observatories of the world. There is no pleasure quite like that of removing one's self from the busy cares of everyday life and taking the time in an evening to stand in the presence of the authentic, and, with telescope at hand, taking flight among the original objects of this study.

In order to appreciate the science of astronomy and all of its wonder one must begin with a sense of where we are in the midst of the grand cosmos, for indeed astronomy is all around us, as it is written: the Earth is “under the whole heaven” (Genesis 7:19). Let us, therefore, begin with the Earth, the world we live on. The Earth is a sphere nearly 8,000 miles in diameter, and 25,000 miles in circumference at the equator. If you are five feet tall it would take more than 26,000,000 of you laid end to end to reach around the world. Now, if you were to walk that distance at average walking speed, which is around three miles per hour, it would require of you about one year of continuous walking without stopping, day or night. The Earth is indeed vary large. Our nearest celestial neighbor, the Moon which is Earth's natural satellite, averages about 240,000 miles away. By the same token, it would require eight and a half years of continuous walking at the expense of wearing out 100 pairs of good hiking shoes to walk the distance of the Moon. Continuing with this illustration, the distance to the Sun is truly astronomical. At 93,000,000 miles away, it would take you no less than 3,500 years non-stop to walk to the Sun, if that were possible. To further this illustration we are going to have to shift gears in order to keep up with the sheer magnitude of the size and space relationships involved. Let us now take the distance between the Earth and the Sun as our unit of measurement, thus 93,000,000 miles is one astronomical unit (”AU”). The most distant planet in the solar system, Pluto, is about 40 AU's from the Sun. Thus the solar system itself is about 80 AU's across.
Once we leave the solar system even the astronomical unit begins to lose its meaning as a useful gauge of distance. So we switch gears again and start talking about light years. A light year is the distance that a beam of light, which travels at 186,282 miles per second, travels in a year. Hence, light can travel a distance equal to nearly eight times around the world in one second, or 5,880,000,000,000 miles in a year - one light year. By a convenient circumstance the number of inches in a mile (63,360) is very nearly equal to the number of astronomical units in one light year. Now let us imagine a scale model of our solar system, with the Earth represented by a tiny speck one inch away from the pin point Sun. Pluto is then a very tiny mote about three and a half feet from the Sun. The nearest star, Alpha Centauri, is another Sun-sized pinpoint nearly four and one half miles away. On the average the rest of the stars are as far from each other as the nearest ones are from us. The great “star city” of our own Milky Way Galaxy on this scale is a truly enormous 100,000 miles across. The nearest galaxy, Andromeda is 2,200,000 miles away respectively. Again we have approached the incomprehensible. We now need to remodel our model yet again just to keep control of the numbers. If we now reduce the 100,000 mile diameter scale model of the Milky Way Galaxy to one inch representing its entire actual 100,000 light-year diameter and place the Andromeda galaxy, similar in size to our own Milky Way galaxy, at about two feet away respectively, the furthest extent of the known universe would be perhaps 50 miles away. We have yet to see how much further this exercise could be carried on.

There are, however, other factors that should be considered in our estimation of the universe. The shape, or form of the universe has remained a topic of debate among scientists for some time. One model of the universe represents it as being flat or linear, while another represents it as being “curved.” Of interest is the fact that the latter model places the most distant object at a little more than 15 light years away from Earth. Such a possibility would limit the age of the cosmos to just a few thousand years. Furthermore the assumption that the speed of light has always remained constant at its present velocity is now suspect. There is evidence that the speed of light was far greater in the distant past than it is at present. Light from distant sources would therefore not require the enormous extent of time to reach us as currently held. This would certainly have a significant impact on cosmogony and on how most cosmologists view the dimensions, physics, and age of the universe. Since we live in a universe, not a “multiverse,” there is good reason to regard it as a unified whole by deliberate design with a time frame virtually paralleling human history, consistent with the Biblical account of creation and Earth history. Thus, from man's perspective, the universe remains as wonderful and mysterious as ever, and full of intriguing unanswered questions. Yet, true science, and hence the exploration of our universe, really involves “thinking God's thoughts after Him.”

For my thoughts are not your thoughts, neither are your ways my ways, saith the Lord. For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts.

 — Isaiah 55:8-9

Copyright © 1994, J. Timothy Unruh

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Translated from WS2000 on 11 February 2005 by ws2html.