Light and Time
Published 4-6-2016
As a science teacher one of my favorite curricular topics was astronomy. Some years I extended the unit beyond the time our teaching syllabus actually prescribed. Our supervisor understood that the interests and talents of individual staff members might supersede strict rigidity in applying curricular time allotments.
Time, space, distance, and speed were a few topics supporting my pedagogical offerings within the astronomy unit. Some students found these concepts fascinating; some did not. Almost all students, however, were enlivened by the hypothetical prospect that if we were located in distant space looking back at earth through a powerful telescope, we could observe past events as if they were occurring in the present. For example, if at this moment we were on a planet located in Andromeda galaxy, the nearest major galaxy outside our home Milky Way galaxy, we would observe events occurring on Earth 2 1/2 million years ago. Similarly, from our present location on Planet Earth, we now observe Andromeda galaxy as it was 2 1/2 million years ago.
In a sense, we look into the past when we observe light from any object. Light from the room in which we sit reaches us in a fraction of a millisecond. Our Earth, 240,000 miles distant from the moon, receives moonlight 1 1/2 seconds “old.” Sunlight reaches us in about eight minutes; we say it is eight light minutes away. The nearest star is four light years away because its light travels four years to reach us. As already noted, Andromeda is 2 1/2 million light years away. Light seconds, light minutes, and light years are units of distance.
Light has a finite speed of approximately 300 million meters/sec (approx. 186,000 miles/sec). This speed of light in a vacuum is an unalterable physical constant—one of the many physical constants by which our orderly universe operates. It is an ultimate speed—a maximum speed limit of the universe—a fact related to Einstein’s proposal of special relativity. Time relates to light, however. It proceeds slower as we travel faster. Light speed is a constant enabling us, among other constants, to calculate cosmic distances. A changing light speed would create disorder in our cosmos as would fluctuations in any other physical constant.
Scientists such as Isaac Newton thought entities of time and space were absolute entities, not related or comparative to other things. Relativity, however, has superseded Newton’s laws when dealing with very massive objects, or concepts describing gravity fields or electromagnetic fields. For every day experiences Newton’s laws accurately described and predicted events. In Newton’s day these everyday experiences were not concerned with concepts such as the dilation of time or apparent changes in length and mass when objects were accelerated toward the speed of light. In Newton’s day various outcomes of relativity may have seemed like science fiction. Brilliant as he was, the idea of space-time curvature or gravity waves were beyond his understanding. His descriptions of reality were adequate for his time but are somewhat out of date in the 21st century.
The recent detection of gravity waves and the renewed emphasis on concepts such as the space-time fabric of the universe, to mention only two, give rise to fascination about cosmic operation. We are gaining additional knowledge of the universe and its secrets at an ever increasing pace, from the microcosmos to the macrocosmos. For believers in the God of Creation, our theistic beliefs intensify with each new discovery.
Recently I encountered a mysterious statement: “Nobody has a clue about the absolutely biggest questions.” Such statements could be interpreted in different ways: (1) The universe is inscrutable, even disorderly, or (2) The universe reveals the ordered planning and design of an omnipotent God. We trust our blog calls attention to the divine Designer of cosmic order.
