Slow motion approach to “the speed of light”
By Anke van Eekelen
Let’s face it, some fundamental concepts in science are just too hard to get your head around. The average person may get a hint of their meaning, but only if the issue is simplified at large. A good example of such a notion beyond grasp is light and the properties of its motion.
Brian Greene, author of the book entitled “The Elegant Universe”, goes to great length to bring the scaringly complicated physics of the universe closer to the reader. In his chapter on “The Speed of Light” (pp 31-33), he demystifies the idea of relative motion with a sequel of examples that gradually build up a story of increasing complexity. The feeling that you, as the reader, are the main character in the tale is quite effective as well.
This engaging approach starts with a basic observation of a down to earth experience: a game of throw & catch with a baseball. Greene then wants you to take a next step: imagine now that it is no longer a ball but a grenade that is thrown at you. You would want to run away as quickly as you can and because you do, the perception of its speed will be less than if you would have remained in place and attempted to catch it like a ball. The same message comes across when the reader is placed in the mountains and faces an avalanche of snow.
What the reader has experienced in his or her mind can be explained by the classical theory of motion according to Newton. But what follows reaches the limits of most people’s comprehension. As soon as the grenade is swapped for a light beam or laser in the remainder of examples, running away is as useless as “hitching a ride on spaceship Enterprise and zipping away”. Why? Because “the speed of light is always the same”, it is always 670 million miles per hour.
Greene softens the blow of this ‘hard to swallow’ climax of his enjoyable lesson on the physics of motion by indicating that only a few bright lights in history, among which Einstein, were able to embrace this fact.
For all ordinary people, it is encouraging to know that common experiences and basic observations compellingly placed in a context that speaks to the imagination, can shine light on complex scientific ideas you otherwise would have wanted to run away from.
Greene, B. (1999). The Speed of Light : Space, time, and the eye of the beholder. In The Elegant Universe (pp 31-33). New York: W.W. Norton & Company.