Relativity for Relatives

I asked my wife, "Do you want to hear more about Einstein's theory of relativity?" She answered, "Not at the moment. Why don't you tell Mei Mei about it." Said I, "Well, she doesn't really fit the clever title of this article." "Sure she does. She's a member of the family, you know." "But Shih Tzus are not known for their complex thoughts," I protested. My wife replied, "However, she will give you her full attention."

"All right; listen up, Mei Mei," I announced to my loyal dog as she chewed on one of her dozen chews currently in circulation. She lifted her head and looked at me, expecting a kibble for her effort.

I began the story: Once upon a time, actually in the late 1800's, several scientists decided to detect for certain the ethereal substance that supposedly filled the universe in which the waves of light traveled. Since all waves are vibrations of something, then, they reasoned, light waves had to be traveling through some medium. This substance was called "aether".

Since this must be true, the scientists speculated, then as the earth whizzes through the aether on its trip around the sun, they should be able to see an effect on the speed of light caused by that motion.

Two scientists, Michelson and Morley, set up a very sensitive apparatus in 1887 that would detect even the slightest change in this speed by using the interaction of two beams of light, one beam parallel to the direction of the earth's motion in space, and the other beam at right angles to the first beam.

Mei Mei's eyes were beginning to wander, so I added some zooming motions with my arms and made swishing noises of the earth's path in the aether around the sun that would have made my grandson proud.

Michelson and his partner saw absolutely no change in speed. Maybe the aether was moving at the same speed as the earth. They waited 6 months later to repeat the experiment, when the earth's direction would be reversed in its solar orbit. Again, no change. This was very puzzling, for it seemed to indicate that the speed of light was a constant which did not vary with Earth's movement.

In stepped the theoretical physicists, including Einstein. They hypothesized that experimenters in a laboratory which was traveling at constant speed in a straight line would always measure the speed of light to be 186,000 miles/second no matter how fast the lab was moving, and that aether did not exist.

Mei Mei kindly licked my face and went over to take a nap. I exclaimed, "Mei Mei, don't you want to know what the consequences of such a radical theory would be?" No response.

Next week I will tell why this discovery requires rulers to get shorter and clocks to slow down if they are traveling in a fast moving laboratory. The true light, which enlightens everyone, was coming into the world (John 1:10)

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