I stood in the center of my living room, faced north, and asked my friend to watch me. I held my left forearm across my body, and pointing with my right hand I asked, “How far is it from here [touching my left elbow] to there [touching my left fingertips]?”
“I would say its about seventeen or eighteen inches,” my friend replied. “That’s what the Bible calls a cubit, isn’t it?”
“True, but that’s not what I mean. Let me do it again.” I repeated the exercise.
“I still say it’s around eighteen inches,” he answered.
“Think again. Where was I when I pointed to my elbow, and where was I when I pointed to my fingertips?”
“Why, right here in your living room, both times!”
“But it took me one second to move my hand from my elbow to my fingertip, didn’t it?”
“So?” he frowned. I perceived that my visitor was beginning to wonder about my degree of sanity.
“Consider this,” I countered. “The earth rotates on its axis from west to east. At our latitude of around 40 degrees, the speed of rotation is about 667 miles per hour. In one second, our position ‘here’ moves about two-tenths of a mile — .185 mile, to be exact. So that was the distance from ‘here’ to ‘there.’”
You’re goofy,” he exclaimed. “Or a dork.”
“No, seriously. I was facing north, so my left forearm was parallel to the direction of the earth’s rotation. But that wouldn’t have made much difference, only the difference between seventeen inches and .185 of a mile.”
My visitor groaned. “And I suppose you can calculate how many angels can dance on the head of a pin?”
“It depends on how long their bounce lasts. Now, the better dancers can stay up . . .”
He rose from his seat on the sofa. “I’m getting out of here before this conversation affects my sanity!”
“Wait! we’re not through.”
He paused. “Well, make it quick. I have an appointment in fifteen minutes with my therapist. At least he’s not crazy — I think.”
“This won’t take long. Think about it this way. The earth’s orbit around the sun is about 600 million miles. In a 365-day year there are 31,536,000 seconds. So the earth moves about nineteen miles per second — more or less, depending on which side of the earth we happen to be on when we do our measurement, because the direction of the rotation on the earth’s surface either adds or subtracts from that orbital speed.”
“Then you’re saying that the distance from ‘here’ to ‘there’ was nineteen miles?” He turned toward the front door, looking as though he would like to exit my house at that same speed.
“No, there’s more. The solar system orbits around the center of the galaxy at a speed of 220 kilometers per second. So from ‘here’ to ‘there’ is actually 136 miles, plus or minus the other factors. But then, we have to consider the rotational speed of our galaxy around the galactic center, and the speed of our cluster through ‘absolute space,’ if we could ever measure that. Michelsen and Morley’s experiment in 1887 was inconclusive . . .”
But my friend was out the door by this time. Therefore he failed to hear my final point. “So this all shows that whenever we try to state a truth, we always need to ask from what perspective we’re gauging the accuracy of our statements. Now this could apply to anything we care to talk about, such as . . . oh, I guess he’s gone.”