Are All Things Relative?

June 24th, 2021 3:38pm


There is a place in western Nebraska where two sets of train tracks run parallel to the North Platte River. I like to sit by the tracks with a wireless speaker and drink diet margaritas. (The diet margarita, invented by my brother, is a Diet 7-Up mixed with tequila).  It’s relaxing and inspires my creative side.

I was sitting by the tracks the other evening. In a lawn chair with a cup holder. There is no shortage of trains in western Nebraska, and a freight train passed me about every twenty minutes. Some heading east carrying coal, others heading west to get more coal. A light rain started to fall and it evolved into a thunderstorm.  A long freight was exactly halfway past me when I saw a bolt of lightning strike each end of it.

There was a man riding on one of the rail cars at the midpoint on the train. I waived.  He waived back.  I’m sure he saw the lightning strikes, too. But this got me to thinking. I sipped my drink and started thinking. (Thinking and drinking both come from the root word – inking).  Because the lightning strikes were the same distance from me, their light reached my eyes at the same moment, so it appeared to me they happened simultaneously.

But things had to be different for the man on the train. Because the train was moving, the light from the lightning in the rear had to travel farther to reach that man’s eyes, so it reached his eyes an instant later than the light coming from the lightning strike at the front of the train. To him, it appeared that the lightning strike at the front of the train happened before the lightning strike at the back end of the train. That sort of freaked me out, so I took another sip.

How could two events that I felt had taken place simultaneously appear to have taken place at different times for someone else? Then it hit me. Space and time are the same thing, and simultaneity is relative to your frame of reference.

I was excited. I called my brother. “Hey,” I said.

“What’s up, Pelt?” Pelt was my nickname in high school.

“Imagine the Broncos had a great quarterback.”

“I’m drawing a blank,” he replied.

“Okay, imagine an emu.”

“Okay, I see it.”

“Now imagine the emu emits two identical pulses of light from its eyes in opposite directions.”

“Got it.”

“The emu just sits there, but because each pulse carries off a certain amount of energy, the emu’s energy content decreases.”


“The emu is stationary, but you are running past it.”

“There’s no way an emu could catch me even if he wanted to,” my brother said. “I would kick that emu’s butt.”

“Don’t worry about that,” I said.  “You’re running past the emu in the direction of one of the pulses.  You’re moving, so to you it looks like the emu is moving.”


“Both pulses are traveling at the speed of light, but their energies are different. The pulse moving forward along the direction of travel has to have a higher energy than the one moving backward relative to you.”

“Wait,” my brother said. “For that to be consistent, the emu has to lose energy when it emits the light pulses, but it also has to lose a bit of mass.”

“Exactly,” I said. “Mass and energy are interchangeable. Emu is equal to mass times the speed of light squared.”

“Makes sense,” my brother said.

“I even created an equation for it,” I said.  “Emu is equal to mass times the speed of light squared.”

“Just shorten it to E=mc²,” he said.

“But let’s take it one step further,” I said. “Everything is relative to your frame of reference.”

“Give me an example.”

“Remember when were kids and we got into an argument about what to watch on TV, and you kicked me in the nuts?”

“I just thought Flipper was a better show than Get Smart.”

“That’s the difference between us,” I said. “You’re attracted to dolphins, I’m attracted to brunettes.”

“I’ve got two words for you,” he said.

“Anyhow,” I said, “From my frame of reference, I was in a world of pain, but from your frame of reference your actions were justified.”

“They were justified,” he said. “I would do it again in a heartbeat.”

“But get this,” I said, “There was some intelligent being trillions of light years away from us who did not give pinch of raccoon poop what show you and I watched on TV in 1967. From that being’s frame of reference, it was insignificant.”

So, there you have it – everything is relative to your frame of reference. Science.

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