why does time dilation work? Using this intuitive example.

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In this thought experiment, my twin brother and I are both turning 20 at the airport.

At midnight on our birthday, we are both exactly age 20 years.

He stays put while I get on a 777 and fly around the world. The flight takes me 24 hours and so he waits 24 hours. I arrive and we are both age 20 years plus 24 hours.

If I instead get on an SR-71 and fly around the world at 3x speed of the 777, the flight takes me 8 hours so he waits 8 hours. I arrive and we are both age 20 years plus 8 hours. Clearly, we are both younger in this scenario than the first one.

If I got onto a super plane flying at 0.99x light speed and fly around the world, the flight takes me 1 second. Since I’m so fast, he should also only wait one second. Intuitively, I’m back and we’re both 20 years and 1 second old.

But my understanding of time dilation is that I’m 20 years and 1 second old when I’m back, but he would be much older since I was almost going at light speed.

Why is that? My flight and his wait time should both be much much shorter since I was flying much much faster.

In: Physics

34 Answers

Anonymous 0 Comments

The weirdest part is that for some reason, c is just the max speed.

“Aging” is what we call all the chemical reactions that add up and degrade our cells. Let’s picture breathing in and out for this. Like we can imagine the air as little balls you breathe in and out. Each cycle ages you by one breath.

The weird part is, you only have a maximum budget for both of these things. Imagine you’re in that space ship going .99x the speed of light and it’s a turn based game. On turns 1-99, you’re spending your motion budget being basically a beam of light. All the “balls” of air that would go in and out of your lungs to spend a breath spent their speed budget going the same direction as the ship at almost the speed of light. On turn 100 they had enough momentum to move “sideways” going in and out of your lungs to spend one breath. You don’t notice this because all the atoms in your brain that do the work of perceiving time are themselves moving in the direction of the ship for almost all of their c budget.

If you could somehow go 1.00c, all your atoms would spend all of their motion (or “turns”) moving in the direction of the ship at the speed of light. They’d have no extra budget to go 1.000000001c needed to have any vector to move “sideways” to chemically react with each other and cause what we’d call aging. So in that sense, going 1c freezes time for atoms relative to each other. You can’t die from lack of oxygen because nothing in your body can react while “frozen”. You can’t perceive that you’re frozen because all your brain neurons and chemicals are frozen. At all lesser speeds, this ratio just keeps working out from your point of view, although people outside your frame of reference see you as closer and closer to stasis the faster you get towards c.

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