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
The problem with using increasingly fast airplane flights this way is that the “clock” of all the space and matter on the plane runs slower than the clock of everything back on the ground. Given a VERY fast and very long flight (completely hypothetical), a banana you bought at the airport would be fresh when it landed while all the other bananas from its bunch would have spoiled. The stationary bananas would age; the traveling banana would not.
The difference doesn’t really add up unless you’re traveling a LONG way/time moving at a VERY fast speed. For trips that start on Earth and go up and back down, we’re talking about billionths of a second in difference. For a near-light speed trip to the Moon and back, you would experience about 3 seconds less than your twin on Earth.
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