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
What you’re missing is that your example isn’t intuitive, because it’s on such a small time frame.
Light can travel around the earth seven times in a second. You’re not going to have enough of an effect from time dilation to see a significant change.
If you were flying 99 light years at 99% the speed of light, someone on earth would see you flying for 100 years, but for you it would only take about 14 years.
It’s not that being at near light speed instantaneously makes a many-year time difference happen, it has to be for long enough for the time difference to build up.
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