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
Think of driving towards a mountain, if you change course 45 degrees you’re still getting closer to that mountain but half as fast despite moving at the same speed.
Our universal speed limit c can also be seen as our constant velocity through both time and space. So if we move through space we’re deviating on our course toward the mountain [time] but still moving at c. Likewise if we stay perfectly still in space we’re moving full speed through time.
So the observer in the rocket ship moves really fast (almost exactly equal to c) and travels 30 lightyears from their point of view as instantaneous, they experienced very little time during their journey. The observer on earth spent their budget entirely on time so when the rocket arrives 30 years have passed for them.
Latest Answers