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 whole problem is the formula for speed being time divided by distance. We normally think of this formula as fixed but the problem is time is not fixed. 5,000 Miles is kind of a fixed number but time isn’t fixed. For the overwhelming majority of Life circumstances we can view time is fixed but things begin to break down when we start hitting speeds like that. We know that time is tied to gravity. We know this because very accurate clocks in satellites have to be adjusted occasionally due to the greater distance of satellite is from the gravity well ( that gravity well in this case being the center of the Earth.) Humans standing on the crust of the Earth are much closer to the Center of the Earth than the orbiting satellite. Because the satellites have such sensitive clocks we can tell the difference and need to adjust them.
Okay… way way waaaay off topic.
Bear with me…
If we combine time dilation caused by speed, with the uncertainty principle, stating that it is impossible to know the position and speed of an object at the same time.
How do I make an argument that my speeding ticket is invalid?
If you went for a 1 second flight (from your perspective) at 0.99c, your brother on the ground would have to wait for about 7 seconds. The difference between you and your brother’s experienced time will grow massively as you approach the speed of light. That’s what time dilation is. It’s a difference in measured time between two observers.
This is a topic that basically can’t be understood in an ELI5 way. There’s nothing intuitive about it and no easy way to understand it since the very concept is counter to all of our life experience.
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