In my undergrad physics course we were taught the basics of relativity. It was explained to us that something moving near the speed of light can somewhat time travel when compared to a stationary observer. So, how much younger would [Astronaut Koch](https://www.google.com/amp/s/amp.usatoday.com/amp/4676940002) be than us and how does this phenomena work?
In: Physics
The ISS experiences about 0.007 seconds less time for ever 6 months. Or about 14 milliseconds a year.
It all stems from the speed of light being the same in all reference frames. Normally if you run in the same direction as a bicyclist is cycling they will seem slower, and if you run in the opposite direction, they will seem faster.
This isn’t true with the hard cap on lights speed. If you run toward light or away from some massless particle at light speed, it doesn’t go faster or slower.
So while that car going 20mph is going 25 mph relative to you if you run at it 5mph, and it is only going 15mph relative to you if you try and Chase it, light will always be going light speed no matter how fast you Chase it or run from it
The only way this can happen is if time itself is happening differently for both you and that massless light
This has been confirmed as real and not math errors, as gps systems and the like need to account for it to work, otherwise they’re off.
I’m sorry I didn’t do a great job, I just don’t think there’s a truly eli5 way for this. You just have to accept some stuff because the human experience has no real reference for near lightspeed so it doesn’t make sense to our brains. It’s like trying to tell a turtle that’s only ever lived in a sheltered cave about how when you run really fast you have to take wind resistance into account, but it doesn’t really matter if you’re just plodding along. He will have no real experience with it.
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