It can look dumb, but I always had this question as a kid, what physical principles would prevent this?
this post was submitted on 11 Feb 2025
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Ok so since there's a bunch of science nerds on here and I'm sleep deprived I'm gonna ask my dumb ftl question.
If you're on a train and you walk towards the front of the train, your speed measured from outside of the train is the speed of the train (T) plus the speed of you walking (W).
So if there was a train inside of that train, and you walked inside of that, you'd go the speed of the outside train, plus the speed of the inside train, plus your own walking speed.
So what if we had a Russian nesting doll of trains, so that the inner most train was, from the outside, going as fast as light and you walked towards the front? Wouldn't you be going faster than light if you measured your speed from the outside?
Didn't come at me with how hard it would be to build a Russian nesting doll of super trains it's a hypothetical and I'm tired.
https://www.quora.com/What-if-you-walk-forward-on-a-ship-moving-at-light-speed#:~:text=You%20would%20experience%20nothing.,of%20travel%20wouldn't%20exist.
Because of relativistic effects, from your point of view on the train you would just walk forward. But you would notice a strange effect while the trains were accelerating: ~~your atomically synchronized wristwatch~~ the clock you can see out the window has slowed down and stopped counting time. So it seems that your journey to the front of the train takes no time at all.
From someone standing on the side of the tracks catching a glimpse of you and the train as you whizz by, the front of the train is moving at light speed. You're at the back of the train completely frozen still, unable to move forward because the front of the train is moving away at light speed.
Weird things happen when you're talking about the limits of physical reality.
Wait, surely time would move at a normal speed within your own reference frame. The act of you walking to the front of the inner-most train you are in would be a normal occurence to you, but if you looked out of the window you would see a completely frozen scene.
Only once you measure time afterwards with an observer would you notice the gaping time difference.
You are correct, I should have said there was an atomic clock out the window that the walker looked out at.