- #1
MrSimp
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- TL;DR Summary
- Came up with a thought experiment, and since I'm only 18 I assumed there likely would be a simple answer that someone older than me would know. I went to my high school physics teacher and his response made me more interested.
Imagine a plane 1 light minute across. Now imagine 1 person on either and of that plane. Between them, is a thin indestructible bar that is 1 light minute in length. In the center of this plane, a simple device has a wire that leads to a motion sensor on the left side of the bar. If the left side of the bar moves, 30 seconds later, the device in the center will make it known. Perhaps a green light on the left side will activate. Vice versa for the right side, another sensor is present on the other end and another light is present on the right side of this same device.
My question:
To my understanding, if the person on the left side of the bar pushed the bar forward by 1 meter, the device 30 light seconds away would light up on its left side after a delay of 30 seconds. But since the bar is being moved forward, towards the opposing end, the right side would have to move too. My question is, would both lights on this device go off at the same time (meaning by pushing one end of this bar, the other end moved in unison), or would there be a delay of 1 minute 30 second for the right-sided light, since the force would travel along at the speed of light.
I asked this to my physics teacher, and he compared the question to asking, "If I were to turn off the sun's gravity, would all the planets start drifting away at the same time, or would Mercury start to drift several minutes before Jupiter." He wondered if this question was about general or special relativity. We both understood the speed of light to be a hard limit, but if this hypothetical, indestructible, 1-light-minute-long bar existed, what would happen in this experiment? Would both lights go off at the same time, meaning both ends of the bar moved, or not?
My teacher made another good point though, he said that asking this question is like asking "If dragons were real, could they breath fire?" The question itself, like with turning off the sun's gravity, already breaks the laws of physics with its premise. Meaning, its answer lay outside the laws of physics too, the entire question is pure fantasy, only possible in an imagination, improvable.
But does anyone think they have an answer, as I'm genuinely quite curious to learn what people who know more than me have to say about it, without it being written off as impossible to answer, simply because the premise would be difficult to replicate. Say this was done with an atom, instead of a long bar.
My question:
To my understanding, if the person on the left side of the bar pushed the bar forward by 1 meter, the device 30 light seconds away would light up on its left side after a delay of 30 seconds. But since the bar is being moved forward, towards the opposing end, the right side would have to move too. My question is, would both lights on this device go off at the same time (meaning by pushing one end of this bar, the other end moved in unison), or would there be a delay of 1 minute 30 second for the right-sided light, since the force would travel along at the speed of light.
I asked this to my physics teacher, and he compared the question to asking, "If I were to turn off the sun's gravity, would all the planets start drifting away at the same time, or would Mercury start to drift several minutes before Jupiter." He wondered if this question was about general or special relativity. We both understood the speed of light to be a hard limit, but if this hypothetical, indestructible, 1-light-minute-long bar existed, what would happen in this experiment? Would both lights go off at the same time, meaning both ends of the bar moved, or not?
My teacher made another good point though, he said that asking this question is like asking "If dragons were real, could they breath fire?" The question itself, like with turning off the sun's gravity, already breaks the laws of physics with its premise. Meaning, its answer lay outside the laws of physics too, the entire question is pure fantasy, only possible in an imagination, improvable.
But does anyone think they have an answer, as I'm genuinely quite curious to learn what people who know more than me have to say about it, without it being written off as impossible to answer, simply because the premise would be difficult to replicate. Say this was done with an atom, instead of a long bar.
