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Combining two different internet debates
(sopuli.xyz)
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this post was submitted on 18 Aug 2023
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The only way it could be B in this universe is if the train also decelerates equivalent to how the people accelerate. If the people accelerate and the train maintains velocity you've created energy in a closed system.
Portals don't abide by the laws of physics. Portal above + portal below = infinitely falling object (and thus infinite kinetic energy)
Portals don't abide by physics, but people still do. Even in the infinite fall scenario there isn't infinite energy because the object accelerating is still subject to terminal velocity, and it's change in momentum comes from gravity. For the people to change their velocity, there has to be energy imparted onto them. My theory is that the train would have to slow.
The issue with being able to get infinite amounts of energy out of a portal can be solved by thinking with entropy.
If you only look at the entropic system of the portal and the object falling through it, say for instance a magnet inside of a vacuum tube that is perfectly abutted to both ends of the portal, the energy that you are able to extract from the system using a set of coils would come from gravity, and that gravity energy would come from the Earth.
In that case, one of two things would have to happen, either the mass of the Earth would decrease by being converted into energy, or two, the amount of energy needed to maintain the portal would be equal to or greater than the amount of energy that you're capable of extracting from it with an infinitely falling magnet and coil.
I think that the tram would not have to slow down, and that there would be no additional momentum added to the victims as they pass through the portal, and any energy that is lost in those two equations would come from the energy needed to maintain the portals operation.
You see, shit like this is why I love theoretical discussions about impossible crap. Somewhere else in this thread we use the idea that a moving portal can impart momentum in combination with the idea that portals need to maintain a minimum energy level to explain why moving portals collapse in a way that would at least be satisfying to someone reading a sci-fi novel. It's now my head canon.
So scenario A?
Yep. I've been advocating A since the beginning
Objects coming out of the portal in "a" have to have velocity coming out (they don't magically appear outside of the portal, they move out inch by inch/ cm by cm). So in a you would actually have double the deceleration on the train because it has to accelerate people leaving the portal and then instantly decelerate them once they have fully exited the portal.