Random walks and conservation laws in average

[cesiumfrog]

Perpetual motion idea: Sit on a bench with a collimated laser, single slit and detector screen.

This prepares particles with identical and symmetric spatial wave-functions, so each measurement transfers an independent, random quantity of transverse momentum (from a symmetric distribution) to the screen. So the total amount of transverse momentum transferred to the screen increases in proportion to the http://en.wikipedia.org/wiki/Random_walk" of the total number of particles measured so far.

Hence, the bench begins to move transversely. Also, if the photons do not lose or gain energy as they move from the laser to the screen, despite adopting transverse velocity when the collimated beam undergoes diffraction, then some of their longitudinal momentum has disappeared, so the bench also accelerates longitudinally. Accelerations without any external force and the energy accounting has broken.

Or not, but how not? I'm arguing that it is insufficient for QM to only "on average" obey conservation laws, and I think the resolution has to do with entanglement prior to the measurement. Any ideas?

 

[DrChinese]

Ok, so if you have a laser and you are imagining that there is recoil from the light being emitted. Of course we know that requires energy in, so there isn't much opportunity for perpertual motion from that.

Second, you are saying that the traverse momentum imparted to the screen is at the expense of momentum in the direction of the laser beam (longitudinal direction). And that leads to there being more longitudinal recoil than there is longitudinal momentum transfer.

But I would say that the "recoil" would match the transferred momentum. I guess that if the position of the absorption on the screen is known precisely, there would be a large uncertainty in the momentum itself. So it would seem that the accounting would work out fine.

 

[Entropia]

it is important for us to critically evaluate any proposed ideas or theories, especially when it comes to concepts like perpetual motion. While the idea of using a collimated laser, single slit, and detector screen to create a perpetual motion machine may seem intriguing, there are several scientific principles and laws that need to be considered.

First and foremost, the concept of perpetual motion goes against the fundamental laws of thermodynamics, which state that energy cannot be created or destroyed, only transformed. In this case, the proposed perpetual motion machine would seemingly create energy out of nothing, which goes against this law.

Furthermore, the idea of using random walks and conservation laws in average is not a sufficient explanation for how this proposed machine would work. While it may seem that the total amount of transverse momentum transferred to the screen would increase with each measurement, this does not take into account the fact that some of the photons may also lose energy as they travel from the laser to the screen. This would result in a decrease in momentum and therefore would not lead to perpetual motion.

Moreover, the concept of entanglement prior to measurement is not a viable explanation for the proposed perpetual motion machine. Entanglement is a phenomenon in quantum mechanics where two particles become correlated and share a state, but it does not violate the laws of conservation. In this scenario, the particles being measured are not entangled and therefore cannot be used to explain the proposed perpetual motion.

In conclusion, while the idea of a perpetual motion machine may seem intriguing, it is not supported by scientific principles and laws. As scientists, it is important for us to critically evaluate ideas and theories and to rely on evidence and established laws to guide our understanding of the world around us.